GDI Incompatibilities: win98 vs XP

[LyMc]

I have created a graphical application using MSVS .NET, in C++. I used the SDK interface as opposed to MFC or the fancier new interfaces (essentially Petzold 2nd Ed). It works great on XP, makes great drawings, allows scrolling and zooming. I took the app over to a newly minted Win98 SE machine (and later, ME as well) and the drawings are all screwed up. The drawings are not stable; they shift violently when I zoom in or out or scroll; there are lines going every which way (some recognizeable from what I expect, some not). Huge lettering (in some cases I can only see the edge of a part of a character).

What essential incompatibility am I running into here? It seems to me it has to be something in the respective GDIs, but I haven't a clue what is wrong. Anyone who can point me to some documentation about how the two regimes differ will have my appreciation.

 

[GMX]

Have you tried recompiling the program on a 98 or ME machine? it might solve the problem.

 

[LyMc]

Thanks for the reply, GMX. The problem there is that the .NET compiler won't even load on Win98 systems, even if MS allowed it (MSVS.net has to be activated). I could, I suppose, whip out my old v5.0 compiler and do that, but I'd probably be a week just getting the extensions ironed out....

At any rate, I've found out what the problem is: integer overflow. I thought that win98 (and even win95) was 32 bit capable, but apparently in some way it is not. I measure in 1/500ths of an inch, and handle simulated lengths of 12,000" in either dimension, so a lot of 16-bit integers overflow, causing the chaotic effects. When I change the resolution to 1/10th inch (about the roughest the app can stand), it works fine until I zoom out to the limits.

So the question becomes, what can I do about it? The code is 32 bit - XP and w2k work just fine at 1/500th inch resolution. So it's a win9x vs NT difference. Gdi.dll differences? Video drivers, maybe? Anyone have any data on this? And better yet, what can I do about it on win9x?