display.c

// gcc -framework ApplicationServices -framework CoreFoundation -framework IOKit display.c -o display

/* This code was based on SetDisplay from the University of Utah Student
 * Computing Labs. 
 * The code has since been modified by Rob Braun (bbraun@synack.net)
 * Please do not contact Utah Student Computing Labs with problems with
 * this software.  I probably introduced them.
 */

/*

main.c

This tool sets the display resolution.  This tool exists so that we
can set the display to a setting when the display manager says it can't,
mainly, when a Mac starts up and the monitor is off, or if the Mac is on
a KVM.

Copyright (c) 2002 University of Utah Student Computing Labs.
All Rights Reserved.

Permission to use, copy, modify, and distribute this software and
its documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appears in all copies and
that both that copyright notice and this permission notice appear
in supporting documentation, and that the name of The University
of Utah not be used in advertising or publicity pertaining to
distribution of the software without specific, written prior
permission. This software is supplied as is without expressed or
implied warranties of any kind.

WARNING:
In testing garbage values, I did get this to tool to change the display so that absolutely
nothing displayed.  I don't remember what I did to get that.  And I can't duplicate it anymore.
I could remotely control it, so I could fix it.  But beware, if you can't remotely control the
machine and fix bad display settings, well, you might have to resort to drastic measures to fix
a mac with bad display settings (like boot off of a different disk and delete the display 
preferences.

In other words, this tool will change the display settings regardless of what the display
manager says is possible.  So be careful!!!

*/


#include <ApplicationServices/ApplicationServices.h>
#include <CoreFoundation/CoreFoundation.h>
#include <IOKit/IOKitLib.h>
#include <stdlib.h>
#include <unistd.h>

struct myMode
{
    size_t width;
    size_t height;
    size_t bitsPerPixel;
    CGRefreshRate refresh;
};

struct myMode myMode;

static void setdisplay( CGDirectDisplayID dspy)
{
    CFDictionaryRef mode;
    CFDictionaryRef originalMode;
    boolean_t exactMatch;
    CGDisplayErr err; // or is this suppose to be CGError???

    CGDisplayConfigRef configRef;
    const void *value;
    int no;
    int width, height, refresh, depth;
   
    originalMode = CGDisplayCurrentMode( dspy );
    if ( originalMode == NULL )
    {
        printf( "Display is invalid\n" );
        return;
    }

    if ( myMode.bitsPerPixel == 0 ) {
       value = CFDictionaryGetValue(originalMode, kCGDisplayBitsPerPixel);
       CFNumberGetValue(value, kCFNumberSInt32Type, &myMode.bitsPerPixel);
    }
    if ( myMode.width == 0 ) {
       value = CFDictionaryGetValue(originalMode, kCGDisplayWidth);
       CFNumberGetValue(value, kCFNumberSInt32Type, &myMode.width);
    }
    if ( myMode.height == 0 ) {
       value = CFDictionaryGetValue(originalMode, kCGDisplayHeight);
       CFNumberGetValue(value, kCFNumberSInt32Type, &myMode.height);
    }
    if ( myMode.refresh == 0 ) {
       value = CFDictionaryGetValue(originalMode, kCGDisplayRefreshRate);
       CFNumberGetValue(value, kCFNumberDoubleType, &myMode.refresh);
    }
   
    printf( "Display 0x%x: Looking for %ld x %ld, %ld Bits Per Pixel @ %f Hz\n", (unsigned int)dspy, myMode.width, myMode.height, myMode.bitsPerPixel, myMode.refresh );


    mode = CGDisplayBestModeForParametersAndRefreshRate(dspy, myMode.bitsPerPixel, myMode.width, myMode.height, myMode.refresh, &exactMatch);
    
//    mode = CGDisplayBestModeForParametersAndRefreshRateWithProperty(dspy, myMode.bitsPerPixel, myMode.width, myMode.height, myMode.refresh, kCGDisplayModeIsSafeForHardware, &exactMatch);

    value = CFDictionaryGetValue(originalMode, kCGDisplayWidth);
    CFNumberGetValue(value, kCFNumberSInt32Type, &width);
    value = CFDictionaryGetValue(originalMode, kCGDisplayHeight);
    CFNumberGetValue(value, kCFNumberSInt32Type, &height);
    value = CFDictionaryGetValue(originalMode, kCGDisplayRefreshRate);
    CFNumberGetValue(value, kCFNumberSInt32Type, &refresh);
    value = CFDictionaryGetValue(originalMode, kCGDisplayBitsPerPixel);
    CFNumberGetValue(value, kCFNumberSInt32Type, &depth);
    printf( "Display 0x%x: found %ld x %ld, %ld Bits Per Pixel @ %d Hz\n", (unsigned int)dspy, width, height, depth, refresh );
    

    CGBeginDisplayConfiguration(&configRef);

    err = CGConfigureDisplayMode(configRef, dspy, mode);

    CGCompleteDisplayConfiguration( configRef, kCGConfigurePermanently );

    if ( err != CGDisplayNoErr )
    {
        printf( "Oops!  Mode switch failed?!?? (%d)\n", err );
    }
}

static void printdisplay( CGDirectDisplayID dspy, int num )
{
    static int firsttime = 0;
    CFDictionaryRef originalMode;
    uint32_t unitno, vendorno, modelno, serialno;
    int isprimary = 0, isbuiltin = 0, n;
    CFIndex count;
    CFTypeID type;
    const void *value;
    int32_t height, width, refresh, depth;

    originalMode = CGDisplayCurrentMode( dspy );
    if ( originalMode == NULL )
    {
        printf( "Display is invalid\n" );
        return;
    }

    unitno = CGDisplayUnitNumber(dspy);
    vendorno = CGDisplayVendorNumber(dspy);
    modelno = CGDisplayModelNumber(dspy);
    serialno = CGDisplaySerialNumber(dspy);

    if( CGDisplayIsMain(dspy) ) {
       isprimary = 1;
    }
    if( CGDisplayIsBuiltin(dspy) ) {
       isbuiltin = 1;
    }

    value = CFDictionaryGetValue(originalMode, kCGDisplayWidth);
    CFNumberGetValue(value, kCFNumberSInt32Type, &width);
    value = CFDictionaryGetValue(originalMode, kCGDisplayHeight);
    CFNumberGetValue(value, kCFNumberSInt32Type, &height);
    value = CFDictionaryGetValue(originalMode, kCGDisplayRefreshRate);
    CFNumberGetValue(value, kCFNumberSInt32Type, &refresh);
    value = CFDictionaryGetValue(originalMode, kCGDisplayBitsPerPixel);
    CFNumberGetValue(value, kCFNumberSInt32Type, &depth);
    
    if( firsttime == 0 ) {
       printf("Display Unit Width Height Depth Refresh Vendor     Model Serial\n");
       firsttime = 1;
    }

    printf("%-7d %-4d %-5d %-6d %-5d %-7d %-10d %-5d %-6d", num, unitno, width, height, depth, refresh, vendorno, modelno, serialno);   
    if( isprimary )
        printf("\t Primary Display");
    if( isbuiltin )
        printf("\t Builtin Display");

    printf("\n");

}

#define kMaxDisplays    16

void usage(char *prog)
{
        printf("%s [-x width] [-y height] [-b bit depth] [-r refresh] [-d display] [-l]\n", prog);
        printf("\t-l lists all displays and their current settings\n");
        printf("\tIf no display is specified (-d), the settings will be applied to all displays\n");
}

int
main(int argc, char *argv[])
{
    CGDirectDisplayID display[kMaxDisplays];
    CGDisplayCount numDisplays;
    CGDisplayCount i;
    CGDisplayErr err;
    int displayno = -1;
    int ch;
    int listonly = 0;
    int xset = 0, yset = 0, rset = 0, bset = 0;

    memset(&myMode, 0, sizeof(myMode));

    while ((ch = getopt(argc, argv, "x:y:r:b:ld:")) != -1) {
        switch(ch) {
        case 'x':
           myMode.width = atoi(optarg);
           xset = 1;
           break;
        case 'y':
           myMode.height = atoi(optarg);
           yset = 1;
           break;
        case 'r':
           myMode.refresh = atoi(optarg);
           rset = 1;
           break;
        case 'b':
           myMode.bitsPerPixel = atoi(optarg);
           bset = 1;
           break;
        case 'l':
           listonly = 1;
           break;
        case 'd':
           displayno = atoi(optarg);
           break;
        default:
           usage(argv[0]);
           exit(1);
        };
    }

    if( argc == 1 ) {
        usage(argv[0]);
        exit(1);
    }
    
    // printf( "Width: %d Height: %d BitsPerPixel: %d Refresh rate: %d\n", (int)myMode.width, (int)myMode.height, (int)myMode.bitsPerPixel, (int)myMode.refresh );
    
    err = CGGetActiveDisplayList(kMaxDisplays,
                                 display,
                                 &numDisplays);
    if ( err != CGDisplayNoErr )
    {
        printf("Cannot get displays (%d)\n", err);
        exit( 1 );
    }
    printf( "%d displays found\n", (int)numDisplays );
   for ( i = 0; i < numDisplays; ++i )
   {
        if( listonly ) {
           printdisplay(display[i], i);
        } else if( (displayno == -1) || (displayno == i) ) {
           setdisplay(display[i]);
        }
   }
    printf( "Done.\n" );

    exit(0);
}





static int numberForKey( CFDictionaryRef desc, CFStringRef key )
{
    CFNumberRef value;
    int num = 0;

    if ( (value = CFDictionaryGetValue(desc, key)) == NULL )
        return 0;
    CFNumberGetValue(value, kCFNumberIntType, &num);
    return num;
}

static void printDesc( CFDictionaryRef desc )
{
    char * msg;
    if ( CFDictionaryGetValue(desc, kCGDisplayModeUsableForDesktopGUI) == kCFBooleanTrue )
        msg = "Supports Aqua GUI";
    else
        msg = "Not for Aqua GUI";

    printf( "\t%d x %d,\t%d BPP,\t%d Hz\t(%s)\n",
            numberForKey(desc, kCGDisplayWidth),
            numberForKey(desc, kCGDisplayHeight),
            numberForKey(desc, kCGDisplayBitsPerPixel),
            numberForKey(desc, kCGDisplayRefreshRate),
            msg );
}