Patent Publication Number: US-9886179-B2

Title: Anchored approach to scrolling

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application Ser. No. 62/042,779, filed on Aug. 27, 2014, the entire content of which is incorporated by reference for all purposes. 
    
    
     BACKGROUND 
     1. Field 
     This application relates generally to displaying multiple graphical objects on a display, and, more specifically, to techniques for configuring layouts of graphical objects in response to user navigation. 
     2. Description of Related Art 
     Modern computing devices can display multiple graphical objects on-screen. These graphical objects may represent file system objects such as files and folders. These graphical objects also may represent applications-specific objects such as e-mail and text messages. The display of graphical objects may be affected by user input, such as input to navigate a viewport. The display of graphical objects may also be affected by background processes that are obtaining or deleting underlying data objects (e.g., files and messages) that are represented on-screen. 
     A device may take into consideration a variety of factors and conditions in determining what updates should be made to a displayed set of graphical objects in response to the user input and/or background processes. As these inputs and processes can occur frequently, a device&#39;s ability to update displayed information quickly and consistently with user expectations has a significant effect on the quality of overall usability of displayed content and user experience. 
     BRIEF SUMMARY 
     In some embodiments, a method of updating a user interface window at an electronic device configured to access a plurality of data objects comprises: displaying a viewport comprising graphical representations of a first subset of the plurality of data objects that are ordered; while displaying the graphical representations of the first subset, receiving a request to navigate through graphical representations of the plurality of data objects in the viewport, where the request is associated with an input magnitude. In response to the request, generating a layout for a second subset of the plurality of data objects based on the input magnitude and an anchor within the plurality of data objects that was selected based on user input; and changing the content of the viewport by displaying graphical representations of the data objects of the second subset according to the layout. 
     In some embodiments, a system configured to access a plurality of data objects and display graphical representations of subsets of the plurality of data objects comprises: means for displaying a viewport comprising graphical representations of a first subset of the plurality of data objects that are ordered; means for, while displaying the graphical representations of the first subset, receiving a request to navigate through graphical representations of the plurality of data objects in the viewport, where the request is associated with an input magnitude. Means responsive to the request, for generating a layout for a second subset of the plurality of data objects based on the input magnitude and an anchor within the plurality of data objects that was selected based on user input; and means for changing the content of the viewport by displaying graphical representations of the data objects of the second subset according to the layout. 
    
    
     
       DESCRIPTION OF THE FIGURES 
       For a better understanding of the various described embodiments, reference should be made to the Detailed Description of embodiments below, in conjunction with the following drawings in which like reference numerals refer to corresponding parts throughout the figures. 
         FIG. 1A  is a block diagram illustrating a portable multifunction device with a touch-sensitive display in accordance with some embodiments. 
         FIG. 1B  is a block diagram illustrating exemplary components for event handling in accordance with some embodiments. 
         FIG. 2  illustrates a portable multifunction device having a touch-sensitive display in accordance with some embodiments. 
         FIG. 3  is a block diagram of an exemplary multifunction device with a display and a touch-sensitive surface in accordance with some embodiments. 
         FIG. 4  illustrates an exemplary user interface for a menu of applications on a portable multifunction device in accordance with some embodiments. 
         FIG. 5  illustrates an exemplary user interface for a multifunction device with a touch-sensitive surface that is separate from the display in accordance with some embodiments. 
         FIGS. 6A-6H  illustrate an exemplary embodiment of techniques for configuring the layout of graphical representations of data objects, in response to user input. 
         FIGS. 7A-7J  illustrate an exemplary embodiment of techniques for configuring the layout of graphical representations of data objects, in response to user input. 
         FIG. 8  is an exemplary flow diagram illustrating a process for configuring the layout of graphical representations of data objects. 
         FIG. 9  is a functional block diagram of an electronic device configured to layout graphical representations of data objects in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The following description sets forth exemplary methods, parameters and the like. It should be recognized, however, that such description is not intended as a limitation on the scope of the present disclosure but is instead provided as a description of exemplary embodiments. 
       FIG. 6A  depicts an implementation of embodiments of the techniques described herein for laying out graphical representations of data objects. As shown, laptop  600  is executing an active e-mail application that causes the display of application window  602 . Window  602  has a viewport  608  for displaying e-mail message previews  603 - 607 . A message preview may include an identification of the message&#39;s sender, a subject line, and the initial line(s) of the e-mail message. Window  602  also has a region  609  for displaying the body of a selected e-mail message, in this case the e-mail message represented by preview region  603 . 
     In some circumstances, a user may wish to change the content displayed within window  602  or viewport  608 . For example, a user may scroll preview viewport  608  intending to reveal other messages for display. When this occurs, it would be helpful for device  600  to update preview viewport  608  smoothly (e.g., quickly) and consistently with the user&#39;s scrolling input. In some circumstances, a user may wish for the displayed content to remain steady. For example, if the user is viewing preview viewport  608  and not providing navigation input, it would be helpful for device  600  to maintain the content of viewport  608 , even if new e-mail messages are incoming. 
     Below,  FIGS. 1A-1B, 2, 3, 4, 5, and 9  provide a description of exemplary devices that may perform techniques for controlling the display layout of graphical representations of data objects.  FIGS. 6B-6H and 7A-7J  illustrate exemplary aspects of these techniques. The figures are also used to illustrate the processes described below, including the processes in  FIG. 8 . 
     Although the following description uses terms “first,” “second,” etc. to describe various elements, these elements should not be limited by the terms. These terms are only used to distinguish one element from another. For example, a first touch could be termed a second touch, and, similarly, a second touch could be termed a first touch, without departing from the scope of the various described embodiments. The first touch and the second touch are both touches, but they are not the same touch. 
     The terminology used in the description of the various described embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various described embodiments and the appended claims, the singular forms “a”, “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and/or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     The term “if” may be construed to mean “when” or “upon” or “in response to determining” or “in response to detecting,” depending on the context. Similarly, the phrase “if it is determined” or “if [a stated condition or event] is detected” may be construed to mean “upon determining” or “in response to determining” or “upon detecting [the stated condition or event]” or “in response to detecting [the stated condition or event],” depending on the context. 
     Embodiments of electronic devices, user interfaces for such devices, and associated processes for using such devices are described. In some embodiments, the device is a portable communications device, such as a mobile telephone, that also contains other functions, such as PDA and/or music player functions. Exemplary embodiments of portable multifunction devices include, without limitation, the iPhone®, iPod Touch®, and iPad® devices from Apple Inc. of Cupertino, Calif. Other portable electronic devices, such as laptops or tablet computers with touch-sensitive surfaces (e.g., touch screen displays and/or touchpads), are, optionally, used. It should also be understood that, in some embodiments, the device is not a portable communications device, but is a desktop computer with a touch-sensitive surface (e.g., a touch screen display and/or a touchpad). 
     In the discussion that follows, an electronic device that includes a display and a touch-sensitive surface is described. It should be understood, however, that the electronic device optionally includes one or more other physical user-interface devices, such as a physical keyboard, a mouse, and/or a joystick. 
     The device may support a variety of applications, such as one or more of the following: a drawing application, a presentation application, a word processing application, a website creation application, a disk authoring application, a spreadsheet application, a gaming application, a telephone application, a video conferencing application, an e-mail application, an instant messaging application, a workout support application, a photo management application, a digital camera application, a digital video camera application, a web browsing application, a digital music player application, and/or a digital video player application. 
     The various applications that are executed on the device optionally use at least one common physical user-interface device, such as the touch-sensitive surface. One or more functions of the touch-sensitive surface as well as corresponding information displayed on the device are, optionally, adjusted and/or varied from one application to the next and/or within a respective application. In this way, a common physical architecture (such as the touch-sensitive surface) of the device optionally supports the variety of applications with user interfaces that are intuitive and transparent to the user. 
     Attention is now directed toward embodiments of portable devices with touch-sensitive displays.  FIG. 1A  is a block diagram illustrating portable multifunction device  100  with touch-sensitive display system  112  in accordance with some embodiments. Touch-sensitive display  112  is sometimes called a “touch screen” for convenience and is sometimes known as or called a “touch-sensitive display system.” Device  100  includes memory  102  (which optionally includes one or more computer-readable storage mediums), memory controller  122 , one or more processing units (CPUs)  120 , peripherals interface  118 , RF circuitry  108 , audio circuitry  110 , speaker  111 , microphone  113 , input/output (I/O) subsystem  106 , other input control devices  116 , and external port  124 . Device  100  optionally includes one or more optical sensors  164 . Device  100  optionally includes one or more contact intensity sensors  165  for detecting intensity of contacts on device  100  (e.g., a touch-sensitive surface such as touch-sensitive display system  112  of device  100 ). Device  100  optionally includes one or more tactile output generators  167  for generating tactile outputs on device  100  (e.g., generating tactile outputs on a touch-sensitive surface such as touch-sensitive display system  112  of device  100  or touchpad  355  of device  300 ). These components optionally communicate over one or more communication buses or signal lines  103 . 
     As used in the specification and claims, the term “intensity” of a contact on a touch-sensitive surface refers to the force or pressure (force per unit area) of a contact (e.g., a finger contact) on the touch-sensitive surface, or to a substitute (proxy) for the force or pressure of a contact on the touch-sensitive surface. The intensity of a contact has a range of values that includes at least four distinct values and more typically includes hundreds of distinct values (e.g., at least 256). Intensity of a contact is, optionally, determined (or measured) using various approaches and various sensors or combinations of sensors. For example, one or more force sensors underneath or adjacent to the touch-sensitive surface are, optionally, used to measure force at various points on the touch-sensitive surface. In some implementations, force measurements from multiple force sensors are combined (e.g., a weighted average) to determine an estimated force of a contact. Similarly, a pressure-sensitive tip of a stylus is, optionally, used to determine a pressure of the stylus on the touch-sensitive surface. Alternatively, the size of the contact area detected on the touch-sensitive surface and/or changes thereto, the capacitance of the touch-sensitive surface proximate to the contact and/or changes thereto, and/or the resistance of the touch-sensitive surface proximate to the contact and/or changes thereto are, optionally, used as a substitute for the force or pressure of the contact on the touch-sensitive surface. In some implementations, the substitute measurements for contact force or pressure are used directly to determine whether an intensity threshold has been exceeded (e.g., the intensity threshold is described in units corresponding to the substitute measurements). In some implementations, the substitute measurements for contact force or pressure are converted to an estimated force or pressure, and the estimated force or pressure is used to determine whether an intensity threshold has been exceeded (e.g., the intensity threshold is a pressure threshold measured in units of pressure). Using the intensity of a contact as an attribute of a user input allows for user access to additional device functionality that may otherwise not be accessible by the user on a reduced-size device with limited real estate for displaying affordances (e.g., on a touch-sensitive display) and/or receiving user input (e.g., via a touch-sensitive display, a touch-sensitive surface, or a physical/mechanical control such as a knob or a button). 
     As used in the specification and claims, the term “tactile output” refers to physical displacement of a device relative to a previous position of the device, physical displacement of a component (e.g., a touch-sensitive surface) of a device relative to another component (e.g., housing) of the device, or displacement of the component relative to a center of mass of the device that will be detected by a user with the user&#39;s sense of touch. For example, in situations where the device or the component of the device is in contact with a surface of a user that is sensitive to touch (e.g., a finger, palm, or other part of a user&#39;s hand), the tactile output generated by the physical displacement will be interpreted by the user as a tactile sensation corresponding to a perceived change in physical characteristics of the device or the component of the device. For example, movement of a touch-sensitive surface (e.g., a touch-sensitive display or trackpad) is, optionally, interpreted by the user as a “down click” or “up click” of a physical actuator button. In some cases, a user will feel a tactile sensation such as an “down click” or “up click” even when there is no movement of a physical actuator button associated with the touch-sensitive surface that is physically pressed (e.g., displaced) by the user&#39;s movements. As another example, movement of the touch-sensitive surface is, optionally, interpreted or sensed by the user as “roughness” of the touch-sensitive surface, even when there is no change in smoothness of the touch-sensitive surface. While such interpretations of touch by a user will be subject to the individualized sensory perceptions of the user, there are many sensory perceptions of touch that are common to a large majority of users. Thus, when a tactile output is described as corresponding to a particular sensory perception of a user (e.g., an “up click,” a “down click,” “roughness”), unless otherwise stated, the generated tactile output corresponds to physical displacement of the device or a component thereof that will generate the described sensory perception for a typical (or average) user. 
     It should be appreciated that device  100  is only one example of a portable multifunction device, and that device  100  optionally has more or fewer components than shown, optionally combines two or more components, or optionally has a different configuration or arrangement of the components. The various components shown in  FIG. 1A  are implemented in hardware, software, or a combination of both hardware and software, including one or more signal processing and/or application-specific integrated circuits. 
     Memory  102  may include one or more computer-readable storage mediums. The computer-readable storage mediums may be tangible and non-transitory. Memory  102  may include high-speed random access memory and may also include non-volatile memory, such as one or more magnetic disk storage devices, flash memory devices, or other non-volatile solid-state memory devices. Memory controller  122  may control access to memory  102  by other components of device  100 . 
     Peripherals interface  118  can be used to couple input and output peripherals of the device to CPU  120  and memory  102 . The one or more processors  120  run or execute various software programs and/or sets of instructions stored in memory  102  to perform various functions for device  100  and to process data. In some embodiments, peripherals interface  118 , CPU  120 , and memory controller  122  may be implemented on a single chip, such as chip  104 . In some other embodiments, they may be implemented on separate chips. 
     RF (radio frequency) circuitry  108  receives and sends RF signals, also called electromagnetic signals. RF circuitry  108  converts electrical signals to/from electromagnetic signals and communicates with communications networks and other communications devices via the electromagnetic signals. RF circuitry  108  optionally includes well-known circuitry for performing these functions, including but not limited to an antenna system, an RF transceiver, one or more amplifiers, a tuner, one or more oscillators, a digital signal processor, a CODEC chipset, a subscriber identity module (SIM) card, memory, and so forth. RF circuitry  108  optionally communicates with networks, such as the Internet, also referred to as the World Wide Web (WWW), an intranet and/or a wireless network, such as a cellular telephone network, a wireless local area network (LAN) and/or a metropolitan area network (MAN), and other devices by wireless communication. The RF circuitry  108  optionally includes well-known circuitry for detecting near field communication (NFC) fields, such as by a short-range communication radio. The wireless communication optionally uses any of a plurality of communications standards, protocols, and technologies, including but not limited to Global System for Mobile Communications (GSM), Enhanced Data GSM Environment (EDGE), high-speed downlink packet access (HSDPA), high-speed uplink packet access (HSUPA), Evolution, Data-Only (EV-DO), HSPA, HSPA+, Dual-Cell HSPA (DC-HSPDA), long term evolution (LTE), near field communication (NFC), wideband code division multiple access (W-CDMA), code division multiple access (CDMA), time division multiple access (TDMA), Bluetooth, Bluetooth Low Energy (BTLE), Wireless Fidelity (Wi-Fi) (e.g., IEEE 802.11a, IEEE 802.11b, IEEE 802.11g, IEEE 802.11n, and/or IEEE 802.11ac), voice over Internet Protocol (VoIP), Wi-MAX, a protocol for e-mail (e.g., Internet message access protocol (IMAP) and/or post office protocol (POP)), instant messaging (e.g., extensible messaging and presence protocol (XMPP), Session Initiation Protocol for Instant Messaging and Presence Leveraging Extensions (SIMPLE), Instant Messaging and Presence Service (IMPS)), and/or Short Message Service (SMS), or any other suitable communication protocol, including communication protocols not yet developed as of the filing date of this document. 
     Audio circuitry  110 , speaker  111 , and microphone  113  provide an audio interface between a user and device  100 . Audio circuitry  110  receives audio data from peripherals interface  118 , converts the audio data to an electrical signal, and transmits the electrical signal to speaker  111 . Speaker  111  converts the electrical signal to human-audible sound waves. Audio circuitry  110  also receives electrical signals converted by microphone  113  from sound waves. Audio circuitry  110  converts the electrical signal to audio data and transmits the audio data to peripherals interface  118  for processing. Audio data may be retrieved from and/or transmitted to memory  102  and/or RF circuitry  108  by peripherals interface  118 . In some embodiments, audio circuitry  110  also includes a headset jack (e.g.,  212 ,  FIG. 2 ). The headset jack provides an interface between audio circuitry  110  and removable audio input/output peripherals, such as output-only headphones or a headset with both output (e.g., a headphone for one or both ears) and input (e.g., a microphone). 
     I/O subsystem  106  couples input/output peripherals on device  100 , such as touch screen  112  and other input control devices  116 , to peripherals interface  118 . I/O subsystem  106  optionally includes display controller  156 , optical sensor controller  158 , intensity sensor controller  159 , haptic feedback controller  161 , and one or more input controllers  160  for other input or control devices. The one or more input controllers  160  receive/send electrical signals from/to other input control devices  116 . The other input control devices  116  optionally include physical buttons (e.g., push buttons, rocker buttons, etc.), dials, slider switches, joysticks, click wheels, and so forth. In some alternate embodiments, input controller(s)  160  are, optionally, coupled to any (or none) of the following: a keyboard, an infrared port, a USB port, and a pointer device such as a mouse. The one or more buttons (e.g.,  208 ,  FIG. 2 ) optionally include an up/down button for volume control of speaker  111  and/or microphone  113 . The one or more buttons optionally include a push button (e.g.,  206 ,  FIG. 2 ). 
     A quick press of the push button may disengage a lock of touch screen  112  or begin a process that uses gestures on the touch screen to unlock the device, as described in U.S. patent application Ser. No. 11/322,549, “Unlocking a Device by Performing Gestures on an Unlock Image,” filed Dec. 23, 2005, U.S. Pat. No. 7,657,849, which is hereby incorporated by reference in its entirety. A longer press of the push button (e.g.,  206 ) may turn power to device  100  on or off. The user may be able to customize a functionality of one or more of the buttons. Touch screen  112  is used to implement virtual or soft buttons and one or more soft keyboards. 
     Touch-sensitive display  112  provides an input interface and an output interface between the device and a user. Display controller  156  receives and/or sends electrical signals from/to touch screen  112 . Touch screen  112  displays visual output to the user. The visual output may include graphics, text, icons, video, and any combination thereof (collectively termed “graphics”). In some embodiments, some or all of the visual output may correspond to user-interface objects. 
     Touch screen  112  has a touch-sensitive surface, sensor, or set of sensors that accepts input from the user based on haptic and/or tactile contact. Touch screen  112  and display controller  156  (along with any associated modules and/or sets of instructions in memory  102 ) detect contact (and any movement or breaking of the contact) on touch screen  112  and convert the detected contact into interaction with user-interface objects (e.g., one or more soft keys, icons, web pages, or images) that are displayed on touch screen  112 . In an exemplary embodiment, a point of contact between touch screen  112  and the user corresponds to a finger of the user. 
     Touch screen  112  may use LCD (liquid crystal display) technology, LPD (light emitting polymer display) technology, or LED (light emitting diode) technology, although other display technologies may be used in other embodiments. Touch screen  112  and display controller  156  may detect contact and any movement or breaking thereof using any of a plurality of touch sensing technologies now known or later developed, including but not limited to capacitive, resistive, infrared, and surface acoustic wave technologies, as well as other proximity sensor arrays or other elements for determining one or more points of contact with touch screen  112 . In an exemplary embodiment, projected mutual capacitance sensing technology is used, such as that found in the iPhone® and iPod Touch® from Apple Inc. of Cupertino, Calif. 
     A touch-sensitive display in some embodiments of touch screen  112  may be analogous to the multi-touch sensitive touchpads described in the following U.S. Patents: U.S. Pat. No. 6,323,846 (Westerman et al.), U.S. Pat. No. 6,570,557 (Westerman et al.), and/or U.S. Pat. No. 6,677,932 (Westerman), and/or U.S. Patent Publication 2002/0015024A1, each of which is hereby incorporated by reference in its entirety. However, touch screen  112  displays visual output from device  100 , whereas touch-sensitive touchpads do not provide visual output. 
     A touch-sensitive display in some embodiments of touch screen  112  may be as described in the following applications: (1) U.S. patent application Ser. No. 11/381,313, “Multipoint Touch Surface Controller,” filed May 2, 2006; (2) U.S. patent application Ser. No. 10/840,862, “Multipoint Touchscreen,” filed May 6, 2004; (3) U.S. patent application Ser. No. 10/903,964, “Gestures For Touch Sensitive Input Devices,” filed Jul. 30, 2004; (4) U.S. patent application Ser. No. 11/048,264, “Gestures For Touch Sensitive Input Devices,” filed Jan. 31, 2005; (5) U.S. patent application Ser. No. 11/038,590, “Mode-Based Graphical User Interfaces For Touch Sensitive Input Devices,” filed Jan. 18, 2005; (6) U.S. patent application Ser. No. 11/228,758, “Virtual Input Device Placement On A Touch Screen User Interface,” filed Sep. 16, 2005; (7) U.S. patent application Ser. No. 11/228,700, “Operation Of A Computer With A Touch Screen Interface,” filed Sep. 16, 2005; (8) U.S. patent application Ser. No. 11/228,737, “Activating Virtual Keys Of A Touch-Screen Virtual Keyboard,” filed Sep. 16, 2005; and (9) U.S. patent application Ser. No. 11/367,749, “Multi-Functional Hand-Held Device,” filed Mar. 3, 2006. All of these applications are incorporated by reference herein in their entirety. 
     Touch screen  112  may have a video resolution in excess of 100 dpi. In some embodiments, the touch screen has a video resolution of approximately 160 dpi. The user may make contact with touch screen  112  using any suitable object or appendage, such as a stylus, a finger, and so forth. In some embodiments, the user interface is designed to work primarily with finger-based contacts and gestures, which can be less precise than stylus-based input due to the larger area of contact of a finger on the touch screen. In some embodiments, the device translates the rough finger-based input into a precise pointer/cursor position or command for performing the actions desired by the user. 
     In some embodiments, in addition to the touch screen, device  100  may include a touchpad (not shown) for activating or deactivating particular functions. In some embodiments, the touchpad is a touch-sensitive area of the device that, unlike the touch screen, does not display visual output. The touchpad may be a touch-sensitive surface that is separate from touch screen  112  or an extension of the touch-sensitive surface formed by the touch screen. 
     Device  100  also includes power system  162  for powering the various components. Power system  162  may include a power management system, one or more power sources (e.g., battery, alternating current (AC)), a recharging system, a power failure detection circuit, a power converter or inverter, a power status indicator (e.g., a light-emitting diode (LED)) and any other components associated with the generation, management and distribution of power in portable devices. 
     Device  100  may also include one or more optical sensors  164 .  FIG. 1A  shows an optical sensor coupled to optical sensor controller  158  in I/O subsystem  106 . Optical sensor  164  may include charge-coupled device (CCD) or complementary metal-oxide semiconductor (CMOS) phototransistors. Optical sensor  164  receives light from the environment, projected through one or more lenses, and converts the light to data representing an image. In conjunction with imaging module  143  (also called a camera module), optical sensor  164  may capture still images or video. In some embodiments, an optical sensor is located on the back of device  100 , opposite touch screen display  112  on the front of the device so that the touch screen display may be used as a viewfinder for still and/or video image acquisition. In some embodiments, an optical sensor is located on the front of the device so that the user&#39;s image may be obtained for video conferencing while the user views the other video conference participants on the touch screen display. In some embodiments, the position of optical sensor  164  can be changed by the user (e.g., by rotating the lens and the sensor in the device housing) so that a single optical sensor  164  may be used along with the touch screen display for both video conferencing and still and/or video image acquisition. 
     Device  100  optionally also includes one or more contact intensity sensors  165 .  FIG. 1A  shows a contact intensity sensor coupled to intensity sensor controller  159  in I/O subsystem  106 . Contact intensity sensor  165  optionally includes one or more piezoresistive strain gauges, capacitive force sensors, electric force sensors, piezoelectric force sensors, optical force sensors, capacitive touch-sensitive surfaces, or other intensity sensors (e.g., sensors used to measure the force (or pressure) of a contact on a touch-sensitive surface). Contact intensity sensor  165  receives contact intensity information (e.g., pressure information or a proxy for pressure information) from the environment. In some embodiments, at least one contact intensity sensor is collocated with, or proximate to, a touch-sensitive surface (e.g., touch-sensitive display system  112 ). In some embodiments, at least one contact intensity sensor is located on the back of device  100 , opposite touch screen display  112 , which is located on the front of device  100 . 
     Device  100  may also include one or more proximity sensors  166 .  FIG. 1A  shows proximity sensor  166  coupled to peripherals interface  118 . Alternately, proximity sensor  166  may be coupled to input controller  160  in I/O subsystem  106 . Proximity sensor  166  may perform as described in U.S. patent application Ser. No. 11/241,839, “Proximity Detector In Handheld Device”; Ser. No. 11/240,788, “Proximity Detector In Handheld Device”; Ser. No. 11/620,702, “Using Ambient Light Sensor To Augment Proximity Sensor Output”; Ser. No. 11/586,862, “Automated Response To And Sensing Of User Activity In Portable Devices”; and Ser. No. 11/638,251, “Methods And Systems For Automatic Configuration Of Peripherals,” which are hereby incorporated by reference in their entirety. In some embodiments, the proximity sensor turns off and disables touch screen  112  when the multifunction device is placed near the user&#39;s ear (e.g., when the user is making a phone call). 
     Device  100  optionally also includes one or more tactile output generators  167 .  FIG. 1A  shows a tactile output generator coupled to haptic feedback controller  161  in I/O subsystem  106 . Tactile output generator  167  optionally includes one or more electroacoustic devices such as speakers or other audio components and/or electromechanical devices that convert energy into linear motion such as a motor, solenoid, electroactive polymer, piezoelectric actuator, electrostatic actuator, or other tactile output generating component (e.g., a component that converts electrical signals into tactile outputs on the device). Contact intensity sensor  165  receives tactile feedback generation instructions from haptic feedback module  133  and generates tactile outputs on device  100  that are capable of being sensed by a user of device  100 . In some embodiments, at least one tactile output generator is collocated with, or proximate to, a touch-sensitive surface (e.g., touch-sensitive display system  112 ) and, optionally, generates a tactile output by moving the touch-sensitive surface vertically (e.g., in/out of a surface of device  100 ) or laterally (e.g., back and forth in the same plane as a surface of device  100 ). In some embodiments, at least one tactile output generator sensor is located on the back of device  100 , opposite touch screen display  112 , which is located on the front of device  100 . 
     Device  100  may also include one or more accelerometers  168 .  FIG. 1A  shows accelerometer  168  coupled to peripherals interface  118 . Alternately, accelerometer  168  may be coupled to an input controller  160  in I/O subsystem  106 . Accelerometer  168  may perform as described in U.S. Patent Publication No. 20050190059, “Acceleration-based Theft Detection System for Portable Electronic Devices,” and U.S. Patent Publication No. 20060017692, “Methods And Apparatuses For Operating A Portable Device Based On An Accelerometer,” both of which are incorporated by reference herein in their entirety. In some embodiments, information is displayed on the touch screen display in a portrait view or a landscape view based on an analysis of data received from the one or more accelerometers. Device  100  optionally includes, in addition to accelerometer(s)  168 , a magnetometer (not shown) and a GPS (or GLONASS or other global navigation system) receiver (not shown) for obtaining information concerning the location and orientation (e.g., portrait or landscape) of device  100 . 
     In some embodiments, the software components stored in memory  102  include operating system  126 , communication module (or set of instructions)  128 , contact/motion module (or set of instructions)  130 , graphics module (or set of instructions)  132 , text input module (or set of instructions)  134 , Global Positioning System (GPS) module (or set of instructions)  135 , and applications (or sets of instructions)  136 . Furthermore, in some embodiments, memory  102  ( FIG. 1A ) or  370  ( FIG. 3 ) stores device/global internal state  157 , as shown in  FIGS. 1A and 3 . Device/global internal state  157  includes one or more of: active application state, indicating which applications, if any, are currently active; display state, indicating what applications, views or other information occupy various regions of touch screen display  112 ; sensor state, including information obtained from the device&#39;s various sensors and input control devices  116 ; and location information concerning the device&#39;s location and/or attitude. 
     Operating system  126  (e.g., Darwin, RTXC, LINUX, UNIX, OS X, iOS, WINDOWS, or an embedded operating system such as VxWorks) includes various software components and/or drivers for controlling and managing general system tasks (e.g., memory management, storage device control, power management, etc.) and facilitates communication between various hardware and software components. 
     Communication module  128  facilitates communication with other devices over one or more external ports  124  and also includes various software components for handling data received by RF circuitry  108  and/or external port  124 . External port  124  (e.g., Universal Serial Bus (USB), FIREWIRE, etc.) is adapted for coupling directly to other devices or indirectly over a network (e.g., the Internet, wireless LAN, etc.). In some embodiments, the external port is a multi-pin (e.g., 30-pin) connector that is the same as, or similar to and/or compatible with, the 30-pin connector used on iPod® (trademark of Apple Inc.) devices. 
     Contact/motion module  130  optionally detects contact with touch screen  112  (in conjunction with display controller  156 ) and other touch-sensitive devices (e.g., a touchpad or physical click wheel). Contact/motion module  130  includes various software components for performing various operations related to detection of contact, such as determining if contact has occurred (e.g., detecting a finger-down event), determining an intensity of the contact (e.g., the force or pressure of the contact or a substitute for the force or pressure of the contact), determining if there is movement of the contact and tracking the movement across the touch-sensitive surface (e.g., detecting one or more finger-dragging events), and determining if the contact has ceased (e.g., detecting a finger-up event or a break in contact). Contact/motion module  130  receives contact data from the touch-sensitive surface. Determining movement of the point of contact, which is represented by a series of contact data, optionally includes determining speed (magnitude), velocity (magnitude and direction), and/or an acceleration (a change in magnitude and/or direction) of the point of contact. These operations are, optionally, applied to single contacts (e.g., one finger contacts) or to multiple simultaneous contacts (e.g., “multitouch”/multiple finger contacts). In some embodiments, contact/motion module  130  and display controller  156  detect contact on a touchpad. 
     In some embodiments, contact/motion module  130  uses a set of one or more intensity thresholds to determine whether an operation has been performed by a user (e.g., to determine whether a user has “clicked” on an icon). In some embodiments, at least a subset of the intensity thresholds are determined in accordance with software parameters (e.g., the intensity thresholds are not determined by the activation thresholds of particular physical actuators and can be adjusted without changing the physical hardware of device  100 ). For example, a mouse “click” threshold of a trackpad or touch screen display can be set to any of a large range of predefined threshold values without changing the trackpad or touch screen display hardware. Additionally, in some implementations, a user of the device is provided with software settings for adjusting one or more of the set of intensity thresholds (e.g., by adjusting individual intensity thresholds and/or by adjusting a plurality of intensity thresholds at once with a system-level click “intensity” parameter). 
     Contact/motion module  130  optionally detects a gesture input by a user. Different gestures on the touch-sensitive surface have different contact patterns (e.g., different motions, timings, and/or intensities of detected contacts). Thus, a gesture is, optionally, detected by detecting a particular contact pattern. For example, detecting a finger tap gesture includes detecting a finger-down event followed by detecting a finger-up (liftoff) event at the same position (or substantially the same position) as the finger-down event (e.g., at the position of an icon). As another example, detecting a finger swipe gesture on the touch-sensitive surface includes detecting a finger-down event followed by detecting one or more finger-dragging events, and subsequently followed by detecting a finger-up (liftoff) event. 
     Graphics module  132  includes various known software components for rendering and displaying graphics on touch screen  112  or other display, including components for changing the visual impact (e.g., brightness, transparency, saturation, contrast, or other visual property) of graphics that are displayed. As used herein, the term “graphics” includes any object that can be displayed to a user, including, without limitation, text, web pages, icons (such as user-interface objects including soft keys), digital images, videos, animations, and the like. 
     In some embodiments, graphics module  132  stores data representing graphics to be used. Each graphic is, optionally, assigned a corresponding code. Graphics module  132  receives, from applications etc., one or more codes specifying graphics to be displayed along with, if necessary, coordinate data and other graphic property data, and then generates screen image data to output to display controller  156 . 
     Haptic feedback module  133  includes various software components for generating instructions used by tactile output generator(s)  167  to produce tactile outputs at one or more locations on device  100  in response to user interactions with device  100 . 
     Text input module  134 , which may be a component of graphics module  132 , provides soft keyboards for entering text in various applications (e.g., contacts  137 , e-mail  140 , IM  141 , browser  147 , and any other application that needs text input). 
     GPS module  135  determines the location of the device and provides this information for use in various applications (e.g., to telephone  138  for use in location-based dialing; to camera  143  as picture/video metadata; and to applications that provide location-based services such as weather widgets, local yellow page widgets, and map/navigation widgets). 
     Applications  136  may include the following modules (or sets of instructions), or a subset or superset thereof:
         Contacts module  137  (sometimes called an address book or contact list);   Telephone module  138 ;   Video conferencing module  139 ;   E-mail client module  140 ;   Instant messaging (IM) module  141 ;   Workout support module  142 ;   Camera module  143  for still and/or video images;   Image management module  144 ;   Video player module;   Music player module;   Browser module  147 ;   Calendar module  148 ;   Widget modules  149 , which may include one or more of: weather widget  149 - 1 , stocks widget  149 - 2 , calculator widget  149 - 3 , alarm clock widget  149 - 4 , dictionary widget  149 - 5 , and other widgets obtained by the user, as well as user-created widgets  149 - 6 ;   Widget creator module  150  for making user-created widgets  149 - 6 ;   Search module  151 ;   Video and music player module  152 , which merges video player module and music player module;   Notes module  153 ;   Map module  154 ; and/or   Online video module  155 .       

     Examples of other applications  136  that may be stored in memory  102  include other word processing applications, other image editing applications, drawing applications, presentation applications, JAVA-enabled applications, encryption, digital rights management, voice recognition, and voice replication. 
     In conjunction with touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , and text input module  134 , contacts module  137  may be used to manage an address book or contact list (e.g., stored in application internal state  192  of contacts module  137  in memory  102  or memory  370 ), including: adding name(s) to the address book; deleting name(s) from the address book; associating telephone number(s), e-mail address(es), physical address(es) or other information with a name; associating an image with a name; categorizing and sorting names; providing telephone numbers or e-mail addresses to initiate and/or facilitate communications by telephone  138 , video conference  139 , e-mail  140 , or IM  141 ; and so forth. 
     In conjunction with RF circuitry  108 , audio circuitry  110 , speaker  111 , microphone  113 , touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , and text input module  134 , telephone module  138  may be used to enter a sequence of characters corresponding to a telephone number, access one or more telephone numbers in contacts module  137 , modify a telephone number that has been entered, dial a respective telephone number, conduct a conversation, and disconnect or hang up when the conversation is completed. As noted above, the wireless communication may use any of a plurality of communications standards, protocols, and technologies. 
     In conjunction with RF circuitry  108 , audio circuitry  110 , speaker  111 , microphone  113 , touch screen  112 , display controller  156 , optical sensor  164 , optical sensor controller  158 , contact/motion module  130 , graphics module  132 , text input module  134 , contacts module  137 , and telephone module  138 , video conference module  139  includes executable instructions to initiate, conduct, and terminate a video conference between a user and one or more other participants in accordance with user instructions. 
     In conjunction with RF circuitry  108 , touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , and text input module  134 , e-mail client module  140  includes executable instructions to create, send, receive, and manage e-mail in response to user instructions. In conjunction with image management module  144 , e-mail client module  140  makes it very easy to create and send e-mails with still or video images taken with camera module  143 . 
     In conjunction with RF circuitry  108 , touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , and text input module  134 , the instant messaging module  141  includes executable instructions to enter a sequence of characters corresponding to an instant message, to modify previously entered characters, to transmit a respective instant message (for example, using a Short Message Service (SMS) or Multimedia Message Service (MMS) protocol for telephony-based instant messages or using XMPP, SIMPLE, or IMPS for Internet-based instant messages), to receive instant messages, and to view received instant messages. In some embodiments, transmitted and/or received instant messages may include graphics, photos, audio files, video files and/or other attachments as are supported in an MMS and/or an Enhanced Messaging Service (EMS). As used herein, “instant messaging” refers to both telephony-based messages (e.g., messages sent using SMS or MMS) and Internet-based messages (e.g., messages sent using XMPP, SIMPLE, or IMPS). 
     In conjunction with RF circuitry  108 , touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , text input module  134 , GPS module  135 , map module  154 , and music player module, workout support module  142  includes executable instructions to create workouts (e.g., with time, distance, and/or calorie burning goals); communicate with workout sensors (sports devices); receive workout sensor data; calibrate sensors used to monitor a workout; select and play music for a workout; and display, store, and transmit workout data. 
     In conjunction with touch screen  112 , display controller  156 , optical sensor(s)  164 , optical sensor controller  158 , contact/motion module  130 , graphics module  132 , and image management module  144 , camera module  143  includes executable instructions to capture still images or video (including a video stream) and store them into memory  102 , modify characteristics of a still image or video, or delete a still image or video from memory  102 . 
     In conjunction with touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , text input module  134 , and camera module  143 , image management module  144  includes executable instructions to arrange, modify (e.g., edit), or otherwise manipulate, label, delete, present (e.g., in a digital slide show or album), and store still and/or video images. 
     In conjunction with RF circuitry  108 , touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , and text input module  134 , browser module  147  includes executable instructions to browse the Internet in accordance with user instructions, including searching, linking to, receiving, and displaying web pages or portions thereof, as well as attachments and other files linked to web pages. 
     In conjunction with RF circuitry  108 , touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , text input module  134 , e-mail client module  140 , and browser module  147 , calendar module  148  includes executable instructions to create, display, modify, and store calendars and data associated with calendars (e.g., calendar entries, to-do lists, etc.) in accordance with user instructions. 
     In conjunction with RF circuitry  108 , touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , text input module  134 , and browser module  147 , widget modules  149  are mini-applications that may be downloaded and used by a user (e.g., weather widget  149 - 1 , stocks widget  149 - 2 , calculator widget  149 - 3 , alarm clock widget  149 - 4 , and dictionary widget  149 - 5 ) or created by the user (e.g., user-created widget  149 - 6 ). In some embodiments, a widget includes an HTML (Hypertext Markup Language) file, a CSS (Cascading Style Sheets) file, and a JavaScript file. In some embodiments, a widget includes an XML (Extensible Markup Language) file and a JavaScript file (e.g., Yahoo! Widgets). 
     In conjunction with RF circuitry  108 , touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , text input module  134 , and browser module  147 , the widget creator module  150  may be used by a user to create widgets (e.g., turning a user-specified portion of a web page into a widget). 
     In conjunction with touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , and text input module  134 , search module  151  includes executable instructions to search for text, music, sound, image, video, and/or other files in memory  102  that match one or more search criteria (e.g., one or more user-specified search terms) in accordance with user instructions. 
     In conjunction with touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , audio circuitry  110 , speaker  111 , RF circuitry  108 , and browser module  147 , video and music player module  152  includes executable instructions that allow the user to download and play back recorded music and other sound files stored in one or more file formats, such as MP3 or AAC files, and executable instructions to display, present, or otherwise play back videos (e.g., on touch screen  112  or on an external, connected display via external port  124 ). In some embodiments, device  100  optionally includes the functionality of an MP3 player, such as an iPod (trademark of Apple Inc.). 
     In conjunction with touch screen  112 , display controller  156 , contact/motion module  130 , graphics module  132 , and text input module  134 , notes module  153  includes executable instructions to create and manage notes, to-do lists, and the like in accordance with user instructions. 
     In conjunction with RF circuitry  108 , touch screen  112 , display controller  156 , contact module  130 , graphics module  132 , text input module  134 , GPS module  135 , and browser module  147 , map module  154  may be used to receive, display, modify, and store maps and data associated with maps (e.g., driving directions, data on stores and other points of interest at or near a particular location, and other location-based data) in accordance with user instructions. 
     In conjunction with touch screen  112 , display controller  156 , contact module  130 , graphics module  132 , audio circuitry  110 , speaker  111 , RF circuitry  108 , text input module  134 , e-mail client module  140 , and browser module  147 , online video module  155  includes instructions that allow the user to access, browse, receive (e.g., by streaming and/or download), play back (e.g., on the touch screen or on an external, connected display via external port  124 ), send an e-mail with a link to a particular online video, and otherwise manage online videos in one or more file formats, such as H.264. In some embodiments, instant messaging module  141 , rather than e-mail client module  140 , is used to send a link to a particular online video. Additional description of the online video application can be found in U.S. Provisional Patent Application No. 60/936,562, “Portable Multifunction Device, Method, and Graphical User Interface for Playing Online Videos,” filed Jun. 20, 2007, and U.S. patent application Ser. No. 11/968,067, “Portable Multifunction Device, Method, and Graphical User Interface for Playing Online Videos,” filed Dec. 31, 2007, the contents of which are hereby incorporated by reference in their entirety. 
     Each of the above-identified modules and applications corresponds to a set of executable instructions for performing one or more functions described above and the methods described in this application (e.g., the computer-implemented methods and other information processing methods described herein). These modules (e.g., sets of instructions) need not be implemented as separate software programs, procedures, or modules, and thus various subsets of these modules may be combined or otherwise rearranged in various embodiments. For example, video player module may be combined with music player module into a single module (e.g., video and music player module  152 ,  FIG. 1A ). In some embodiments, memory  102  may store a subset of the modules and data structures identified above. Furthermore, memory  102  may store additional modules and data structures not described above. 
     In some embodiments, device  100  is a device where operation of a predefined set of functions on the device is performed exclusively through a touch screen and/or a touchpad. By using a touch screen and/or a touchpad as the primary input control device for operation of device  100 , the number of physical input control devices (such as push buttons, dials, and the like) on device  100  may be reduced. 
     The predefined set of functions that are performed exclusively through a touch screen and/or a touchpad optionally include navigation between user interfaces. In some embodiments, the touchpad, when touched by the user, navigates device  100  to a main, home, or root menu from any user interface that is displayed on device  100 . In such embodiments, a “menu button” is implemented using a touchpad. In some other embodiments, the menu button is a physical push button or other physical input control device instead of a touchpad. 
       FIG. 1B  is a block diagram illustrating exemplary components for event handling in accordance with some embodiments. In some embodiments, memory  102  ( FIG. 1A ) or  370  ( FIG. 3 ) includes event sorter  170  (e.g., in operating system  126 ) and a respective application  136 - 1  (e.g., any of the aforementioned applications  137 - 151 ,  155 ,  380 - 390 ). 
     Event sorter  170  receives event information and determines the application  136 - 1  and application view  191  of application  136 - 1  to which to deliver the event information. Event sorter  170  includes event monitor  171  and event dispatcher module  174 . In some embodiments, application  136 - 1  includes application internal state  192 , which indicates the current application view(s) displayed on touch-sensitive display  112  when the application is active or executing. In some embodiments, device/global internal state  157  is used by event sorter  170  to determine which application(s) is (are) currently active, and application internal state  192  is used by event sorter  170  to determine application views  191  to which to deliver event information. 
     In some embodiments, application internal state  192  includes additional information, such as one or more of: resume information to be used when application  136 - 1  resumes execution, user interface state information that indicates information being displayed or that is ready for display by application  136 - 1 , a state queue for enabling the user to go back to a prior state or view of application  136 - 1 , and a redo/undo queue of previous actions taken by the user. 
     Event monitor  171  receives event information from peripherals interface  118 . Event information includes information about a sub-event (e.g., a user touch on touch-sensitive display  112 , as part of a multi-touch gesture). Peripherals interface  118  transmits information it receives from I/O subsystem  106  or a sensor, such as proximity sensor  166 , accelerometer(s)  168 , and/or microphone  113  (through audio circuitry  110 ). Information that peripherals interface  118  receives from I/O subsystem  106  includes information from touch-sensitive display  112  or a touch-sensitive surface. 
     In some embodiments, event monitor  171  sends requests to the peripherals interface  118  at predetermined intervals. In response, peripherals interface  118  transmits event information. In other embodiments, peripherals interface  118  transmits event information only when there is a significant event (e.g., receiving an input above a predetermined noise threshold and/or for more than a predetermined duration). 
     In some embodiments, event sorter  170  also includes a hit view determination module  172  and/or an active event recognizer determination module  173 . 
     Hit view determination module  172  provides software procedures for determining where a sub-event has taken place within one or more views when touch-sensitive display  112  displays more than one view. Views are made up of controls and other elements that a user can see on the display. 
     Another aspect of the user interface associated with an application is a set of views, sometimes herein called application views or user interface windows, in which information is displayed and touch-based gestures occur. The application views (of a respective application) in which a touch is detected may correspond to programmatic levels within a programmatic or view hierarchy of the application. For example, the lowest level view in which a touch is detected may be called the hit view, and the set of events that are recognized as proper inputs may be determined based, at least in part, on the hit view of the initial touch that begins a touch-based gesture. 
     Hit view determination module  172  receives information related to sub-events of a touch-based gesture. When an application has multiple views organized in a hierarchy, hit view determination module  172  identifies a hit view as the lowest view in the hierarchy which should handle the sub-event. In most circumstances, the hit view is the lowest level view in which an initiating sub-event occurs (e.g., the first sub-event in the sequence of sub-events that form an event or potential event). Once the hit view is identified by the hit view determination module  172 , the hit view typically receives all sub-events related to the same touch or input source for which it was identified as the hit view. 
     Active event recognizer determination module  173  determines which view or views within a view hierarchy should receive a particular sequence of sub-events. In some embodiments, active event recognizer determination module  173  determines that only the hit view should receive a particular sequence of sub-events. In other embodiments, active event recognizer determination module  173  determines that all views that include the physical location of a sub-event are actively involved views, and therefore determines that all actively involved views should receive a particular sequence of sub-events. In other embodiments, even if touch sub-events were entirely confined to the area associated with one particular view, views higher in the hierarchy would still remain as actively involved views. 
     Event dispatcher module  174  dispatches the event information to an event recognizer (e.g., event recognizer  180 ). In embodiments including active event recognizer determination module  173 , event dispatcher module  174  delivers the event information to an event recognizer determined by active event recognizer determination module  173 . In some embodiments, event dispatcher module  174  stores in an event queue the event information, which is retrieved by a respective event receiver  182 . 
     In some embodiments, operating system  126  includes event sorter  170 . Alternatively, application  136 - 1  includes event sorter  170 . In yet other embodiments, event sorter  170  is a stand-alone module, or a part of another module stored in memory  102 , such as contact/motion module  130 . 
     In some embodiments, application  136 - 1  includes a plurality of event handlers  190  and one or more application views  191 , each of which includes instructions for handling touch events that occur within a respective view of the application&#39;s user interface. Each application view  191  of the application  136 - 1  includes one or more event recognizers  180 . Typically, a respective application view  191  includes a plurality of event recognizers  180 . In other embodiments, one or more of event recognizers  180  are part of a separate module, such as a user interface kit (not shown) or a higher level object from which application  136 - 1  inherits methods and other properties. In some embodiments, a respective event handler  190  includes one or more of: data updater  176 , object updater  177 , GUI updater  178 , and/or event data  179  received from event sorter  170 . Event handler  190  may utilize or call data updater  176 , object updater  177 , or GUI updater  178  to update the application internal state  192 . Alternatively, one or more of the application views  191  include one or more respective event handlers  190 . Also, in some embodiments, one or more of data updater  176 , object updater  177 , and GUI updater  178  are included in a respective application view  191 . 
     A respective event recognizer  180  receives event information (e.g., event data  179 ) from event sorter  170  and identifies an event from the event information. Event recognizer  180  includes event receiver  182  and event comparator  184 . In some embodiments, event recognizer  180  also includes at least a subset of: metadata  183 , and event delivery instructions  188  (which may include sub-event delivery instructions). 
     Event receiver  182  receives event information from event sorter  170 . The event information includes information about a sub-event, for example, a touch or a touch movement. Depending on the sub-event, the event information also includes additional information, such as location of the sub-event. When the sub-event concerns motion of a touch, the event information may also include speed and direction of the sub-event. In some embodiments, events include rotation of the device from one orientation to another (e.g., from a portrait orientation to a landscape orientation, or vice versa), and the event information includes corresponding information about the current orientation (also called device attitude) of the device. 
     Event comparator  184  compares the event information to predefined event or sub-event definitions and, based on the comparison, determines an event or sub-event, or determines or updates the state of an event or sub-event. In some embodiments, event comparator  184  includes event definitions  186 . Event definitions  186  contain definitions of events (e.g., predefined sequences of sub-events), for example, event  1  ( 187 - 1 ), event  2  ( 187 - 2 ), and others. In some embodiments, sub-events in an event ( 187 ) include, for example, touch begin, touch end, touch movement, touch cancellation, and multiple touching. In one example, the definition for event  1  ( 187 - 1 ) is a double tap on a displayed object. The double tap, for example, comprises a first touch (touch begin) on the displayed object for a predetermined phase, a first liftoff (touch end) for a predetermined phase, a second touch (touch begin) on the displayed object for a predetermined phase, and a second liftoff (touch end) for a predetermined phase. In another example, the definition for event  2  ( 187 - 2 ) is a dragging on a displayed object. The dragging, for example, comprises a touch (or contact) on the displayed object for a predetermined phase, a movement of the touch across touch-sensitive display  112 , and liftoff of the touch (touch end). In some embodiments, the event also includes information for one or more associated event handlers  190 . 
     In some embodiments, event definition  187  includes a definition of an event for a respective user-interface object. In some embodiments, event comparator  184  performs a hit test to determine which user-interface object is associated with a sub-event. For example, in an application view in which three user-interface objects are displayed on touch-sensitive display  112 , when a touch is detected on touch-sensitive display  112 , event comparator  184  performs a hit test to determine which of the three user-interface objects is associated with the touch (sub-event). If each displayed object is associated with a respective event handler  190 , the event comparator uses the result of the hit test to determine which event handler  190  should be activated. For example, event comparator  184  selects an event handler associated with the sub-event and the object triggering the hit test. 
     In some embodiments, the definition for a respective event ( 187 ) also includes delayed actions that delay delivery of the event information until after it has been determined whether the sequence of sub-events does or does not correspond to the event recognizer&#39;s event type. 
     When a respective event recognizer  180  determines that the series of sub-events do not match any of the events in event definitions  186 , the respective event recognizer  180  enters an event impossible, event failed, or event ended state, after which it disregards subsequent sub-events of the touch-based gesture. In this situation, other event recognizers, if any, that remain active for the hit view continue to track and process sub-events of an ongoing touch-based gesture. 
     In some embodiments, a respective event recognizer  180  includes metadata  183  with configurable properties, flags, and/or lists that indicate how the event delivery system should perform sub-event delivery to actively involved event recognizers. In some embodiments, metadata  183  includes configurable properties, flags, and/or lists that indicate how event recognizers may interact, or are enabled to interact, with one another. In some embodiments, metadata  183  includes configurable properties, flags, and/or lists that indicate whether sub-events are delivered to varying levels in the view or programmatic hierarchy. 
     In some embodiments, a respective event recognizer  180  activates event handler  190  associated with an event when one or more particular sub-events of an event are recognized. In some embodiments, a respective event recognizer  180  delivers event information associated with the event to event handler  190 . Activating an event handler  190  is distinct from sending (and deferred sending) sub-events to a respective hit view. In some embodiments, event recognizer  180  throws a flag associated with the recognized event, and event handler  190  associated with the flag catches the flag and performs a predefined process. 
     In some embodiments, event delivery instructions  188  include sub-event delivery instructions that deliver event information about a sub-event without activating an event handler. Instead, the sub-event delivery instructions deliver event information to event handlers associated with the series of sub-events or to actively involved views. Event handlers associated with the series of sub-events or with actively involved views receive the event information and perform a predetermined process. 
     In some embodiments, data updater  176  creates and updates data used in application  136 - 1 . For example, data updater  176  updates the telephone number used in contacts module  137 , or stores a video file used in video player module. In some embodiments, object updater  177  creates and updates objects used in application  136 - 1 . For example, object updater  177  creates a new user-interface object or updates the position of a user-interface object. GUI updater  178  updates the GUI. For example, GUI updater  178  prepares display information and sends it to graphics module  132  for display on a touch-sensitive display. 
     In some embodiments, event handler(s)  190  includes or has access to data updater  176 , object updater  177 , and GUI updater  178 . In some embodiments, data updater  176 , object updater  177 , and GUI updater  178  are included in a single module of a respective application  136 - 1  or application view  191 . In other embodiments, they are included in two or more software modules. 
     It shall be understood that the foregoing discussion regarding event handling of user touches on touch-sensitive displays also applies to other forms of user inputs to operate multifunction devices  100  with input devices, not all of which are initiated on touch screens. For example, mouse movement and mouse button presses, optionally coordinated with single or multiple keyboard presses or holds; contact movements such as taps, drags, scrolls, etc. on touchpads; pen stylus inputs; movement of the device; oral instructions; detected eye movements; biometric inputs; and/or any combination thereof are optionally utilized as inputs corresponding to sub-events which define an event to be recognized. 
       FIG. 2  illustrates a portable multifunction device  100  having a touch screen  112  in accordance with some embodiments. The touch screen optionally displays one or more graphics within user interface (UI)  200 . In this embodiment, as well as others described below, a user is enabled to select one or more of the graphics by making a gesture on the graphics, for example, with one or more fingers  202  (not drawn to scale in the figure) or one or more styluses  203  (not drawn to scale in the figure). In some embodiments, selection of one or more graphics occurs when the user breaks contact with the one or more graphics. In some embodiments, the gesture optionally includes one or more taps, one or more swipes (from left to right, right to left, upward and/or downward), and/or a rolling of a finger (from right to left, left to right, upward and/or downward) that has made contact with device  100 . In some implementations or circumstances, inadvertent contact with a graphic does not select the graphic. For example, a swipe gesture that sweeps over an application icon optionally does not select the corresponding application when the gesture corresponding to selection is a tap. 
     Device  100  may also include one or more physical buttons, such as “home” or menu button  204 . As described previously, menu button  204  may be used to navigate to any application  136  in a set of applications that may be executed on device  100 . Alternatively, in some embodiments, the menu button is implemented as a soft key in a GUI displayed on touch screen  112 . 
     In one embodiment, device  100  includes touch screen  112 , menu button  204 , push button  206  for powering the device on/off and locking the device, volume adjustment button(s)  208 , subscriber identity module (SIM) card slot  210 , headset jack  212 , and docking/charging external port  124 . Push button  206  is, optionally, used to turn the power on/off on the device by depressing the button and holding the button in the depressed state for a predefined time interval; to lock the device by depressing the button and releasing the button before the predefined time interval has elapsed; and/or to unlock the device or initiate an unlock process. In an alternative embodiment, device  100  also accepts verbal input for activation or deactivation of some functions through microphone  113 . Device  100  also, optionally, includes one or more contact intensity sensors  165  for detecting intensity of contacts on touch screen  112  and/or one or more tactile output generators  167  for generating tactile outputs for a user of device  100 . 
       FIG. 3  is a block diagram of an exemplary multifunction device with a display and a touch-sensitive surface in accordance with some embodiments. Device  300  need not be portable. In some embodiments, device  300  is a laptop computer, a desktop computer, a tablet computer, a multimedia player device, a navigation device, an educational device (such as a child&#39;s learning toy), a gaming system, or a control device (e.g., a home or industrial controller). Device  300  typically includes one or more processing units (CPUs)  310 , one or more network or other communications interfaces  360 , memory  370 , and one or more communication buses  320  for interconnecting these components. Communication buses  320  optionally include circuitry (sometimes called a chipset) that interconnects and controls communications between system components. Device  300  includes input/output (I/O) interface  330  comprising display  340 , which is typically a touch screen display. I/O interface  330  also optionally includes a keyboard and/or mouse (or other pointing device)  350  and touchpad  355 , tactile output generator  357  for generating tactile outputs on device  300  (e.g., similar to tactile output generator(s)  167  described above with reference to  FIG. 1A ), sensors  359  (e.g., optical, acceleration, proximity, touch-sensitive, and/or contact intensity sensors similar to contact intensity sensor(s)  165  described above with reference to  FIG. 1A ). Memory  370  includes high-speed random access memory, such as DRAM, SRAM, DDR RAM, or other random access solid state memory devices; and optionally includes non-volatile memory, such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid state storage devices. Memory  370  optionally includes one or more storage devices remotely located from CPU(s)  310 . In some embodiments, memory  370  stores programs, modules, and data structures analogous to the programs, modules, and data structures stored in memory  102  of portable multifunction device  100  ( FIG. 1A ), or a subset thereof. Furthermore, memory  370  optionally stores additional programs, modules, and data structures not present in memory  102  of portable multifunction device  100 . For example, memory  370  of device  300  optionally stores drawing module  380 , presentation module  382 , word processing module  384 , website creation module  386 , disk authoring module  388 , and/or spreadsheet module  390 , while memory  102  of portable multifunction device  100  ( FIG. 1A ) optionally does not store these modules. 
     Each of the above-identified elements in  FIG. 3  may be stored in one or more of the previously mentioned memory devices. Each of the above-identified modules corresponds to a set of instructions for performing a function described above. The above-identified modules or programs (e.g., sets of instructions) need not be implemented as separate software programs, procedures, or modules, and thus various subsets of these modules may be combined or otherwise rearranged in various embodiments. In some embodiments, memory  370  may store a subset of the modules and data structures identified above. Furthermore, memory  370  may store additional modules and data structures not described above. 
     Attention is now directed towards embodiments of user interfaces that may be implemented on, for example, portable multifunction device  100 . 
       FIG. 4  illustrates an exemplary user interface for a menu of applications on portable multifunction device  100  in accordance with some embodiments. Similar user interfaces may be implemented on device  300 . In some embodiments, user interface  400  includes the following elements, or a subset or superset thereof:
         Signal strength indicator(s)  402  for wireless communication(s), such as cellular and Wi-Fi signals;   Time  404 ;   Bluetooth indicator  405 ;   Battery status indicator  406 ;   Tray  408  with icons for frequently used applications, such as:
           Icon  416  for telephone module  138 , labeled “Phone,” which optionally includes an indicator  414  of the number of missed calls or voicemail messages;   Icon  418  for e-mail client module  140 , labeled “Mail,” which optionally includes an indicator  410  of the number of unread e-mails;   Icon  420  for browser module  147 , labeled “Browser;” and   Icon  422  for video and music player module  152 , also referred to as iPod (trademark of Apple Inc.) module  152 , labeled “iPod;” and   
           Icons for other applications, such as:
           Icon  424  for IM module  141 , labeled “Messages;”   Icon  426  for calendar module  148 , labeled “Calendar;”   Icon  428  for image management module  144 , labeled “Photos;”   Icon  430  for camera module  143 , labeled “Camera;”   Icon  432  for online video module  155 , labeled “Online Video;”   Icon  434  for stocks widget  149 - 2 , labeled “Stocks;”   Icon  436  for map module  154 , labeled “Maps;”   Icon  438  for weather widget  149 - 1 , labeled “Weather;”   Icon  440  for alarm clock widget  149 - 4 , labeled “Clock;”   Icon  442  for workout support module  142 , labeled “Workout Support;”   Icon  444  for notes module  153 , labeled “Notes;” and   Icon  446  for a settings application or module, labeled “Settings,” which provides access to settings for device  100  and its various applications  136 .   
               

     It should be noted that the icon labels illustrated in  FIG. 4  are merely exemplary. For example, icon  422  for video and music player module  152  may optionally be labeled “Music” or “Music Player.” Other labels are, optionally, used for various application icons. In some embodiments, a label for a respective application icon includes a name of an application corresponding to the respective application icon. In some embodiments, a label for a particular application icon is distinct from a name of an application corresponding to the particular application icon. 
       FIG. 5  illustrates an exemplary user interface on a device (e.g., device  300 ,  FIG. 3 ) with a touch-sensitive surface  551  (e.g., a tablet or touchpad  355 ,  FIG. 3 ) that is separate from the display  550  (e.g., touch screen display  112 ). Device  300  also, optionally, includes one or more contact intensity sensors (e.g., one or more of sensors  357 ) for detecting intensity of contacts on touch-sensitive surface  551  and/or one or more tactile output generators  359  for generating tactile outputs for a user of device  300 . 
     Although some of the examples which follow will be given with reference to inputs on touch screen display  112  (where the touch sensitive surface and the display are combined), in some embodiments, the device detects inputs on a touch-sensitive surface that is separate from the display, as shown in  FIG. 5 . In some embodiments the touch sensitive surface (e.g.,  551  in  FIG. 5 ) has a primary axis (e.g.,  552  in  FIG. 5 ) that corresponds to a primary axis (e.g.,  553  in  FIG. 5 ) on the display (e.g.,  550 ). In accordance with these embodiments, the device detects contacts (e.g.,  560  and  562  in  FIG. 5 ) with the touch-sensitive surface  551  at locations that correspond to respective locations on the display (e.g., in  FIG. 5, 560  corresponds to  568  and  562  corresponds to  570 ). In this way, user inputs (e.g., contacts  560  and  562 , and movements thereof) detected by the device on the touch-sensitive surface (e.g.,  551  in  FIG. 5 ) are used by the device to manipulate the user interface on the display (e.g.,  550  in  FIG. 5 ) of the multifunction device when the touch-sensitive surface is separate from the display. It should be understood that similar methods are, optionally, used for other user interfaces described herein. 
     Additionally, while the following examples are given primarily with reference to finger inputs (e.g., finger contacts, finger tap gestures, finger swipe gestures), it should be understood that, in some embodiments, one or more of the finger inputs are replaced with input from another input device (e.g., a mouse based input or stylus input). For example, a swipe gesture is, optionally, replaced with a mouse click (e.g., instead of a contact) followed by movement of the cursor along the path of the swipe (e.g., instead of movement of the contact). As another example, a tap gesture is, optionally, replaced with a mouse click while the cursor is located over the location of the tap gesture (e.g., instead of detection of the contact followed by ceasing to detect the contact). Similarly, when multiple user inputs are simultaneously detected, it should be understood that multiple computer mice are, optionally, used simultaneously, or a mouse and finger contacts are, optionally, used simultaneously. 
     As used here, the term “affordance” refers to a user-interactive graphical user interface object that may be displayed on the display screen of device  100  and/or  300  ( FIGS. 1 and 3 ). For example, an image (e.g., icon), a button, and text (e.g., hyperlink) may each constitute an affordance. 
     As used herein, the term “focus selector” refers to an input element that indicates a current part of a user interface with which a user is interacting. In some implementations that include a cursor or other location marker, the cursor acts as a “focus selector” so that when an input (e.g., a press input) is detected on a touch-sensitive surface (e.g., touchpad  355  in  FIG. 3  or touch-sensitive surface  551  in  FIG. 5 ) while the cursor is over a particular user interface element (e.g., a button, window, slider or other user interface element), the particular user interface element is adjusted in accordance with the detected input. In some implementations that include a touch screen display (e.g., touch-sensitive display system  112  in  FIG. 1A  or touch screen  112  in  FIG. 4 ) that enables direct interaction with user interface elements on the touch screen display, a detected contact on the touch screen acts as a “focus selector” so that when an input (e.g., a press input by the contact) is detected on the touch screen display at a location of a particular user interface element (e.g., a button, window, slider, or other user interface element), the particular user interface element is adjusted in accordance with the detected input. In some implementations, focus is moved from one region of a user interface to another region of the user interface without corresponding movement of a cursor or movement of a contact on a touch screen display (e.g., by using a tab key or arrow keys to move focus from one button to another button); in these implementations, the focus selector moves in accordance with movement of focus between different regions of the user interface. Without regard to the specific form taken by the focus selector, the focus selector is generally the user interface element (or contact on a touch screen display) that is controlled by the user so as to communicate the user&#39;s intended interaction with the user interface (e.g., by indicating, to the device, the element of the user interface with which the user is intending to interact). For example, the location of a focus selector (e.g., a cursor, a contact, or a selection box) over a respective button while a press input is detected on the touch-sensitive surface (e.g., a touchpad or touch screen) will indicate that the user is intending to activate the respective button (as opposed to other user interface elements shown on a display of the device). 
     As used herein, an “installed application” refers to a software application that has been downloaded onto an electronic device (e.g., devices  100  and/or  300 ) and is ready to be launched (e.g., become opened) on the device. In some embodiments, a downloaded application becomes an installed application by way of an installation program that extracts program portions from a downloaded package and integrates the extracted portions with the operating system of the computer system. 
     As used herein, the term “open application” or “executing application” refers to a software application with retained state information (e.g., as part of device/global internal state  157  and/or application internal state  192 ). An open or executing application may be any one of the following types of applications:
         an active application, which is currently displayed on a display screen of the device that the application is being used on;   a background application (or background processes), which is not currently displayed, but one or more processes for the application are being processed by one or more processors; and   a suspended or hibernated application, which is not running, but has state information that is stored in memory (volatile and non-volatile, respectively) and that can be used to resume execution of the application.       

     As used herein, the term “closed application” refers to software applications without retained state information (e.g., state information for closed applications is not stored in a memory of the device). Accordingly, closing an application includes stopping and/or removing application processes for the application and removing state information for the application from the memory of the device. Generally, opening a second application while in a first application does not close the first application. When the second application is displayed and the first application ceases to be displayed, the first application becomes a background application. 
     Attention is now directed to towards user interfaces (“UI”) and associated processes that may be implemented on a multifunction device with a display and a touch-sensitive surface, such as devices  100  and/or  300  ( FIGS. 1A and 3A ), to provide displays of graphical representations of data objects. These techniques may be collectively referred to as an “anchored” approach to updating a viewport. 
     1. Exemplary Layouts of Data Objects 
       FIGS. 6B-6L  describe an exemplary technique for laying out graphical representations of data objects in response to user input. Exemplary application window  610 , illustrated in  FIG. 6B , may be window  602  ( FIG. 6A ) in some embodiments, meaning that window  610  may be part of an e-mail application. Window  610  has viewport  612  having content in the form of message preview regions  613 - 617 . Window  610  also has region  619  where the body of a selected e-mail message is displayed. An e-mail message may become selected via touch or mouse input on a message preview region of viewport  612 . 
     As viewport  612  is scrollable, the number of underlying e-mail messages that can be previewed through viewport  612  exceeds the five exemplary preview regions  613 - 617  depicted in  FIG. 6B .  FIG. 6C  illustrates exemplary e-mail messages  621 - 631  that may be accessed via window  610  ( FIG. 6B ). Although the number of e-mail messages  621 - 631  depicted in  FIG. 6B  is limited, it should be noted that window  610  can support the display of more than the illustrated e-mail messages, which is being limited for clarity and brevity. Indeed, it is when a large number of email messages is being dealt with that the techniques describe herein provide the greatest benefit in terms of efficiency and control, thereby creating a more efficient machine-user interface and consequently reducing the energy used by the device and increasing battery life for battery powered devices. 
     In  FIG. 6C , rectangle  640  is used to indicate the messages ( 623 - 627 ) being previewed in viewport  612  ( FIG. 6B ). Specifically, preview  613  ( FIG. 6B ) is displaying a preview of e-mail message  623 , and preview  617  ( FIG. 6B ) is displaying a preview of message  627 . For purposes of illustration, if content in viewport  612  is scrolled, the positioning of rectangle  640  with respect to underling messages  621 - 631  changes correspondingly. 
     Turning back to  FIG. 6B , preview  615  can be seen as being associated with anchor  618 . Anchor  618  need not be displayed on-screen, and is preferably hidden from on-screen display. Rather, anchor  618  represents an indication that the display element the user is most likely focused on, in this case preview region  615  corresponding to underlying message  625 . The relationship between anchor  618  and message  625  is similarly depicted in  FIG. 6C . The association of an anchor to a preview region (and a corresponding underlying message) can be tracked using data (e.g., program data or other meta-data) maintained by viewport  612 , window  610 , the underlying e-mail application, and/or other processes running on device  600 . 
     In some embodiments, anchor  618  is set based on a user interaction. For example, a user selection (e.g., touch) of preview region  615  causes preview region  615  to become associated with an anchor. In some embodiments, anchor  618  is set by an upstream computing process. For example, anchor information provided by an earlier process can be obtained from a memory location. In some embodiments, anchor  618  is set through defaulting rules. For example, when viewport  612  is initially displayed, an anchor is assigned by default to the middle or top preview region. In some embodiments, a combination of these anchor setting processes is used, as they are not mutually exclusive. 
       FIG. 6D  depicts user navigation input  650  of content displayed within viewport  612 . The direction of arrow  652  indicates that the input is an upward movement (e.g., an upward swipe gesture detected on a touch-sensitive surface, selection of an up arrow, selection of a page up button on a keyboard, or rotation of a knob or wheel that corresponds to scrolling the content within the viewport). In order to determine the resulting movement of anchor  618  (if any), in some embodiments, the magnitude of navigation input  650  is converted into a unit of measure suitable for determining on-screen placement of content. For example, the magnitude of navigation input  650  is converted into pixels, and added to the initial pixel position of anchor  618 , to determine if a new position for anchor  618  is needed responsive to input  650 . 
     In some embodiments, navigational inputs of large magnitude are handled differently than those of small magnitude. The determination of whether a user has scrolled the content of a viewport by a “large” amount can be made by converting the magnitude of a navigational input into a unit of measure (e.g., pixels) that can be compared with the size (e.g., height in pixels) of the viewport. In some embodiments, an input magnitude is considered large if it exceeds some multiple of the size of the viewport (e.g., 1×, 2×, 3× the height of viewport  612 ). In some embodiments, an input magnitude is considered large if it exceeds a threshold number of pixels (e.g., 768, 800, 1024, 1200 pixels). 
       FIG. 6E  illustrates a method of laying out display content using an anchor in response to an input of smaller magnitude. In some embodiments, when dealing with small navigational movements, actual information (e.g., dimension in pixels) regarding the graphical representations that are to be displayed data objects are used to configure the layout of graphical representations. The use of actual information in this instance is still computationally efficient because, under the anchored scrolling techniques described below, small navigational movements require a proportionately small amount of computation. 
     Consider the situation in which anchor  618  is initially placed at a vertical position defined by y=199 pixels. In response to an upward swipe corresponding to 100 pixels in magnitude, anchor  618  moves to a new vertical position of y=99 pixels. Once the new position of anchor  618  is determined, content that should be displayed in viewport  612  is identified. Recall that, as discussed above and as and illustrated in  FIG. 6F , anchor  618  was associated with underlying e-mail message  625  prior to navigation input  650 . After navigation user input  650 , anchor  618  remains associated with e-mail message  625 , even if the on-screen position of anchor  618  has changed. Due to this continuing relationship between anchor  618  and e-mail message  625 , a preview region for e-mail message  625  can be earmarked for displayed at the new on-screen position corresponding to anchor  618 . That is, as can be seen in  FIG. 6G , preview region  615  corresponding to email message  625  becomes configured for display approximately 100 pixels above its previous display position, moving from the third row to the second row position within viewport  612 . (Note that the actual on-screen display of preview region  615  may be withheld, in some embodiments, until the layout of content to be displayed in viewport  612  is complete.) 
     From the new position of anchor  618 , additional content for display can be laid out by identifying display content in an outward manner from anchor  618  towards the top and the bottom boundaries of viewport  612 . For instance, viewport  612  may determine that a number of pixels are available for displaying graphical representations above and below preview region  615  associated with anchor  618 . 
     In some embodiments, to determine the exact number of preview regions that may be fitted above and below anchor  618  (corresponding to preview region  615 ), device  600  determines the actual sizes of adjacent preview regions that could be included in the display layout. For example, viewport  612  may process the markup language contained in e-mail message  624  (abutting message  625  which is also associated with the anchor) and determine that a preview region for message  624  would be of a pixel height that occupies all of the available pixels between the top of viewport  612  and anchor  618  (preview region  615 ). In this example, a preview region for just message  624  will be included in the layout of viewport  612 , above anchor  618 . 
     Device  600  also can layout preview regions below anchor  618 . For example, this can be done by at least partially rendering messages  626 - 628 , beginning with message  626 , to determine a display height associated with the preview of each message. After calculating the preview heights for messages  626 - 628 , device  600  may determine that the display of previews for these messages would occupy all of the available space between anchor  618  (preview region  615 ) and the bottom of viewport  612 . In this example, preview regions for just messages  626 - 628  will be included in the layout of viewport  612 , below anchor  618 . 
     In some embodiments, to determine the exact number of preview regions that can be fitted above and below the anchor (preview region  615 ), device  600  obtains sizing information of relevant preview regions from a memory location. In these embodiments, an upstream process (such as the operating system) has pre-determined the sizes of graphical represents (e.g., preview regions) of underlying data objects and saved the sizing information into an accessible memory location. 
     After the preview regions (e.g., graphical representations) that are to be displayed in response navigation input  650  have been laid out, device  600  may display the preview regions in viewport  612  according to the layout. In some embodiments, device  600  holds off on the on-screen display of any one of the graphical representations that are to be displayed, until a layout of all of the representations to be displayed is complete. In some embodiments, device  600  begins to display certain graphical representations after some portions of the layout have been configured. 
     As shown in  FIG. 6H , this result of the processing described with respect to  FIGS. 6B-6G  has the effect of scrolling viewport  612  by one row of information. That is, whereas viewport  612  displayed previews of messages within rectangle  640  before navigation input  650 , after navigation input  650 , viewport  612  updates to display previews of messages within rectangle  642 . Indeed, this shift is consistent with user expectation as the user&#39;s navigation input  650  has a relatively small magnitude that roughly translates to the display height of one displayed preview region. 
     Importantly, the layout techniques described with reference to  FIGS. 6B-6H  do not impose significant burden on modern computer processors because the techniques did not involve calculating display heights of messages previews from a top-most or bottom-most e-mail message. Rather, the calculations described with respect to  FIG. 6G  originated from anchor  618  and radiated outwards to the boundaries of viewport  612 . This technique is advantageous, in that the calculation of display heights of message previews from a top-most or bottom-most e-mail message could be computationally expensive if viewport  612  is positioned in the middle of a large set of e-mail messages, meaning that a large number of calculations must be performed before reaching those slated for preview in viewport  612 . Instead, the techniques described herein for laying out content is based on a limited set of calculations originating from anchor  618  towards the top and bottom of viewport  612 . In this way, viewport  612  is able to refresh quickly in response to user input by incurring a reduced number of computations that is proportional to the size of viewport  612 . As can be appreciated, this technique brings significant efficiency when the number of data objects (e.g., e-mail messages) represented in viewport  612  is a small subset of the total number of available data objects (e.g., e-mail messages in a large mail folder). 
     Attention is now directed to another exemplary technique for laying out data objects in a viewport in response to user input, with reference to  FIGS. 7A-7J . This technique is particularly applicable to laying out display content in response to an input of larger magnitude.  FIG. 7A  illustrates exemplary application window  700 , which may be window  602  ( FIG. 6A ) in some embodiments, meaning that window  700  may be part of an active e-mail application running on device  600  ( FIG. 6A ). Window  700  has viewport  702  showing message preview regions  703 - 707 . Window  700  also has region  709  for displaying the body of a selected message. In the illustrated example, an anchor  708  is associated with preview region  704 . 
       FIG. 7B  illustrates the correspondence between preview regions  703 - 707  and underlying e-mail messages that are accessible to the e-mail application. Specifically, the e-mail application may have access to at least messages  751 - 795  depicted via  FIG. 7B . As before, for brevity and clarity, the figure illustrates only a subset of the possible number of messages that can be processed by the e-mail application. It should be understood that a large number of e-mail messages can be visually represented in viewport  702 . Rectangle  710  identifies messages  751 - 755  as those being previewed in viewport  702  ( FIG. 7A ), meaning that preview region  703  partially shows message  751 , preview region  704  partially shows message  752 , so forth. 
     Turning to  FIG. 7C , user navigation input  712  to content within viewport  702  is received. Input  712  includes multiple upward swipes as indicated by arrows  714 . The number and lengths of arrows  714  indicate the magnitude of the user input: the user has scrolled by a much larger amount than as depicted above in the examples of  FIGS. 6D-6I . 
     In response to navigational input of a large magnitude, device  600  may identify a new anchor for purposes of layout out updated content, instead of tracking anchor  708  through the entire movement corresponding to the input magnitude. Further, the positioning of the new anchor can involve some approximation in order to reduce computational cost. The use of an approximation without impacting user experience negatively is possible for at least two reasons. First, when on-screen object movement spans a large distance and/or occurs at a fast rate, users are unable to judge whether the actual movement tracks navigational input, pixel for pixel. Restated, as the user cannot discern the approximate positioning, the approximation itself would not distract from the user&#39;s experience. 
     Second, under the layout techniques described above with respect to  FIG. 6G  (particularly in terms of radiating outward from an anchor), “errors” in the approximation become inconsequential if a viewport accepts the approximated anchor position as a source of truth, and lays out content based on the accepted approximation. This is the case because the laying out of content originating from an on-screen position can occur in the same way regardless of whether the position originated from an estimated anchor or a precisely calculated anchor. So as long as the (approximated) positioning of an anchor is agreeable to the user (who cannot tell the difference), content may be laid out correctly within viewport  702  without introducing further errors into the displayed content. 
     This outcome stands in contrast to and is advantageous to techniques relying on the top-most or bottom-most data object for configuring on-screen layout of data objects, as errors introduced under those techniques accumulate and are excerabated by each additional incoming data object. Consider the situation in which, instead of relying on an anchor, a display layout is determined based on the approximated display height of the X most recently received data objects (e.g., messages). As additional data object(s) X+1 (e.g., a message) is received, the overall approximation is revised to account for the additional (approximated) height of the newly received object, thereby adding to the uncertainly of the overall approximation from which display content is to be determined. The resolution of these errors is computationally expensive, particularly if a large number of intervening data objects exist between the current display position of a viewport and a first or last of the underlying data objects that is being represented in the viewport. Left in place, however, errors in the approximations manifest on-screen as sudden jarring movements of displayed content, which distracts from the user experience. 
     Attention is now directed to a method for approximating a new anchor in response to user input with reference to  FIGS. 7D-7F .  FIG. 7D  illustrates that preview regions in viewport  702  may have a characteristic size (e.g., height in terms of pixels). As used here, “characteristic size” refers to an approximation of display size that may be based on the average size of graphical representations for the type of data objects being displayed (or some predetermined approximate size that is selected by the user or set by the application developer). For example, a user interface designer may calculate that the amount of (vertical) pixels used to display the sender and the initial twenty words of an e-mail using particular type fonts, on average, requires 80 pixels of display area, vertically. As another example, an application designer may set forth application-specific constraints—such as each message preview showing only one line of sender information, one line of subject information, and a maximum of two lines of message body—which has the effect of constraining message previews within a deterministic range of pixel height, from which a characteristic height (e.g., a mean) can be determined. 
     In some embodiments, the magnitude of input  712  is converted into an appropriate unit of measure and divided against the characteristic size of the preview regions of viewport  702  to determine a number of preview regions that should be traversed in response to the user input. For example, the magnitude of input  712  may be converted into pixels and divided against the characteristic height  720  (also in pixels) to approximate a number of preview regions that should be traversed in response to input  712 . 
     Turning to  FIG. 7E , the approximated number of preview regions to traverse is also used to determine the number of underlying e-mail messages that should be traversed. For example, if the magnitude of input  712  corresponds to scrolling over approximately 40 preview regions in viewport  702 , then the input is also taken as removing the designation of message  752  as the anchor designating message  792  as the (new) anchor. 
     Turning to  FIG. 7F , the graphical representation of message  792 —preview region  744 —also becomes associated with new anchor  730 . Preview region  704  is no longer displayed in  FIG. 7F  as it is associated with anchor  708  which has scrolled off-screen. Instead, preview region  744 , which is positioned forty positions after preview region  704 , becomes configured for display. Note that preview region  744  is designated as the new anchor even though its identification involved approximations. 
     Turning to  FIG. 7H , having determined new anchor  730 , device  600  can determine the number of preview regions that could be laid out for display in viewport  702  above and below anchor  730  (preview region  744 ). Reading  FIGS. 7H and 71  together, device  600  may determine that one preview region for message  791  fits into viewport  702  above anchor  730 , and four preview regions corresponding to messages  793 - 795  fit in viewport  702  below anchor  730 . Rectangle  726  thus identifies the e-mail messages that can be laid out for preview in viewport  702  according to a layout based on anchor  730 . After determining this layout, device  600  may display the corresponding preview regions on-screen, as shown by  FIG. 7J . In some embodiments, device  600  holds off on the on-screen display of any one of the graphical representations that are to be displayed, until a layout of all of the representations to be displayed is complete. In some embodiments, device  600  begins to display certain graphical representations after some portions of the layout have been configured. 
     Attention is now directed to the exemplary nature of  FIGS. 6B-6H  and  FIGS. 7A-7J . Although the discussion of these figures concentrates on e-mail messages and previews of e-mail messages, it is noted that viewports can be used to scroll content other than previews of e-mail messages. In general, the above-described techniques can be implemented with any plurality of data objects that can be displayed in a viewport in an ordered fashion. The term “data objects” refer to objects accessible on a computing system, such as file system objects (e.g., folders, files including executable applications), application-specific objects (e.g., messages, photo thumbnails, bookmarks, rendered output from a structured document element), and so forth. It is also noted that the techniques described in  FIGS. 6B-6H and 7A-7J  are not mutually exclusive. Indeed, a given application may practice the techniques explained with reference to  FIGS. 6B-6H  under some circumstances (e.g., small magnitude of navigation input) and practice the techniques explained with reference to  FIGS. 7A-7J  under some circumstances (e.g., large magnitude of navigation input). Further, it is noted that an anchor need not be associated with a particular graphical representation (e.g., message preview). Rather, an anchor can be associated with a position before, after, or in-between an object (e.g., after the last message preview). An anchor can also be associated with an on-screen position such as a particular pixel location (0, 127). An anchor can also be defined to be “last displayed graphical representation, whatever that may be, is at 127px from the bottom of the screen”. If data objects are added or removed at the end, this anchor will refer to whatever the new last data object and corresponding graphical representation is (as it does not correspond to a specific data object). Further still, it is noted that viewports are not limited to message preview panes in an e-mail application, but in general may be any scrollable window capable of displaying graphical representations of underlying data objects. For example, navigation screens within iTunes® and iPhoto®, and the Finder® aspect of MacOS® made by Apple, Inc. of Cupertino, Calif. constitute additional examples of viewports. Thus, the descriptions provided with respect to  FIGS. 6B-6H  and  FIGS. 7A-7J  should not be viewed as limited; rather, they should be viewed as enabling one of ordinary skill in the art to practice the described techniques across an array of graphical user interface elements and data objects. 
     2. Exemplary Processes for Laying-Out Data Objects 
       FIG. 8  is a flow diagram illustrating exemplary process  800  for laying out data objects. Process  800  can be carried out by electronic devices such as devices  100  and/or  300  ( FIG. 1A or 3A ) in various embodiments. At block  802 , the device displays a viewport having content in the form of graphical representations of a first subset of a plurality of data objects that are ordered. In the exemplary user interfaces discussed above with respect to  FIGS. 6A-6H and 7A-7J , graphical representations are preview regions that partially display the content of corresponding e-mail messages. Other graphical representations may be used. For example, graphical representations in the form of icons and photo thumbnails are also possible. The displayed graphical representations and/or the plurality of data objects may be ordered based on meta-data associated with the data objects such as name, date, size, so forth. 
     At block  804 , while displaying the graphical representations of the first subset of the plurality of data objects in the viewport, a request is received to navigate through graphical representations of the plurality of data objects in the viewport. For example, as discussed with reference to  FIG. 6D , input  650  is received while viewport  612  displays graphical representations of e-mail messages. The request is associated with an input magnitude, which may be based on a distance and/or speed of a swipe or mouse input. The input magnitude also may be based on movement of a progress indicator such as a scroll bar. The input magnitude may also be based on a repetition of keyboard input (e.g., number and/or duration of directional-key key-presses). 
     At block  806 , input magnitude corresponds to less than a threshold amount of movement of the graphical representations an anchor used to layout and display the viewport is identified. Such an anchor may be anchors  618  or  708  as discussed above with respect to  FIGS. 6B and 7A . At block  808 , a determination is made as to whether the magnitude of the received input corresponds to less than a threshold amount of movement of the graphical representations. The threshold amount may be based on a value such as a multiple of the size of the viewport (e.g., 1×, 2×, 3× the height of the viewport). The threshold amount also may be based on a number of pixels (e.g., 768, 800, 1024, 1200 pixels). As an example, a navigational input could be considered to exceed a threshold if the amount of scroll bar movement causes content within a viewport to scroll by more than three screens of content. 
     If the input magnitude exceeds the threshold amount, processing proceeds to blocks  810 - 814  where a layout of graphical representations of a second subset of data objects is generated by selecting a new anchor based on the input magnitude and generating a layout of graphical representations of the second subset of data objects based on that new anchor. 
     At block  810 , the new anchor may be approximated by determining an approximate amount of movement through the plurality of data objects that corresponds to the input magnitude and selecting the second anchor based on the approximate amount of movement. The approximation may rely on a speed, length, or other characteristic of the input. Restated, the input from block  804  to scroll through the graphical representations of data objects is interpreted as an instruction to advance by some approximate number X of graphical representations and/or data objects, and not as an instruction to advance to a specific graphical representation or data object Y. The approximation may also rely on characteristic size of the graphical representations of the data objects. For example, the input magnitude may be converted to a number of pixels and compared against the characteristic height of a graphical representation to determine an approximate number of graphical representations to advance. 
     At block  812 , a layout of graphical representations of the second plurality of data objects is configured based on the position of the new anchor. The configuration may be determined by “radiating out” from the new anchor, as described above with respect to  FIG. 7H . At block  814 , the new anchor is saved in memory for later retrieval, so that it may be used to process a subsequent scrolling input, for example. 
     Returning to decision block  808 , if the input magnitude does not exceed the threshold amount, processing proceeds to blocks  816  where a layout of graphical representations of a second subset of data objects is generated based on the anchor obtained at block  806 , and the magnitude of the input received at block  804 . At block  816 , the on-screen position of the graphical representation associated with the anchor may be moved by an amount corresponding to the input magnitude received at block  804 . Once the on-screen of the anchor is determined, a layout of graphical representations can be generated by “radiating out” from the anchor as described above with respect to  FIG. 6G . 
     The operations described above with reference to  FIG. 8  are, optionally, implemented by components depicted in  FIGS. 1A-1B, 3, and 9 . For example, detection operation  802 , receive operation  804 , find operation  806 , estimate operation  810 , layout operations  812 ,  816 , save operation  814 , and render operation  818  are, optionally, implemented by event sorter  170 , event recognizer  180 , and event handler  190 . Event monitor  171  in event sorter  170  detects a contact on touch-sensitive display  112 , and event dispatcher module  174  delivers the event information to application  136 - 1 . A respective event recognizer  180  of application  136 - 1  compares the event information to respective event definitions  186 , and determines whether a first contact at a first location on the touch-sensitive surface (or whether rotation of the device) corresponds to a predefined event or sub-event, such as selection of an object on a user interface, or rotation of the device from one orientation to another. When a respective predefined event or sub-event is detected, event recognizer  180  activates an event handler  190  associated with the detection of the event or sub-event. Event handler  190  optionally uses or calls data updater  176  or object updater  177  to update the application internal state  192 . In some embodiments, event handler  190  accesses a respective GUI updater  178  to update what is displayed by the application. Similarly, it would be clear to a person having ordinary skill in the art how other processes can be implemented based on the components depicted in  FIGS. 1A-1B, 3 and 9 . 
       FIG. 9  shows exemplary functional blocks of an electronic device  900  that, in some embodiments, performs the above-described features. As shown in  FIG. 9 , an electronic device  900  may include display unit  902  configured to display graphical objects; human input interface unit  904  configured to receive user input; data object obtaining unit  906  configured to obtain data objects; and processing unit  908  coupled to display unit  902 , human input interface unit  904 , and data object obtaining unit  906 . 
     In some embodiments, data object obtaining unit  906  is configured to obtain data objects that are to be displayed by device  900 . For example, data object obtaining unit  906  may obtain a message (e-mail, SMS messages, MMS messages, WiFi-based short messages), a file, an application, so forth. Data object obtaining unit  906  may be configured to obtain data objects from a local source, such as a local storage drive, or a networked source, such as a cloud-based storage service. 
     In some embodiments, processing unit  908  includes a display enabling unit  910  and a layout configuring unit  912 . Display enabling unit  910  is configured to cause a display of a user interface (or portions of a user interface) in conjunction with the display unit  902 . The displayed user interface may include one or more windows and/or viewports. A displayed viewport may contain graphical representations of data objects obtained by data object obtaining unit  906 . 
     In some embodiments, human input interface unit  904  is configured to receive user interface navigation input while a viewport having graphical representations of data objects is displayed. Layout configuring unit  912  may receive data representing the navigation input from human input interface unit  904  and determine a new layout of graphical representations in a displayed viewport. In some embodiments, layout configuring unit is configured to perform the operations associated with blocks  810 - 816  of process  800  ( FIG. 8 ). For example, layout configuration  912  can perform one or more of the following operations:
         in accordance with a determination that the magnitude of input received by human input interface unit  904  corresponds to less than a threshold amount of movement of the graphical representations, generate layout of graphical representations of new content in the displayed viewport based on an existing anchor and the input magnitude;   in accordance with a determination that the input magnitude received by human input interface unit  904  corresponds to more than the threshold amount of movement of the graphical representations, selecting a new anchor based on the input magnitude and generating layout of graphical representations of new content in the displayed viewport based on the new anchor;   select a new anchor by determining an approximate amount of movement through the plurality of data objects that corresponds to the input magnitude;   determine an amount of viewport navigation corresponding to the input magnitude; identify at least one data object abutting the anchor within the ordered plurality of data objects; determine an actual size of one or more graphical representations of the at least one data objects abutting the existing anchor; and select one or more of the at least one data objects as new content to be displayed in the viewport, based on the actual size of the one or more graphical representations of the at least one data objects and the corresponding amount of viewport navigation;   obtain a characteristic size of graphical representations of the plurality of data objects; convert the input magnitude into a corresponding change in position within the order of the plurality of data objects based on the characteristic size of graphical representations of the plurality of data objects; and determine the new anchor using the position within the order of the plurality of data objects corresponding to the existing anchor, and the corresponding change in position.       

     In some embodiments, display enabling unit  910  and display unit  902  are configured to display the layout after layout configuring unit  912  has completed the layout. 
     The units of  FIG. 9  may be used to implement the various techniques and methods described above with respect to  FIGS. 6A-6H and 7A-7J . The units of device  900  are, optionally, implemented by hardware, software, or a combination of hardware and software to carry out the principles of the various described examples. It is understood by persons of skill in the art that the functional blocks described in  FIG. 9  are, optionally, combined or separated into sub-blocks to implement the principles of the various described examples. Therefore, the description herein optionally supports any possible combination or separation or further definition of the functional blocks described herein. 
     Although the disclosure and examples have been fully described with reference to the accompanying figures, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the disclosure and examples as defined by the appended claims.