Q23308: PRB: Debugging High Resolution EGA or VGA Graphics with CodeView
Article: Q23308
Product(s): Microsoft Programming Utilities
Version(s): 2.2,3.0,3.11,3.12,3.14,3.5,4.0,4.01,4.05,4.1
Operating System(s):
Keyword(s): kb16bitonly
Last Modified: 26-JUN-2001
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The information in this article applies to:
- Microsoft CodeView for MS-DOS, versions 2.2, 3.0, 3.11, 3.14, 4.0, 4.01, 4.05, 4.1
- Microsoft CodeView for OS/2, versions 2.2, 3.0, 3.11, 3.12, 3.5
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SYMPTOMS
========
Debug a program that does EGA, VGA, or SVGA graphics. When you continue from a
breakpoint after the program has painted the screen, the screen appears
differently than before the breakpoint; all colors seemingly have been turned to
black. The program is using the EGA in 640x350, 16-color mode.
CAUSE
=====
This behavior is partly related to the size of the buffer that CodeView creates
for storing screen information. If you are running on a CGA, EGA, or VGA board,
this buffer is 16K by default. If you are running on a monochrome board, this
buffer is 4K by default. As you are finding, 16K is not enough memory for a
color image using 640x350 resolution (the maximum resolution supported is
640x200), hence the loss of color after the breakpoint.
RESOLUTION
==========
The best way to work around this limitation is to use a dual-monitor setup for
debugging applications that run in a high resolution graphics mode. Invoke
CodeView with the /2 switch and the CodeView display will appear on the
secondary monitor while the program's graphical output will remain on the main
monitor. Because the output is going to a different screen, CodeView won't have
to worry about changing the video modes or the buffering.
Additional query words: 3.00 3.50 4.00 4.10
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Keywords : kb16bitonly
Technology : kbAudDeveloper kbCodeView kbZNotKeyword3 kbCodeView220DOS kbCodeView300DOS kbCodeView311DOS kbCodeView314DOS kbCodeView400DOS kbCodeView401DOS kbCodeView405DOS kbCodeView410DOS kbCodeView220OS2 kbCodeView300OS2 kbCodeView311OS2 kbCodeView312OS2 kbCodeView350OS2
Version : :2.2,3.0,3.11,3.12,3.14,3.5,4.0,4.01,4.05,4.1
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