[Xcb-commit] opengl.mdwn
XCB site
xcb at freedesktop.org
Tue Jun 30 01:31:08 PDT 2009
opengl.mdwn | 216 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 216 insertions(+)
New commits:
commit 084fceb5a3ec798957aa9fca81b0d44318f1f7e3
Author: riku <riku at web>
Date: Tue Jun 30 01:31:08 2009 -0700
Added table of contents and OpenGL sample code
diff --git a/opengl.mdwn b/opengl.mdwn
index 0adbe74..144f9ea 100644
--- a/opengl.mdwn
+++ b/opengl.mdwn
@@ -1,3 +1,5 @@
+[[!toc]]
+
# The big picture: OpenGL, Xlib and GLX
A typical X Windowing System application is built using Xlib to communicate with the X server. Xlib has been the standard programming interface to the X Windowing System for decades. An OpenGL application on X Windows must use GLX, a standardized API, to set up a rendering context. The GLX API is closely coupled with Xlib.
@@ -29,3 +31,217 @@ The obvious problem is that the GLX is a standardized API and has dozens of diff
A proof-of-concept design and implementation could be done using MESA, an open source OpenGL implementation.
To maintain backward compatibility and providing an incremental porting path, the current GLX API could be implemented using the XCB’ified API underneath like the XCB-based Xlib implementation does.
+# Sample code of OpenGL with XCB and Xlib
+
+ #include <stdio.h>
+ #include <stdlib.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>
+
+ void draw()
+ {
+ glClearColor(0.2, 0.4, 0.9, 1.0);
+ glClear(GL_COLOR_BUFFER_BIT);
+ }
+
+ 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;
+ }
+
+ int setup_and_run(Display* display, xcb_connection_t *connection, int default_screen, xcb_screen_t *screen)
+ {
+ int visualID = 0;
+
+ /* Query framebuffer configurations */
+ GLXFBConfig *fb_configs = 0;
+ int num_fb_configs = 0;
+ fb_configs = glXGetFBConfigs(display, default_screen, &num_fb_configs);
+ if(!fb_configs || num_fb_configs == 0)
+ {
+ fprintf(stderr, "glXGetFBConfigs failed\n");
+ return -1;
+ }
+
+ /* Select first framebuffer config and query visualID */
+ GLXFBConfig fb_config = fb_configs[0];
+ glXGetFBConfigAttrib(display, fb_config, GLX_VISUAL_ID , &visualID);
+
+ GLXContext context;
+
+ /* Create OpenGL context */
+ 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 */
+ xcb_create_colormap(
+ connection,
+ XCB_COLORMAP_ALLOC_NONE,
+ colormap,
+ screen->root,
+ visualID
+ );
+
+ /* Create window */
+ uint32_t eventmask = XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_KEY_PRESS;
+ uint32_t valuelist[] = { eventmask, colormap, 0 };
+ uint32_t valuemask = XCB_CW_EVENT_MASK | XCB_CW_COLORMAP;
+
+ xcb_create_window(
+ connection,
+ XCB_COPY_FROM_PARENT,
+ window,
+ screen->root,
+ 0, 0,
+ 150, 150,
+ 0,
+ XCB_WINDOW_CLASS_INPUT_OUTPUT,
+ visualID,
+ valuemask,
+ valuelist
+ );
+
+
+ // NOTE: window must be mapped before glXMakeContextCurrent
+ xcb_map_window(connection, window);
+
+ /* 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, window);
+
+ xcb_destroy_window(connection, window);
+
+ glXDestroyContext(display, context);
+
+ return retval;
+ }
+
+ int main(int argc, char* argv[])
+ {
+ Display *display;
+ int default_screen;
+
+ /* Open Xlib Display */
+ display = XOpenDisplay(0);
+ if(!display)
+ {
+ fprintf(stderr, "Can't open display\n");
+ return -1;
+ }
+
+ default_screen = DefaultScreen(display);
+
+ /* 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 */
+ xcb_screen_t *screen = 0;
+ xcb_screen_iterator_t screen_iter =
+ xcb_setup_roots_iterator(xcb_get_setup(connection));
+ for(int screen_num = default_screen;
+ screen_iter.rem && screen_num > 0;
+ --screen_num, xcb_screen_next(&screen_iter));
+ screen = screen_iter.data;
+
+ /* Initialize window and OpenGL context, run main loop and deinitialize */
+ int retval = setup_and_run(display, connection, default_screen, screen);
+
+ /* Cleanup */
+ XCloseDisplay(display);
+
+ return retval;
+ }
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