Amask and SDL_SRCALPHA (Sam?)

SDL Development
1

Mattias Engdeg?rd wrote:

Okay, this is the bit that doesn’t make sense to me. Why is SDL_SRCALPHA
set if Amask != 0?

I think it was Sam who put it in so I’ll let him answer. Anyway it’s just

Sam?

but rather a behaviour for SDL_BlitSurface. It seems like [SDL_SRCALPHA]

would make more sense for SDL_SRCALPHA to be given in a “flags” argument

to SDL_BlitSurface than being a surface property.
my opinion as well and one of many things I would like to change for
an API revision, but in 1.2 we’re stuck with this

Okay, fair enough.

make it

SDL_SetAlpha(rgba, rgba->flags & (SDL_RLEACCEL | SDL_RLEACCELOK), 0);

and it should work. This is another quirk: when you set SDL_RLEACCEL
(either by calling SetAlpha or SetColorKey), SDL_RLEACCEL isn’t set at
once but just SDL_RLEACCELOK to mark the surface as RLE-able, and at
the next blit it will be RLE-coded and SDL_RLEACCEL will be set to
mark it as such

yes, this is another thing that should be cleaned up

Great, thanks for all your help.

  • Mike
2

Mattias Engdeg?rd wrote:

Okay, this is the bit that doesn’t make sense to me. Why is SDL_SRCALPHA
set if Amask != 0?

I think it was Sam who put it in so I’ll let him answer. Anyway it’s just

Sam?

Presumeably if you have a surface with an alpha channel, you want to do
alpha blending. :slight_smile:

See ya!
-Sam Lantinga, Lead Programmer, Loki Software, Inc.