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From: bert@helix.nih.gov (Bert Tyler)
Newsgroups: comp.windows.ms.programmer
Subject: WinApps detecting 24-bit Video Drivers
Message-ID: <599@nih-csl.nih.gov>
Date: 5 Nov 90 12:52:37 GMT
Sender: news@nih-csl.nih.gov
Organization: National Institutes of Health, Bethesda
Lines: 39

How should a WinApp check for the presence of a 24-bit (IE, > 256 colors)
video driver?

When I wrote WINFRACT, I had access to a 16-color driver (vanilla VGA)
and a 256-color driver (the 8514/A), and didn't consider 24-bit video
drivers at all.  Now I'm getting a little concerned that the program
won't act correctly if it finds itself on a 256-color driver.

Given that WINFRACT is, for other reasons, pretty much limited to the
256-color world at the moment, I would like it to treat a 24-bit video
driver just like a 256-color driver (I'm assuming that Windows will
automatically handle the fact that *my* 256 colors can be different
from the *other guy's* 256 colors).

So, anyway, what is going to happen to the current detection logic
(copied below) if it finds itself on a 24-bit video driver?  What
should I be doing differently?

(At the moment, 'iNumColors' and 'colors' are both declared 'int').

---------------------------

    hDC = GetDC(NULL);
    iPalSize    = GetDeviceCaps (hDC, SIZEPALETTE);
    iRasterCaps = GetDeviceCaps (hDC, RASTERCAPS);
    iRasterCaps = (iRasterCaps & RC_PALETTE) ? TRUE : FALSE;
    if (iRasterCaps)
       iNumColors = GetDeviceCaps(hDC, SIZEPALETTE);
    else
       iNumColors = GetDeviceCaps(hDC, NUMCOLORS);
    ReleaseDC(NULL,hDC);

    colors = iNumColors;
    if (colors != 2 && colors != 16 && colors != 256) {
        /* NOTE:  the next two statements were *reversed* in the
        public versions of WINFRACT - oops */
        if (colors > 16) colors = 256;
        if (colors > 2) colors = 16;
        }