static void
update_viewport( struct st_context *st )
{
- GLcontext *ctx = st->ctx;
+ struct gl_context *ctx = st->ctx;
GLfloat yScale, yBias;
/* _NEW_BUFFERS
*/
if (st_fb_orientation(ctx->DrawBuffer) == Y_0_TOP) {
+ /* Drawing to a window. The corresponding gallium surface uses
+ * Y=0=TOP but OpenGL is Y=0=BOTTOM. So we need to invert the viewport.
+ */
yScale = -1;
yBias = (GLfloat)ctx->DrawBuffer->Height;
}
else {
+ /* Drawing to an FBO where Y=0=BOTTOM, like OpenGL - don't invert */
yScale = 1.0;
yBias = 0.0;
}