Mono display attributes and number of screen lines wrong on Leading Edge Model D set to Hercules mode

MobyGamer / total-dos-launcher

A system for easily loading and running thousands of DOS programs on vintage hardware

MIT License

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Mono display attributes and number of screen lines wrong on Leading Edge Model D set to Hercules mode #36

Closed MobyGamer closed 6 years ago

MobyGamer commented 6 years ago

On a pure Hercules system (Leading Edge Model D with monochrome screen running MS-DOS 3.1), two bugs were observed:

Number of screen lines was incorrectly determined. Thought it had 200+ lines and the screen didn't repaint properly. Code review required.
The display attribute for the file dialog resulted in a border drawn with underlined graphics characters.

MobyGamer commented 6 years ago

BIOS in that system somehow puts 4000h bytes as part of a text screen when it should be 80x25. As a result, the calculations go horribly wrong. This was addressed by adding code to adjust to 25 if things look really wrong.

MobyGamer commented 6 years ago

Code in question that was adjusted was TPLibs/TOTT/TOTSYS.PAS. https://github.com/MobyGamer/TPLibs/commit/2c9c37f5d08800cee8faa8dbae26797513226e1f has the details.