This function is useful for accumulating relative mouse motion if you want to only handle whole pixel movement.
e.g.
static float dx_frac, dy_frac;
float dx, dy;
/* Accumulate new motion with previous sub-pixel motion */
dx = event.motion.xrel + dx_frac;
dy = event.motion.yrel + dy_frac;
/* Split the integral and fractional motion, dx and dy will contain whole pixel deltas */
dx_frac = SDL_modff(dx, &dx);
dy_frac = SDL_modff(dy, &dy);
if (dx != 0.0f || dy != 0.0f) {
...
}
I ran this script in the include directory:
```sh
sed -i '' -e 's,#include "\(SDL.*\)",#include <SDL3/\1>,' *.h
```
I ran this script in the src directory:
```sh
for i in ../include/SDL3/SDL*.h
do hdr=$(basename $i)
if [ x"$(echo $hdr | egrep 'SDL_main|SDL_name|SDL_test|SDL_syswm|SDL_opengl|SDL_egl|SDL_vulkan')" != x ]; then
find . -type f -exec sed -i '' -e 's,#include "\('$hdr'\)",#include <SDL3/\1>,' {} \;
else
find . -type f -exec sed -i '' -e '/#include "'$hdr'"/d' {} \;
fi
done
```
Fixes https://github.com/libsdl-org/SDL/issues/6575
Include guards in most changed files were missing, I added them keeping
the same style as other SDL files. In some cases I moved the include
guards around to be the first thing the header has to take advantage of
any possible improvements compiler may have for inclusion guards.
Vitaly Novichkov
Once I ran build of my codecs collection on AppVeyor where my CMake script downloads latest SDL2 from HG repo, failed to link because of math functions conflict:
https://ci.appveyor.com/project/Wohlstand/audiocodecs/build/1.0.44
The revision is b9ff5f8b2303
There are both vanilla MinGW and MinGW-w64 are failed to build.
```
[100%] Linking C shared library libSDL2.dll
c:/mingw/bin/../lib/gcc/mingw32/5.3.0/../../../libmingwex.a(scalbn.o):(.text+0x0): multiple definition of `scalbln'
CMakeFiles\SDL2.dir/objects.a(s_scalbn.c.obj):C:/projects/audiocodecs/build-MinGW-Release-Win32/external/SDL2/src/SDL2HG/src/libm/s_scalbn.c:30: first defined here
