Allow using libsamplerate with CMake on Windows

[ericoporto]

Libsamplerate provides binary releases for Windows and even include a cmake script, it would be nice if it was possible to use it on Windows too!

[madebr]

All binary releases of the next SDL2 release will ship with a CMake script that allows the following use:

find_package(SDL2 REQUIRED)
add_executable(mygame mysource.c)
target_link_libraries(mygame PRIVATE SDL2::SDL2)

[ericoporto]

libsamplerate is only checked in Linux

SDL/CMakeLists.txt

Line 1307 in a5949d7

CheckLibSampleRate()

this should be list(APPEND ... instead of set(, othewise it's hard to pass additional module paths in the command line.

SDL/CMakeLists.txt

Line 54 in a5949d7

set(CMAKE_MODULE_PATH "${SDL2_SOURCE_DIR}/cmake")

it would be better to use find_package directly - it looks like it is used eventually, but now you need to first pass the include directory to look for it somehow in the command line before it's added through it's own cmake config module.

SDL/cmake/sdlchecks.cmake

Line 372 in a5949d7

check_include_file(samplerate.h HAVE_LIBSAMPLERATE_H)

It would be perfect if it had the dynamic api to look for samplerate.dll built by default in the SDL2.dll file.

I also need this to workaround #5538

[ericoporto]

Hey thanks! This worked for me!

I ended up adding an additional HINTS "${SAMPLERATE_DIR}" on the find_package, just so I could pass the directory from command line, so now I can do this -DSDL_LIBSAMPLERATE=1 -DSAMPLERATE_DIR="C:\\Lib\\libsamplerate\\lib\\cmake\\SampleRate" when building,

[madebr]

I tested it by adding -DCMAKE_PREFIX_PATH=/tmp/libsamplerate-0.2.2-win64 to the cmake call.
(I extracted the binary tarball in the /tmp folder)