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main.cpp
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main.cpp
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/*
* Code adapted from:
* https://www.opengl.org/wiki/Tutorial:_OpenGL_3.0_Context_Creation_(GLX)
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <GL/glew.h>
#include <GL/gl.h>
#include <GL/glx.h>
#include "common/error.h"
#define GLX_CONTEXT_MAJOR_VERSION_ARB 0x2091
#define GLX_CONTEXT_MINOR_VERSION_ARB 0x2092
typedef GLXContext (*glXCreateContextAttribsARBProc)
(Display*, GLXFBConfig, GLXContext, Bool, const int*);
const int visual_attribs[] = {
GLX_X_RENDERABLE , true,
GLX_DRAWABLE_TYPE , GLX_WINDOW_BIT,
GLX_RENDER_TYPE , GLX_RGBA_BIT,
GLX_X_VISUAL_TYPE , GLX_TRUE_COLOR,
GLX_RED_SIZE , 8,
GLX_GREEN_SIZE , 8,
GLX_BLUE_SIZE , 8,
GLX_ALPHA_SIZE , 8,
GLX_DEPTH_SIZE , 0,
GLX_STENCIL_SIZE , 0,
GLX_DOUBLEBUFFER , true,
None
};
void checkGlxVersion(Display* display) {
int glx_major, glx_minor;
// FBConfigs were added in GLX version 1.3.
if (!glXQueryVersion(display, &glx_major, &glx_minor) ||
((glx_major == 1) && (glx_minor < 3)) || (glx_major < 1))
fail("Invalid GLX version");
}
GLXFBConfig chooseFBConfig(Display* display) {
printf("Getting matching framebuffer configs\n");
int fbcount;
GLXFBConfig* fbc = glXChooseFBConfig(display, DefaultScreen(display),
visual_attribs, &fbcount);
if (!fbc)
fail("Failed to retrieve a framebuffer config\n");
printf("Found %d matching FB configs.\n", fbcount);
// Pick the FB config/visual with the most samples per pixel
printf("Getting XVisualInfos\n");
int best_fbc = -1, worst_fbc = -1, best_num_samp = -1,
worst_num_samp = 999;
for (int i = 0; i < fbcount; ++i) {
XVisualInfo *vi = glXGetVisualFromFBConfig(display, fbc[i]);
if (vi) {
int samp_buf, samples;
glXGetFBConfigAttrib(display, fbc[i], GLX_SAMPLE_BUFFERS,
&samp_buf);
glXGetFBConfigAttrib(display, fbc[i], GLX_SAMPLES, &samples);
printf("\tMatching fbconfig %d, visual ID 0x%2lx: "
"SAMPLE_BUFFERS = %d, SAMPLES = %d\n",
i, vi -> visualid, samp_buf, samples);
if (best_fbc < 0 || (samp_buf && samples) > best_num_samp)
best_fbc = i, best_num_samp = samples;
if (worst_fbc < 0 || !samp_buf || samples < worst_num_samp)
worst_fbc = i, worst_num_samp = samples;
}
XFree(vi);
}
XFree(fbc);
return fbc[best_fbc];
}
GLXContext createContext(Display* display, GLXFBConfig bestFbc) {
// NOTE: It is not necessary to create or make current to a context before
// calling glXGetProcAddressARB
glXCreateContextAttribsARBProc glXCreateContextAttribsARB = 0;
glXCreateContextAttribsARB = (glXCreateContextAttribsARBProc)
glXGetProcAddressARB((const GLubyte *) "glXCreateContextAttribsARB");
int context_attribs[] = {
GLX_CONTEXT_MAJOR_VERSION_ARB, 3,
GLX_CONTEXT_MINOR_VERSION_ARB, 0,
//GLX_CONTEXT_FLAGS_ARB, GLX_CONTEXT_FORWARD_COMPATIBLE_BIT_ARB,
None
};
printf("Creating context\n");
GLXContext context = 0;
context = glXCreateContextAttribsARB(display, bestFbc, 0,
true, context_attribs);
// Sync to ensure any errors generated are processed.
XSync(display, false);
if (context) printf("Created GL 3.0 context\n");
else fail("Failed to create GL 3.0 context\n");
// Sync to ensure any errors generated are processed.
XSync(display, false);
if (! glXIsDirect(display, context))
printf("Indirect GLX rendering context obtained\n");
else
printf("Direct GLX rendering context obtained\n");
return context;
}
void initGlew() {
glewExperimental = GL_TRUE;
GLenum err = glewInit();
if(err != GLEW_OK)
fail("glewInit failed: %s\n", glewGetErrorString(err));
printGlErrors();
}
int main(int argc, char* argv[]) {
Display *display = XOpenDisplay(NULL);
if (!display)
fail("Failed to open X display\n");
checkGlxVersion(display);
auto bestFbc = chooseFBConfig(display);
// Get a visual
XVisualInfo *vi = glXGetVisualFromFBConfig(display, bestFbc);
printf("Chosen visual ID = 0x%lx\n", vi->visualid);
printf("Creating colormap\n");
XSetWindowAttributes swa;
Colormap cmap;
swa.colormap = cmap = XCreateColormap(display,
RootWindow(display, vi->screen),
vi->visual, AllocNone);
swa.background_pixmap = None ;
swa.border_pixel = 0;
swa.event_mask = StructureNotifyMask;
printf("Creating window\n");
Window win = XCreateWindow(display, RootWindow(display, vi->screen),
0, 0, 100, 100, 0, vi->depth, InputOutput,
vi->visual,
CWBorderPixel|CWColormap|CWEventMask, &swa);
if (!win)
fail("Failed to create window.\n");
// Done with the visual info data
XFree(vi);
XStoreName(display, win, "GL 3.0 Window");
printf("Mapping window\n");
XMapWindow(display, win);
auto context = createContext(display, bestFbc);
printf("Making context current\n");
glXMakeCurrent(display, win, context);
initGlew();
printf("Version: %s\n", glGetString(GL_VERSION));
GLint alpha_bits = 0;
GLint depth_bits = 0;
GLint stencil_bits = 0;
printGlErrors();
if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
fail("framebuffer not initialized properly");
printGlErrors();
glBindFramebuffer(GL_FRAMEBUFFER, 0);
glGetFramebufferAttachmentParameteriv(GL_FRAMEBUFFER, GL_BACK_LEFT,
GL_FRAMEBUFFER_ATTACHMENT_ALPHA_SIZE, &alpha_bits);
printGlErrors();
printf("alpha bits: %d\n", alpha_bits);
glGetFramebufferAttachmentParameteriv(
GL_FRAMEBUFFER, GL_DEPTH,
GL_FRAMEBUFFER_ATTACHMENT_DEPTH_SIZE, &depth_bits);
printGlErrors();
printf("depth bits: %d\n", depth_bits);
glGetFramebufferAttachmentParameteriv(
GL_FRAMEBUFFER, GL_STENCIL,
GL_FRAMEBUFFER_ATTACHMENT_STENCIL_SIZE, &stencil_bits);
printGlErrors();
printf("stencil bits: %d\n", stencil_bits);
glClearColor(0, 0.5, 1, 1);
glClear(GL_COLOR_BUFFER_BIT);
glXSwapBuffers(display, win);
glBindFramebuffer(GL_FRAMEBUFFER, 0);
sleep(1);
glClearColor(1, 0.5, 0, 1);
glClear(GL_COLOR_BUFFER_BIT);
glXSwapBuffers(display, win);
sleep(1);
glXMakeCurrent(display, 0, 0);
glXDestroyContext(display, context);
XDestroyWindow(display, win);
XFreeColormap(display, cmap);
XCloseDisplay(display);
return 0;
}