+ GLint stencilbits = 0;
+ glGetIntegerv(GL_STENCIL_BITS, &stencilbits);
+ if ( stencilbits < 1 ) {
+ fprintf(stderr, "Failed to get a stencil buffer!\n");
+ SDL_Quit();
+ return false;
+ }
+
+ fprintf(stderr, "Stencil buffer has %i bits, good.\n", stencilbits);
+ fprintf(stderr, "Screen width is %i, height is %i\n", kContextWidth, kContextHeight);
+
+ glEnable( GL_STENCIL_TEST);
+ glClearStencil(0);
+ glClear( GL_STENCIL_BUFFER_BIT );
+ glStencilFunc(GL_ALWAYS, 0x1, 0x1);
+ glStencilOp(GL_REPLACE, GL_REPLACE, GL_REPLACE);
+
+
+ glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
+ glPixelStorei(GL_UNPACK_ROW_LENGTH, 3);
+ glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
+ glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
+ glColorMask( 1.0, 1.0, 1.0, 1.0 );
+ char stencil[] = {64,127,255};
+
+ glViewport(0,0, kContextWidth, kContextHeight);
+ glMatrixMode(GL_PROJECTION);
+ glLoadIdentity();
+ glOrtho((GLdouble)0, (GLdouble)kContextWidth, (GLdouble)kContextHeight, 0, -1, 1);
+ glMatrixMode(GL_MODELVIEW);
+ glLoadIdentity();
+
+ for(int y=0;y<kContextHeight;y+=2) {
+
+ for(int x=0;x<kContextWidth;x++) {
+ glRasterPos2i(x, y);
+ glDrawPixels(1, 1, GL_RGB, GL_UNSIGNED_BYTE, &stencil);
+ }
+ }
+
+ glStencilFunc(GL_NOTEQUAL, 0x01, 0x01);
+ glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
+
+ // Something gets screwed up due to the changes above
+ // revert to default.
+ glPixelStorei(GL_UNPACK_ALIGNMENT, 4);
+ glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
+ glPixelStorei(GL_UNPACK_SKIP_ROWS, 0);
+ glPixelStorei(GL_UNPACK_SKIP_PIXELS, 0);
+