OS_Word 21

The calls to control the mouse and pointer settings are accessed through OS_Word 21. In order to ensure that the interfaces are complete, a new reason code has been defined to read the mouse bounding box.

OS_Word 21,7 (Read mouse bounding box)
On entry
   R0 = 21
   R1 = pointer to 9 byte block, first byte of which is 7
On exit
   R0, R1 preserved
         Block at R1 updated to contain :
               +1 = LSB of left coordinate
               +2 = MSB of left coordinate
               +3 = LSB of bottom coordinate
               +4 = MSB of bottom coordinate
               +5 = LSB of right coordinate
               +6 = MSB of right coordinate
               +7 = LSB of top coordinate
               +8 = MSB of top coordinate

This SWI call is used to read the mouse bounding box which was set using OS_Word 21,1. The parameters in the block in R1 are in the same order. As with OS_Word 21,1, the coordinates are relative to the screen origin at the time of this call. This means that the bounding box can be preserved with this call, modified, and later restored using OS_Word 21,1.

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