For those interested in how this issue is solved I have this working. So I will post some code snippets.
The header file looks like this:
typedef double ramp_type;
#ifdef __WIN32__
#include <windows.h>
typedef unsigned short ramp_type_private;
typedef HDC displayHandle;
#elif defined (__APPLE__)
#ifndef DEBUG
#define DEBUG 0
#endif
#include <Carbon/Carbon.h>
#include <CoreServices/CoreServices.h>
#include <IOKit/Graphics/IOGraphicsLib.h>
typedef CGGammaValue ramp_type_private;
typedef CGDirectDisplayID displayHandle;
#elif defined (UNIX)
typedef unsigned short ramp_type_private;
typedef int displayHandle;
#else
#error "no typedef for ramp_type_private and displayHandle are available for your platform"
#endif
class gamma_ramp
{
public:
int size;
ramp_type *red, *green, *blue;
gamma_ramp(int screen, int leftIn, int topIn); // screen is ignored on OS/X and Windows
// leftIn and topIn are ignored on X11
~gamma_ramp();
void getGammaRamp(); // returns size
void setGammaRamp();
void setLinearGammaRamp();
private:
int getGammaRampSize();
void convertPrivShort2ramp_type();
void convert_ramp_type2short();
ramp_type_private* ramp_buffer;
int screen, left, top;
displayHandle display;
};
typedef double ramp_type;
#ifdef __WIN32__
#include <windows.h>
typedef unsigned short ramp_type_private;
typedef HDC displayHandle;
#elif defined (__APPLE__)
#ifndef DEBUG
#define DEBUG 0
#endif
#include <Carbon/Carbon.h>
#include <CoreServices/CoreServices.h>
#include <IOKit/Graphics/IOGraphicsLib.h>
typedef CGGammaValue ramp_type_private;
typedef CGDirectDisplayID displayHandle;
#elif defined (UNIX)
typedef unsigned short ramp_type_private;
typedef int displayHandle;
#else
#error "no typedef for ramp_type_private and displayHandle are available for your platform"
#endif
class gamma_ramp
{
public:
int size;
ramp_type *red, *green, *blue;
gamma_ramp(int screen, int leftIn, int topIn); // screen is ignored on OS/X and Windows
// leftIn and topIn are ignored on X11
~gamma_ramp();
void getGammaRamp(); // returns size
void setGammaRamp();
void setLinearGammaRamp();
private:
int getGammaRampSize();
void convertPrivShort2ramp_type();
void convert_ramp_type2short();
ramp_type_private* ramp_buffer;
int screen, left, top;
displayHandle display;
};
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The main thing of interest is how the code gets the handle to the display device so that it manipulates the correct video card gamma table.
For OS/X it looks like this:
CGPoint point;
CGDirectDisplayID getDisplay()
{
const int maxDisplays = 64; // 64 should be enough for any system
CGDisplayErr displayStatus;
CGDisplayCount displayCount; // Total number of display IDs
CGDirectDisplayID displayIDs[maxDisplays]; // Array of display IDs
displayStatus = CGGetDisplaysWithPoint ( point, maxDisplays, displayIDs, &displayCount);
if (displayStatus != kCGErrorSuccess || displayCount!= 1)
{
printf("CGGetDisplaysWithPoint returned error or the wrong number of displays\n");
return NULL;
}
else
return displayIDs[0];
}
gamma_ramp::gamma_ramp(int Screen, int leftIn, int topIn)
{
// screen = Screen;
left = leftIn;
top = topIn;
point.y = float(top);
point.x = float(left);
display = getDisplay();
screen = 0;
if (display == NULL)
{
ramp_buffer = 0;
red = 0;
green = 0;
blue = 0;
printf("gamma_ramp::gamma_ramp - error failed to get display handle");
}
else // do what needs to be done to set up the gamma tables
}
CGPoint point;
CGDirectDisplayID getDisplay()
{
const int maxDisplays = 64; // 64 should be enough for any system
CGDisplayErr displayStatus;
CGDisplayCount displayCount; // Total number of display IDs
CGDirectDisplayID displayIDs[maxDisplays]; // Array of display IDs
displayStatus = CGGetDisplaysWithPoint ( point, maxDisplays, displayIDs, &displayCount);
if (displayStatus != kCGErrorSuccess || displayCount!= 1)
{
printf("CGGetDisplaysWithPoint returned error or the wrong number of displays\n");
return NULL;
}
else
return displayIDs[0];
}
gamma_ramp::gamma_ramp(int Screen, int leftIn, int topIn)
{
// screen = Screen;
left = leftIn;
top = topIn;
point.y = float(top);
point.x = float(left);
display = getDisplay();
screen = 0;
if (display == NULL)
{
ramp_buffer = 0;
red = 0;
green = 0;
blue = 0;
printf("gamma_ramp::gamma_ramp - error failed to get display handle");
}
else // do what needs to be done to set up the gamma tables
}
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On Windows it looks like this:
static int numMatchingDisplays;
static RECT clipRegion;
static BOOL CALLBACK MonitorEnumProc(
HMONITOR hMonitor, // handle to display monitor
HDC hdcMonitor, // NULL, because EnumDisplayMonitors hdc is NULL
LPRECT displayCoordintes, // Virtual screen coordinates of this monitor
LPARAM name // Context data used to pass back display name in our case
)
{
MONITORINFOEX pmi;
if (displayCoordintes -> left <= clipRegion.left &&
displayCoordintes -> bottom >= clipRegion.top &&
displayCoordintes -> right >= clipRegion.left &&
displayCoordintes -> top <= clipRegion.top)
{
// display contains the widget
pmi.cbSize = sizeof(MONITORINFOEX);
if (GetMonitorInfo(hMonitor, (MONITORINFO *)&pmi) == 0)
{
printf("MonitorEnumProc - get_displays failed GetMonitorInfo\n");
return FALSE;
}
else // it worked we have the device we want
{
numMatchingDisplays++;
return TRUE;
}
}
else // this is OK as the device is not the one we want
{
return TRUE;
}
}
HDC getDisplay()
{
BOOL (WINAPI* pEnumDisplayDevices)(PVOID,DWORD,PVOID,DWORD);
char name[256];
HDC dispHand;
pEnumDisplayDevices = (BOOL (WINAPI*)(PVOID,DWORD,PVOID,DWORD)) GetProcAddress(LoadLibrary("USER32"), "EnumDisplayDevicesA");
numMatchingDisplays = 0;
if (EnumDisplayMonitors(NULL, NULL, MonitorEnumProc, (LPARAM)&name) == 0)
{
printf("getDisplay - EnumDisplayMonitors failed\n");
return NULL;
}
if (numMatchingDisplays != 1 ) // there is a problem we should only have one
{
printf("getDisplay - wrong number of displays %i", numMatchingDisplays);
return NULL;
}
else
{
if ((dispHand = CreateDC(name, name, NULL, NULL)) == NULL)
{
printf("getDisplay - CreateDC failed");
return NULL;
}
else
{
return dispHand;
}
}
}
gamma_ramp::gamma_ramp(int Screen, int leftIn, int topIn)
{
screen = Screen;
left = leftIn;
top = topIn;
clipRegion.left = left;
clipRegion.top = top;
display = getDisplay();
if (display == NULL)
{
ramp_buffer = 0;
red = 0;
green = 0;
blue = 0;
printf("gamma_ramp::gamma_ramp - error failed to get display handle");
}
else // set up the gamma tables
}
static int numMatchingDisplays;
static RECT clipRegion;
static BOOL CALLBACK MonitorEnumProc(
HMONITOR hMonitor, // handle to display monitor
HDC hdcMonitor, // NULL, because EnumDisplayMonitors hdc is NULL
LPRECT displayCoordintes, // Virtual screen coordinates of this monitor
LPARAM name // Context data used to pass back display name in our case
)
{
MONITORINFOEX pmi;
if (displayCoordintes -> left <= clipRegion.left &&
displayCoordintes -> bottom >= clipRegion.top &&
displayCoordintes -> right >= clipRegion.left &&
displayCoordintes -> top <= clipRegion.top)
{
// display contains the widget
pmi.cbSize = sizeof(MONITORINFOEX);
if (GetMonitorInfo(hMonitor, (MONITORINFO *)&pmi) == 0)
{
printf("MonitorEnumProc - get_displays failed GetMonitorInfo\n");
return FALSE;
}
else // it worked we have the device we want
{
numMatchingDisplays++;
return TRUE;
}
}
else // this is OK as the device is not the one we want
{
return TRUE;
}
}
HDC getDisplay()
{
BOOL (WINAPI* pEnumDisplayDevices)(PVOID,DWORD,PVOID,DWORD);
char name[256];
HDC dispHand;
pEnumDisplayDevices = (BOOL (WINAPI*)(PVOID,DWORD,PVOID,DWORD)) GetProcAddress(LoadLibrary("USER32"), "EnumDisplayDevicesA");
numMatchingDisplays = 0;
if (EnumDisplayMonitors(NULL, NULL, MonitorEnumProc, (LPARAM)&name) == 0)
{
printf("getDisplay - EnumDisplayMonitors failed\n");
return NULL;
}
if (numMatchingDisplays != 1 ) // there is a problem we should only have one
{
printf("getDisplay - wrong number of displays %i", numMatchingDisplays);
return NULL;
}
else
{
if ((dispHand = CreateDC(name, name, NULL, NULL)) == NULL)
{
printf("getDisplay - CreateDC failed");
return NULL;
}
else
{
return dispHand;
}
}
}
gamma_ramp::gamma_ramp(int Screen, int leftIn, int topIn)
{
screen = Screen;
left = leftIn;
top = topIn;
clipRegion.left = left;
clipRegion.top = top;
display = getDisplay();
if (display == NULL)
{
ramp_buffer = 0;
red = 0;
green = 0;
blue = 0;
printf("gamma_ramp::gamma_ramp - error failed to get display handle");
}
else // set up the gamma tables
}
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On X11 I just pass in the desktop -> screenNumber since X11 uses this to allow access to the video card gamma table. For for OS/X and Windows I needed to pass in a set of coordinates that were located on the display I wanted to manipulate the gamma table for and then parse through a list of devices to find the one that contained these coordinates and then get it's handle to use internal in the gamma_ramp class.
OS/X how to get physical display handle
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