[Xcb] [PATCH] Improve opengl tutorial

[Thomas Fischer]

---
diff --git a/opengl.mdwn b/opengl.mdwn
index 4573512..8b9ec9e 100644
--- a/opengl.mdwn
+++ b/opengl.mdwn
@@ -51,6 +51,28 @@ To maintain backward compatibility and providing an
incremental porting path, th
                #include <GL/glx.h>
                #include <GL/gl.h>

+               /*
+                       Attribs filter the list of FBConfigs returned by
glXChooseFBConfig().
+                       Visual attribs further described in
glXGetFBConfigAttrib(3)
+               */
+               static 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, 24,
+                       GLX_STENCIL_SIZE, 8,
+                       GLX_DOUBLEBUFFER, True,
+                       //GLX_SAMPLE_BUFFERS  , 1,
+                       //GLX_SAMPLES         , 4,
+                       None
+               };
+
                void draw()
                {
                        glClearColor(0.2, 0.4, 0.9, 1.0);
@@ -95,16 +117,17 @@ To maintain backward compatibility and providing an
incremental porting path, th
                {
                        int visualID = 0;

-                       /* Query framebuffer configurations */
+                       /* Query framebuffer configurations that match
visual_attribs */
                        GLXFBConfig *fb_configs = 0;
                        int num_fb_configs = 0;
-                       fb_configs = glXGetFBConfigs(display,
default_screen, &num_fb_configs);
+                       fb_configs = glXChooseFBConfig(display,
default_screen, visual_attribs, &num_fb_configs);
                        if(!fb_configs || num_fb_configs == 0)
                        {
                                fprintf(stderr, "glXGetFBConfigs failed\n");
                                return -1;
                        }
-
+                       printf("Found %d matching FB configs",
num_fb_configs);
+
                        /* Select first framebuffer config and query
visualID */
                        GLXFBConfig fb_config = fb_configs[0];
                        glXGetFBConfigAttrib(display, fb_config,
GLX_VISUAL_ID , &visualID);
---
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