Re: [AD] alpha blending in new GFX API

[Robert Jr Ohannessian <rohannessian@xxxxxxxxxx>]

This was really not the intent. The intent here to have memory/video 
bitmaps inherit the necessary parameters from the parent bitmaps for 
being able to be blited properly. For example, we'd probably want the 
OpenGL context handle ((HGLRC, HDC) pair in Windows), or the proper 
component ordering.

al_create_bitmap_2() (which probably needs a better name) is there to 
actually explicitly allow differing formats.


Milan Mimica wrote:
> The short question: Will alpha blending will available in color depth
> lower then 32-bit?
>
>
> How I see it in http://allegro.dotsrc.org/future/gfx-api.txt, the
> programmer won't be able to create a RGBA bitmap in 16-bit color depth
> (or any other lower then 32-bit mode). The only assumption I'm making is
> that al_create_display_bitmap() will fail with other then desktop's 
> color depths on platforms that not allow changing color depth on the 
> fly, like X11.
>
> Bitmaps created with al_create_bitmap() inherit color format from the
> parent. Hence, you can only create video bitmaps with the same color
> format as the display bitmap. You see the problem? No way to create a 
> RGBA video bitmap. No way to do hardware accelerated blending in 16-bit 
> mode. OpenGL does allow that.
>
> Allegro 4.2.1 + AllegroGL suffers from the same design problem. I was
> looking if I could implement alpha blending in AGL, but couldn't because 
> I cannot run my X server in 32-bit color depth.