Composite graphics rendered using multiple frame buffers

• US 20050168471A1
• Filed: 12/18/2003
• Published: 08/04/2005
• Est. Priority Date: 12/18/2003
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Paquette, Michael J.
• Granted Patent: US 7,274,370 B2
• Time in Patent Office: Days
• US Class Current: 345/536
• CPC Class Codes: G09G 5/14 Display of multiple viewports
• CPC Class Codes: G09G 5/393 Arrangements for updating the contents of the bit-mapped memory

Abstract

A secondary frame buffer is provided for use by classic applications designed to paint directly to a frame buffer. Classic applications paint their windows to the secondary frame buffer, not to the primary frame buffer. A compositor reads window data from the secondary frame buffer and paints it to the primary frame buffer. The compositor also reads window data written to back buffers by other applications and paints that data to the primary frame buffer. Since the compositor maintains visible region data for all windows, the windows are correctly painted to the primary frame buffer whether they are from the back-buffered windows or from classic applications. In addition, optimizations in classic applications that cause classic windows to be inappropriately painted over newer style windows no longer have this effect, since the compositor is responsible for painting legacy windows to the frame buffer, not the applications themselves.

Claims

1. A system for rendering application windows, comprising:

a primary frame buffer for providing window data for output to a display device;

a secondary frame buffer for receiving window data from a plurality of applications;

a compositor configured to;

receive window data from a plurality of back buffers;

maintain first visible region data associated with window data in the secondary frame buffer;

maintain second visible region data associated with window data in the back buffers and window data in the secondary frame buffer; and

output to the primary frame buffer a final frame buffer content composited from the first visible region data and the second visible region data.

2. The system of claim 1 wherein the primary frame buffer forms part of a computer memory device.

3. The system of claim 1 wherein the primary frame buffer forms part of a graphics processing unit (GPU).

4. The system of claim 1 wherein the secondary frame buffer forms part of a computer memory device.

5. The system of claim 1 wherein the secondary frame buffer forms part of a graphics processing unit (GPU).

10. The system of claim 1 wherein the second visible region data includes a list of windows that are being displayed by the system.

11. The system of claim 10 wherein the list of windows is ordered from front to back.

12. The system of claim 10 wherein the list of windows is ordered from top to bottom.

6. A computer program product for rendering application windows, the computer program product comprising a computer-readable medium containing computer program code comprising:

a primary frame buffer module for providing window data for output to a display device;

a secondary frame buffer module for receiving window data from a plurality of applications;

a compositor module, communicatively coupled to the primary frame buffer module and the secondary frame buffer module, configured to;

receive window data from a plurality of back buffers;

maintain first visible region data associated with window data in the secondary frame buffer;

maintain second visible region data associated with window data in the back buffers and window data in the secondary frame buffer; and

output to the primary frame buffer a final frame buffer content composited from the first visible region data and the second visible region data.

7. The computer program product of claim 6 wherein the primary frame buffer module forms part of a computer memory device module.

8. The computer program product of claim 6 wherein the primary frame buffer module forms part of a graphics processing unit (GPU) module.

9. The computer program product of claim 6 wherein the secondary frame buffer module forms part of a computer memory device module.

13. The computer program product of claim 6 wherein the secondary frame buffer module forms part of a graphics processing unit (GPU) module.

14. A method for rendering application windows, comprising:

maintaining first visible region data associated with window data in a secondary frame buffer, the secondary frame buffer including window data from a plurality of applications;

maintaining second visible region data associated with window data received from a plurality of back buffers; and

outputting to a primary frame buffer a final frame buffer content composited from the first visible region data and the second visible region data.

15. The method of claim 14 wherein the primary frame buffer forms part of a computer memory device.

16. The method of claim 14 wherein the primary frame buffer forms part of a graphics processing unit (GPU).

17. The method of claim 14 wherein the secondary frame buffer forms part of a computer memory device.

18. The method of claim 14 wherein the secondary frame buffer forms part of a graphics processing unit (GPU).

19. The method of claim 14 further comprising:

responsive to receiving new window data from the plurality of back buffers;

determining for each window an area of the window to be obscured; and

updating the second visible region data in accordance with the area determined to be obscured.

20. The method of claim 19 further comprising outputting to the primary frame buffer an updated final frame buffer content composited from the first visible region data and the updated second visible region data.

21. A compositor for rendering application windows, the compositor comprising:

a receiving module for receiving window data from a plurality of back buffers;

a first visible region module for maintaining first visible region data associated with window data in a secondary frame buffer;

a second visible region module for maintaining second visible region data associated with window data in the back buffers and window data in the secondary frame buffer; and

an output module for outputting to a primary frame buffer a final frame buffer content composited from the first visible region data and the second visible region data.

22. A method for rendering application windows, the method comprising:

detecting a change in a geometry of a first window;

redrawing the first window;

for each of a plurality of lower windows located below the first window;

determining a visible area of the lower window;

determining whether the lower window is a classic window;

responsive to the lower window being a classic window, updating a classic visible regions list to include the visible area of the window;

outputting each lower window to a primary frame buffer in accordance with the determined visible area of the lower window.

23. The method of claim 22 further comprising:

responsive to the lower window being a classic window, sending a repaint message to an application owning the lower window.

24. The method of claim 23 further comprising:

receiving a request to hide a mouse curser for a specified area of the primary frame buffer; and

flushing the specified area to the frame buffer.