Patent Publication Number: US-7917861-B2

Title: User interface elements cloning and transitions

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to graphical user interfaces and more particularly to a graphical user interface for a portable electronic device. 
     2. Description of the Related Art 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art. 
     The graphical user interface (“GUI”) of an electronic device may accomplish a variety of tasks and present a variety of information to a user. The user sees and interacts with the GUI, so it is beneficial if the GUI presents information and choices to a user in a way that is not only pleasing and natural to the eye but conducive to efficient use of the underlying application and hardware. For example, a user may expect a certain amount of performance and responsiveness, in addition to a pleasing and natural interface. 
     One particular area that may greatly affect how a user perceives the interface is special effects, such as transitions, that may be used between different screens. A transition that is too jarring or abrupt may result in an unpleasant interface. Alternatively, a transition that is inefficient or poorly designed may be interpreted by the user as a slow or unresponsive user interface. Many special effects may be used as transitions to avoid these problems, such as fading screens in and out (changing opacity), sliding or moving screens in and out, scaling or resizing screens, etc. 
     However, as the demand for smaller portable electronic devices with a wide range of functionality increases, processing and memory resources may not be available and may constrain the ability of a device to provide these special effects. In addition, providing these special effects should not result in an accompanying decrease in speed or responsiveness of the user interface. 
     SUMMARY 
     Certain aspects of embodiments disclosed herein by way of example are summarized below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms an invention disclosed and/or claimed herein might take and that these aspects are not intended to limit the scope of any invention disclosed and/or claimed herein. Indeed, any invention disclosed and/or claimed herein may encompass a variety of aspects that may not be set forth below. 
     A portable electronic device having a user interface is provided. In one embodiment, one or more graphics layers of the user interface may dynamically attach or detach to or from hardware layers. A graphics layer may also attach or detach to or from a software renderer. For various special effects, such as transitions between graphics layers, a graphics layer may attach to a specific hardware layer to facilitate execution of the special effect. In response to a user input or other input prompting a transition, a graphics layer may detach from a software renderer, attach to a hardware layer, execute the transition, and then detach from the hardware layer and attach to the software renderer. 
     In one embodiment, the user interface may include screens, templates, and UI components, such that a screen may include one or more templates, and a template may include one or more UI components. In addition, transitions may occur between screens sharing the same template. To allow UI components on a template to be displayed at the same time during the transition, each UI component may be cloned in memory such that identical clones having unique identifiers exist. An active clone may be updated with the properties of the entering or target screen of the transition, and an inactive clone may be displayed on the exiting or previous screen of the transition. 
     In another embodiment, screens may be classified into different screen classes. A transition between screens may be selected based on the classification of the entering or target screen and the exiting or previous screen. 
     In another embodiment, a menu having one or more list items is provided. Each list item may include different elements, such as text, graphics, or dynamic items. Each list item may include a layout that specifies properties for the elements of the list items, such as size, position, etc. All possible list item layouts are classified and stored in a flyweight object in memory, allowing list items to share layout information instead of storing a layout for each list item. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description of certain exemplary embodiments is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
         FIG. 1  is a perspective view illustrating an electronic device, such as a portable media player, in accordance with one embodiment of the present invention; 
         FIG. 2  is a simplified block diagram of the portable media player of  FIG. 1  in accordance with one embodiment of the present invention; 
         FIG. 3  is a flowchart depicting dynamically reconfigurable graphics layers in accordance with an embodiment of the present invention; 
         FIGS. 4A-D  depict a simplified series of screens of a user interface illustrating a dynamically reconfigurable graphics layer according to an embodiment of the present invention. 
         FIG. 5  is a block diagram depicting a hierarchy of components of one embodiment of a user interface in accordance with an embodiment of the present invention; 
         FIG. 6  is a flowchart of one embodiment of a process for a transition between clones of a user interface element in accordance with an embodiment of the present invention; 
         FIGS. 7A-E  depict simplified diagrams of a transition between clones of a user interface element in accordance with an embodiment of the present invention; 
         FIG. 8  depicts a selection matrix that may be used to select a specific transition for a combination of screen classes of a user interface in accordance with an embodiment of the present invention; 
         FIG. 9  depicts a simplified menu screen of a user interface depicting a list of items in accordance with an embodiment of the present invention; and 
         FIG. 10  is block diagram illustrating a classification of list item layouts and corresponding flyweight object in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     One or more specific embodiments of the present invention will be described below. These described embodiments are only exemplary of the present invention. Additionally, in an effort to provide a concise description of these exemplary embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     Turning now to the figures,  FIG. 1  depicts an electronic device  10  in accordance with one embodiment of the present invention. In some embodiments, the electronic device  10  may be a media player for playing music and/or video, a cellular phone, a personal data organizer, or any combination thereof. Thus, the electronic device  10  may be a unified device providing any one of or a combination of the functionality of a media player, a cellular phone, a personal data organizer, and so forth. In addition, the electronic device  10  may allow a user to connect to and communicate through the Internet or through other networks, such as local or wide area networks. For example, the electronic device  10  may allow a user to communicate using e-mail, text messaging, instant messaging, or using other forms of electronic communication. By way of example, the electronic device  10  may be a model of an iPod® having a display screen or an iPhone® available from Apple Inc. 
     In certain embodiments the electronic device  10  may be powered by a rechargeable or replaceable battery. Such battery-powered implementations may be highly portable, allowing a user to carry the electronic device  10  while traveling, working, exercising, and so forth. In this manner, a user of the electronic device  10 , depending on the functionalities provided by the electronic device  10 , may listen to music, play games or video, record video or take pictures, place and take telephone calls, communicate with others, control other devices (e.g., the device  10  may include remote control and/or Bluetooth functionality, for example), and so forth while moving freely with the device  10 . In addition, in certain embodiments the device  10  may be sized such that it fits relatively easily into a pocket or hand of the user. In such embodiments, the device  10  is relatively small and easily handled and utilized by its user and thus may be taken practically anywhere the user travels. While the present discussion and examples described herein generally reference an electronic device  10  which is portable, such as that depicted in  FIG. 1 , it should be understood that the techniques discussed herein may be applicable to any electronic device having a display, regardless of the portability of the device. 
     In the depicted embodiment, the electronic device  10  includes an enclosure  12 , a display  14 , user input structures  16 , and input/output connectors  18 . The enclosure  12  may be formed from plastic, metal, composite materials, or other suitable materials or any combination thereof. The enclosure  12  may protect the interior components of the electronic device  10  from physical damage, and may also shield the interior components from electromagnetic interference (EMI). 
     The display  14  may be a liquid crystal display (LCD) or may be a light emitting diode (LED) based display, an organic light emitting diode (OLED) based display, or other suitable display. In accordance with certain embodiments of the present technique, the display  14  may display a user interface as well as various images  15 , such as logos, avatars, photos, album art, and so forth. Additionally, in one embodiment the display  14  may be a touch screen through which a user may interact with the user interface. The display  14  may also display various function and/or system indicators to provide feedback to a user, such as power status, call status, memory status, etc. These indicators may be in incorporated into the user interface displayed on the display  14 . 
     In one embodiment, one or more of the user input structures  16  are configured to control the device  10 , such as by controlling a mode of operation, an output level, an output type, etc. For instance, the user input structures  16  may include a button to turn the device  10  on or off. In general, embodiments of the electronic device  10  may include any number of user input structures  16 , including buttons, switches, a control pad, keys, knobs, a scroll wheel, or any other suitable input structures. The input structures  16  may work with a user interface displayed on the device  10  to control functions of the device  10  or of other devices connected to or used by the device  10 . For example, the user input structures  16  may allow a user to navigate a displayed user interface or to return such a displayed user interface to a default or home screen. 
     The electronic device  10  may also include various input and output ports  18  to allow connection of additional devices. For example, a port  18  may be a headphone jack that provides for connection of headphones. Additionally, a port  18  may have both input/output capabilities to provide for connection of a headset (e.g. a headphone and microphone combination). Embodiments of the present invention may include any number of input and/or output ports, including headphone and headset jacks, universal serial bus (USB) ports, Firewire or IEEE-1394 ports, and AC and/or DC power connectors. Further, the device  10  may use the input and output ports to connect to and send or receive data with any other device, such as other portable electronic devices, personal computers, printers, etc. For example, in one embodiment the electronic device  10  may connect to a personal computer via a Firewire or IEEE-1394 connection to send and receive data files, such as media files. 
     Turning now to  FIG. 2 , a block diagram of components of an illustrative electronic device  10  is shown. The block diagram includes the display  14  and I/O ports  18  discussed above. In addition, the block diagram illustrates the user interface  20 , one or more processors  22 , a memory  24 , storage  26 , card interface(s)  28 , networking device  30 , and power source  32 . 
     As discussed herein, in certain embodiments the user interface  20  may be displayed on the display  14 , and may provide a means for a user to interact with the electronic device  10 . The user interface may be a textual user interface, a graphical user interface (GUI), or any combination thereof, and may include various layers, windows, screens, templates, elements or other components that may be displayed in all of or areas of the display  14 . 
     The user interface  20  may, in certain embodiments, allow a user to interface with displayed interface elements via the one or more user input structures  16  and/or via a touch sensitive implementation of the display  14 . In such embodiments, the user interface provides interactive functionality, allowing a user to select, by touch screen or other input structure, from among options displayed on the display  14 . Thus the user can operate the device  10  by appropriate interaction with the user interface  20 . 
     The processor(s)  22  may provide the processing capability required to execute the operating system, programs, user interface  20 , and any other functions of the device  10 . The processor(s)  22  may include one or more microprocessors, such as one or more “general-purpose” microprocessors, a combination of general and special purpose microprocessors, and/or ASICS. For example, the processor(s)  22  may include one or more reduced instruction set (RISC) processors, such as a RISC processor manufactured by Samsung, as well as graphics processors, video processors, and/or related chip sets. 
     Embodiments of the electronic device  10  may also include a memory  24 . The memory  24  may include a volatile memory, such as RAM, and a non-volatile memory, such as ROM. The memory  24  may store a variety of information and may be used for a variety of purposes. For example, the memory  24  may store the firmware for the device  10 , such as an operating system for the device  10  and/or any other programs or executable code necessary for the device  10  to function. In addition, the memory  24  may be used for buffering or caching during operation of the device  10 . 
     The device  10  in  FIG. 2  may also include non-volatile storage  26 , such as ROM, flash memory, a hard drive, any other suitable optical, magnetic, or solid-state storage medium, or a combination thereof. The storage  26  may store data files such as media (e.g., music and video files), software (e.g., for implementing functions on device  10 ), preference information (e.g., media playback preferences), lifestyle information (e.g., food preferences), exercise information (e.g., information obtained by exercise monitoring equipment), transaction information (e.g., information such as credit card information), wireless connection information (e.g., information that may enable media device to establish a wireless connection such as a telephone connection), subscription information (e.g., information that maintains a record of podcasts or television shows or other media a user subscribes to), telephone information (e.g., telephone numbers), and any other suitable data. 
     The embodiment in  FIG. 2  also includes one or more card slots  28 . The card slots  28  may receive expansion cards that may be used to add functionality to the device  10 , such as additional memory, I/O functionality, or networking capability. The expansion card may connect to the device  10  through any type of connector and may be accessed internally or externally to the enclosure  12 . For example, in one embodiment the card may be a flash memory card, such as a SecureDigital (SD) card, mini- or microSD, CompactFlash card, Multimedia card (MMC), etc. Additionally, in some embodiments a card slot  28  may receive a Subscriber Identity Module (SIM) card, for use with an embodiment of the electronic device  10  that provides mobile phone capability. 
     The device  10  depicted in  FIG. 2  also includes a network device  30 , such as a network controller or a network interface card (NIC). In one embodiment, the network device  30  may be a wireless NIC providing wireless connectivity over any 802.11 standard or any other suitable wireless networking standard. The network device  30  may allow the device  10  to communicate over a network, such as a LAN, WAN, MAN, or the Internet. Further, the device  10  may connect to and send or receive data with any device on the network, such as other portable electronic devices, personal computers, printers, etc. For example, in one embodiment, the electronic device  10  may connect to a personal computer via the network device  30  to send and receive data files, such as media files. Alternatively, in some embodiments the electronic device may not include a network device  30 . In such an embodiment, a NIC may be added into card slot  28  to provide similar networking capability as described above. 
     The device  10  may also include or be connected to a power source  32 . In one embodiment, the power source  32  may be a battery, such as a Li-Ion battery. In such embodiments, the battery may be rechargeable, removable, and/or attached to other components of the device  10 . Additionally, in certain embodiments the power source  32  may be an external power source, such as a connection to AC power and the device  10  may be connected to the power source  32  via the I/O ports  18 . 
     Turning now in more detail to the user interface  20 , the user interface  20  may of any suitable design to allow interaction between a user and the device  10 . Thus, the user interface  20  may provide windows, menus, graphics, text, keyboards or numeric keypads, scrolling devices, or any other elements. In one embodiment, the user interface  20  may include screens, templates, and UI components, and may include or be divided into any number of these or other elements. The arrangement of the elements of user interface  20  may be hierarchical, such that a screen includes one or more templates, a template includes one or UI components. It should be appreciated that other embodiments may arrange user interface elements in any hierarchical or non-hierarchical structure and still utilize the techniques discussed herein. 
     A screen may be displayed on all or a portion of the display  20  and, thus, may comprise the entire user interface  20  or only a portion of the user interface  20 . The user interface  20  may include any number of screens of the same or different configurations and/or sizes. According to an embodiment using a hierarchical arrangement of elements, a screen may include one or more templates. Templates may be reused by different screens and may have properties associated with each template that affect the use and display of that template. Further, a screen may affect display of a template by overriding such properties and customizing a template for a particular use. 
     A template may include several user interface (UI) components, and a set of UI components may collectively form a template. Each UI component may also include properties that define how that component is displayed, such as the model from which data for the component is collected, the property identification of data, position, width, height, background color, etc. A UI component may be any type of element useful for display on the user interface  20 , such as single or multi-line text fields, progress bars, bitmaps or any other image, power status indicator, lists, etc. 
     In conjunction with such a hierarchical arrangement of user interface elements, elements may be divided into classes. For example, in one embodiment, screens may be classified into screen classes, wherein each screen class represents a general layout of the templates that comprise the screen. For example, the screen classes may include a menu-half screen, a menu-full screen, a background-full screen, a foreground-full screen, a “Now Playing” screen, a “cover flow” screen, a menu showcase screen, a clock-full screen, a menu clock, and so forth, each of which have different layouts of templates. 
     As the user interface  20  in such an embodiment may include any number of screens, templates, and UI components, various elements can be added or removed from the user interface as needed. For example, selection of an item from a menu screen may prompt display of another screen, or selection of a different function may prompt removal of one screen and insertion of another. Such actions may be referred to as transitions, and such transitions may be a subset of a larger category of user interface actions known as special effects. 
     Special effects may include any number of visual or non-visual actions on a user interface, such as fading or changing opacity, sliding or moving, resizing or scaling, blurring, rotating, pseudo-coloring, etc. Thus a transition may be a special effect in which these actions of changing opacity, resizing, moving, etc., are used to facilitate the addition and removal of screens, templates, UI components or any other element to or from the user interface  20 . In one embodiment, a transition may include moving one screen, template, or UI component off of the user interface  20  and moving another screen, window, template, or UI component onto the user interface  20 . In such a transition between screens, for example, the entering screen may be referred to as the “target” screen, and the exiting screen may be referred to as the “previous” screen. 
     To facilitate execution and display of the user interface  20 , the user interface may be abstracted into different graphics layers. Graphics layers may be defined such that a graphics layer includes one or more elements of the user interface  20 . A graphics layer may include properties to control how the graphics layer and the elements included in that graphics layer are used in the user interface  20  and/or displayed on the display  22 . Further, as discussed further below, the graphics layer abstraction may advantageously provide for utilization of the software or hardware included in the device  10  for display of the user interface  20 . 
     Turning now to the processor(s)  22 , one or more of the processor(s)  22  may provide various features for use by the user interface  20 . For example, a processor  22  may provide a plurality of hardware layers that may be used to display screens, templates, and/or UI components of the user interface  20 . According to an embodiment using the graphics layer abstraction discussed above, each hardware layer may be utilized by one or more graphics layer in the user interface  20 . Alternatively, instead of utilizing the features provided by the processor(s)  22 , the graphics layers may utilize a software renderer to display the screens, templates, and UI components of the user interface  20 . 
     In some embodiments, the hardware layers and software renderer may each provide different advantages to the user interface  20 , such as by providing different or faster execution of special effects for manipulating the screens, templates, and elements that comprise the user interface  20 . For example, in one embodiment, the hardware layers may include a set of LCD controller registers that can be used to specify various parameters for a user interface component. In such an embodiment, the parameters may include the position on the display  14 , the location in the memory  16 , and the stride, i.e. the width of each line. The hardware layers may also provide a global opacity parameter that affects an entire layer, and may include a setting to determine if a layer is active (visible). However, in certain implementations, use of the hardware layers provided by the processor(s)  22  may result in increased power consumption by the device  10 . Thus, in such implementations, use of the software renderer may be preferred to extend battery life of a device  10 . 
     In one embodiment, the hardware layers may include a set of layers referred to as layers G 0 , G 1 , . . . Gn. In such an embodiment, different layers may include different functions and/or properties. In an embodiment having layers G 0 -G 3  and video, for example, layers G 0  and G 1  may include 90-degree hardware rotators providing for rotation of a layer when the device  10  and display  14  are rotated from a “portrait” to a “landscape” orientation. Layers G 2  and G 3  may not have hardware rotators, but may provide other properties or functions to provide for faster special effects in the user interface  20 , such as opacity change or transitional movements for example. Different hardware layers may also utilize different pixel formats. For example, in one embodiment, a video layer may utilize YCbCr color format while the G 0 , G 1 , G 2 , and G 3  layers may utilize a RGB pixel format. 
     Due to the different advantages of the different hardware layers and of the software renderer, the various special effects, such as transitions, and other functions implemented by the portable electronic device  10  may be provided or executed faster or more efficiently by one or more of the hardware layers or by software renderer. For example, for certain images or transitions, the hardware layers may provide faster resizing, moving, opacity changes, scaling, blurring, and/or pseudo-coloring for images, screens, templates, UI components, or other elements of the user interface  20 . However, in such implementations, for other effects or images, such as for images below a certain size threshold, the software renderer may provide faster or more efficient execution. 
     As the hardware layers and software renderer may each provide different advantages, one embodiment of the present technique provides a dynamically reconfigurable graphics layer abstraction to better utilize these advantages.  FIG. 3  illustrates one example of a process  100  in which one or more graphics layers of a user interface  20  dynamically attaches and detaches to one or more hardware layers and/or to a software renderer. In this example, a graphics layer of the user interface  20  is first initialized (block  102 ), such as if the device  10  is switched on from an off state, or if the device  10  is activated after a suspended or hibernating state. 
     As discussed above, a user interface  20  may include multiple graphics layers, and while the process  100  depicts the process for a single graphics layer for the purpose of explanation, the process may be applied to multiple graphics layers of a user interface  20 . In the depicted example, the graphics layer is attached to a software renderer (block  104 ) such that the graphics is not utilizing any of the hardware layers. In one embodiment, the software renderer is a software compositing pipeline, such as implemented in an iPod® or an iPhone® available from Apple Inc. In such an embodiment, the software compositing pipeline facilitates display of the graphics layer on the display  14 . 
     The process  100  may receive an input  105  that invokes (block  106 ) the use of a special effect, such as a transition. The input  105  may be in response to an interaction between a user and the user interface  20 , such as selection of a menu item from the user interface  20 . Alternatively, the input  105  may be in response to a non-user initiated action, such as an incoming call, text message, network message or alert, power message or alert, or any other action. 
     The invoked special effects may include transitions, display of images, videos, or any other effect displayed in the user interface  20 . To facilitate execution of a special effect by utilizing one or more hardware layers, the graphics layer may be detached from the software renderer (block  108 ). The graphics layer is then attached to one or more of the hardware layers (block  110 ). In other words, one or more the hardware layers G 0 , G 1 , G 2 , G 3  and video are utilized to perform the special effect and, once the effect is performed, control of the graphics layers returns to the software renderer. 
     In some embodiments, the attachment of the graphics layer to the hardware layer may require additional conversions, calculations, or other transformations so that the graphics layer displays consistently on the user interface  20 . For example, the attachment may require a color format conversion if the hardware layer or layers being attached to uses a YCbCr color format and the software renderer uses an RGB color format. Additionally, recalculation of coordinates may be required if the software renderer and the one or more respective hardware layers represent position on the display  14  using different coordinate schemes. 
     Once the graphics layer is attached to one or more hardware layers, the special effect, such as a transition, may be performed (block  112 ) and is facilitated by the specific functionality provided by the hardware layer, such as increased speed, decreased memory utilization, hardware enhanced effects such as opacity, rotation, and so forth. For example, if the transition includes fading in and out, such as by changing opacity of various user interface screens, then the hardware layer may execute such a transition faster than the software renderer. 
     As discussed above, hardware layers provided by the microprocessor(s)  22  may provide various features, such as rotators, scalars, etc. Thus, it may be advantageous to use a specific hardware layer for a specific type of special effect. In one embodiment, the hardware layer selected for a specific special effect may be preselected during the design of the user interface  20 . Thus, for a specific special effect, a lookup table or other stored association may be used to select the appropriate hardware layer for that special effect. Alternatively, in other embodiments, the hardware layers may be dynamically allocated by software. For example, for a specific special effect, the first available hardware layer capable of executing the special effect may be allocated by software to a graphics layer, such that hardware layers are allocated as needed. 
     Once the special effect is completed, such as by the completion of a transition from one user interface screen to another, the graphics layer can then detach from the hardware layer (block  114 ) and then attach to the software renderer (block  116 ) and return to using software rendering to display the user interface  20 . In such an implementation, detaching the graphics layer from the hardware layer and reattaching the graphics layer to the software renderer may free the hardware layer and/or the processor(s)  22  for other purposes and may minimize the power consumption of the device  10 . 
     With the foregoing discussion in mind,  FIG. 4A  depicts a series of simplified screen depictions of a user interface  20  illustrating a dynamically reconfigurable graphics layer according to an embodiment of the present invention. In  FIG. 4A , the user interface  20  is split into two screens, the left screen  202  depicting a list of menu items  204 , and the right screen  206  depicting an image  208 . The graphics layers displaying the screens  202 ,  206  are initially attached to the software renderer. A user may initiate a transition in the user interface by, for example, selecting a menu item from the list of menu items  204 . After receiving this selection, the graphics layers providing the two screens  202  and  206  may attach to one or more hardware layers to utilize the features of those hardware layers while executing a transition. 
     For example, referring now to  FIG. 4B , in an embodiment that includes hardware layers G 0 , G 1 , G 2 , G 3  and Video, the graphics layer associated with left screen  202  may attach to hardware layer G 1  and the graphics layer associated with right screen  206  may attach to hardware layer G 2 . These hardware layers may provide features that facilitate, enhance, or accelerate the specific transition that will occur. Further, as discussed above, the selection of the transition may be predetermined or the selection may occur “on-the-fly” via software allocation. As part of the transition, a third screen  210  associated with its own graphics layer may be attached to yet another hardware layer, such as the Video layer, as seen in  FIGS. 4C and 4D . 
     After the graphics layers have attached to respective hardware layers, the transition, such as a sliding transition, occurs as depicted in  FIG. 4C . Current screens  202  and  206  “slide out” in direction of arrows revealing screen  210  that is a “background” screen or video layer. As can been seen in  FIG. 4C , a third screen  210  that includes image  214  appears as the screens  202  and  206  slide out of the user interface  20 . Display of the third screen  210  is facilitated by the Video hardware layer, which may be allocated to the graphics layer of screen  210  as discussed above. 
     As depicted in  FIG. 4D , the transition is complete when screens  202  and  206  are no longer displayed on user interface  20  and when the third screen  210  is fully displayed on user interface  20 . At this point, the graphics layers of screens  202 ,  206 , and  210  may detach from hardware layers G 1 , G 2 , and Video respectively. The graphics layers of third screen  210  may attach to the software renderer; alternatively, if further special effects will occur that may utilize the features of hardware layer Video, the graphics layer of screens  210  may remain attached to the hardware layer Video to facilitate faster execution of those special effects. 
     Turning now to other aspects of a user interface  20  for use with a portable electronic device  10 ,  FIG. 5  depicts a block diagram  300  of a hierarchy of elements of one embodiment of a user interface  20 . As mentioned above, other embodiments may arrange user interface elements in any hierarchical or non-hierarchical structure. Further, the diagram depicted in  FIG. 5  is a simplified diagram illustrating only some elements of an embodiment of a user interface  20 , and other elements may be included or excluded. 
     The top level of the block diagram of  FIG. 5  is a screen  302 . In one embodiment, a screen  302  may include one or more templates  304 , such as a menu template  306 , a status bar template  308 , and an image template  310 . The templates  304  may be reused by different screens, and may have properties associated with each template that affect the use and display of that template. Further, as illustrated in  FIG. 5 , a template may include one or more UI components  312 . For example, in  FIG. 5 , the status bar template  308  is depicted as including UI components  312  such as a bitmap  314 , a title  316 , and a power status indicator  318 . 
     As will be discussed below in  FIGS. 6 and 7 , to facilitate transitions between screens, templates, and other elements, each UI component  312  may be cloned such that two identical clones of each UI component  312  exist in the memory of the device  10 , each with a unique identifier. For example, in  FIG. 5  each UI component  312  is divided into two identical clones. Thus, bitmap  314  is divided into two clones  320  and  322 , title  316  is divided into two clones  324  and  326 , and the power status indicator  318  is divided into clones  328  and  330 . 
     As each UI component  312  has two clones, one clone may be designated as an “active” clone, and the other clone may be designated as an “inactive” clone. The active clone is the UI component that is modified and drawn on an entering or target screen during a transition, while the inactive clone is the UI component previously displayed on the exiting or previous screen of a transition. 
     For example, a user may enter an input from a first screen that results in a second screen being transitioned into the user interface  20 . Because the second screen may also use the status bar template  308  and the corresponding UI components, the transition between the two screens may require the UI components comprising the status bar template  308  to be displayed at the same time, both for the entering or target screen and for the exiting or previous screen. Thus, cloning of the UI components  312  allows for two UI components to be displayed at the same time. Further, because two UI components  312  are available in memory, one UI component clone may be modified based on the entering or target screen by changing the properties discussed above, in preparation for the transition, yet the other clone may remain unchanged on the display. 
       FIG. 6  depicts a flowchart of one embodiment of a cloning UI components process  400 . Turning now to the flowchart, the user interface may be initialized (block  402 ), such as by turning on the portable electronic device  10 . A UI component for a template, such as the bitmap  314 , title  316 , and power status indicator  318  components shown in  FIG. 5  is copied to create identical clones each having unique identifiers (block  404 ), i.e., active clone  406  and inactive clone  408 . One or more screens using a template and corresponding UI components are displayed (block  410 ) in the display of the device  10 , and the inactive clone  408  of a UI component is displayed. Next, the user interface may receive an input, such as a user selection of a menu item, prompting a transition to a target screen (block  412 ). Alternatively, the input may be a non-user initiated item, such as an incoming phone call, text message, email, network message or alert, etc. 
     Upon receiving the input that prompts a transition, the properties for the UI component for the target screen are applied to the active clone  406  (block  414 ), while the inactive clone  508  remains on the exiting or previous screen. The transition between the exiting or previous screen and the entering or target screen then occurs (block  416 ) and includes the transition between the inactive clone  408  and the active clone  406 . During the transition, the active clone  406  and inactive clone  408  are displayed on the target screen and previous screen respectively (blocks  418  and  420 ). After the transition is complete, the active clone  406  with the updated properties for the target screen is displayed on the user interface (block  422 ). The inactive clone  408  is then updated by applying the properties of the active clone  406  to the inactive clone  408  (block  424 ), such that both clones of the UI component are once again identical. As shown by line  426 , the process then returns to the original state of two identical clones in memory, one active and one inactive, and is ready for the further screen transitions. 
     To further illustrate the process depicted in  FIG. 6 , a simplified transition between clones of an element of a user interface is depicted in  FIGS. 7A-7E . The left column illustrates the properties of the clones in memory, and the right column is the user interface  20  as displayed on a display  14 . For illustrative purposes, the transition is divided into steps, and each step in the transition is identified as t 0 , t 1 , t 2 , etc. Beginning with t 0  in  FIG. 7A , two clones  504  and  506  of a “title” UI component  507  are depicted in column  500 . Each clone is stored in memory with a unique identifier, so that each clone may be identified and manipulated separately. In one implementation, the first clone  504  may be designated as the active clone, while the second clone  506  may be designated as the inactive clone. Initially, each clone is identical, as illustrated by the value “TITLE1,” indicative of the value of a property for each clone. 
     At t 0 , right column  502  displays a simplified user interface  508  having two screens  510  and  512 . The first screen  410  includes the title component, and thus may be a template that includes a title component, such as the status bar template  308 . Other UI components may be included in screen  510  but are not shown in the simplified illustration of  FIG. 6 . The second screen  512  may also include any number of templates and UI components. At t 0  of the transition, the screen  510  displays the inactive clone  506 . 
     Turning to  FIG. 7B , at t 1 , the user interface  508  may receive input, such as a selection from a user, prompting a transition to occur. The transition may utilize a target screen using the same status bar template  306  and the title component  507 . However, as discussed above, the new incoming screen may include components of the status bar template  306  having different properties. Thus, the properties of the title component  507  may be modified on the target screen for display in the user interface  508 . As illustrated in  FIG. 7B , these modifications are applied to the active clone  504 . Thus, at t 1  in  FIG. 7B , the active clone  504  has been updated to have value “TITLE2.” The inactive clone retains the value “TITLE1,” as the screen  510  displaying the inactive clone  506  is still viewable on the user interface  508 . 
     At t 2  in  FIG. 7C , the transition between the previous screen  510  and the target screen  514  occurs. The screen  510 , the exiting screen, is transitioned off of the user interface  508 , and the incoming screen  514  is entering the user interface  508 . As seen in the user interface  508 , both the active clone  504  and the inactive clone  506  are visible at the same time during the transition. Further, because active clone  504  has already been modified, the transition shows the incoming screen  514  with the updated value “TITLE2,” while the exiting screen  510  displays the value “TITLE1.” 
     Referring now to  FIG. 7D , at t 3  the transition is complete and the target screen  514  is now fully displayed on the user interface  508 . The target screen  514  is displayed with the updated UI components, such as the active clone  504  of the title component  507  with the updated value “TITLE2.” At t 3 , the active clone  504  and inactive clone  506  are in memory with the property values “TITLE2” and “TITLE1” respectively. 
     Finally, referring to  FIG. 7E , at t 4  the properties of the active clone  504  are applied to the inactive clone  506 . Thus, inactive clone  506  now has the property value “TITLE2,” thus returning the title component  507  to exist as two identical clones in memory. Further transitions may utilize the same technique shown in  FIG. 6 , with the formerly inactive clone  506  becoming the active clone and receiving the updated properties in preparation for a transition. Alternatively, the designations of active and inactive may simply be switched after completion of the transition such that the previously active clone is now inactive and the previously inactive clone is now active. Further, in some embodiments the application of the properties to each clone may occur simultaneously, such as during the execution of the transition. 
     To facilitate selection of a transition, an embodiment of the present technique may use the classification of user interface components for transition selection. For example, in an embodiment having the screen classifications discussed above, a transition may be determine based the screen classes of the target and/or previous screens. For each possible combination of target screen class and previous screen class, there are a number of possible transitions. 
     For example,  FIG. 8  depicts a selection matrix  600  that may be used to select or designate a specific transition for any combination of screen class in accordance with an embodiment of the present invention. The row  602  and the column  604  of the matrix  600  depict the nine screen classes discussed above as included in one embodiment of the present invention. The cells of row  602  may represent an entering or target screen, and the cells of column  604  may represent an exiting or previous screen. Each cell in the matrix  600  where a screen class from row  602  and a screen class from column  604  intersect indicate the specific transition that may be used. Thus, for those cells in the matrix  600  that are at the intersection of identical screen classes, such as cell  608 , no transition is present as there is no need to transition between identical screen classes. 
     Thus, different combinations of screen classes may have specified transition effects and types. For example, if the exiting or previous screen is classified background-full, as in block  610 , and the entering screen is classified as menu-half, such as block  612 , the transition selected is a slide. Thus, the entering screen, classified as a menu-half screen, will slide into the exiting screen, classified as a background-full screen. In another example, if the entering screen is a menu showcase, as in block  614 , and exiting screen is classified as a foreground-full class, as in block  616 , then the selected transition is a fade. Thus, for that transition, a menu showcase screen will fade in over a fading out foreground-full screen. Further, a pair of screen classes may have different transitions designated for the pair, depending on the direction of the transition. For example transitioning from a foreground-full screen class to a menu showcase screen class may be accomplished with a fade transition however, transitioning from the menu showcase screen class to the foreground-full screen class may be accomplished with a sliding transition. 
     For some possible transitions in the matrix  600 , no specific transition may be specified, such as in cells  618 . In these particular cases, a default transition may be used. If during the selection process, no transition is found in the selection matrix  600 , the default or fallback transition will be used. The matrix  600  may be pre-populated during the design of the user interface or the matrix  600  may be populated or changed according to user preferences, allowing users to specify their preferred transitions. Alternatively, multiple selection matrices may be used, such as one for pre-populated selections, one for user preferred selections, one for further subclasses of screens, etc. 
     As mentioned above in discussion of the user interface  20 , menus may be one of the possible elements displayed in the user interface  20 . For example, according to one embodiment of the user interface  20 , screens displayed in the user interface  20  may include menus, in which each menu may comprise a list of items. Each list item may have a particular layout associated with that item, such that the layout specifies the position, size, and other properties of those components of the list item. For example,  FIG. 9  depicts a simplified menu screen  700  of a user interface  20  showing a list of items. These list items may represent items selectable by the user or may also be items used to display information that are not selectable. Additionally, as will be discussed below, the items may include static or dynamic components. Beginning with the first item  702 , this item includes text  706  shown as “TEXT1.” The second item  704  in the list of the menu screen  700  includes text  705  displayed as “TEXT2.” Thus, both items  702  and  704  include only text items, and a stored layout for those items need only store the layout of the text. The third item  706  includes both the text  707 , displayed as “TEXT3,” and a graphic  708 , such as a bitmap, as illustrated by the arrow. Thus, the layout for item  706  may store the position, size, and other properties of the text and the graphic  708 . The fourth item  710  in the list includes the text  711  (“TEXT4”), a graphic  712  represented by the arrow, and a dynamic, i.e. known only at runtime, item  714 . Therefore, the layout for the item  710  may need to include the position, size, and other properties of the text  711 , the graphic  712 , and the dynamic item  714 . 
     Because each item in a list may be different than other items, storing individualized layouts for each list item may result in increasing memory usage as the menus options increase. Such memory usage may be disadvantageously large in some embodiments of a portable electronic device  10  in which memory may be constrained due to the size of the device  10 .  FIG. 10  depicts a block diagram  800  showing a classification of list item layouts in accordance with an embodiment of the present technique that minimizes the memory usage of those list item layouts. The top of the block diagram  800  is a list view  802 . Underneath the list view  802  is a list child view  804  that contains the list item layouts  805 . All the possible list item layouts may be determined, and these are identified in  FIG. 10  as layout 1   806 , layout 2   808 , layout 3   810 , and so on through layout “n”  812 . 
     Each list item layout includes layout information for list item elements. For example, layout 1   806  may include layout information for a text view  814  and a bitmap  816 . Layout 2   808  may include layout information for text view  818  only, whereas layout 3   810  may include that information for a text view  820  and a bitmap  822 . Thus, layouts may be specified for various elements of the list items, so that the list items may be displayed such as in the embodiment depicted in  FIG. 9 . 
     Additionally, list items may be associated with layouts dynamically at the time a list item is rendered. For example, the renderer for a list item can request a layout from software, such as from a model. The model can return a layout to the renderer, and the list item will use that layout. Thus, in some embodiments, the layout can be dynamically based on a status, condition, or other data. For example, if a media file stored on the device  10  has not been played by a user, at the time the list item is rendered a list item may use layout 1   806 . If the media file stored on the device  10  has already been played by a user, then at the time the list item is rendered, the same list item may use layout 3   810 . 
     In accordance with an embodiment of the present invention, list item layouts may be defined inside an object  826 . In one implementation, the object may be a flyweight object, wherein the flyweight object is shared among multiple contexts simultaneously. In each context, the flyweight object acts as an independent object, may be used the same as an instance of an independent object. The flyweight object  826  minimizes the total memory usage of storing a layout, and allows any number of items with the same layout to share the memory cost of the layout. Further, dynamic list items may be displayed, next to static list items. 
     For example, a menu list item that includes a text view and a bitmap may refer to the layout 1   806  for layout information. A second menu list item that includes a text view and a bitmap may also refer to layout 1   806  for layout information. Thus, instead of storing a list item layout for each list item, list items may refer to the same layout information stored in the flyweight object  826 . Further, because all possible list item layouts for the device  10  may be determined and stored in the flyweight object  826 , any list item may refer to the layouts in the flyweight object to obtain layout information. 
     While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.