Konrad
This kind of blending is rather quite useful and in my opinion should be available for all renderers. I do need it myself, but since I didn't want to use a custom blending mode which is supported only by certain renderers (e.g. not in software which is quite important for me) I did write implementation of SDL_BLENDMODE_MUL for all renderers altogether.
SDL_BLENDMODE_MUL implements following equation:
dstRGB = (srcRGB * dstRGB) + (dstRGB * (1-srcA))
dstA = (srcA * dstA) + (dstA * (1-srcA))
Background:
https://i.imgur.com/UsYhydP.png
Blended texture:
https://i.imgur.com/0juXQcV.png
Result for SDL_BLENDMODE_MOD:
https://i.imgur.com/wgNSgUl.png
Result for SDL_BLENDMODE_MUL:
https://i.imgur.com/Veokzim.png
I think I did cover all possibilities within included patch, but I didn't write any tests for SDL_BLENDMODE_MUL, so it would be lovely if someone could do it.
suffix to the temp Pixel local in the DUFFS_LOOP.
SDL_blit.h (ASSEMBLE_RGB): add _ prefix to temp Pixel locals to avoid
any possible shadowings.
The warnings were like the following:
In file included from src/video/SDL_blit_N.c:26:0:
src/video/SDL_blit_N.c: In function 'BlitNtoNKeyCopyAlpha':
src/video/SDL_blit_N.c:2421:24: warning: declaration of 'Pixel' shadows a previous local [-Wshadow]
Uint32 Pixel = ((*src32 & rgbmask) == ckey) ? *dst32 : *src32;
^
src/video/SDL_blit.h:475:21: note: in definition of macro 'DUFFS_LOOP8'
case 0: do { pixel_copy_increment; /* fallthrough */ \
^
src/video/SDL_blit_N.c:2419:13: note: in expansion of macro 'DUFFS_LOOP'
DUFFS_LOOP(
^
src/video/SDL_blit_N.c:2399:12: warning: shadowed declaration is here [-Wshadow]
Uint32 Pixel;
^
Ozkan Sezer
The attached patch removes SDLCALL attribute from SDL_BlitFunc() funcptr.
As far as I can see, *SDL_BlitFunc() is completely internal to SDL with
no specific calling convention requirements. The actual functions assigned
to SDL_BlitFunc seem to not have any calling conventions specified. So,
easy solution is simply removing the strict calling convention from the
type.
For example, if sR is 0 and dR is 255, we will get -255*sA casted to an unsigned value. Basically results are quite large numbers instead of the expected 0-255 range.
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().
