Daniel Gibson
Currently, SDL_CreateRGBSurface() and SDL_CreateRGBSurfaceFrom() take Uint32 masks for RGBA to "describe" the Pixelformat of the surface.
Internally those value are only used to map to one of the SDL_PIXELFORMAT_* enum values that are used for further processing.
I think it would be both handy and more efficient to be able to specify SDL_PIXELFORMAT_* yourself without using SDL_PixelFormatEnumToMasks() to create masks first, so I implemented functions that do that:
SDL_CreateRGBSurfaceWithFormat() and SDL_CreateRGBSurfaceWithFormatFrom() which are like the versions without "WithFormat" but instead of taking 4 Uint32s for R/G/B/A masks, they take one for a SDL_PIXELFORMAT_* enum value.
Together with https://bugzilla.libsdl.org/show_bug.cgi?id=2923 creating a SDL_Surface* from RGBA data (e.g. from stb_image) is as easy as
surf = SDL_SDL_CreateRGBSurfaceWithFormat(0, w, h, bppToUse*8, SDL_PIXELFORMAT_RGBA32);
Simon Hug
The current SDL_SaveBMP_RW function that saves surfaces to a BMP uses an old bitmap header which doesn't officially support alpha channels. Applications just ignore the byte where the alpha is stored. This can easily be extended by using a newer header version and setting the alpha mask.
The attached patch has these changes:
- Extending the description of the function in the SDL_surface.h header with the supported formats.
- Refining when surfaces get stored to a 32-bit BMP. (Must have bit depth of 8 or higher and must have an alpha mask or colorkey.)
- Fixing a small bug that saves 24-bit BGR surfaces with a colorkey in a 24-bit BMP.
- Adding code that switches to the bitmap header version 4 if the surface has an alpha mask or colorkey. (I chose version 4 because Microsoft didn't lose its documentation behind a file cabinet like they did with version 3.)
- Adding a hint that can disable the use of the version 4 header. This is for people that need the legacy header or like the old behavior better. (I'm not sure about the hint name, though. May need changing if there are any rules to that.)
The internal function SDL_EGL_LoadLibrary() did not delete and remove a mostly
uninitialized data structure if loading the library first failed. A later try to
use EGL then skipped initialization and assumed it was previously successful
because the data structure now already existed. This led to at least one crash
in the internal function SDL_EGL_ChooseConfig() because a NULL pointer was
dereferenced to make a call to eglBindAPI().
