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From: rick@jessica.Stanford.EDU (Rick Wong)
Newsgroups: comp.sys.mac.programmer
Subject: New SetDepth call
Keywords: System 6.0.5, Graphics Devices Manager
Message-ID: <1990Jul26.183633.10926@portia.Stanford.EDU>
Date: 26 Jul 90 18:36:33 GMT
Sender: news@portia.Stanford.EDU (USENET News System)
Reply-To: rick@jessica.Stanford.EDU (Rick Wong)
Organization: Stanford University
Lines: 67

Tech Note 276 details a new call available in System 6.0.5 to set the
bit-depth of a device, called SetDepth.  The TN gives the following example:

	someResult := SetDepth(myGDevice, {newDepth:} 8,
			{whichFlags:} 1, {newFlags:} 0);

    In this call, newDepth = 8 sets an eight-bit depth, whichFlags = 1
    indicates that only bit one of newFlags is important, and newFlags = 0
    clears the gdDevType flag in the device record (0 = monochrome, 
    1 = color).  SetDepth returns zero if successful or a non-zero value
    if it cannot impose the desired depth on the requested device.

Armed with this information, I tried to write an FKEY to toggle the depth
of my main screen between one-bit and eight-bit.  Can anyone explain why
the following does not work?  My system has all the necessary hardware, etc.


#include <Types.h>
#include <OSUtils.h>
#include <Devices.h>


pascal short SetDepth(GDHandle gd, short newDepth,
    short whichFlags, short newFlags)
    = {0x203C, 0x000A, 0x0013, 0xAB1D};

pascal short HasDepth(GDHandle gd, short newDepth,
    short whichFlags, short newFlags)
    = {0x203C, 0x000A, 0x0014, 0xAB1D};


#define    kSysEnvVersion    1
#define    kSystem6_0_5    0x0605


int
main()
{
SysEnvRec gWorld;
GDHandle  mainDev;
int       oldDepth;
Boolean   successful;

    successful = false;
    (void) SysEnvirons(kSysEnvVersion, &gWorld);
    if (gWorld.systemVersion >= kSystem6_0_5 && gWorld.hasColorQD)    {
        mainDev = GetMainDevice();
        oldDepth = (**(**mainDev).gdPMap).pixelSize;
        if (oldDepth == 1)    {
            successful = (SetDepth(mainDev, 8, 0, 0) == noErr);
        } else {
            successful = (SetDepth(mainDev, 1, 0, 0) == noErr);
        }
    }
    if (!successful)    {
        SysBeep(1);
    }
    return 0;
}

When I try to set the depth to one-bit, the result code returned is 257;
eight-bit, 264.

Thanks,

Rick Wong
rick@jessica.stanford.edu