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Method and system for flipping images in a window using overlays

  • US 5,850,232 A
  • Filed: 04/25/1996
  • Issued: 12/15/1998
  • Est. Priority Date: 04/25/1996
  • Status: Expired due to Term
First Claim
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1. In a computer system including a processor, system memory, video memory and a display controller for converting a pixmap in the video memory to a display image on a display monitor and for superimposing an image at an overlay address onto the display image, a method for flipping images in a window of the display image, the method comprising:

  • a) allocating a primary surface in the video memory;

    b) allocating a front and back buffer in the video memory;

    c) creating an overlay flipping structure including a front buffer structure and back buffer structure representing the front and back buffers, respectively;

    d) storing memory locations of the front and back buffers in the front and back buffer structures, respectively;

    e) controlling rendering of an overlay image into the back buffer;

    in response to a request to flip the overlay flipping structure;

    f) determining when to write the memory location of the back buffer into the overlay address of the display controller to avoid tearing of the overlay image;

    g) writing the memory location of the back buffer into the overlay address; and

    h) updating the memory locations stored in the front and back buffer structures;

    i) repeating at least steps e through h to display subsequent rendered overlays in the window.

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