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#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <X11/Xlib.h>
/*
If you get linking errors when using C++, you need
to add extern "C" here or in X11-xcb.h, unless
this bug is already fixed in your version:
http://bugs.freedesktop.org/show_bug.cgi?id=22252
*/
#include <X11/Xlib-xcb.h> /* for XGetXCBConnection, link with libX11-xcb */
#include <xcb/xcb.h>
#include <GL/glx.h>
#include <GL/gl.h>
static
void draw()
{
glClearColor(0.2, 0.4, 0.9, 1.0);
glClear(GL_COLOR_BUFFER_BIT);
}
static
int main_loop(
Display *display,
xcb_connection_t *connection,
xcb_window_t window,
GLXDrawable drawable )
{
int running = 1;
while(running) {
/* Wait for event */
xcb_generic_event_t *event = xcb_wait_for_event(connection);
if( !event ) {
fprintf(stderr, "i/o error in xcb_wait_for_event");
return -1;
}
switch(event->response_type & ~0x80) {
case XCB_KEY_PRESS:
/* Quit on key press */
running = 0;
break;
case XCB_EXPOSE:
/* Handle expose event, draw and swap buffers */
draw();
glXSwapBuffers(display, drawable);
break;
default:
break;
}
free(event);
}
return 0;
}
static
int setup_and_run(
Display* display,
xcb_connection_t *connection,
int default_screen,
xcb_screen_t *screen )
{
xcb_generic_error_t *error;
/* Query framebuffer configurations */
int num_fb_configs = 0;
GLXFBConfig * const fb_configs = glXGetFBConfigs(display, default_screen, &num_fb_configs);
if( !fb_configs || !num_fb_configs ){
fprintf(stderr, "glXGetFBConfigs failed\n");
return -1;
}
GLXFBConfig fb_config;
int visualID = 0;
for(int i = 0; !visualID && i < num_fb_configs; ++i) {
/* Select first framebuffer config with a valid visual and query visualID */
fb_config = fb_configs[i];
XVisualInfo * const visual = glXGetVisualFromFBConfig(display, fb_config);
if( !visual ) { continue; }
visualID = visual->visualid;
}
if( !visualID ) {
return -1;
}
/* Create OpenGL context */
GLXContext const context = glXCreateNewContext(display, fb_config, GLX_RGBA_TYPE, 0, True);
if( !context ) {
fprintf(stderr, "glXCreateNewContext failed\n");
return -1;
}
/* Create XID's for colormap and window */
xcb_colormap_t colormap = xcb_generate_id(connection);
xcb_window_t window = xcb_generate_id(connection);
/* Create colormap */
if((error = xcb_request_check(connection, xcb_create_colormap_checked(
connection,
XCB_COLORMAP_ALLOC_NONE,
colormap,
screen->root,
visualID)
)
)){
fprintf(stderr, "error creating colormap: %d\n", error->error_code);
free(error);
return -1;
}
/* Create window */
uint32_t const eventmask = XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_KEY_PRESS;
uint32_t const valuelist[] = { eventmask, colormap };
uint32_t const valuemask = XCB_CW_EVENT_MASK | XCB_CW_COLORMAP;
if((error= xcb_request_check(connection, xcb_create_window_checked(
connection,
XCB_COPY_FROM_PARENT,
window,
screen->root,
0, 0,
150, 150,
0,
XCB_WINDOW_CLASS_INPUT_OUTPUT,
visualID,
valuemask,
valuelist)
)
)){
fprintf(stderr, "error creating window: %d\n", error->error_code);
return -1;
}
// NOTE: window must be mapped before glXMakeContextCurrent
if((error= xcb_request_check(connection, xcb_map_window(connection, window)) )) {
fprintf(stderr, "error mapping window");
return -1;
}
/* Create GLX Window */
GLXDrawable drawable = 0;
GLXWindow glxwindow = glXCreateWindow(display, fb_config, window, 0);
if( !window ) {
xcb_destroy_window(connection, window);
glXDestroyContext(display, context);
fprintf(stderr, "glXDestroyContext failed\n");
return -1;
}
drawable = glxwindow;
/* make OpenGL context current */
if( !glXMakeContextCurrent(display, drawable, drawable, context) ) {
xcb_destroy_window(connection, window);
glXDestroyContext(display, context);
fprintf(stderr, "glXMakeContextCurrent failed\n");
return -1;
}
/* run main loop */
int retval = main_loop(display, connection, window, drawable);
/* Cleanup */
glXDestroyWindow(display, glxwindow);
xcb_destroy_window(connection, window);
glXDestroyContext(display, context);
return retval;
}
static
void screen_from_Xlib_Display(
Display * const display,
xcb_connection_t *connection,
int * const out_screen_num,
xcb_screen_t ** const out_screen)
{
xcb_screen_iterator_t screen_iter = xcb_setup_roots_iterator(xcb_get_setup(connection));
int screen_num = DefaultScreen(display);
while( screen_iter.rem && screen_num > 0 ) {
xcb_screen_next(&screen_iter);
--screen_num;
}
*out_screen_num = screen_num;
*out_screen = screen_iter.data;
}
int main(int argc, char* argv[])
{
Display *display;
/* Open Xlib Display */
display = XOpenDisplay(0);
if( !display ) {
fprintf(stderr, "Can't open display\n");
return -1;
}
/* Get the XCB connection from the display */
xcb_connection_t *connection = XGetXCBConnection(display);
if( !connection ) {
XCloseDisplay(display);
fprintf(stderr, "Can't get xcb connection from display\n");
return -1;
}
/* Acquire event queue ownership */
XSetEventQueueOwner(display, XCBOwnsEventQueue);
/* Find XCB screen */
int screen_num;
xcb_screen_t *screen = 0;
screen_from_Xlib_Display(display, connection, &screen_num, &screen);
if( !screen ) {
return -1;
}
/* Initialize window and OpenGL context, run main loop and deinitialize */
int retval = setup_and_run(display, connection, screen_num, screen);
/* Cleanup */
XCloseDisplay(display);
return retval;
}
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