Horizontal Mouse Position in CGA and MCGA Modes (67338)
The information in this article applies to:
• Microsoft Mouse driver for MS-DOS 6.x
• Microsoft Mouse driver for MS-DOS 7.x
• Microsoft Mouse driver for MS-DOS 8.x
• Microsoft Mouse driver for MS-DOS 9.0
This article was previously published under Q67338
When you use the 320 by 200 CGA or MCGA graphics modes and a mouse,
the horizontal coordinates returned by the driver are from 0 to 638 in
increments of two.
The mouse driver returns a horizontal coordinate, which is twice the
actual screen coordinate. However, the vertical coordinates correspond
directly to the actual position on the screen.
Because the virtual screen for the mouse is in the range of 640 by 200
to 640 by 480, the virtual coordinate that maps to the actual screen
coordinate must therefore be double the actual. The vertical
coordinates in each case are 200 pixels, so there is a one-to-one
mapping of the virtual and actual coordinates.
"Microsoft Mouse Programmer's Reference Guide" Chapter 6
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