Set display gamma value on Linux using Xlib

set_display_gamma_linux.cpp

#include <iostream>
#include <X11/Xlib.h>
#include <X11/extensions/xf86vmode.h>

/* How to compile:
g++ -o set_gamma_linux.o -c set_gamma_linux.cpp
g++ -o set_gamma_linux set_gamma_linux.o -L/usr/lib -L/usr/local/lib -lX11 -lXxf86vm
*/

void log(const char* message);

int main(int argc, char **argv)
{
	// open default display
	Display* display = XOpenDisplay(NULL);

	if(!display)
	{
		log("XOpenDisplay(NULL) failed.");
		return -1;
	}

	log("XOpenDisplay(NULL) ok.");

	// get default screen
	int screen = DefaultScreen(display);

	// init gamma value
	XF86VidModeGamma gamma;
	gamma.red = 0.5;
	gamma.green = 0.5;
	gamma.blue = 0.5;

	// set gamma
	if(!XF86VidModeSetGamma(display, screen, &gamma))
	{
		log("XF86VidModeSetGamma failed.");
		return -1;
	}

	log("XF86VidModeSetGamma ok.");

	XCloseDisplay(display);

	return 0;
}

void log(const char* message)
{
	std::cout << message << std::endl;
}