int width = 64;
int height = 64;
+static void
+set_2d_projection (void)
+{
+ glMatrixMode (GL_PROJECTION);
+ glLoadIdentity ();
+ glOrtho (0, width, height, 0, 0, 1);
+ glMatrixMode (GL_MODELVIEW);
+}
+
+static void
+draw_fullscreen_quad (void)
+{
+ glBegin (GL_QUADS);
+ glVertex2f (0, 0);
+ glVertex2f (width, 0);
+ glVertex2f (width, height);
+ glVertex2f (0, height);
+ glEnd ();
+}
+
+static void
+draw_fullscreen_textured_quad (void)
+{
+ glBegin (GL_QUADS);
+ glTexCoord2f(0, 0); glVertex2f (0, 0);
+ glTexCoord2f(1, 0); glVertex2f (width, 0);
+ glTexCoord2f(1, 1); glVertex2f (width, height);
+ glTexCoord2f(0, 1); glVertex2f (0, height);
+ glEnd ();
+}
+
static void
paint_rgb_using_clear (double r, double g, double b)
{
glUniform4f (color, r, g, b, 1.0);
- glMatrixMode (GL_PROJECTION);
- glLoadIdentity ();
- glOrtho (0, width, height, 0, 0, 1);
- glMatrixMode (GL_MODELVIEW);
-
- glBegin (GL_QUADS);
- glVertex2f (0, 0);
- glVertex2f (width, 0);
- glVertex2f (width, height);
- glVertex2f (0, height);
- glEnd ();
+ draw_fullscreen_quad ();
glUseProgram (0);
}
+static GLuint
+create_rgb_texture (double r, double g, double b)
+{
+ uint8_t data[3];
+ GLuint texture = 0;
+
+ data[0] = (uint8_t) (255.0 * r);
+ data[1] = (uint8_t) (255.0 * g);
+ data[2] = (uint8_t) (255.0 * b);
+
+ glGenTextures (1, &texture);
+
+ glBindTexture (GL_TEXTURE_2D, texture);
+
+ glTexImage2D (GL_TEXTURE_2D,
+ 0, GL_COMPRESSED_RGBA,
+ 1, 1, 0,
+ GL_RGB, GL_UNSIGNED_BYTE, data);
+
+ return texture;
+}
+
+static void
+paint_using_texture (GLuint texture)
+{
+ glBindTexture (GL_TEXTURE_2D, texture);
+
+ glEnable (GL_TEXTURE_2D);
+
+ draw_fullscreen_textured_quad ();
+
+ glDisable (GL_TEXTURE_2D);
+}
+
static void
draw (Display *dpy, Window window, int width, int height)
{
+#define PASSES 2
+ int i;
GLenum glew_err;
+ GLuint texture[PASSES];
int visual_attr[] = {
GLX_RGBA,
glViewport(0, 0, width, height);
- /* Frame 1: Draw a solid (magenta) frame using glClear. */
- paint_rgb_using_clear (1, 0, 1);
- glXSwapBuffers (dpy, window);
+ set_2d_projection ();
+
+/* Simply count through some colors, frame by frame. */
+#define RGB(frame) (((frame+1)/4) % 2), (((frame+1)/2) % 2), ((frame+1) % 2)
+
+ int frame = 0;
+ for (i = 0; i < PASSES; i++) {
+
+ /* Frame: Draw a solid frame using glClear. */
+ paint_rgb_using_clear (RGB(frame));
+ glXSwapBuffers (dpy, window);
+ frame++;
+
+ /* Frame: Draw a solid frame using GLSL. */
+ paint_rgb_using_glsl (RGB(frame));
+ glXSwapBuffers (dpy, window);
+ frame++;
+
+ /* Frame: Draw a solid frame using a texture. */
+ texture[i] = create_rgb_texture (RGB(frame));
+ paint_using_texture (texture[i]);
+ glXSwapBuffers (dpy, window);
+ frame++;
+ }
- /* Frame 2: Draw a solid (yellow) frame using GLSL. */
- paint_rgb_using_glsl (1, 1, 0);
- glXSwapBuffers (dpy, window);
+ /* Draw another frame with a re-used texture. */
+ paint_using_texture (texture[0]);
+ glXSwapBuffers (dpy, window);
+ frame++;
/* Cleanup */
glXDestroyContext (dpy, ctx);