[Scummvm-devel] Overlay handling

Marcus Comstedt marcus at mc.pp.se
Wed Jan 21 02:37:31 CET 2009


Max Horn <max at quendi.de> writes:

> Right now we implement transparency for the overlays by making a copy  
> of the game graphics to the overlay, then blitting our data atop it.  
> Makes it difficult for backends to speed up things with OpenGL etc.  
> and of course also impossible (with sane computation time) to work  
> atop changing game graphics.

Actually, an OpenGL accelerated overlay should not be difficult
at all.  You just need to do what I do in the Dreamcast port:

* Use a pixel format with a couple of alpha bits for the overlay
* Make the OSystem return true for the kFeatureOverlaySupportsAlpha
  feature
* Make clearOverlay() fill the overlay with transparent pixels,
  nothing should be copied from the game graphics

Then the overlay will work just fine atop changing game graphics.
This support has been there for almost 4 years.  :-)


  // Marcus






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