=> R0 = 0 disable changed box calculations
1 enable changed box calculations
2 reset changed box to null rectangle
-1 read changed box information
<= R0 = previous enable state in bit 0
R1 = pointer to a fixed block of 5 words:
0 new disable/enable flag
4 x-coordinate of left edge of box
8 y-coordinate of bottom edge of box
12 x-coordinate of right edge of box
16 y-coordinate of top edge of box
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.
See PRM 1, page 724.
[sh-index] Back to list of manuals
|
| |
