Depth buffer clipping for window management

• US 5,241,656 A
• Filed: 12/13/1991
• Issued: 08/31/1993
• Est. Priority Date: 02/06/1989
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Simpson, Richard O., Loucks, Larry K.
• Primary Examiner(s): Nguyen, Phu K.
• Application Number:
  US07/807,798
• Time in Patent Office: 627 Days
• Field of Search: 395/157, 395/158, 395/155, 340/747, 340/750
• US Class Current: 715/794
• CPC Class Codes: G06F 3/0481 based on specific properties of the displayed interaction object or a metaphor-based environment, e.g. interaction with desktop elements like windows or icons, or assisted by a cursor's changing behaviour or appearance
• CPC Class Codes: G09G 5/14 Display of multiple viewports

Abstract

In a computer system with a screen display on which is formed a plurality of at least partially overlapping windows associated with different applications, a depth buffer is added to the display adapter for providing with different applications, a depth buffer is added to the display adapter for providing clipping assistance to the software-based window manager. A refresh buffer stores pixel data for each pixel of the display. The window manager monitors the current depth position of each of the pixels within the display and generates a depth value for each pixel. In response to an input request for window rearrangement, the window manager assigns a new depth value to each pixel in a window affected by the request, requests that each application affected by the rearrangement to retransmit pixel values for the pixels associated with at least the portion of a affected window which will become visible as a result of the rearrangement, and transmits new depth values for at least the pixels within the affected portions of such windows. The depth buffer receives and compares the new depth values with the current depth value for each pixel. If the comparator determines that the new pixel value has a depth value associated with the same window or a window closer to the viewer, the depth buffer notifies the refresh buffer to store the new pixel values for each of the applications affected by the rearrangement.

Claims

1. In a computer system having a refresh buffer and an interactive display terminal with a screen display on which is formed a plurality of at least partially overlapping windows, each window currently displaying subject matter generated by one of a plurality of applications running on the computer system, the improvement comprising:

means for requesting a rearrangement of the depth of the plurality of windows relative to

a reference position from a current arrangement to a new arrangement;

manager means for determining the depth of the subject matter associated with each of the windows, wherein said manager means, in response to the input request, determines the new depth of the subject matter in each of the plurality of windows affected by the requested rearrangement, transmits new depth values for the affected subject matter, and instructs each application with a window with affected subject matter to retransmit at least the portion of the subject matter associated with each window which will become visible as a result of the rearrangement; and

buffer means for storing the depth values of the subject matter associated with each of the windows currently being displayed on the screen, wherein said buffer means includes means for comparing the depth value for the retransmitted subject matter to the depth value for the currently displayed subject matter in response to the input request and, if the retransmitted subject matter has a depth value associated with the same window or a window closer to the viewer, the comparator means instructs the refresh buffer to store the retransmitted subject matter whereby only the subject matter to be displayed is passed to the refresh buffer from which the screen display is refreshed.

2. In a computer system having a refresh buffer and an interactive display terminal with a screen display on which is formed a plurality of at least partially overlapping windows, each window currently displaying subject matter generated by one of a plurality of applications running on the computer system, the improvement comprising:

means for determining the depth of the subject matter shown in each of said windows relative to a reference position;

depth buffer means for storing the depth values of the subject matter in said windows currently visible on said display;

means for requesting a change in the depth of at least one of said overlapping windows from the current window arrangement to a new arrangement;

means responsive to said change requesting means for providing an output to be stored in said refresh buffer comprising at least a portion of the subject matter in said windows upon said new arrangement including subject matter which will become not visible on said display as a result of said change;

means responsive to said output for comparing the depth values of the subject matter in said output to the depth values, stored in said depth buffer, of said currently visible subject matter; and

,

means responsive to said comparing means for permitting the storage in said refresh buffer of only those portions of the subject matter in said output which said comparing means determines to have a depth value associated with a window either as close as or closer to the viewer than the depth values of said currently visible subject matter.

3. The computer system of claim 2 further including means responsive to said comparing means for storing in said depth buffer the depth values of those portions of said output subject matter permitted to be stored in said refresh buffer.

4. The computer system of claim 3 further including means responsive to said comparing means for inhibiting the storage in said refresh buffer of said output subject matter determined to have a depth value associated with a window further from the viewer than the depth values of said currently visible subject matter.

5. The computer system of claim 2 wherein

said visible subject matter in said display is formed by a matrix of pixels;

said refresh buffer stores a matrix of pixel values, each stored pixel value coinciding with a visible pixel position, and

said depth buffer stores the depth values of each visible pixel.

6. The computer system of claim 5 further including means for storing in said depth buffer, the depth values of the pixels in those portions of said output subject matter stored in said refresh buffer.

7. The computer system of claim 6 further including means responsive to said comparing means for inhibiting the storage in said refresh buffer of the pixel values of pixel positions in said output subject matter determined to have depth values associated with a window further from the viewer than the depth values of said currently visible pixels.

8. In a computer system having a refresh buffer and an interactive display terminal with a screen display on which is formed a plurality of at least partially overlapping windows, each window currently displaying subject matter generated by one of a plurality of applications running on the computer system, the method comprising:

determining the depth of the subject matter shown in each of said windows relative to a reference position;

storing the depth values of the subject matter in said windows currently visible on said display;

requesting a change in the depth of at least one of said overlapping windows from the current window arrangement to a new arrangement;

in response to said change request, providing an output to be stored in said refresh buffer comprising at least a portion of the subject matter in said windows upon said new arrangement including subject matter which will become not visible on said display as a result of said change;

comparing the depth values of the subject matter in said output to the stored depth values of the subject matter in said current arrangement; and

,

storing in said refresh buffer, only those portions of the subject matter in said output which said comparison determines to have a depth value associated with a window either as close as or closer to the viewer than the depth values of said currently visible subject matter.

9. The matter of claim 8 further including the step of storing the depth values of those portions of the output subject matter stored in said refresh buffer.

10. The method of claim 9 further including the step of inhibiting the storage in said refresh buffer of said output subject matter determined to have a depth value associated with a window further from the viewer than the depth values of said currently visible subject matter.