Showing changes from revision #1 to #2:
Added | Removed | Changed
Entry | |
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R0 | 0 = Disable changed box calculations |
1 = Enable changed box calculations | |
2 = Reset changed box to null rectangle | |
-1 = Read changed box information |
Exit | |
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R0 | Previous enable state in bit 0 |
R1 | Pointer to a fixed block of 5 words |
The purpose of this call is to determine which areas of the screen have changed.
The data pointed to by R1 on exit at offsets 4 – 16 are only valid if the change box calculations were in an enabled state immediately after the call; otherwise they are undefined.
This call checks which areas of the screen were changed by VDU commands and returns the smallest rectangle which covers all changed pixels.