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Graphics cursor handler

  • US 5,161,212 A
  • Filed: 10/12/1989
  • Issued: 11/03/1992
  • Est. Priority Date: 10/12/1989
  • Status: Expired due to Term
First Claim
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1. A method for handling a cursor during execution of a graphics drawing routine comprising the steps of:

  • halting said drawing routine during a frame scan any time before a line by line scan reaches the line corresponding to the top of said cursor in screen memory;

    saving the cursor-free image background of said cursor;

    placing said cursor in screen memory;

    setting a cursor violation region to inform said drawing routine about the location the said cursor;

    proceeding with said drawing routine, while checking whether said drawing routine attempts to write to a pixel protected by said cursor violation region; and

    halting said drawing routine if said drawing routine attempts to write to a pixel protected by said cursor violation region;

    waiting until said scan is at the scan line corresponding to the bottom of said cursor; and

    restoring said cursor-free image background.

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