Use glBlendFuncSeparate for alpha masking in tex.c

[grits] / examples / tex / tex.c

diff --git a/examples/tex/tex.c b/examples/tex/tex.c
index bef3a340c309b29124f0606fa2cd1920680446dc..5041226abce59f3dae5b93d463110ca64e66c25f 100644 (file)
--- a/examples/tex/tex.c
+++ b/examples/tex/tex.c
@@ -21,6 +21,28 @@
 #include <GL/gl.h>
 #include <GL/glu.h>
 
+#define crazy_draw(tex) \
+       for (int _i = 0; ({ \
+               if (_i == 0) { \
+                       /* Clear alpha buffer */ \
+                       glBindTexture(GL_TEXTURE_2D, tex); \
+                       glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); \
+                       glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); \
+                       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER); \
+                       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER); \
+                       glBlendFuncSeparate(GL_ZERO, GL_ONE, GL_ONE, GL_ZERO); \
+               } else if (_i == 1) { \
+                       /* Draw pixels */ \
+                       glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); \
+                       glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); \
+                       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP); \
+                       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP); \
+                       glBlendFuncSeparate(GL_DST_ALPHA, GL_ONE_MINUS_DST_ALPHA, GL_ZERO, GL_ZERO); \
+               } else { \
+                       glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA); \
+               } \
+       }), _i < 2; _i++)
+
 guint tex, texl, texr;
 
 gboolean on_key_press(GtkWidget *widget, GdkEventKey *event, gpointer _)
@@ -32,7 +54,7 @@ gboolean on_key_press(GtkWidget *widget, GdkEventKey *event, gpointer _)
 
 gboolean on_expose(GtkWidget *drawing, GdkEventExpose *event, gpointer _)
 {
-       gdouble y = 0.875;
+       gdouble y = 0;
 
        /* Setup view */
        glMatrixMode(GL_PROJECTION);
@@ -55,44 +77,33 @@ gboolean on_expose(GtkWidget *drawing, GdkEventExpose *event, gpointer _)
        glVertex3f( 0.25, -0.75, 0.0);
        glEnd();
 
-       /* Clear background for GL_ONE */
-       glEnable(GL_COLOR_MATERIAL);
-       glDisable(GL_TEXTURE_2D);
-       glColor4f(0.0, 0.0, 0.0, 0.0);
-       glBegin(GL_QUADS);
-       glVertex3f(-0.75,  0.0, 0.0);
-       glVertex3f(-0.75,  0.5, 0.0);
-       glVertex3f( 0.75,  0.5, 0.0);
-       glVertex3f( 0.75,  0.0, 0.0);
-       glEnd();
-
        /* Setup for textures */
        glEnable(GL_TEXTURE_2D);
        glEnable(GL_BLEND);
        glColor4f(1.0, 1.0, 1.0, 1.0);
        glDisable(GL_COLOR_MATERIAL);
-       glBlendFunc(GL_ONE, GL_ONE);
 
        /* Left */
-       glBindTexture(GL_TEXTURE_2D, texl);
-       glBegin(GL_QUADS);
-       glTexCoord2f( 0.0, y);     glVertex3f(-0.75,  0.0, 0.0);
-       glTexCoord2f( 0.0, 1.0);   glVertex3f(-0.75,  0.5, 0.0);
-       glTexCoord2f( 2.0, 1.0);   glVertex3f( 0.75,  0.5, 0.0);
-       glTexCoord2f( 2.0, y);     glVertex3f( 0.75,  0.0, 0.0);
-       glEnd();
+       crazy_draw(texl) {
+               glBegin(GL_QUADS);
+               glTexCoord2f( 0.0, y);     glVertex3f(-0.75,  0.0, 0.0);
+               glTexCoord2f( 0.0, 1.0);   glVertex3f(-0.75,  0.5, 0.0);
+               glTexCoord2f( 2.0, 1.0);   glVertex3f( 0.75,  0.5, 0.0);
+               glTexCoord2f( 2.0, y);     glVertex3f( 0.75,  0.0, 0.0);
+               glEnd();
+       }
 
        /* Right */
-       glBindTexture(GL_TEXTURE_2D, texr);
-       glBegin(GL_QUADS);
-       glTexCoord2f(-1.0, y);     glVertex3f(-0.75, 0.0, 0.0);
-       glTexCoord2f(-1.0, 1.0);   glVertex3f(-0.75, 0.5, 0.0);
-       glTexCoord2f( 1.0, 1.0);   glVertex3f( 0.75, 0.5, 0.0);
-       glTexCoord2f( 1.0, y);     glVertex3f( 0.75, 0.0, 0.0);
-       glEnd();
+       crazy_draw(texr) {
+               glBegin(GL_QUADS);
+               glTexCoord2f(-1.0, y);     glVertex3f(-0.75, 0.0, 0.0);
+               glTexCoord2f(-1.0, 1.0);   glVertex3f(-0.75, 0.5, 0.0);
+               glTexCoord2f( 1.0, 1.0);   glVertex3f( 0.75, 0.5, 0.0);
+               glTexCoord2f( 1.0, y);     glVertex3f( 0.75, 0.0, 0.0);
+               glEnd();
+       }
 
        /* Bottom */
-       glBlendFunc(GL_ONE, GL_ZERO);
        glBindTexture(GL_TEXTURE_2D, tex);
        glBegin(GL_QUADS);
        glTexCoord2f( 0.0, 0.0);   glVertex3f(-0.75, -0.5, 0.0);
@@ -132,8 +143,8 @@ guint load_tex(gchar *filename)
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
 
-       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER);
-       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_BORDER);
+       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
+       glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
        g_object_unref(pixbuf);
        return tex;
 }