Patent Publication Number: US-9412329-B2

Title: Methods and apparatuses for controlling display devices

Description:
This application is a divisional of co-pending U.S. application Ser. No. 11/499,047, filed on Aug. 4, 2006. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to methods and apparatuses for controlling display devices. 
     BACKGROUND OF THE INVENTION 
     Typical graphical user interfaces are designed for display devices of standard resolutions. Until recently a “high resolution” display device typically had a large number of pixels on a large display area, when compared to a standard resolution display device. Thus, most display devices have similar numbers of pixels in a given size of a display area. However, recent developments in display devices, especially in high resolution LCD display panels, allow significantly more pixels to be displayed on an area of a fixed size. The pixel size of a high resolution display device is typically smaller than the pixel size of a low resolution display device. 
     A graphical user interface environment may include drawing and moving windows on a display device and interacting with a mouse, other cursor control devices, and/or a keyboard. In a buffered window system, application software draws contents in the window buffers. The window system transfers the images buffered in the window buffers to frame buffers to display the corresponding windows on the display screen. 
     A typical display system with a high resolution display and a low resolution display can be used to display the same window on each display. The pixel size of the high resolution display device is smaller than the pixel size of the low resolution display device. If the area of the high resolution display is similar or less than the area of the low resolution display device, then the contents of a window such as an image (e.g., an icon or a button on a window or menu of buttons) will be much smaller on the high resolution display device compared to the low resolution display device. The dimensions of the image of the high resolution display device are much smaller than the dimensions of the image of the low resolution display device. Thus, the high resolution device can display more pixels on the same area than the low resolution device. The image designed for the low resolution device appears much smaller when displayed on the high resolution devices. 
     Graphical user interface (GUI) components are typically designed in the unit of pixels. Thus, when the GUI components designed for a low resolution device is displayed on a high resolution device, the GUI components may appear too small to be comfortable for a user. It is often desirable to scale up the GUI components so that a user can comfortably interact with the GUI components displayed on the high resolution display device. 
     For example, a multiple display system may include a laptop with a scale factor set at 200 dots per inch (dpi) screen resolution and a external display with a scale factor set at 100 dpi screen resolution. A prior implementation would set the scale factor of the laptop and external display both to 200 dpi or alternatively both set to a scale factor of 100 dpi. Setting both scale factors to 200 dpi would result in increasing the image displayed on the external display beyond the size of the screen, thus defeating the purpose of the external display. Setting both scale factors to 100 dpi would make the laptop nearly unusable because the image displayed on the laptop would be too small to effectively view. 
     SUMMARY OF THE DESCRIPTION 
     Methods and apparatuses for controlling a data processing system having multiple displays with different scale factors (e.g., different pixel resolutions) are described here. 
     In one aspect of the invention, a machine implemented method includes setting a scale factor for each window buffer equal to an extreme scale factor among a plurality of displays; and transferring data from each window buffer into a corresponding frame buffer for one of the plurality of displays by setting a scale factor of each frame buffer equal to the scale factor of the corresponding display. 
     In one example according to this aspect, the method further includes displaying on a high resolution display and a low resolution display an image, stored in the corresponding frame buffers, with substantially the same physical size even though the displays have different scale factors and pixel densities. In an implementation, the scale factor is an extreme scale factor. The extreme scale factor is one of the largest scale factor or the smallest scale factor. 
     In another aspect of the invention, a machine implemented method in a data processing system having a window buffer for each window being displayed on display devices includes setting a scale factor for each window buffer equal to a selected scale factor among a plurality of displays having a plurality of scale factors. In one embodiment, the selected scale factor may be predetermined. The method further includes transferring data from each window buffer into a corresponding frame buffer for one of the plurality of displays by setting a scale factor of each frame buffer equal to the scale factor of the corresponding display. 
     In another aspect of the invention, a machine implemented method in a data processing system having a window buffer for each window being displayed on display devices includes setting a scale factor for each window buffer and corresponding frame buffer equal to a selected scale factor among a plurality of displays having a plurality of scale factors. In one embodiment, the selected scale factor may be predetermined. The method further includes transferring data from each frame buffer onto the corresponding display according to the scale factor of the corresponding display by executing a task, on each screen refresh interval, which converts from the scale factor in the corresponding frame buffer to the scale factor of the corresponding display. 
     The present invention includes methods and apparatuses which perform these methods, including data processing systems which perform these methods, and computer readable media which when executed on data processing systems cause the systems to perform these methods. 
     Other features of the present invention will be apparent from the accompanying drawings and from the detailed description which follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is illustrated by way of example and not limitation in the figures of the accompanying drawings in which like references indicate similar elements. 
         FIG. 1  shows a block diagram example of a data processing system which may be used with the present invention. 
         FIG. 2  shows a block diagram example of a window buffering system according to one embodiment of the present invention. 
         FIG. 3  shows multiple displays of a window buffering system that each displays the same image according to one embodiment of the present invention. 
         FIG. 4  shows moving a window from a first display to a second display according to one embodiment of the present invention. 
         FIG. 5  shows a high resolution display and low resolution display each displaying the same image according to one embodiment of the present invention. 
         FIG. 6  shows a flow chart for a method to scale a window on multiple displays according to one embodiment of the present invention. 
         FIG. 7  shows a flow chart for a method to scale a window on multiple displays according to one embodiment of the present invention. 
         FIG. 8  shows a flow chart for a method to scale a window on multiple displays according to one embodiment of the present invention. 
         FIG. 9  shows a flow chart for a method to scale a window on multiple displays according to one embodiment of the present invention. 
         FIG. 10  shows an example of a machine readable media, which may be used to store software and data which when executed by a data processing system causes the system to perform various methods of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following description and drawings are illustrative of the invention and are not to be construed as limiting the invention. Numerous specific details are described to provide a thorough understanding of the present invention. However, in certain instances, well known or conventional details are not described in order to avoid obscuring the description of the present invention. 
       FIG. 1  shows one example of a typical computer system which may be used with the present invention. Note that while  FIG. 1  illustrates various components of a computer system, it is not intended to represent any particular architecture or manner of interconnecting the components as such details are not germane to the present invention. It will also be appreciated that personal digital assistants (PDAs), handheld computers, cellular telephones, media players (e.g., an iPod), devices which combine aspects or functions of these devices (e.g., a media player combined with a PDS and a cellular telephone in one device), an embedded processing device within another device, network computers and other data processing systems which have fewer components or perhaps more components may also be used to implement one or more embodiments of the present inventions. The computer system of  FIG. 1  may, for example, be an Apple Macintosh computer. 
     As shown in  FIG. 1 , the computer system  101 , which is a form of a data processing system, includes a bus  102  which is coupled to a microprocessor  103  and a ROM  107  and volatile RAM  105  and a non-volatile memory  106 . The microprocessor  103 , which may be, for example, a microprocessor from Intel or a G3 or G4 microprocessor from Motorola, Inc. or IBM is coupled to cache memory  104  as shown in the example of  FIG. 1 . The bus  102  interconnects these various components together and also interconnects these components  103 ,  107 ,  105 , and  106  to a display controller and display device(s)  108 , which may include display devices and corresponding frame buffers, and to peripheral devices such as input/output (I/O) devices which may be mice, keyboards, modems, network interfaces, printers, scanners, video cameras and other devices which are well known in the art. The display controller  108  may include one or more frame buffers which are used to refresh multiple display devices or the frame buffers may be in a system RAM (e.g., RAM  105 ). Typically, the input/output devices  110  are coupled to the system through input/output controllers  109 . The volatile RAM  105  is typically implemented as dynamic RAM (DRAM) which requires power continually in order to refresh or maintain the data in the memory. The non-volatile memory  106  is typically a magnetic hard drive or a magnetic optical drive or an optical drive or a DVD RAM or other type of memory systems which maintain data even after power is removed from the system. Typically, the non-volatile memory will also be a random access memory although this is not required. While  FIG. 1  shows that the non-volatile memory is a local device coupled directly to the rest of the components in the data processing system, it will be appreciated that the present invention may utilize a non-volatile memory which is remote from the system, such as a network storage device which is coupled to the data processing system through a network interface such as a modem or Ethernet interface. The bus  102  may include one or more buses connected to each other through various bridges, controllers and/or adapters as is well known in the art. In one embodiment the I/O controller  109  includes a USB (Universal Serial Bus) adapter for controlling USB peripherals, and/or an IEEE-1394 bus adapter for controlling IEEE-1394 peripherals. 
     It will be apparent from this description that aspects of the present invention may be embodied, at least in part, in software. That is, the techniques may be carried out in a computer system or other data processing system in response to its processor, such as a microprocessor, executing sequences of instructions contained in a memory, such as ROM  107 , volatile RAM  105 , non-volatile memory  106 , cache  104  or a remote storage device. In various embodiments, hardwired circuitry may be used in combination with software instructions to implement the present invention. Thus, the techniques are not limited to any specific combination of hardware circuitry and software nor to any particular source for the instructions executed by the data processing system. In addition, throughout this description, various functions and operations are described as being performed by or caused by software code to simplify description. However, those skilled in the art will recognize what is meant by such expressions is that the functions result from execution of the code by a processor, such as the microprocessor  103 . 
     At least one embodiment of the present invention seeks to optimize scale factors on a per display device basis within a multiple display device system having different scale factors between display devices. Scale factors are optimized for each display device according to the resolution of the particular display device in order to obtain optimum viewing and operation of each window being displayed on the display device within the multiple display device system. 
       FIG. 2  shows a block diagram example of a window buffering system according to one embodiment of the present invention. The window buffering system  200  includes a bus  201 , application software  202 , window server  203 , window buffers  210 , frame buffers  220 , and corresponding display devices  230 . The window buffering system  200  is an example implementation of the data processing system  100 . Application software  202  draws contents in the window buffers  210  and the window server  203  transfers the images buffered in window buffers  210  into frame buffers  220  to display the corresponding windows on the display devices  230 . The window server  203  operates within an operating system environment. 
     For example, application software  202  draws contents in a first window buffer  211 , which is typically allocated from system memory (e.g., volatile RAM  105  in  FIG. 1 ). When the size of the window is changed, a new window buffer is allocated to replace the old one in order to accommodate the window of the new size. A first frame buffer  221  contains data for the screen image of the first window buffer  211  that are displayed on the screen of a first display device  231 . When the window corresponding to the first window buffer  211  is moved on the screen of the first display device  231 , the content in the window is not changed; and the application software does not have to update the first window buffer  211 . The window server  203  copies the data in the first window buffer  211  to the correct position in the first frame buffer  221  to display the window in the new location on the screen of the first display device  231 . When the window is partially covered by other windows, a portion of data in the first window buffer  211  is copied onto the first frame buffer  221  to display the corresponding portion of the window that is visible. Frame buffers  220  are typically under control of graphics hardware (e.g., graphics/video card) which controls the display of the windows on the screen of display devices  230  using the data in the frame buffers  220 . 
     In one embodiment of a window buffering system  200 , a plurality of window buffers  210  are coupled to a plurality of frame buffers  220 . Each frame buffer is coupled to one of a plurality of display devices  230  that each has a scale factor different than the other displays because each display device has a different resolution or pixel density, pixels per inch. A window server  203  is coupled to the plurality of window buffers  210  and the plurality of frame buffers  220 . The window server  203  is configured, in one exemplary embodiment, to set the scale factor for each window buffer equal to the largest scale factor among the plurality of display devices  230 . The window server  203  transfers, in one exemplary embodiment, data from each window buffer into the corresponding frame buffer for one of the display devices by setting the scale factor of each frame buffer equal to the scale factor of the corresponding display device. 
     Each display device of the plurality of display devices  230  can display a different window or windows compared to the other display devices. Alternatively, each display device of the plurality of display devices  230  can display the same window having the same image, stored in the corresponding frame buffers  220 . The image displayed on the plurality of display devices  230  has substantially the same physical size even though the displays have different scale factors and pixel densities. 
     For example,  FIG. 3  shows multiple displays of a window buffering system that each displays the same image according to one embodiment of the present invention. The displays are a high resolution display  301 , a low resolution display  302 , and a low resolution display  303  that each display an image, stored in the corresponding frame buffers, with substantially the same physical size even though the displays have different scale factors and pixel densities. 
     In an embodiment, high resolution display  301  and low resolution display  302  may each have the same size display screen. Each of these displays is able to display image  304  with substantially the same physical size (e.g., the “hello” image on display  301  is about 1″ long and the “hello” image on display  302  is about 1″ long or about 80% to 120% of the length of “hello” on display  301 ) even though the displays  301  and  302  have significantly different scale factors and pixel densities. “Substantially the same physical size” is being defined as having the size of the smallest image displayed on a display device being 80 to 120 percent the size of the largest image displayed on the other display device(s). A user can effectively view and operate a window buffering system, which is a multiple display system with multiple display devices, having significantly different scale factors between the display devices based on the images displayed being substantially the same physical size for all display devices. 
     In an embodiment, high resolution display  301  and low resolution display  303  have significantly different display screen sizes, pixel densities, and scale factors. However, each of these displays is able to display image  304  with substantially the same physical size even though the displays  301  and  303  have significantly different scale factors and pixel densities. A user can effectively view and operate a multiple display system having significantly different scale factors between the displays based on the images displayed being substantially the same physical size. 
       FIG. 4  shows moving a window from a first display to a second display according to one embodiment of the present invention. In this embodiment, the window buffering system  200  includes at least one window buffer coupled to a plurality of frame buffers  220 . Each frame buffer is coupled to one of a plurality of display devices  230  each having a scale factor different than the other displays. The window server  203  is coupled to the at least one window buffer and the plurality of frame buffers  220 . A user input such as a mouse cursor movement or keystroke represents a command to move a window  402  from a first display  401  with a first scale factor to a second display  403  with a second scale factor. 
     The window server  203  is configured such that if the first scale factor does not equal the second scale factor, then the window server  203  tears down the first window buffer, rebuilds the first window buffer, sets the first window buffer equal to the scale factor of the second display  403 , transfers data from the first window buffer into the frame buffer corresponding to the second display  403 , and displays the window  401  on the second display  403 . However, if the first scale factor equals the second scale factor, then the window server  203  displays the window  401  on the second display  403  with no change in scale factor for the window  401 . 
     For example, the first display  401  can be a high resolution display and the second display  403  can be a low resolution display with significantly lower pixel density compared to the high resolution display  401 . Each display non-contemporaneously, at different times, displays the window  402  with substantially the same physical size even though the displays have different scale factors and pixel densities. 
     The window server  203  can be easily implemented with this embodiment. The window buffers  210  take up the necessary amount of memory for storing the window one display at a time, rather than having multiple window buffers to support the window for multiple displays. 
     In one embodiment of a window buffering system, at least one window buffer is coupled to at least one frame buffer, which is coupled to a plurality of display devices  230  each having a scale factor different than the other displays. A window server  203  is coupled to the at least one window buffer and the at least one frame buffer. The window server  203  is configured in a mode to set the scale factor for each window buffer and corresponding frame buffer equal to the largest scale factor among the plurality of displays. Next, a screen refresh task transfers data from each frame buffer onto the corresponding display device according to the scale factor of the corresponding display device. The screen refresh task is executed during the screen refresh interval and refreshes the entire display device screen. 
     Anti-aliasing may be necessary if the screen refresh task is converting the largest scale factor in the frame buffer corresponding to a high resolution display to match the scale factor of a low resolution display device. Anti-aliasing is the technique of minimizing aliasing (jagged or blocky patterns) when representing a high resolution signal at a lower resolution. 
     For example,  FIG. 5  shows a high resolution display and low resolution display each displaying the same image. The high resolution display  501  and the low resolution display  501  have significantly different pixel densities and scale factors, but the same physical dimensions. Each display device displays the same image  502 , stored in the corresponding frame buffers, with the same physical size, length A, even though the displays have different scale factors and pixel densities. 
       FIGS. 6-9  show various methods for scaling a window per each display within a multiple display system such as the data processing system  100 . 
       FIG. 6  shows a flow chart for a machine implemented method to scale a window on multiple displays according to one embodiment of the present invention. A machine implemented method  600  includes setting a scale factor for each window buffer equal to an extreme scale factor among a plurality of display devices at block  601 . The machine implemented method  600  further includes transferring data from each window buffer into a corresponding frame buffer for one of the plurality of display devices by setting a scale factor of each frame buffer equal to the scale factor of the corresponding display at block  602 . The extreme scale factor is one of the largest scale factor or the smallest scale factor. The extreme scale factor corresponding to the highest resolution display is the largest scale factor. The scale factor for each window buffer is set to the largest scale factor to obtain optimum resolution in the highest resolution display. 
     For an example embodiment, the method  600  converts data in a window buffer for a window displayed on a lower resolution display to data corresponding to the lower resolution of the lower resolution display at a lower scale factor for storage in the frame buffer which is used to drive/refresh the lower resolution display at block  602 . The method  600  does not need to convert data in a window buffer for a window displayed on a highest resolution display because the scale factor for this display has already been set to the extreme scale factor corresponding to the highest resolution display at block  601 . 
     In one embodiment of a scaled mode, the method  600  further includes displaying on a high resolution display and a low resolution display an image, stored in the corresponding frame buffers, with substantially the same physical size even though the displays have different scale factors and pixel densities. A user can view and operate both high and low resolution displays with optimal resolution and minimal image distortion in accordance with method  600 . 
     In one embodiment of a non-scaled mode, the method  600  further includes setting the scale factor for each window buffer equal to 1.0 which represents a 1:1 ratio between window buffer pixel density and a corresponding display screen pixel density. The method  600  further includes transferring data from each window buffer into the corresponding frame buffer. The non-scaled mode is useful for certain software applications that already perform a scaling transformation or other compensation in switching from one display to another display with each display having different scale factors. 
       FIG. 7  shows a flow chart for a machine implemented method to scale a window on multiple displays according to one embodiment of the present invention. A machine implemented method  700  includes receiving an input indicating a moving of a window from a first display with a first scale factor to a second display with a second scale factor at block  701 . The method  700  further includes determining if the first scale factor equals the second scale factor at decision block  702 . Rebuilding of a window buffer occurs at block  703  if the first scale factor does not equal the second scale factor. Rebuilding occurs by tearing down the window buffer at block  703 , setting the window buffer equal to the scale factor of the second display at block  704 , and displaying the window on the second display at block  704 . In one implementation, rebuilding of the window buffer includes redrawing the window&#39;s contents into the window buffer using the scale factor of the second display. Rebuilding the window buffer can occur when moving the window to the second display is temporarily delayed. Alternatively, rebuilding the window buffer can occur when moving the window to the second display is 50 percent to 100 percent completed. 
     If the first scale factor equals the second scale factor at block  702 , then the method  700  further includes displaying the window on the second display with no change in scale factor and no rebuilding of the window at block  706 . 
     In one embodiment of the method  700 , the first display is a high resolution display, the second display is a low resolution display, and each non-contemporaneously, at different times, displays the window with substantially the same physical size even though the displays have different scale factors and pixel densities. The first display continues to display the window until the rebuilding occurs at which point the second display starts to display the window. A user can view and operate both high and low resolution displays with optimal resolution and minimal image distortion in accordance with method  700 . 
       FIG. 8  shows a flow chart for a machine implemented method to scale a window on multiple displays according to one embodiment of the present invention. A machine implemented method  800  includes setting the scale factor for each window buffer and corresponding frame buffer equal to an extreme scale factor among a plurality of displays at block  801 . The method  800  further includes transferring data from each frame buffer onto the corresponding display according to the scale factor of the corresponding display by executing a task, on each screen refresh interval, which converts from the scale factor in the corresponding frame buffer to the scale factor of the corresponding display at block  802 . If the scale factor stored in the frame buffer equals the scale factor of the corresponding display, then no conversion of the scale factor is necessary. 
     The extreme scale factor is one of the largest scale factor or the smallest scale factor. The extreme scale factor corresponding to the highest resolution display is the largest scale factor. The scale factor for each window buffer is set to the largest scale factor to obtain optimum resolution in the highest resolution display. 
     In one embodiment of a scaled mode, the method  800  further includes displaying on a high resolution display and a low resolution display an image, stored in the corresponding frame buffers, with substantially the same physical size even though the displays have different scale factors and pixel densities. A user can view and operate both high and low resolution displays with optimal resolution and minimal image distortion in accordance with method  800 . 
       FIG. 9  shows a flow chart for a machine implemented method to scale a window on multiple displays according to one embodiment of the present invention. The method  900  is adaptable for use with other scaled mode implementations and can be used during a scaled projector mode having displays with different dimensions and scale factors. The method  900  includes setting a window buffer of a high resolution display equal to the scale factor of the high resolution display, if necessary. The window buffer of the high resolution display may have previously been set to the scale factor of the high resolution display. The method  900  further includes setting the frame buffer of the high resolution display equal to the scale factor of a low resolution display at block  901 . The method  900  further includes rebuilding the window buffer of the low resolution display with the scale factor of the low resolution display at block  902 . The method further includes setting the frame buffer of the low resolution display equal to the scale factor of the low resolution display. Thus, the high resolution display with a window buffer set equal to the scale factor of the high resolution display is displayed with the scale factor corresponding to the low resolution display. 
       FIG. 10  shows an example of a machine readable media, which may be used to store software and data which when executed by a data processing system causes the system to perform various methods of the present invention. As noted above, this executable software and data may be stored in various places including for example ROM  107 , volatile RAM  105 , non-volatile memory  106  and/or cache  104  as shown in  FIG. 1 . Portions of this software and/or data may be stored in any one of these storage devices. Media  1000  for example may be primarily volatile RAM  105  and non-volatile memory  106  in one embodiment. OS  1010  represents an operating system. Window server  1015  represents a window managing system, which is typically a part of OS  1010 . Applications  1031 - 1035  represent application software, which display contents in corresponding windows on the system. Window buffers  1021 - 1025  represent the data for the images of the windows drawn by applications  1031 - 1035 , respectively. Frame buffers  1041 - 1045  represents the data for the screen image to be displayed on multiple display devices. Window buffers  1020  may be primarily on volatile RAM  105 , or primarily on video memory (e.g., in display controller  108 ). Frame buffers  1040  may be primarily on video memory in display controller  108 , or primarily on volatile RAM  105 . 
     Using the methods of various embodiments of the present invention, scale factors for window buffers and/or frame buffers are set per each display with data being transferred from window buffers to corresponding frame buffers in a multiple display system. 
     In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will be evident that various modifications may be made thereto without departing from the broader spirit and scope of the invention as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.