Edmund Horner
When a 16-bit "565 format" surface has a colour key set, it will blit with correct transparency. If, however, it has its colour key set then is converted to a 32-bit ARGB format surface, the colour key in the converted image will not necessarily be the same pixel value as the transparent pixels. It may not blit correctly, because the colour key does not match the right pixels.
In my case, with an image using 0xB54A for transparency, the colour key was converted to 180,170,82; but the corresponding pixels (with the same original value) were converted to 180,169,82. Blitting the converted image did not use transparency where expected.
I have attached a test case. The bug has been replicated on both x86_64 Linux (SDL 2.0.2), and 32-bit MS C++ 2010 on Windows (SDL 2.0.0).
Sylvain
Let's you have a SDL_Surface that has ColorKey, but no Alpha Modulation.
When this surface is duplicated with SDL_ConvertSurface function, the result has ColorKey and Alpha Modulation (BLEND, and Opaque 255).
I think SDL_ConvertSurface should strictly keeps the input format.
example
=======
SDL_Surface *input; // ... Set up a surface with ColorKey and no AlphaMod
SDL_Surface *output = SDL_ConvertSurface(input, input->format, input->flags);
// "output" surface has a ColorKey but *also* AlphaMod (BLEND, and Opaque 255).
Simon Hug
The SDL_BlitScaled function runs into an access violation for specific blit coordinates and surface sizes. The attached testcase blits a 800x600 surface to a 1280x720 surface at the coordinates -640,-345 scaled to 1280x720. The blit function that moves the data then runs over and reads after the pixel data from the src surface causing an access violation.
I can't say where exactly it goes wrong, but I think it could have something to do with the rounding in SDL_UpperBlitScaled. final_src.y is 288 and final_src.h is 313. Together that's 601, which I believe is one too much, but I just don't know the code enough to make sure that's the problem.
Sylvain
I think this patch fix the issue, but maybe it's worth re-writing "SDL_UpperBlitScaled" using SDL_FRect.
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);
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().
