It would be good to have a somewhat fuller explanation of what surface and channel alpha actually mean and how they compare, and a few use cases for common things that people want to do (like composing transparent PNGs). Right now it appears to be explained more or less directly in terms of the underlying C API symbols and not in terms of results (i.e. what you will see.)
> I need to type up a description of how lispbuilder-sdl handles surfaces. > Here is a short description of the :SURFACE-ALPHA, :CHANNEL-ALPHA and > :ALPHA flags. > > :ALPHA - Deprecated. Don't use anymore. > > :SURFACE-ALPHA - Sets SDL_SRCALPHA as well as the SDL_Surface alpha value. > > :CHANNEL-ALPHA - Sets the alpha mask for the pixels of a SURFACE (the A of > RGBA). > > However reading through SDL_SetAlpha it seems that we should allow setting > the SDL_Surface alpha value, without mandating that SDL_SRCALPHA is also > set. > > I need to figure out how to do this without breaking everything. I'll > probably add a :SRCALPHA keyword which will default to T if :SURFACE-ALPHA > is set, but can also be explicitely set to NIL. > > - Luke > _______________________________________________ > application-builder mailing list > [email protected] > http://www.lispniks.com/mailman/listinfo/application-builder _______________________________________________ application-builder mailing list [email protected] http://www.lispniks.com/mailman/listinfo/application-builder
