Patent Publication Number: US-8982045-B2

Title: Using movement of a computing device to enhance interpretation  of input events produced when interacting with the computing device

Description:
BACKGROUND 
     Handheld computing devices often allow users to input information by making direct contact with the display surfaces of the devices. These types of input mechanisms are referred to as contact-type input mechanisms herein. For instance, a touch input mechanism provides direct touch input events when a user touches a display surface of the computing device with a finger (or multiple fingers). A pen input mechanism provides direct pen input events when a user touches the display surface with a pen device, also known as a stylus. 
     Computing devices also permit a user to perform gestures by using one or more fingers or a pen device. For example, a gesture may correspond to a telltale mark that a user traces on the display surface with a finger or pen input device. The computing device correlates this gesture with an associated command. The computing device then executes the command. Such execution can occur in the course of the user&#39;s input action (as in direct-manipulation drag actions), or after the user finishes the input action. 
     Generally, a developer may wish to provide an expressive contact-type input mechanism that accommodates a rich set of input gestures. However, increasing the number of gestures may introduce a number of challenges. For instance, assume that a computing device accommodates two or more predefined intentional gestures that are nonetheless similar. In this case, the user may intend to enter a particular gesture, but the computing device may mistakenly interpret that gesture as another, but similar, gesture. In another case, the user may seek to perform a task using the computing device that does not involve intended interaction with a contact-type input mechanism. Yet the user may handle the computing device in a manner which causes inadvertent contact with the contact-type input mechanism. Or the user may accidently brush or bump against the display surface of the contact-type input mechanism while inputting information, which causes accidental contact with the contact-type input mechanism. The contact-type input mechanism may incorrectly interpret these accidental contacts as legitimate input events. These problems may understandably frustrate the user if they become a frequent occurrence, or, even if uncommon, if they cause significant disruption in the task that the user is performing. 
     A developer can address some of these concerns by developing compound idiosyncratic gestures. However, this is not a fully satisfactory solution because the user may have difficulty remembering and executing these gestures, particularly when these gestures are complex and “unnatural.” Furthermore, complex gestures often take longer for the user to articulate. For this reason, adding these types of gestures to a set of possible gestures yields diminishing returns. 
     SUMMARY 
     A computing device is described herein which collects plural input events that describe an input action. For instance, the computing device receives one or more input events from at least one contact-type input mechanism, such as a touch input mechanism and/or a pen input mechanism. The computing device also receives one or more input events from at least one movement-type input mechanism, such as an accelerometer and/or gyro device. The movement-type input mechanism indicates the orientation or dynamic motion of the computing device. (More specifically, as used herein, the term “movement” broadly encompasses either orientation of the computing device or the dynamic motion of the computing device, or both). Based on these input events, optionally in conjunction with other factors, the computing device interprets the type of the input action that has occurred. And based on this detection, the computing device can then execute a desired behavior, such as ignoring at least part of the input events. 
     More briefly stated, described herein is a computing device that takes the movement of the computing device into account when interpreting the intentional or unintentional contact-type inputs of the user (via a touch and/or pen input mechanism). The movements are characterized as background movements insofar as they are incidental to any goal-directed behavior currently exhibited by the user (if any). That is, the user may not be focused on performing these background movements as an intentional act. 
     In one case, the computing device is configured to repeatedly analyze input events received from the contact-type input mechanism(s) and the movement-type input mechanism(s) in a course of the input action. This is performed to improve a level of confidence at which the computing device detects the type of input action. 
     The Detailed Description sets forth numerous scenarios in which the movement of the computing device is used to refine an analysis of contact input event(s). Some of these examples are summarized below. 
     In one scenario, the computing device concludes that at least part of the input action is unintentional when the movement input event(s) exceed a prescribed threshold over a prescribed time window. In this case, the input action may be associated with picking up or setting down the computing device. 
     In another scenario, the computing device concludes that at least part of the input action is unintentional when movement input event(s) exhibit noise-like motion characteristics indicative of operation of the computing device in a noisy environment. 
     In another scenario, the computing device concludes that at least part of the input action is unintentional due to unintentional movement that occurs during application or removal of a touch contact. 
     In another scenario, the computing device more accurately discriminates a type of gesture that has been performed based on a combination of contact input event(s) and movement input event(s). 
     In another example, the computing device concludes that the input action is associated with an unintentional application of a finger or other hand part when the movement input event(s) indicate that the computing device is being held upright in a hand, which, in turn, can be detected by determining the orientation of the computing device. 
     The computing device can perform various behaviors in response to its analysis. In one case, the computing device can reject at least part of the contact input event(s) when the computing device determines that at least part of the input action is unintentional. In addition, or alternatively, the computing device can restore a pre-action state when the computing device determines that at least part of the input action is unintentional. In addition, or alternatively, the computing device can correct an interpretation of contact input event(s) to remove effects of the movement input event(s) when the computing device determines that at least part of the input action is unintentional. In addition, or alternatively, the computing device can modify a user interface presentation based on a type of input action that has been detected. 
     The above functionality can be manifested in various types of systems, components, methods, computer readable media, data structures, articles of manufacture, and so on. 
     This Summary is provided to introduce a selection of concepts in a simplified form; these concepts are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an illustrative computing device that includes functionality for interpreting contact input events in the context of movement input events, and/or for interpreting movement input events in the context of contact input events. 
         FIG. 2  shows an interpretation and behavior selection module (IBSM) used in the computing device of  FIG. 1 . 
         FIG. 3  shows an illustrative system in which the computing device of  FIG. 1  can be used. 
         FIGS. 4 and 5  show examples of rotational movements that can be used in intentional gestures. 
         FIGS. 6-9  show different gestures that can incorporate the type of rotational movement shown in either  FIG. 4  or  FIG. 5 . 
         FIG. 10  shows an intentional gesture that involves pointing a computing device towards a target entity. 
         FIG. 11  shows an intentional gesture that involves moving a computing device against a stationary finger. 
         FIG. 12  shows an intentional gesture that involves applying a touch to two display parts of a computing device that has at least two display parts. 
         FIG. 13  shows an intentional gesture which is enabled by the application of an idiosyncratic multi-touch gesture. 
         FIG. 14  shows an intentional gesture which involves applying a contact point to a computing device and then rotating the computing device. 
         FIG. 15  shows functionality for using movement input events to enhance the interpretation of contact input events, e.g., upon the application or removal of a finger (or other hand part) from the display surface of a computing device. 
         FIG. 16  shows background movement that typically causes large movement input events. 
         FIGS. 17 and 18  illustrate circumstances in which a computing device may disregard touch input events based on the orientation of the computing device. 
         FIG. 19  shows a flowchart which explains one manner of operation of the computing device of  FIG. 1  in a foreground mode of operation. 
         FIG. 20  shows a flowchart which explains one manner of operation of the computing device of  FIG. 1  in a background mode of operation. 
         FIG. 21  shows illustrative processing functionality that can be used to implement any aspect of the features shown in the foregoing drawings. 
     
    
    
     The same numbers are used throughout the disclosure and figures to reference like components and features. Series 100 numbers refer to features originally found in  FIG. 1 , series 200 numbers refer to features originally found in  FIG. 2 , series 300 numbers refer to features originally found in  FIG. 3 , and so on. 
     DETAILED DESCRIPTION 
     This disclosure is organized as follows. Section A describes an illustrative computing device that takes the movement of the computing device into account when assessing contact input events. Section B describes illustrative methods which explain the operation of the computing device of Section A. Section C describes illustrative processing functionality that can be used to implement any aspect of the features described in Sections A and B. 
     This application is related to commonly-assigned patent application Ser. No. 12/970,939, entitled, “Detecting Gestures Involving Intentional Movement of a Computing Device,” naming the inventors of Kenneth Hinckley, et al., and filed on the same date as the instant application. That application is incorporated by reference herein in its entirety. 
     As a preliminary matter, some of the figures describe concepts in the context of one or more structural components, variously referred to as functionality, modules, features, elements, etc. The various components shown in the figures can be implemented in any manner by any physical and tangible mechanisms (such as by hardware, software, firmware, etc., or any combination thereof). In one case, the illustrated separation of various components in the figures into distinct units may reflect the use of corresponding distinct components in an actual implementation. Alternatively, or in addition, any single component illustrated in the figures may be implemented by plural actual components. Alternatively, or in addition, the depiction of any two or more separate components in the figures may reflect different functions performed by a single actual component.  FIG. 21 , to be discussed in turn, provides additional details regarding one illustrative implementation of the functions shown in the figures. 
     Other figures describe the concepts in flowchart form. In this form, certain operations are described as constituting distinct blocks performed in a certain order. Such implementations are illustrative and non-limiting. Certain blocks described herein can be grouped together and performed in a single operation, certain blocks can be broken apart into plural component blocks, and certain blocks can be performed in an order that differs from that which is illustrated herein (including a parallel manner of performing the blocks). The blocks shown in the flowcharts can be implemented in any manner by any physical and tangible mechanisms (such as by hardware, software, firmware, etc., or any combination thereof). 
     As to terminology, the phrase “configured to” encompasses any way that any kind of physical and tangible functionality can be constructed to perform an identified operation. The functionality can be configured to perform an operation using, for instance, software, hardware, firmware, etc., and/or any combination thereof. 
     The term “logic” encompasses any physical and tangible functionality for performing a task. For instance, each operation illustrated in the flowcharts corresponds to a logic component for performing that operation. An operation can be performed using, for instance, software, hardware, firmware, etc., and/or any combination thereof. When implemented by a computing system, a logic component represents an electrical component that is a physical part of the computing system, however implemented. 
     The following explanation may identify one or more features as “optional.” This type of statement is not to be interpreted as an exhaustive indication of features that may be considered optional; that is, other features can be considered as optional, although not expressly identified in the text. Similarly, the explanation may identify a single instance of a feature, or plural instances of a feature. Recitation of a single instance of a feature does not preclude plural instances of this feature; further, recitation of plural instances does not preclude a singular instance of this feature. Finally, the terms “exemplary” or “illustrative” refer to one implementation among potentially many implementations. 
     A. Illustrative Computing Devices 
     A.1. Overview 
       FIG. 1  shows an example of a computing device  100  that takes into account movement of the computing device  100  when analyzing contact input events. The computing device  100  optionally includes a display mechanism  102  in conjunction with various input mechanisms  104 . If included, the display mechanism  102  provides a visual rendering of digital information on a display surface. The display mechanism  102  can be implemented by any type of display, such as a liquid crystal display, etc. Although not shown, the computing device  100  can also include an audio output mechanism, a haptic (e.g., vibratory) output mechanism, etc. 
     The input mechanisms  104  can include touch input mechanism(s)  106  and pen input mechanism(s)  108 . The touch input mechanism(s)  106  can be implemented using any technology, such as resistive touch screen technology, capacitive touch screen technology, acoustic touch screen technology, bi-directional touch screen technology, and so on. In bi-directional touch screen technology, a display mechanism provides elements devoted to displaying information and elements devoted to receiving information. Thus, a surface of a bi-directional display mechanism is also a capture mechanism. The touch input mechanism(s)  106  and the pen input mechanism(s)  108  can also be implemented using a pad-type input mechanism that is separate from (or at least partially separate from) the display mechanism  102 . A pad-type input mechanism is also referred to as a tablet, a digitizer, a graphics pad, etc. 
     The pen input mechanism(s)  108  can be implemented using any technology, such as passive pen technology, active pen technology, and so on. In the passive case, the computing device  100  detects the presence of the pen device when it touches (or is proximal to) the display surface. In that case, the pen device may represent simply an elongate implement having no independent power source and no processing functionality, or it may be passively powered by inductive coupling with the display mechanism  102 . In the active case, the pen device can incorporate independent detection functionality for sensing its position with respect to the display surface. Further, the active pen device can include independent movement sensing mechanisms. Further, the active pen device can include independent depth sense mechanisms. In these examples, the active pen device can forward its input data to the computing device  100  for analysis. In the following description, it is to be understood that input data regarding the pen device can originate from the computing device  100 , the pen device itself, or a combination thereof. 
     In the terminology used herein, a contact-type input mechanism describes any type of input mechanism in which the user establishes actual or close contact with a display surface of the display mechanism  102  or other part of the computing device  102 . Contact-type input mechanisms include the above-described touch input mechanism(s)  106  and the pen input mechanism(s)  108 , etc. Further, any contact with the computing device  100  may include one or more instances of separate contact. For example, a user can make contact with the display surface by placing one or more fingers in proximal or actual contact with the display surface. 
     The input mechanisms  104  also include various types of movement-type input mechanism(s)  110 . The term movement-type input mechanism describes any type of input mechanism that measures the orientation or motion of the computing device  100 , or both. The movement type input mechanism(s)  110  can be implemented using linear accelerometers, gyroscopic sensors (“gyro devices” according to the terminology used herein), vibratory sensors tuned to various motion frequency bandwidths, mechanical means to detect specific postures or movements of the computing device  100  or parts of the computing device  100  relative to gravity, torque sensors, strain gauges, flex sensors, optical encoder mechanisms, and so on. Furthermore, any movement-type input mechanism can sense movement along any number of spatial axes. For example, the computing device  100  can incorporate an accelerometer and/or a gyro device that measures movement along three spatial axes. 
     The input mechanisms  104  also can include any type of image sensing input mechanism(s)  112 , such as a video capture input mechanism, a depth sensing input mechanism, a stereo image capture mechanism, and so on. The depth sensing input mechanism measures the distance of objects from some part of the computing device  100 . For example, in one case, the depth sensing input mechanism measures the distance of objects from the display surface of the computing device  100 . The depth sensing input mechanism can be implemented using any type of capture technology (e.g., time-of-flight technology) in conjunction with any type of electromagnetic radiation (e.g., visible spectrum radiation, infrared spectrum radiation, etc.). Some of the image sensing input mechanism(s)  112  can also function as movement-type input mechanisms, insofar as they can be used to determine movement of the computing device  100  relative to the surrounding environment. Alternatively, or in addition, some of the image sensing input mechanism(s)  112  can be used in conjunction with the movement-type input mechanism(s)  110 , e.g., to enhance the performance and/or accuracy of the movement-type input mechanism(s)  110 . Although not specifically enumerated in  FIG. 1 , other input mechanisms can include a keypad input mechanism, a mouse input mechanism, a voice input mechanism, and so on. 
     In the terminology used herein, each input mechanism is said to generate an input event when it is invoked. For example, when a user touches the display surface of the display mechanism  102  (or other part of the computing device  100 ), the touch input mechanism(s)  106  generates touch input events. When the user applies a pen device to the display surface, the pen input mechanism(s)  108  generates pen input events. More generally stated, a contact-type input mechanism generates contact input events, which indicate the proximal or actual physical contact of some object with the computing device  100 . A movement-type input mechanism, by contrast, is said to generate movement input events. Any input event may itself include one or more input event components. For ease and brevity of reference, the following explanation will most often describe the output of an input mechanism in the plural, e.g., as “input events.” However, various analyses can also be performed on the basis of a singular input event. 
       FIG. 1  depicts the input mechanisms  104  as partially overlapping the display mechanism  102 . This is because at least some of the input mechanisms  104  may be integrated with functionality associated with the display mechanism  102 . This is the case with respect to the contact-type input mechanisms, such as the touch input mechanism(s)  106  and the pen input mechanism  108 ( s ). For example, the touch input mechanism(s)  106  relies, in part, on functionality provided by the display mechanism  102 . 
     An interpretation and behavior selection module (IBSM)  114  receives input events from the input mechanisms  104 . Namely, it collects the input events over the course of an input action, where that input action is either deliberate or unintentional, or a combination thereof. As the name suggests, the IBSM  114  performs the task of interpreting the input events. In doing so, it interprets contact input events in the context of movement input events (and vice versa), optionally in conjunction with other factors. After performing its interpretation role, the IBSM  114  may perform behavior associated with zero, one, or more of the interpreted input events. 
     From a high-level perspective, the IBSM  114  performs two roles, depending on the nature of movement that occurs during the input action. In a first role, the IBSM  114  analyzes both contact input events and movement input events to determine whether the user has deliberately moved the computing device  100  as part of an intentional gesture. If so, the IBSM  114  recognizes the gesture and executes whatever behavior is mapped to the gesture. In this context, the movement that occurs is foreground movement because the user intentionally performs this action; namely, it is in the foreground of the user&#39;s focus of awareness. 
     More specifically, in a first case, the IBSM  114  executes a behavior at the completion of a gesture. In a second case, the IBSM  114  executes a behavior over the course of the gesture. In any case, the IBSM  114  can also interpret two or more gestures that happen simultaneously and/or in succession, and execute commensurate behaviors associated with the gestures. In any case, the IBSM  114  can also continue to analyze the type of gesture that has occurred (or is presently occurring), and revise its interpretation of that gesture as deemed appropriate. Examples will follow clarify these aspects of the IBSM  114 . 
     In a second role, the IBSM  114  analyzes both contact input events together with movement input events, where the movement input events are attributed to background movement of the computing device  100 . The movement is background in the sense that it is in the background of the user&#39;s awareness. The movement may be incidental to any goal-directed input behavior of the user (if any). In this case, the IBSM  114  attempts to interpret the type of input action associated with the input events, e.g., to determine whether the contact with the display surface is intentional or unintentional. The IBSM  114  can then perform various behaviors in response to its analysis. 
     Section A.2 (below) provides additional details regarding the foreground mode of operation while Section A.3 (below) provides additional details regarding the background mode of operation. Although many of the examples set forth the use of touch input in conjunction with movement input events, any of these examples also apply to the use of pen input (or any other contact input) in conjunction with movement input events. 
     Finally, the computing device  100  may run one or more applications  116  received from any application source or sources. The applications  116  can provide any higher-level functionality in any application domain. 
     In one case, the IBSM  114  represents a separate component with respect to applications  116 . In another case, one or more functions attributed to the IBSM  114  can be performed by one or more applications  116 . For example, in one implementation, the IBSM  114  can interpret a gesture that has been performed, while an application can select and execute behavior that is based on that interpretation. Accordingly, the concept of the IBSM  114  is to be interpreted liberally herein as encompassing functions that can be performed by any number of components within a particular implementation. 
       FIG. 2  shows another depiction of the IBSM  114  introduced in  FIG. 1 . As shown there, the IBSM  114  receives various input events. For example, the IBSM  114  can receive touch input events, pen input events, orientation input events, motion input events, image sensing input events, and so on. In response to these events, the IBSM  114  provides various output behaviors. For example, the IBSM  114  can execute various commands in response to detecting an intentional motion-based gesture. Depending on environment-specific factors, the IBSM  114  can perform these functions in the course of the user&#39;s performance of the gesture and/or upon the completion of the gesture. The IBSM  114  can also provide various visual, audible, haptic, etc. feedback indicators to indicate its present interpretation of the gesture that has most likely been (or is being) performed. Alternatively, or in addition, the IBSM  114  can reject part of the contact input events if it determines that an input action was unintentional, at least in part. Alternatively, or in addition, the IBSM  114  can restore a state (such as a display state and/or an application state) to a point prior to the occurrence of an input action. Alternatively, or in addition, the IBSM  114  can correct an interpretation of the contact input events to remove effects of the movement input events when the IBSM  114  determines that at least part of the input action is unintentional. Alternatively, or in addition, the IBSM  114  can adjust the configuration of the computing device  100  in any way based on its understanding of the input action, e.g., so as to more efficiently receive further intentional contact input events and minimize the impact of unintentional contact input events. Alternatively, or in addition, the IBSM  114  can modify or remove the above-described feedback indicators based on its present interpretation of the input events, e.g., insofar the present interpretation may differ from a preceding interpretation. 
     To function as described, the IBSM  114  can incorporate a suite of analysis modules, where the detection of different gestures and background motion scenarios may rely on different respective analysis modules. Any analysis module can rely on one or more techniques to classify the input events, including pattern-matching techniques, rules-based techniques, statistical techniques, and so on. For example, each gesture or background noise scenario can be characterized by a particular telltale pattern of inputs events. To classify a particular sequence of input events, a particular analysis module can compare those input events against a data store of known patterns. Representative features that may help to distinguish a gesture or background scenario include the manner in which a contact is applied and then removed, the manner in which the contact is moved while being applied (if it all), the magnitude of the movement input events, the particular signal shapes and other characteristics of the movement input events, and so on. And as noted above, an analysis module can continually test its conclusions with respect to new input events that arrive. 
       FIG. 3  shows an illustrative system  300  in which the computing device  100  of  FIG. 1  can be used. In this system  300 , a user interacts with the computing device  100  to provide input events and receive output information. The computing device  100  can be physically implemented as any type of device, including any type of handheld device as well as any type of traditionally stationary device. For example, the computing device  100  can be implemented as a personal digital assistant, a mobile communication device, a pad-type device, a book reader device, a handheld game device, a laptop computing device, a personal computer device, a work station device, a game console device, a set-top box device, and so on. Further, the computing device  100  can include one or more device parts, some (or all or none) of which may have display surface parts. 
       FIG. 3  depicts a representative (but non-exhaustive) collection of implementations of the computing device  100 . In scenario A, the computing device  100  is a handled device having any size. In scenario B, the computing device  100  is a book-reader device having multiple device parts. In scenario C, the computing device  100  includes a pad-type input device, e.g., whereby a user makes touch and/or pen gestures on the surface of the pad-type input device rather than (or in addition to) the display surface of the display mechanism  102 . The pad-type input device can be integrated with the display mechanism  102  or separate therefrom (or some combination thereof). In scenario D, the computing device  100  is a laptop computer having any size. In scenario E, the computing device  100  is a personal computer of any type. In scenario F, the computing device  100  is associated with a wall-type display mechanism. In scenario G, the computing device  100  is associated with a tabletop display mechanism, and so on. 
     In one scenario, the computing device  100  can act in a local mode, without interacting with any other functionality. Alternatively, or in addition, the computing device  100  can interact with any type of remote computing functionality  302  via any type of network  304  (or networks). For instance, the remote computing functionality  302  can provide applications that can be executed by the computing device  100 . In one case, the computing device  100  can download the applications; in another case, the computing device  100  can utilize the applications via a web interface or the like. The remote computing functionality  302  can also implement any aspect or aspects of the IBSM  114 . Accordingly, in any implementation, one or more functions said to be components of the computing device  100  can be implemented by the remote computing functionality  302 . The remote computing functionality  302  can be physically implemented using one or more server computers, data stores, routing equipment, and so on. The network  304  can be implemented by any type of local area network, wide area network (e.g., the Internet), or combination thereof. The network  304  can be physically implemented by any combination of wireless links, hardwired links, name servers, gateways, etc., governed by any protocol or combination of protocols. 
     A.2. Foreground-Related Movement 
     This section describes the operation of the IBSM  114  for the case in which the user deliberately moves or strikes the computing device  100  as part of an intentional gesture. Generally stated, a gesture can be defined which incorporates any type of movement, where, as said, the term movement is given a broad interpretation herein. In some cases, a gesture involves moving the computing device  100  to a prescribed orientation with respect to an initial orientation. Alternatively, or in addition, a gesture may involve applying a prescribed motion (e.g., motion along a path, vibratory motion, etc.) to the computing device  100 . Motion can be characterized by any combination of parameters, such as speed, acceleration, direction, frequency, etc. 
     In some cases, the gesture involves the joint application of a contact (via a touch and/or a pen device, etc.) with movement. For example, a user may touch an object on the display surface and then move the computing device  100  to a prescribed orientation and/or move the computing device  100  in a prescribed dynamic manner, e.g., by tracing out a prescribed gesture path. The IBSM  114  can interpret the resultant input events as a request to perform some action with respect to the designated object or other content on the display surface (for example, the object that the user is touching with a finger or pen device). In this case, the contact input events at least partially overlap the movement input events in time. In other cases, the user may apply a contact to the computing device  100  and then apply some telltale movement to the computing device  100 , or first apply some telltale movement to the computing device  100  and then apply a contact to the computing device  100 . The gestures can include one or more additional sequential phases of contact(s) and/or movement, and/or one or more additional phases of simultaneous contact(s) and movement. In these cases, the contact input events may be interleaved with the movement input events in any manner. In other words, the contact input events need not temporally overlap the movement input events. In other cases, the gesture may solely involve the application of a prescribed movement to the computing device  100 . In other cases, the user may apply two or more gestures at the same time. In other cases, the user may apply a gesture which seamlessly transitions into another gesture, and so on. The following explanation illustrates these general points with respect to particular examples. These examples are representative, not exhaustive of the many gestures that can be created based on intentional movement of the computing device  100 . 
     In many of the examples which follow, the user is depicted as making contact with the display surface of the display mechanism  102 . Alternatively, or in addition, the user can interact with a pad-type input device, e.g., as illustrated in scenario C of  FIG. 3 . Further, in many cases, the user is shown as using a two-handed approach to make selections, e.g., where the user holds the device in one hand and makes a selection with a finger (or fingers) of the other hand. But in any of these cases, the user can alternatively make a selection with a thumb (or other hand portion) of the hand which is holding the device. Finally, a general reference to the user&#39;s hand is to be understanding as encompassing any part of the hand. 
     In any of the examples which follow, the computing device  100  can present any type of feedback to the user which indicates that a gesture has been recognized and a corresponding behavior is about to be applied or is in the process of being applied. For example, the computing device  100  can present any combination of a visual feedback indicator, an audible feedback indicator, a haptic (e.g., vibratory) feedback indicator, and so on. The use of non-visual feedback indicators may be useful in some cases because it may be difficult for the user to notice a visual indicator while moving the computing device. According to another general feature, the computing device  100  can present an undo command to allow a user to remove the effects of any unintended gesture. 
       FIG. 4  shows a scenario in which the user grasps a computing device  402  in a hand  404  (or two hands, not shown). The user then rotates the computing device  402  so that its distal end  406  moves downward, in the direction of the arrow  408 . In a complementary movement, the user can rotate the computing device  402  so that its distal end  406  moves upward in the direction opposite to arrow  408 . 
       FIG. 5  shows a scenario in which the user grasps a computing device  502  in a hand  504 . The user then rotates the computing device  502  so that its side edge  506  moves upward, in the direction of the arrow  508 . In a complementary movement, the user can rotate the computing device  502  so that its side edge  506  moves downward in the direction opposite to arrow  508 . 
     Although not illustrated, in another rotation, the user can rotate a computing device in a plane which is parallel to the floor. More generally, these three axes are merely representative; the user can rotate a computing device about any axis in any plane. Further, the user can combine different types of rotational and/or translational movement into a compound gesture. 
       FIG. 6  shows one gesture that incorporates the type of rotational movement shown in  FIG. 4 . In this case, assume that the user&#39;s intent is to perform some function with respect to object  602  which is displayed on a display surface of a computing device  604 . For example, the user may wish to zoom in and enlarge the object  602 . As part of the gesture, the user applies a contact to the object  602 , such as by touching the object  602  with his or her thumb (in one merely representative case). Note that, in this case, the center of expansion for the zooming action may correspond to the (x, y) point that is associated with the position of the thumb on the display surface. Alternatively, the center of expansion may correspond to a fixed offset from the (x, y) point associated with the thumb position; in this case, the zooming action will be produced at a point directly above the thumb (in one example), rather than underneath it. In another example, the user may wish to enter a value via the object  602 . To do this, the user can touch the object to increase the value (and touch some other object, not shown, to decrease the value). 
     In these scenarios, the angle at which the user holds the computing device  604  controls the rate at which the action is performed, e.g., the rate at which zooming occurs (in the first example cited above) or the rate at which a number in a numeric field is increased or decreased (in the second example cited above), etc. The angle may be measured with respect to an initial orientation of the computing device  604  at the time the user touches the object  602 . Alternatively, the angle may be measured with respect to an initial orientation of the device when a user begins a telltale rotational movement, which generally coincides with a touch action (or other contact action), where such telltale movement may shortly follow contact in some cases and shortly precede contact in other cases. 
     Generally stated, to perform a rotation-based gesture, the user can hold the computing device  604  in a hand  606  (or two hands), touch the object  602 , and tilt the computing device  604 . That is, if the user wishes to increase the rate of behavior by a large amount, then the user will tilt the computing device  604  by a large amount with respect to the original orientation. If the user wishes to increase the rate of behavior by a smaller amount, then the user can tilt the computing device  604  by a smaller amount. The user can decrease the rate at any time by decreasing the tilt angle. In other cases, the IBSM  114  can also map different behaviors to different directions of rotation with respect to an initial tilt angle. For example, the user can zoom in on the object  602  by tilting the computing device  604  downward, and zoom out on the object  602  by tilting the computing device  604  upward. To prevent small inadvertent rate changes, the IBSM  114  can incorporate a range of initial tilt angles in which no change in rate occurs. If the user progresses beyond a threshold at the end of this dead band, the IBSM  114  begins to change the rate. Such a threshold can be defined in both directions of rotation with respect to the initial tilt angle. 
     The IBSM  114  can apply any type of function to map a tilt angle into a zoom amount (or whatever behavior is mapped to tilt angle). In one case, the IBSM  114  can apply a linear rate function. In another case, the IBSM  114  can apply a non-linear rate function of any type. For example, as to the latter case, the IBSM  114  can apply inertia-based functions, control system functions of any type, etc. 
     In the example of  FIG. 6 , the user can also apply a panning command to the content presented by the computing device  604 . For example, as described above, the user can touch one finger to the object  602  in conjunction with rotating the computing device  604  to a prescribed orientation. This may enlarge a portion of the content associated with the object  604 . Simultaneously, or in interleaved fashion, the user can use his or her other hand (or the same hand) to pan the content in a lateral direction, e.g., by touching a finger to the content and moving the finger in a desired direction. The embodiment of  FIG. 6  accommodates this type of complex control because it leaves one hand of the user free to make panning-type gestures (or any other type of meaningful gesture or input command). If performed in an interleaved fashion, this example is also a demonstration of how one gesture (zooming by rotating the device) can be seamlessly integrated with another gesture (such as panning by moving a finger across the display surface). 
     In yet other cases, the user can perform the rotational movement described above without designating any particular object on the display surface. In response, the IBSM  114  can apply the zooming (or any other prescribed behavior) to all of the content presented on the display surface, or to any other global content that is appropriate in the context of an environment-specific scenario. 
       FIG. 7  shows a similar concept to the scenario of  FIG. 6 . Here, a user holds a computing device  702  in one hand  704  (where, in this particular case, the user is not touching any part of the display surface with the hand  704 ). The user then manipulates a scroll mechanism  706  with his or her other hand  708 . To clarify the depiction,  FIG. 7  indicates that the scroll mechanism  706  is associated with an explicit scroll handle. But in other cases, the scroll mechanism can be invoked by touching and moving any content presented on the display surface. This behavior executes a conventional scrolling operation. In addition, the user can tilt the computing device  702  from an initial position to increase and decrease the rate at which scrolling is performed. The scenario shown in  FIG. 7  provides good user experience because it provides a convenient means for quickly advancing through long content items, yet also provides a means for more slowly advancing through a content item when so desired. 
     In the examples of  FIGS. 6 and 7 , the computing devices ( 604 ,  702 ) provide behavior which is governed by the orientation of the devices ( 604 ,  702 ) with respect to an initial starting position. In addition, or alternatively, a computing device can provide behavior which is responsive to the rate at which a user rotates the device or performs some other telltale movement. For example, in the example of  FIG. 6 , the user can touch the object  602  with one finger and tip the computing device  604  in the downward direction as shown. The IBSM  114  interprets the rate at which the user performs this tipping movement as indicative of the rate at which some prescribed behavior is to be performed. For example, if the user rapidly tips the computing device  604  in the downward direction (in the manner of casting a line with a fishing rod), the IBSM  114  can rapidly increase (or decrease) a zoom level. Or assume that the object  602  is associated with a scroll command. The IBSM  114  can interpret the user&#39;s “line-casting” action as indicative of a request to rapidly scroll through a large document. For example, the user can repeatedly snap the device downward in the illustrated manner to make successive large jumps through a long document (or alternatively, to make discrete jumps to the beginning or end of a document). In this mode of illustrative behavior, the IBSM  114  can be configured to ignore the motion of the computing device when the user returns the computing device back to an initial position after completing a downward snap. 
       FIG. 8  shows a scenario that incorporates the rotational movement shown in  FIG. 5 . Here, assume that the user&#39;s intent is to apply a finger to mark an original page, advance to another page in a document, and then move back to the original page. To do so, the user may hold a computing device  802  in a hand  804 . The user may place a finger  806  on a tab  808  to designate a particular page or other location within a multi-part content item. Assume that the user then flips through subsequent pages or other parts of the multi-part content item. To move back to the original page, the user can flip the computing device  802  up in the direction the arrow  810 , in the manner that one might flip over pages of a book. This restores the original page on the display surface of the computing device  802 . 
     The above scenario can be varied in any number of ways. For example, the tab  808  can be located in a different location on the display surface or entirely eliminated in favor of some other visual aid. Alternatively, the computing device  802  can eliminate all such permanent visual aids. Alternatively, or in addition, the computing device  802  can use a visual, audio, and/or haptic feedback indicator, etc. that is dynamically invoked when the user places a finger on the display surface in a manner that is interpreted as a bookmark. The computing device  802  can also provide any type of appropriate visual experience which conveys the page-flipping action to the user, e.g., by displaying a visual simulation of pages being flipped. Further, as set forth below, the interaction illustrated by  FIG. 8  can be realized on a dual-screen device; here, the user may hold one device part while rotating the opposite device part to invoke the “flip back” behavior. 
     The flipping gesture shown in  FIG. 8  can be used to achieve other flipping behavior on the display surface, e.g., as defined by a particular environment or application. In one merely illustrative case, assume that the display surface of the computing device  802  displays an object  812  of any type that has plural sides, dimensions, facets, etc. The user can advance to another side by executing the flipping motion shown in  FIG. 8 . This has the effect of tipping the object  812  on its side to display a new top portion of the object  812 . The user can also perform this type of behavior to switch between different applications, options, filters, views, or the like. The user can also perform this type of behavior to remove a first object which is presented on top of a second, underlying, object. That is, a user can rapidly tilt the computing device  802  to move the overlying object to one side of the underlying object, thereby revealing the underlying object(s), and thus making operations on layered objects simple and intuitive. The user can repetitively perform this tilting operation to successively rotate an object by a certain amount (where the amount can be defined in an application-specific manner), or to successively remove layers, etc. 
       FIG. 9  shows the same basic page-flipping gesture explained above with respect to  FIG. 8 , but in this case in the context of an ebook reader-type computing device  902 . Here, the user may stick his or her thumb  904  (or other finger) on the lower left margin of a display surface of the computing device  902  (or at some other location). This bookmarking operation marks an original page. Then, again assume that the user electronically flips through subsequent pages of a document. In one case, to return to the original page, the user can then flip one device part of the reader-type computing device  902  up in the manner shown in  FIG. 8 . The IBSM  114  can detect this telltale flipping gesture based on motion-sensing input mechanisms. Alternatively, or in addition, the IBSM  114  can detect this gesture based on the movement of the two display parts ( 906 ,  908 ) with respect to each other, e.g., as detected from an angle sensor (which detects the angle between the device parts). 
     In another case, to enable the IBSM  114  to more clearly discriminate a page-turning gesture, the user may close the two device parts ( 906 ,  908 ) of the computing device  902 , pinching his or her thumb  904  (or other finger) between the two device parts ( 906 ,  908 ) in the manner shown. The user may then execute the flipping motion described above to return to the original page. The computing device  902  can determine that the user has closed the device parts ( 906 ,  908 ) around the thumb  904  by sensing the angle between the device parts ( 906 ,  908 ). Even without the flipping action described above, the act of placing a thumb placed between the two device parts ( 906 ,  908 ) serves a useful purpose of registering a bookmark location. 
       FIG. 10  shows a scenario in which the user holds a computing device  1002  in a hand  1004  and then points the computing device  1002  in the direction of some target entity, or some assigned proxy of the target entity. The user then may use the other hand  1006  (or the same hand) to identify some object  1008  (e.g., a document, command, etc.) on the display surface of the computing device  1002 . The IBSM  114  interprets this gesture as a request to send a copy of the object  1008  to the target entity, or to sync up the content and/or status of the object  1008  with the target entity, or to achieve any other application-specific objective vis-à-vis the object  1008  and the target entity. The IBSM  114  can determine the direction at which the computing device  1002  is pointed based on any type of movement-type input mechanism. The IBSM  114  can determine the relative location of target entities in different ways, such as by manually registering the location of the target entities in advance, automatically sensing the location of the target entities based on signals emitted by the target entities, automatically sensing the location of the target entities based on image capture techniques executed by the computing device  1002  itself, and so forth. Alternatively, or in addition, the IBSM  114  can determine the orientation of the computing device  1002 ; the complementary IBSM of a target computing device can also determine the orientation of that target device. The IBSM  114  can then determine that the computing device  1002  is pointed towards the target computing device by determining whether the respective users are pointing their devices towards each other. In other cases, one or more users may be pointing at a shared target object, and the IBSM(s) of the respective computing device(s) can detect this fact in any of the ways described above. For example, the shared target object may correspond to a shared peripheral (e.g., a printer, a display device, etc.). 
     In one example of the scenario shown in  FIG. 10 , the user can select a file (or other content item) by touching a representation of the file on the display surface. The user can then point the device towards a trash bucket in order to delete the file (where it is assumed that the location of the trash bucket has been previously registered, or is otherwise determinable in one or the ways described above). In a variation, the user can touch the representation of the file on the display surface and tilt the computing device  1002  toward a trash icon on the display surface itself, therefore metaphorically shifting the file into the trash bucket. Many other applications are possible. In one case, the IBSM  114  can present a visual representation of an undo command whenever it deletes a content item in this manner. This enables the user to reverse the effect of unintended deletions. 
       FIG. 11  shows another scenario in which the user holds a computing device  1102  in a hand  1104  and moves the computing device  1102  so that it contacts a finger of the user&#39;s other hand  1106  or other portion of the other hand  1106 . This is in contrast to the conventional movement in which a user uses the hand  1106  to press down on the display surface of the computing device  1102 . The IBSM  114  can correlate any type of command with this movement. This type of gesture can be coupled with various safeguards to prevent its inadvertent activation. For example, although not shown, the user can apply the thumb of the left hand  1104  to make contact with an icon or the like which enables this particular gestural mode. 
     In another case (not illustrated), the user can tap down on different objects on the display surface with different degrees of vigor, e.g., with a normal amount of force or with a large amount of force. The IBSM  114  can interpret these two types of touch contacts in a different manner. The IBSM  114  can then perform a first type of behavior for a gentle tap and a second type of behavior for a hard tap. The behaviors that are invoked are application-specific. For example, an application could use a gentle tap to answer an incoming call, and a hard tap to ignore that call. Or an application can use a light tap to mute the ringer and a hard tap to outright ignore the call. 
     To enable this type of gesture, the movement-type input mechanism(s)  110  can provide, for example, input events that correspond to gently resting a finger on the display surface, tapping the display surface with “normal” force, and vigorously tapping the display surface. The IBSM  114  can then examine the input signals associated with these input events to classify the type of input action that has taken place. For example, the IBSM  114  can interpret input events having large-magnitude signal spikes as indicative of a hard-tapping gesture. In addition, or alternatively, the IBSM  114  can use audio signals (e.g., received from one or more microphones) to discriminate between gentle tapping and hard tapping, and/or signals received from any other input mechanism(s) (such as pressure sensor(s), etc.). 
     In a related case, the IBSM  114  can discriminate different types of drag movements based on the degree of force with which the user initially applies a finger to the display surface. This allows, for example, the IBSM  114  to discriminate between a light swipe versus vigorously rapping the screen and dragging. The IBSM  114  can again map any behaviors to different types of tap-and-drag gestures. 
       FIG. 12  describes another scenario in which the user holds a computing device  1202  that has two device parts ( 1204 ,  1206 ) in a hand  1208 . With the other hand  1210 , the user touches the display surfaces provided on the two device parts ( 1204 ,  1206 ), with a prescribed angle  1212  between the two device parts ( 1204 ,  1206 ). The IBSM  114  can map this gesture into any type of behavior. Variations of this gesture can be defined by dynamically changing the angle  1212  between the two device parts ( 1204 ,  1206 ) and/or dynamically changing the positions of the finger and thumb placed on the display surfaces of the two device parts ( 1204 ,  1206 ). 
       FIG. 13 , in scenario A, describes a more general gesture in which a user uses a hand  1302  to place an idiosyncratic combination of fingers  1304  on the display surface of a computing device  1306 . With the other hand  1308 , the user may proceed to move the computing device  1306  in any telltale manner, such as by shaking the computing device  1306  in a particular direction. The computing device  1306  is unlikely to confuse this gesture with incidental motion of the computing device  1306  due to the presence of the idiosyncratic multi-touch touch gesture. The user can also apply different multi-touch gestures in conjunction with the same basic motion to convey different commands. 
     Moreover, to repeat, the user can apply any prescribed type of contact to an individual object or particular region on the display surface and then apply a prescribed movement to the computing device. The combination of focused contact and movement helps discriminate deliberate gesture-based movement from accidental movement. For example, as shown in scenario B of  FIG. 13 , the user can touch an object  1310  on the display surface of a computing device  1312  and then vigorously shake the computing device  1312 . The IBSM  114  can interpret this action in any predetermined manner, such as a request to delete the designated object  1310 , undo the last action that was taken on the designated object  1310 , move the designated object  1310  to a particular folder, shuffle the object  1310  so that it is displayed in the foreground, and so on. 
     In another case, the user can touch an object on the display surface, upon which the IBSM  114  provides a menu. While still touching the display surface, the user can then apply a telltale movement to the computing device. The IBSM  114  can interpret this joint action as a request to enlarge the menu, or to select a particular option from the menu. Note that this approach integrates three steps into a single continuous action: (1) selecting an object; (2) activating a motion-sensing gestural mode; and (3) selecting a particular command or gesture to apply to the selected object(s). Other examples of select-and-move gestures were described above, e.g., with respect to the zooming, scrolling, and page-turning examples. 
     Further, the IBSM  114  can interpret dynamic motion gestures in a different manner based on the orientation of the computing device. For example, in a first scenario, assume that the user holds a computing device in his or her hands and shakes its back and forth. In a second scenario, assume that the user lays the computing device on a table and shakes it back and forth, while the device is lying prone. The IBSM  114  can interpret these two scenarios as conveying two distinct types of gestures. Further, the IBSM  114  can interpret movement-based gestures in the context of whatever application(s) the user is interacting with at the moment. For example, the IBSM  114  can interpret the same movement-type gesture in different ways when it is performed in the context of two respective applications. 
     Finally,  FIG. 14  shows a scenario in which the user wishes to rotate a computing device  1402  from landscape mode to portrait mode (of vice versa) without causing the content presented the computing device  1402  to also rotate. To perform this task, the user can touch any portion of the display surface, such as (but not limited to) a corner  1404 . For example, the user can press down on the display surface while the computing device  1402  lies on a flat surface, such a table, as indicated by the gesture made with the hand  1406 . Or the user can pinch the computing device while holding the computing device  1402 , as indicated by the gesture made with the hand  1408 . The user then rotates the computing device  1402  by approximately 90 degrees (or some other application-specific rotational amount). In one implementation, upon recognizing this gesture, the IBSM  114  can prevent the computing device  1402  from automatically rotating the text. This same behavior can be performed in reverse. That is, as a default, the computing device  1402  will not rotate the content when the computing device  1402  is rotated. Placing a contact on the display surface while rotating the computing device  1402  will then cause the content to also rotate. Rotation can be performed about any axis, such an axis defined by the contact point itself. 
     In another example, the user can establish a contact point and then rotate the computing device, but without moving the computing device relative to the finger(s) which establish the contact point. For example, the user can pinch the computing device to establish a contact point and then lie down on a couch or bed, and, in doing so, rotate the computing device approximately 90 degrees with respect to its initial orientation. In this case too, the IBSM  114  can interpret the device movement together with the application of the contact point as an instruction to disable (or enable) content rotation. 
     In one case, a computing device can maintain a rotation lock after the computing device is moved to the appropriate orientation, even when the user removes the contact point. When finished operating in this mode, the user can then expressly activate a command which removes the rotation lock. In addition, or alternatively, the user can change the orientation of the device to automatically remove the rotation lock. 
     A.3. Background-Related Movement 
     This section describes the operation of the IBSM  114  when the movement applied to the computing device  100  is not a deliberate component of an intentional gesture, and therefore constitutes background movement. The IBSM  114  can interpret the nature of this movement and then act on it to enhance the accurate analysis of an input action. The examples presented in this section are representative, not exhaustive. 
       FIG. 15  shows a first scenario in which a user uses a finger  1502  of a hand  1504  to press down on a display surface of a computing device  1506 . Or assume that the user removes the finger  1502  from the display surface. In response to this action, the IBSM  114  receives touch input events from the touch input mechanism(s)  106 . These events register the actual (or imminent) contact of the finger  1502  with the display surface, or the removal of that contact. The IBSM  114  also receives movement input events from the movement-type input mechanism(s)  110 . These events register motion that is inadvertently caused when the user applies or removes his finger  1502  from the display surface. 
     A first input interpretation module  1508  can analyze the touch input events, e.g., by determining, from its perspective, the position and timing at which a touch contact is applied or removed. The first input interpretation module  1508  bases its conclusion primarily on the extent (and/or shape) of contact between the user&#39;s finger and the display surface. A second input interpretation module  1510  can analyze the movement input events, e.g., by also determining, from its perspective, the position and timing at which a touch contact is applied or removed, together with any jostling that may have occurred in the process. This is possible because the position and timing at which touches are applied and removed can also be inferred from the movement input events. More specifically, the second input interpretation module  1510  bases its conclusion, in part, on the magnitude, the general shape, and frequency characteristics of the movement signals provided by the movement-type input mechanism(s)  110 . This can help pinpoint when the contact has been applied or removed. The second input interpretation module  1510  can also base its conclusion on the manner in which the computing device moves upon the application or removal of a touch. This can help distinguish the position at which the contact is being applied or moved. For example, if the user holds the computing device upright and taps down on a corner, the computing device can be expected to rock in a telltale manner which is indicative of the location at which touch has occurred. 
     A final input interpretation module  1512  can then use the conclusions of the second interpretation module  1510  to modify (e.g., to correct) the conclusions of the first interpretation module  1508 . For example, the final input interpretation module  1512  can conclude that a touch was applied at a true location (x, y), but because of inadvertent movement associated with the application of the touch, there was movement to a position (x+Δx, y+Δy). A similar inadvertent movement can occur when the user removes his finger. Alternatively, or in addition, the final input interpretation module  1512  can adjust the timing at which touch is considered to have been applied or removed. As another example, if a contact is registered with little or no associated movement signal, the final input interpretation module  1512  may conclude that the contact likely represents inadvertent contact with the display surface. The IBSM  114  can thus ignore this contact or otherwise treat it differently than “normal” contact actions. 
     The IBSM  114  can take various actions on the basis of the conclusions reached by the final input interpretation module  1512 . In one case, the IBSM  114  can correct touch input events to account for accidental movement that has been detected, e.g., by refining an indication of a location and/or timing at which the user has applied or removed a touch contact. In addition, the IBSM  114  can restore the display surface and/or an application to a state prior to the time at which any inadvertent movement may have taken place. 
     In the case of  FIG. 15 , plural component interpretation modules feed conclusions into the final interpretation module  1512 . But in another implementation, the final interpretation module  1512  can perform analysis on raw input events provided by the input mechanisms, that is, without the component interpretation modules. 
     The basic functionality of  FIG. 15  can also be used to enhance the recognition of gestures. For example, a flicking-type movement may resemble a quick scrolling action (from the perspective of the nature of contact that is made with the display surface), yet the user may perform these two actions to convey different input commands. To help discriminate between these two input actions, the IBSM  114  can interpret the resultant contact input events in conjunction with the movement input events. The movement input events can help distinguish between the two input actions insofar as a flicking motion has a different motion profile than a scrolling operation. 
     The IBSM  114  may also use the motion signals to detect different ways of articulating a particular action, such as scrolling with the thumb of the hand that is holding the computing device, versus scrolling using the index finger of the opposite hand. Such situations, when detected, may be used to optimize the user&#39;s interaction with the computing device, e.g., by enabling the IBSM  114  to more accurately discriminate the user&#39;s input actions. For example, the computing device can adjust its interpretation of input events based on its understanding of what finger is being used to contact the computing device, e.g., by allowing greater forgiveness for off-axis motions when it is determined that the user is scrolling with a thumb. 
     In another example, IBSM  114  can determine the fingers that the user is using when typing on a soft (touch screen) keyboard. In one case, the user may type with two thumbs. In another case, the user may type with a single finger while holding the device with the opposite hand. These two modes have different respective movement profiles that describe the key strikes. The IBSM  114  can use the different movement profiles to help infer which method the user has employed to strike a given key. The IBSM  114  can then apply an appropriate Gaussian distribution when interpreting each type of touch contact. This may improve the efficiency of touch screen typing while reducing the likelihood of errors. 
     The functionality of  FIG. 15  can also be used to detect input actions that are entirely accidental. For example, in some cases, legitimate input events may have one or more prescribed movement profiles, while inadvertent input events may have one or more other prescribed movement profiles. For example, a “clean” tap on the display surface with an index finger may have a profile which is indicative of a legitimate input activity, while an accidental contact with the display surface may have a profile which is indicative of an inadvertent input activity, e.g., which may be caused by a thumb or pinky finger brushing up against the display surface. 
       FIG. 16  shows another scenario in which the user picks up a computing device  1602  with a hand or sets the computing device  1602  down after use. In the particular example of  FIG. 16 , the user is in the process of placing the computing device  1602  into a pocket  1604  with a hand  1606 . In this circumstance, the IBSM  114  may receive movement input events from the movement-type input mechanism(s)  110  that exceed a prescribed threshold in a temporal window. The input events may also reveal that the device has been moved to an unusual viewing posture. The large movement input events are produced because the user has likely rapidly moved and tumbled the computing device  1602  through space to place the computing device  1602  into the pocket  1604 . Also assume that the user inadvertently touches the display surface of the computing device  1602  in the process of placing the computing device  1602  into the pocket  1604 . If so, the IBSM  114  can conclude (based on the large movement input events, and optionally other factors) that the touch input events are likely inadvertent. The computing device  1602  may also include a light sensor and/or proximity sensor which can independently confirm the fact that the computing device  1602  has been placed in the pocket  1604 , e.g., when the light sensor suddenly indicates that the computing device  1602  has been moved to a darkened environment. The IBSM  114  can then respond to the touch input events by ignoring them. Further, as stated above, the IBSM  114  can restore the display surface to a state prior to the inadvertent input action. In addition, or alternatively, the IBSM  114  can restore a prior application state. 
     For example, assume that the user touches the display surface of the computing device in the course of placing the device in his pocket. The IBSM  114  may be able to conclude on the basis of the movement alone that the touch was inadvertent. The device can then “undo” any command triggered by the inadvertent touch. If the movement is not sufficiently informative, the IBSM  114  can conclude on the basis of the output of the light sensor and/or other sensors that the touch was inadvertent. The computing device  1602  can then again remove the effect of the inadvertent contact. 
     In another scenario (not shown), the user may be operating the computing device  1602  in a noisy environment (e.g., a non-steady environment), such as on a bumpy bus ride or the like. In this case, the IBSM  114  can analyze the movement input events to determine regular perturbations of the computing device  1602 , indicative of a noisy environment. To address this situation, the IBSM  114  can perform the actions described above, such as by ignoring parts of touch input events that are assessed as accidental, as well as restoring a display state and/or application state(s) to remove erroneous changes. In addition, or alternatively, the IBSM  114  can attempt to modify the touch input events to subtract out the background noise associated with the movement input events. In addition, or alternatively, the IBSM  114  can decrease the sensitivity at which it indicates that a valid touch event has occurred. This will force the user to be more deliberate in accurately entering intentional touch input events. But this will also have the desirable effect of more effectively ignoring inadvertent input events caused by the noisy environment. 
       FIG. 17  shows a scenario in which the user holds a computing device  1702  in a hand  1704  during use. In this case, the user&#39;s thumb  1706  may inadvertently contact the display surface of the computing device  1702 . In contrast,  FIG. 18  shows a scenario in which the user rests a computing device  1802  flat on a table or the like. The user then uses a hand  1804  to press down an index finger  1806  in the lower left corner of the display surface of the computing device  1802 . The IBSM  114  can examine the respective orientations of the computing devices ( 1702 ,  1802 ) and conclude that the thumb placement that occurs in  FIG. 17  is more likely to be inadvertent compared to the finger placement shown in  FIG. 18 , even though these contacts occur in the same region of the display surface and may have similar shapes. This is because it is natural for the user to hold the computing device  1702  in the manner shown in  FIG. 17  when holding it aloft. But it is less likely to accidently place a single finger on the display surface when the computing device  1802  is lying prone in the manner shown in  FIG. 18 . The above-described motion analysis can help confirm conclusions based on orientation. In addition, one or more other sensors (such as a light sensor, a proximity sensor, etc.), if placed at appropriate location(s) on the computing device  1802 , can help determine whether a computing device is lying flat on a table in the manner shown in  FIG. 18 . The IBSM  114  can address the accidental touch shown in  FIG. 17  in any of the ways described above, such as by ignoring the touch input events. 
     In the case of  FIG. 17  (and, in fact, in all scenarios), the IBSM  114  can also take other contextual factors into account when interpreting contact input events and movement input events. One such contextual factor is the application with which the user is interacting when the input events occur. For example, assume that a first user is reading content using a book reader type device and then places a thumb on a certain part of the page. Assume that a second user is scrolling through a web page and places a thumb in the same general part of the page. The IBSM  114  may be more likely to interpret the thumb placement as intentional for the first scenario compared to the second scenario. This is because the user may have placed his or her thumb on the page in the first scenario to bookmark that page. Furthermore, the cost of mistakenly bookmarking a page is negligible, whereas the cost of accidentally scrolling or flipping to another page is high in terms of the disruption to the user&#39;s current task. 
     In another dual-screen scenario, the IBSM  114  can use the movement input mechanisms to sense the orientation at which the user is holding the computing device. The determined orientation may fit a profile which indicates that the user is looking at one display part, but not another. That is, the user may have oriented the computing device to optimize interaction with just one of the display parts. In response, the IBSM  114  can place the presumed unused display part in a low-power state. Alternatively, or in addition, the IBSM  114  can rely on other input mechanisms to determine which display part the user is viewing, such as the image sensing input mechanisms  112 . Alternatively, or in addition, in some situations, the IBSM  114  can be configured to ignore input events that are received via an unused display part, classifying them as unintended contacts. 
     Generally, the IBSM  114  can implement the above-described scenarios in different ways. In one case, the IBSM  114  can maintain a data store that provides various profiles that describe the telltale input characteristics of various known actions, including both intentional and unintentional actions. The IBSM  114  can then compare the input events associated with an unknown input action against the data store of pre-stored profiles to help diagnose the unknown input action. The data store can also include information which indicates behavior that may be executed to address the input action, once diagnosed. 
     Alternatively, or in addition, the IBSM  114  can apply any type of algorithmic technique to combine the contact input events with the movement input events. For example, the IBSM  114  can apply a formula which indicates the probable location of a touch contact on a display surface based on movement input events; the IBSM  114  can then apply another formula which indicates how this position (assessed based on movement alone) can be used to correct a position that is assessed based on contact input events. The nature of such algorithms is device-specific and can be developed based on theoretical analysis and/or experimental analysis. 
     B. Illustrative Processes 
       FIGS. 19 and 20  show procedures ( 1900 ,  2000 ) that explain the operation of the computing device  100  of  FIG. 1  in the foreground and background modes of operation described in Section A, respectively. Since the principles underlying the operation of the computing device have already been described in Section A, certain operations will be addressed in summary fashion in this section. 
       FIG. 19  shows a procedure  1900  for controlling the computing device  100  in response to an intentional movement of the computing device  100 . In block  1902 , the IBSM  114  receives first input events from one or more contact-type input mechanisms. In block  1904 , the IBSM  114  receives second input events from one or more movement-type input mechanisms. The second input events are indicative of movement of the computing device in an intentional manner. The right margin of  FIG. 19  enumerates some possible intentional movements that may take place. More generally, blocks  1902  and  1904  can be performed in any order, and/or these operations can overlap. In block  1906 , the IBSM  114  interprets, if possible, the intentional gesture that the user has made based on the first input events and the second input events. In block  1908 , the IBSM  114  applies a behavior that is correlated with the intentional gesture that has been detected. In this sense, the interpretation performed in block  1906  enables the behavior to be executed in block  1908 , where the operations of blocks  1906  and  1908  can be performed by the same component or by different respective components. The right margin of  FIG. 19  enumerates a few behaviors that may be invoked. 
     The feedback loop shown in  FIG. 19  indicates the IBSM  114  repeatedly analyzes the input events over the temporal progression of an input action. In the course of the input action, the IBSM  114  can increase the confidence at which it detects the nature of the input action. At first, the IBSM  114  may be unable to diagnose the nature of the input action. As the action proceeds, the IBSM  114  may then be able to predict the action with a relatively low degree of confidence, and it may, in fact, incorrectly interpret the input action. As the input action proceeds further, the IBSM  114  increases its confidence and, if possible, eventually correctly determines the type of input action that has taken place. Or the IBSM  114  can abandon an interpretation that is no longer supported by the input events that are being received. The IBSM  114  can “back out” of any incorrect assumptions by restoring the display surface and/or any application to a pre-action state in the manner described above. 
       FIG. 20  describes a procedure  2000  for controlling the computing device  100  in response to unintentional movement of the computing device  100 . In block  2002 , the IBSM  114  receives first input events from one or more contact-type input mechanisms. In block  2004 , the IBSM  114  receives second input events from one or more movement-type input mechanisms in response to movement of the computing device  100 . More generally, blocks  2002  and  2004  can be performed in any order, and/or these operations can overlap. The movement in this case is indicative of background movement of the computing device  100 , meaning movement that is not the active focus of the user. The right margin of  FIG. 20  enumerates some of the possible background movements that may occur. In block  2006 , the IBSM  114  detects a type of input action that has taken place based on the first input events and the second input events, in optional conjunction with other factors. In effect, the second input events modify or qualify the interpretation of the first input events. In block  2008 , the IBSM  114  can apply appropriate behavior in response to the detection of the type of input events in block  2006 . The operations of blocks  2006  and  2008  can be performed by the same component or by different respective components. The right margin of  FIG. 20  enumerates some of the possible behaviors that the IBSM  114  may execute. 
     In a similar manner to that set forth for  FIG. 19 , the feedback loop shown in  FIG. 20  indicates that the IBSM  114  can repeat its analysis throughout the course of an input action to progressively improve the confidence of its analysis. 
     C. Representative Processing Functionality 
       FIG. 21  sets forth illustrative electrical data processing functionality  2100  that can be used to implement any aspect of the functions described above. With reference to  FIG. 1 , for instance, the type of processing functionality  2100  shown in  FIG. 21  can be used to implement any aspect of the computing device  100 . In one case, the processing functionality  2100  may correspond to any type of computing device that includes one or more processing devices. In all cases, the electrical data processing functionality  2100  represents one or more physical and tangible processing mechanisms. 
     The processing functionality  2100  can include volatile and non-volatile memory, such as RAM  2102  and ROM  2104 , as well as one or more processing devices  2106 . The processing functionality  2100  also optionally includes various media devices  2108 , such as a hard disk module, an optical disk module, and so forth. The processing functionality  2100  can perform various operations identified above when the processing device(s)  2106  executes instructions that are maintained by memory (e.g., RAM  2102 , ROM  2104 , or elsewhere). 
     More generally, instructions and other information can be stored on any computer readable medium  2110 , including, but not limited to, static memory storage devices, magnetic storage devices, optical storage devices, and so on. The term computer readable medium also encompasses plural storage devices. In all cases, the computer readable medium  2110  represents some form of physical and tangible entity. 
     The processing functionality  2100  also includes an input/output module  2112  for receiving various inputs from a user (via input mechanisms  2114 ), and for providing various outputs to the user (via output modules). One particular output mechanism may include a display mechanism  2116  and an associated graphical user interface (GUI)  2118 . The processing functionality  2100  can also include one or more network interfaces  2120  for exchanging data with other devices via one or more communication conduits  2122 . One or more communication buses  2124  communicatively couple the above-described components together. 
     The communication conduit(s)  2122  can be implemented in any manner, e.g., by a local area network, a wide area network (e.g., the Internet), etc., or any combination thereof. The communication conduit(s)  2122  can include any combination of hardwired links, wireless links, routers, gateway functionality, name servers, etc., governed by any protocol or combination of protocols. 
     Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.