Abstract:
Technologies relating to manipulating visual representations of data. A method is provided that includes displaying a first visual representation including a zoom parameter having a first value; receiving a first input while maintaining a first position of a cursor relative to the first visual representation; modifying the zoom parameter to have a second value, where the first visual representation of the document is adjusted according to the second value to provide a second visual representation; identifying a change in position of the cursor to a second position relative to the second visual representation; receiving a second input to modify the zoom parameter of the second visual representation; and modifying the zoom parameter to have a third value, where the second visual representation of the document is adjusted relative to the second position of the cursor according to the third value to provide a third visual representation of the document.

Description:
BACKGROUND 
       [0001]    The present disclosure relates to user interfaces and data visualization. 
         [0002]    There exists a wide variety of data, e.g., text, raster images, vector images, and combinations thereof, that can be displayed on various display devices. Computer applications are widely used to display and manipulate such data. Commonly, these data can be referred to as documents that include content of different kinds A user of a computer system can access content of documents that are stored locally or remotely. Computer systems generally provide a graphical user interface (GUI) that provides windows of the kind that allow applications to display content in a display pane. Tools that allow the user of a computer to move comfortably through the text of an electronic document or an image display are important and are included in various forms in GUI applications. 
         [0003]    Viewing specific content becomes more challenging with increasing amounts of document content. For example, large text documents require frequent scrolling in order to move to parts of the document that are hidden from the current view. As a result, with large documents, a user has to adjust display parameters of the document and/or the display parameters of a corresponding application window in order to move to different sections of the document. This is necessary because the scale at which a document can be displayed in the user interface in its entirety is usually very different from the scale that facilitates useful interaction with the document contents. The process of moving document contents in an application window is typically referred to as “scrolling.” The presentation of the document may be linear, i.e., the user accesses document contents in an essentially sequential order from the beginning to the end of the document. Alternatively, the presentation of the document may also be non-linear, as for example often seen with hyperlinked documents (e.g., common web pages) that link certain parts of the document to certain parts of the same or other documents and that enable the user to quickly access and jump back and forth between certain parts of the document. 
         [0004]    Common scrolling techniques include scrolling line by line or page by page in a document (or at discrete intervals in documents, such as vector graphics documents, that do not feature inherent elements like a line raster or a pixel raster), for example, performed in response to a key stroke or the use of a scroll wheel of a pointing device such as a mouse. Alternatively, scrolling can be performed in response to a combination of inputs, for example, clicking a button of a pointing device and moving the pointing device, dragging the document along. Specific user interface elements, e.g., scroll bars, can also be used to perform scrolling. A scrollbar can be used by pointing and clicking the pointing device, in connection with or without movement of the pointing device. In connection with scrolling content, and also known from other GUI elements, a function commonly referred to as “autoscroll” serves to scroll the document into the direction indicated by the position of the mouse cursor. 
       SUMMARY 
       [0005]    This specification describes technologies relating to manipulating visual representations of data. In general, one aspect of the subject matter described in this specification can be embodied in methods that include the actions of displaying a first visual representation of a document, the first visual representation having one or more representation parameters including a zoom parameter having a first value; receiving a first input while maintaining a first position of a cursor relative to the first visual representation; modifying the zoom parameter to have a second value in response to the first input, where the visual representation of the document is adjusted according to the second value of the zoom parameter to provide a second visual representation; identifying a change in position of the cursor to a second position relative to the second visual representation; receiving a second input to modify the zoom parameter of the second visual representation; and modifying the zoom parameter to have a third value, where the second visual representation of the document is adjusted relative to the second position of the cursor according to the third value of the zoom parameter to provide a third visual representation of the document. Other embodiments of this aspect include corresponding systems, apparatus, and computer program products. 
         [0006]    These and other embodiments can optionally include one or more of the following features. The method further includes displaying a visual guide in the second visual representation, the visual guide identifying the first visual representation relative to the second visual representation. The method further includes moving the visual guide in response to identifying change in position of the cursor. The method further includes receiving an input to modify a size of the visual guide to provide a modified visual guide and using the modified visual guide to determine the third value of the zoom parameter. 
         [0007]    Modifying the zoom parameter to have a second value further includes determining a first target zoom level for zooming out. Modifying the zoom parameter to have a third value further includes determining a second target zoom level for zooming in. Receiving a first input includes receiving an input to an input device and determining whether a threshold time has elapsed without an additional input to the input device. The method further includes automatically scrolling the second visual representation when the position of the cursor moves to specific areas or across specific areas in the user interface. 
         [0008]    Particular embodiments of the subject matter described in this specification can be implemented to realize one or more of the following advantages. When viewing documents, users often access different parts of the document. Users can view different parts of a document in a quick and easy manner by providing a quick and intuitive way of presenting document contents at different levels of detail. The level of detail associated with one specific scale (or specific scale range) allows for viewing of document contents. The level of detail associated with another specific scale (or specific scale range) allows for presenting a quick overview and repositioning of the view of the document in order to view a different portion of the documents and the corresponding contents. Thus, a user can quickly transition from one level of detail to the other level of detail. In particular, only simple and intuitive user interaction is necessary for changing between the two specific zoom ranges (or scale ranges). 
         [0009]    Furthermore, the techniques disclosed can be integrated into already existing tools. The method can be easily integrated with, for example, a “grabber hand” tool, which is a common tool used in a number of applications. The techniques can be integrated with other tools as well, e.g., “drag and drop” tools or “pointer” tools that are integrated in a user interface of an operating system or application. The techniques can also be integrated into tools that operate across multiple applications or platforms. 
         [0010]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the invention will become apparent from the description, the drawings, and the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1A  is a screenshot showing an example user interface displaying an initial view of a document. 
           [0012]      FIG. 1B  is a screenshot showing the example user interface displaying the document and visual guides after zooming out. 
           [0013]      FIG. 1C  is a screenshot showing the example user interface displaying the document and the visual guides while scrolling. 
           [0014]      FIG. 1D  is a screenshot showing the example user interface displaying the document and visual guides after zooming in. 
           [0015]      FIG. 2  is a flow chart showing an example process for performing zooming and scrolling. 
           [0016]      FIG. 3  is a flow chart showing an example process for determining an operating mode. 
           [0017]      FIG. 4  is a flow chart showing an example process for determining a zoom factor. 
           [0018]      FIG. 5  is a flow chart showing an example process for performing zooming. 
           [0019]      FIG. 6  is a schematic diagram of a generic computer system. 
       
    
    
       [0020]    Like reference numbers and designations in the various drawings indicate like elements. 
       DETAILED DESCRIPTION 
       [0021]      FIG. 1A  is a screenshot  101  showing an example user interface displaying an initial view of a document  130  within an application window  100 . The display also shows a cursor  110  (e.g., corresponding to input received from a mouse or other input device). In particular, the cursor  110  is shown having a form of a hand-shaped icon indicating a specific operating mode (e.g., a “grabber hand”). The application window  100  can include a number of elements, e.g., a title bar, menus, and toolbars including one or more control buttons. The operating mode as well as the particular menus and toolbar elements can vary depending on the particular application presented in application window  100 . 
         [0022]    The contents of the document  130  (e.g., document text  140  and document images  150 ) are only partially displayed due to a size of the document  130  and a scale at which the document is displayed. The particular scale can be selected in order to provide a particular level of magnification to the user in order to perform one or more operations relative to the document  130 . In particular, the document  130  is shown at a scale representing a zoomed-in level such that text and other contents of the document  130  are displayed at a high level of detail (e.g., the document text  140  and images  150  are clear). For example,  FIG. 1A  illustrates the document  130  at a scale  105  having a zoom value of 300%, which represents a scaling factor of three over a defined size of the document contents (e.g., points or pica for textual content, or centimeters, inches for other content). However, a small portion of the document  130  is visible in the application window  100 . 
         [0023]      FIG. 1B  is a screenshot  102  showing the example user interface displaying the document  130  within the application window  100  after zooming out. Additionally, visual guides  120  are displayed within the application window  100 . The visual guides  120  provide a frame that indicates the size and location of the previously displayed portion of the document  130  (e.g., the region bounded by the visual guides  120  represents the portion of the document displayed in the user interface when scaled to the level shown in  FIG. 1A ). One or more properties (e.g., form, shape, size, color, line style or weight, fill, and opacity) of the visual guides  120  can be adjustable. In some alternative implementations, visual guides are not displayed. 
         [0024]      FIG. 1B  illustrates a visual representation displaying a greater portion of the document  130  relative to the portion of the document  130  displayed in  FIG. 1A  according to their relative scales. In particular,  FIG. 1B  illustrates the document  130  at a scale  105  having a zoom value of substantially 50% representing a zoomed-out level at a scaling factor of 0.5 over a defined size of the document contents. In particular, the scale illustrated in  FIG. 1B  facilitates the display of a larger portion of the document  130  at a reduced level of detail—e.g., the document text  140  as shown in  FIG. 1B  is not rendered in enough detail due to the scaling, for a user to read the document text  140  However,  FIG. 1B  also illustrates an increased overall view of the document  130  and its contents, e.g., document text  140  and document images  150 . 
         [0025]      FIG. 1C  is a screenshot  103  showing the example user interface displaying the document  130  and visual guides  120  within the application window  100  after moving the visual guides  120 . The visual guides  120  have been moved, e.g., using the cursor  110 , to a different location within the document  130 . In relation to a center portion of two overleaf pages  134  shown in  FIG. 1B , the visual guides  120  have been moved to the previous overleaf pages  132 . The visual guides  120  indicate the portion of the document  130  that will be displayed after changing the scale to a zooming in level again. The greater portion of the document  130  presented by scaling to a zoomed out level enables the user to position the cursor  110  (and, therefore, the visual guides) to another location within the document  130 . The user can position the visual guides  120  to any location within the document  130 . Additionally, the visual guides  120  can be positioned at locations within the document  130  that are not shown (referred to as hidden portions of the document) within the displayed portion of the document  130 . Positioning the visual guides to hidden areas is described below in  FIG. 2 . 
         [0026]      FIG. 1D  is a screenshot  104  showing the example user interface displaying the document  130  within the application window  100  after zooming in at the location within the document  130  identified by the visual guides  120  in  FIG. 1C . In  FIG. 1D , similar to  FIG. 1A , the document  130  is, once again, shown at a scale representing a zoomed-in level such that text and other contents of the document  130  are displayed at a high level of detail (e.g., the document text  140  and images  150  are clear). The portion of the document  130  on display within the display pane  170  corresponds to the area indicated by the visual guides  120  in  FIG. 1C  before zooming in. In some implementations, a target zoom level, i.e., the size of the portion of the document to be displayed after zooming in, is adjusted according to additional input, for example, as described below in  FIG. 2 . 
         [0027]      FIG. 2  shows a flow chart of an example process  200  for manipulating a visual representation of a document. For convenience, the process  200  will be described with respect to a system that performs the process  200 . 
         [0028]    The system displays  210  document data. The document can be, for example, portable document format (PDF) files, word processor files, spread sheet files, raster image files, vector image files, and files including a combination of different data. An example document  130  containing document text  140  and document images  150  is shown in  FIGS. 1A to 1D . For convenience, a document as used in this specification refers to any displayed data including not only documents such as word processing documents but also includes visual representations of data such as visual representation of audio data (e.g., an audio waveform) and video data (e.g., as represented by a series of discrete screenshots). 
         [0029]    The document can be displayed as part of a particular application (e.g., a word processing application, a desktop publishing application, or a web authoring application). The display of the document includes a visual representation of some or all of the document contents. The contents can include, for example, text and images. Displaying the document includes providing the visual representation of the document contents at a specified scale (e.g., a zoom level). The scale level determines an amount of the document that is displayed in the visual representation. For example, a scale representing a zoomed-in level can present a smaller portion of the document within the visual representation while a scale representing a zoomed-out level that can present a larger portion of the document within the visual representation. 
         [0030]    The value of the scaling can be specified, e.g., as a relation in size between document contents as represented on a display and the same document contents as represented on a printout. For example, in a word processing application, a scale of 100% (or 1:1) indicates that document contents are displayed at the same scale as a defined size of the document contents (e.g., points, pica, inches, centimeters). A scale greater than 1.0 or 100% (e.g., 200% or 2:1) indicates magnification, i.e., zooming in. Similarly, a scale less than 1.0 or 100% (e.g., 50% or 1:2) indicates reduction, i.e., zooming out. Different scale amounts can allow a user to perform different document manipulations while reducing the efficiency or ability to perform other operations. For example, larger scales can allow a user to read and edit document contents while limiting the user&#39;s ability to navigate (scroll) to different portions of the document. Similarly, smaller scales facilitate navigation between different portions of a document while making editing or reading of document content difficult or impossible. 
         [0031]    The system receives  230  an input from an input device (e.g., a mouse or other input device for manipulating the cursor position) associated with changing the scale of the presented document. For example, the user can initiate a change in scale by clicking and holding a left mouse button in a particular operating mode (e.g., in the mode “grabber hand”) without changing the position of the cursor (e.g., without moving the mouse). 
         [0032]    The system determines  230  whether an additional input is received to move the cursor within a specified time period. The time period is specified such that the system determines whether the input is to change the operating mode or to manipulate the document in the current operating mode (e.g., to use the grabber hand to modify the position of the displayed portion of the document  130 ). 
         [0033]    In some implementations, the specified time is substantially 0.5 seconds or one second. Furthermore, the specified time can be adjusted by the user to accommodate for shorter or longer time periods. Additionally, the user can toggle the method on and off depending, e.g., on a specific workflow. 
         [0034]    If the system receives an input to move the cursor within the specified time period, the system does not change to current operating mode, but instead provides  220  the functionality associated with the current operating more (e.g., to use the grabber hand to modify the position of the displayed portion of the document  130 ). If the system does not receive an input within the specified time period (e.g., a timer expires without a movement input), the cursor (e.g., cursor  110 ) is altered to indicate a changed operating mode (e.g., “zooming grabber hand” mode). 
         [0035]    When the operating mode is changed, the system determines  235  a zoom factor and automatically adjusts  240  the view of the document to correspond to the determined zoom level so as to encompass a larger portion of the document. Additionally, the system optionally displays  245  visual guides (e.g., visual guides  120  of  FIG. 1B ). In some implementations, the mouse cursor  110  is not altered when the operating mode is changed. When the system receives  250  an input indicating a change back to the previous (or another) operating mode, the previous (or another) zoom level is restored  260  and the visual guides (e.g. visual guides  120 ) are no longer displayed  265 . The system then continues displaying  210  document data.  FIGS. 1A and 1B  illustrate an example of transitioning from a first zoom level to a second zoom level. 
         [0036]    As shown in  FIGS. 1A and 1B  document  130  is modified from a first zoom level as shown in  FIG. 1A  to a second zoom level as shown in  FIG. 1B  in response to a user input to change operating mode. At the zoom level illustrated in  FIG. 1B , a greater portion of the document  130  is visible within the user interface. The visual guides  120  are presented to illustrate the region of the document  130  visible at the zoom level shown in  FIG. 1A . The user can use the zoomed out view level of the document  130  to identify other portions of the document  130 . 
         [0037]    As shown in  FIG. 2 , the system determines  270  whether a received input (e.g., a user input with the mouse) indicating cursor movement near or beyond a boundary of the display pane  170 . When the cursor movement is not beyond the boundary, the system moves  290  the visual guides in response  275  to the received input to a corresponding location within the document. The visual guides are positioned relative to the location of the mouse cursor  110 . The cursor can be positioned, e.g., at the center of the visual guides. For example, the location of the visual guides can correspond to the movement of the cursor in response to user input (e.g., to the user&#39;s mouse device). In some implementations, system displays the visual guides continuously indicating the position and the size of the portion of the document that will be displayed when the previous zoom level is restored. An example of moving the visual guides is shown in  FIGS. 1B and 1C . 
         [0038]    As shown in  FIGS. 1B and 1C , the visual guides  120  are moved from a first position relative to the document  130  to a second position relative to the document  130 . In the example depicted in  FIG. 1C , the visual guides  120  were moved from the previously displayed portion of two overleaf pages  134  shown in  FIG. 1B  to a lower part of the previous two overleaf pages  132 . The visual guides  120  indicate the position and the size of the portion of the document  130  that will be displayed in the display pane  170  when the previous zoom level is restored. While a vertical movement of the visual guides  120  is shown, movement can be in other directions relative to the document  130 . 
         [0039]    In some implementations, the user can move the visual guides  120  to a location at an edge of the displayed portion of the document in the display pane  170 . The system can automatically scroll the document  130  in order to display additional portions of the document  130 . This automatic scrolling is described in greater detail below. 
         [0040]    As shown in  FIG. 2 , the system receives  250  an input (e.g., from the user) indicating a change to a different operating mode. For example, the user can release a button (e.g., on the mouse or a pressed key). The system, in response to the received input, changes  260  the zoom level (e.g., zooms in on the document) and hides  265  the visual guides, resulting in a display  210  of the document. Additionally, the previous operating mode can be restored (e.g., “grabber hand” mode). The user can again indicate a change in operation mode to modify the zoom level of the displayed document as described above. 
         [0041]    As shown in  FIG. 1D , the document  130  is shown at the same zoom level as in  FIG. 1A . For example, the user can indicate a change in the operating mode from that shown in  FIG. 1C . However, the portion of the document  130  shown in the display pane  170  is different. Specifically, the portion of the document  130  shown in the display pane  170  in  FIG. 1D  corresponds to the region of the document  130  identified by the position of the visual guides  120  in  FIG. 1C . As shown in  FIG. 2 , when the system determines  270  that the received input is near or beyond a boundary of the displayed document, the system autoscrolls  280  the document contents. 
         [0042]    For example, if the portion of the document that the user is scrolling to is not visible in the display pane of the application window at the current zoom level, autoscroll can be performed by the system. If the system receives user input indicating movement of the mouse cursor towards and/or over a boundary of the display pane in direction of the portion of the document to be displayed, autoscroll is performed. The system then performs autoscroll, unless an end of the document is reached, or unless the user performs a movement of the mouse cursor away from the boundary towards the display pane. 
         [0043]    In some implementations, the system accepts other input (e.g., keystrokes) that indicates that scrolling of the document is intended or necessary. The autoscroll function, as known from other GUI elements, serves to scroll the view of the document into the direction indicated by the position of the mouse cursor. For example, as shown in  FIG. 1B , the display pane  170  include a boundary  160 . If a user moves the cursor, and therefore the visual guides, within a specified distance of the boundary  160 , the autoscroll operation can be triggered. As a result, the underlying content of document  130  can scroll to modify the portion of the document  130  displayed in the display pane  170 . 
         [0044]    Sometimes, the direction of scrolling is perceived ambiguously. While the direction of scrolling is sometimes referred to as a document being scrolled into a desired direction, rather the view is scrolled into the desired direction and the document is actually scrolled into the opposite direction. The desired result is the view of the document being repositioned over another part of the document, and the result is the same regardless of the varied language used in describing the process. 
         [0045]    In some implementations, while autoscroll is performed, the scrolling is performed with increasing speed according to a measure of time. The increase in speed facilitates quick scrolling to remote portions of large documents without the use of alternate modes of performing scrolling. 
         [0046]    Adjusting the Visual Guides 
         [0047]    In some implementations, the visual guides, are adjusted in response to a received input, e.g., a user input performed using the scroll wheel of the mouse or specific keys on a keyboard. For example, the visual guides can be increased or decreased in size or shape. As a consequence of the modified visual guides, the user adjusts the zoom level that was previously used before zooming out (i.e., the zoomed-in level) and before the system displayed the visual guides. Thus, the user can adjust not only the position of the portion of the document to be displayed after scrolling, but also the zoom level of the portion of the document. 
         [0048]    This is particularly useful if the size of the previously displayed portion is smaller or larger than the portion of the document the user wants to scroll to. Thus, for example, a specific paragraph of text or a specific image in the document can be displayed at a corresponding zoom level before the zoom level is restored. Scrolling and adjusting the zoom level can be performed in one operation, e.g., by moving the mouse and activating the scroll wheel. 
         [0049]    Determining an Operating Mode 
         [0050]      FIG. 3  is a flow chart showing an example process  300  for determining an operating mode. For example, the system can determine whether to activate a “zooming grabber hand” mode. For convenience, the process  300  will be described with respect to a system that performs the process  300 . 
         [0051]    While displaying  310  the document, before the system can zoom out according to a “zooming grabber hand” mode (e.g., steps  235 ,  240  in the process  200  of  FIG. 2 ), the system determines the operating mode, e.g. “grabber hand” mode or “zooming grabber hand” mode. After the system receives  320  a corresponding user input (e.g., a mouse input), the system optionally adjusts  330  one or more rendering parameters for faster rendering. Documents can be, for example, large and complex (e.g., feature different kinds of content and hundreds or thousands of content items). Therefore, the system can render many different content items. In some implementations, rendering parameters are adjusted to facilitate sufficiently fast and smooth zooming. In some implementations, other methods for achieving a similar result are used, for example, the system can pre-render a representation of a target zoom level as a large bitmap and transfer the bitmap block by block to screen memory, e.g., by blitting. 
         [0052]    The system initializes  340  a timer with a specified value (e.g., 0.5 seconds) and starts the timer. The timer can be implemented as a countdown timer, i.e., the time value is decremented from the initial value. However, the timer can be implemented in a number of other ways to achieve the same behavior. As long as the timer has not expired, the system tracks  350  user input (e.g., cumulative mouse movement). If the system detects  354  a specified amount of movement (e.g., greater than three pixels), the system stops  360  the timer and sets  370  the operating mode (e.g., to “grabber hand” mode). Consequently, no zooming out is performed but regular operation of the previous (and current) mode is performed. In the case of the mode being “grabber hand” mode, scrolling (or panning) of the document is performed as commonly known. 
         [0053]    If the system receives no suitable user input  256  (e.g., no movement of the mouse or mouse movement within a specified threshold, for example, less than three pixels) while the timer is running (e.g., the timer is being decremented) and the timer expires  380  (e.g., the timer reaches zero), the system sets  390  the mode (e.g., to “zooming grabber hand” mode). Then, zooming out is performed as shown in  FIG. 2  above. 
         [0054]    Determining a Zoom Factor 
         [0055]      FIG. 4  shows an example process  400  for determining a zoom factor. For convenience, the process  400  will be described with respect to a system that performs the process  400 . 
         [0056]    Before zooming out, the system determines a zoom factor for the document. The system determines  410  a current zoom level (e.g., the zoom level  105  of 300% as illustrated in  FIG. 1A ). The system determines  415  bounds of the document (e.g., the number of pages, page size and layout). In some implementations, the bounds of a document are determined according to all (visible and hidden) spreads of the document. A spread is a part of a document denoting the portion defined by one or more facing pages (e.g., the spreads of a magazine can usually include two facing pages; however, in some cases, a spread can have additional pages, for example, a foldout spread can include three or more pages). In some implementations, the bounds of the document are determined according to the width and the height of a pasteboard. The pasteboard includes, for example, one or more pages in a spread or one or more spreads and a surrounding space or work area (e.g., as shown by the spreads and background portion in  FIG. 1B ). 
         [0057]    The system determines  420  whether the zoom factor can be determined according to a width of the document. A width of the document can be, for example, the width of a page, the width of a spread, or the width of a pasteboard. In some implementations, the width and height of the pasteboard is determined according to the width and height of all pasteboards (e.g., when each page has it own pasteboard), for example, by determining a rectangle that includes all pasteboards. In some implementations, the width and height are determined according to user input or user preferences. If the zoom factor cannot be determined according to the width of the document, then the system determines  440  whether the zoom factor can be determined according to document height. If the system determines  440  that the zoom factor can be determined according to the height of the document, the system determines  450  the zoom factor according to document height. If the zoom factor cannot be determined according to the height of the document, then the system determines  460  the zoom factor according to a default factor. 
         [0058]    If the system determines  420  that the zoom factor can be calculated according to the width of the pasteboard, the system determines  430  the zoom factor according to the width of the pasteboard. In some implementations, the zoom factor is determined according to the width of the pasteboard as follows: 
         [0059]    A zoom to the pasteboard width z pasteboard , according to a view window width w view window , a pasteboard width w pasteboard  and an original zoom z original , is determined using the following formula, where a specific minimum zoom value is used as a limit: 
         [0000]    
       
         
           
             
               z 
               pasteboard 
             
             = 
             
               
                 ( 
                 
                   
                     w 
                     
                       view 
                        
                       
                           
                       
                        
                       window 
                     
                   
                   
                     w 
                     pasteboard 
                   
                 
                 ) 
               
                
               
                 
                   z 
                   original 
                 
                 . 
               
             
           
         
       
     
         [0060]    Additionally, a fixed zoom z fixed  is determined according to a maximum zoom z max  and the original zoom z original , using the following formula: 
         [0000]        z   fixed =( z   max )( z   original ). 
         [0061]    Then, an ideal zoom z ideal  is determined according to the maximum of the zoom to the pasteboard width z pasteboard  and the fixed zoom z fixed : 
         [0000]        z   deal =max( z   pasteboard   , z   fixed ). 
         [0062]    Whether zooming according to the determined zoom factor z ideal  is possible, is determined according to a maximum width zoom ratio r mw , using to the following formula: 
         [0000]    
       
         
           
             
               ( 
               
                 
                   z 
                   ideal 
                 
                 
                   z 
                   original 
                 
               
               ) 
             
             &lt; 
             
               
                 r 
                 mw 
               
               . 
             
           
         
       
     
         [0063]    In some implementations, the maximum width zoom ratio r mw  is substantially 0.7. This ratio can be used, e.g., to ensure that zooming is performed within specified limits. 
         [0064]    If zooming based on the determined zoom factor z ideal  is not possible, a zoom factor z height  based on the height of the pasteboard is determined. 
         [0065]    In some implementations, the system determines the zoom factor z height  according to the height of the pasteboard, i.e. the constant height zoom ratio r ch , and the original zoom z original , using to the following formula: 
         [0000]        z   height =( z   original )( r   ch ). 
         [0066]    In some implementations, the constant height zoom ratio r ch  is substantially 0.4. 
         [0067]    If zooming based on the determined zoom factor z height  is not possible, the system determines a default zoom factor according to a default small scale factor. 
         [0068]    In some implementations, the system determines the default zoom factor z default , according to the original zoom z original  and the default small scale factor s s , using to the following formula: 
         [0000]    
       
         
           
             
               z 
               default 
             
             = 
             
               
                 ( 
                 
                   
                     z 
                     original 
                   
                   
                     S 
                     S 
                   
                 
                 ) 
               
               . 
             
           
         
       
     
         [0069]    In some implementations, the default small scale factor s s  is substantially 1.0. The default small scale factor s s  can be, for example, 1.02, selected such that the visual guides just fit within the bounds of the zoomed-out display pane. 
         [0070]    In some implementations, the user specifies one or more of the factors, constants, and ratios in order to accommodate specific zooming operations or requirements. 
         [0071]    Zooming In and Zooming Out 
         [0072]      FIG. 5  shows an example process  500  for performing zooming. For convenience, the process  500  will be described with respect to a system that performs the process  500 . 
         [0073]    Zooming is performed, (e.g., in steps  240  and  265  of  FIG. 2 ). As shown in  FIG. 5 , the system creates  510  the necessary structures for displaying the visual guides (e.g., a red rectangle sprite and associated data). The system estimates  515  a time value and initiates  520  a timer. The system determines  530  a first zoom target (i.e., zoom target level). When zooming in, the system determines  540  whether the zoom target is smaller than or equal to the final zoom target (i.e., the final zoom level) or whether the zoom target is the first zoom target that has been determined. If the zoom target is smaller than or equal to the final zoom target or if the zoom target is the first zoom target, the system adjusts  550  the current zoom to the determined zoom target. 
         [0074]    Similarly, when zooming out, the system determines  540  whether the zoom target is greater than or equal to the final zoom target or whether the zoom target is the first zoom target that has been determined. If the zoom target is greater than or equal to the final zoom target or if the zoom target is the first zoom target, the system adjusts  550  the current zoom to the determined zoom target. 
         [0075]    The system adjusts  560  the visual guides to the determined zoom target. The system stores  570  a time taken to zoom to the current zoom target according to a time difference determined based on the estimated time  515  and a measure of time that has expired since the timer was started  520 . The next zoom target is determined by the system according to the time taken for the previous zoom  570  and the final zoom target. In some implementations, the zoom targets are determined by the system according to a function that maps time values to zoom values, whereas the mapping is a linear mapping. Other mapping functions can be used, e.g., including exponential or logarithmic functions. 
         [0076]      FIG. 6  is a schematic diagram of a generic computer system  600 . The system  600  can be used for practicing operations described in association with, for example, the methods  200 ,  300 ,  400 , and  500 . The system  600  can include a processor  610 , a memory  620 , a storage device  630 , and input/output devices  640 . Each of the components  610 ,  620 ,  630 , and  640  are interconnected using a system bus  650 . The processor  610  is capable of processing instructions for execution within the system  600 . In one implementation, the processor  610  is a single-threaded processor. In another implementation, the processor  610  is a multi threaded processor. The processor  610  is capable of processing instructions stored in the memory  620  or on the storage device  630  to display graphical information for a user interface on the input/output device  640 . 
         [0077]    The memory  620  is a computer readable medium such as volatile or non volatile that stores information within the system  600 . The memory  620  can store data structures, for example. The storage device  630  is capable of providing persistent storage for the system  600 . The storage device  630  may be a floppy disk device, a hard disk device, an optical disk device, or a tape device, or other suitable persistent storage means. The input/output device  640  provides input/output operations for the system  600 . In one implementation, the input/output device  640  includes a keyboard and/or pointing device. In another implementation, the input/output device  640  includes a display unit for displaying graphical user interfaces. 
         [0078]    An electronic document (which for brevity will simply be referred to as a document) does not necessarily correspond to a file. A document may be stored in a portion of a file that holds other documents, in a single file dedicated to the document in question, or in multiple coordinated files. 
         [0079]    Embodiments of the subject matter and the functional operations described in this specification can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Embodiments of the subject matter described in this specification can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer-readable medium for execution by, or to control the operation of, data processing apparatus. The computer-readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter effecting a machine-readable propagated signal, or a combination of one or more of them. The term “data processing apparatus” encompasses all apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. The apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. A propagated signal is an artificially generated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal, that is generated to encode information for transmission to suitable receiver apparatus. 
         [0080]    A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub-programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network. 
         [0081]    The processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit). 
         [0082]    Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. The essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto-optical disks, or optical disks. However, a computer need not have such devices. Moreover, a computer can be embedded in another device, e.g., a mobile telephone, a personal digital assistant (PDA), a mobile audio player, a Global Positioning System (GPS) receiver, to name just a few. Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry. 
         [0083]    To provide for interaction with a user, embodiments of the subject matter described in this specification can be implemented on a computer having a display device, e.g., a CRT (cathode ray tube) or LCD (liquid crystal display) monitor, for displaying information to the user and a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input. 
         [0084]    Embodiments of the subject matter described in this specification can be implemented in a computing system that includes a back-end component, e.g., as a data server, or that includes a middleware component, e.g., an application server, or that includes a front-end component, e.g., a client computer having a graphical user interface or a Web browser through which a user can interact with an implementation of the subject matter described is this specification, or any combination of one or more such back-end, middleware, or front-end components. The components of the system can be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include a local area network (“LAN”) and a wide area network (“WAN”), e.g., the Internet. 
         [0085]    The computing system can include clients and servers. A client and server are generally remote from each other and typically interact through a communication network. The relationship of client and server arises by virtue of computer programs running on the respective computers and having a client-server relationship to each other. 
         [0086]    While this specification contains many specifics, these should not be construed as limitations on the scope of the invention or of what may be claimed, but rather as descriptions of features specific to particular embodiments of the invention. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. 
         [0087]    Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. 
         [0088]    Thus, particular embodiments of the invention have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results.