Add OpenGL::GL cmake imported targets

[cajomar]

This allows projects to include OpenGL like so

find_package(OpenGL REQUIRED)
target_link_libraries(myproject OpenGL::GL)

Link to CMake's documentation: https://cmake.org/cmake/help/latest/module/FindOpenGL.html#imported-targets

CMake's FindOpenGL.cmake also produces GLES-related imported targets. While I think they would be nice to add, I've omitted them as I don't know if it would be as simple as duplicating the OpenGL::GL target or more needs to be to communicate that choice of flavor to emscripten.

[sbc100]

Can we test this? Perhaps by adding to the existing test/cmake/find_modules/ test?

[cajomar]

@sbc100 I added a few lines to validate the IMPORTED_LIBNAME property of OpenGL::GL. Please let me know if you had something else in mind.

[sbc100]

Use STATUS here too?

[cajomar]

I didn't add STATUS to pre-existing messages because I thought perhaps the outputting to stderr was intentional (adding STATUS directs it to stdout), but I can certainly do that.

[sbc100]

I think we should be consistent within this file. i don't think anything else is reading the stdout or std of the cmake process.

[sbc100]

Is this creating a new lib variable?

[cajomar]

Yes, although an admittedly lazy naming choice.

[sbc100]

I see. Should we check INTERFACE_LINK_LIBRARIES too?

[sbc100]

lgtm % comments

[dschuff]

This doesn't seem to work on Windows:
https://logs.chromium.org/logs/emscripten-releases/buildbucket/cr-buildbucket/8721741671459149313/+/u/Emscripten_testsuite__other_/stdout

Oddy I tried it locally I got a different error:

test_cmake_find_modules (test_other.other.test_cmake_find_modules) ... configure: cmake C:\src\emr\install\emscripten\test\cmake\find_modules -DCMAKE_TOOLCHAIN_FILE=C:\src\emr\install\emscripten\cmake\Modules\Platform\Emscripten.cmake -DCMAKE_CROSSCOMPILING_EMULATOR=C:/src/emr/emscripten-releases/node-v20.14.0-win-x64/node.exe -G Ninja
-- The C compiler identification is Clang 21.0.0
-- The CXX compiler identification is Clang 21.0.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: C:/src/emr/install/emscripten/emcc.bat - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: C:/src/emr/install/emscripten/em++.bat - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
 test: OPENGL_LIBRARIES: GL;GLU
 test: OPENGL_LIBRARIES:
 test: SDL2_LIBRARIES: -sUSE_SDL=2
 test: SDL2_INCLUDE_DIRS: C:/src/emr/install/emscripten/cache/sysroot/include/SDL2
-- Configuring done
CMake Error in CMakeLists.txt:
  Imported target "SDL2::SDL2" includes non-existent path

    "C:/src/emr/install/emscripten/cache/sysroot/include/SDL2"

  in its INTERFACE_INCLUDE_DIRECTORIES.  Possible reasons include:

  * The path was deleted, renamed, or moved to another location.

  * An install or uninstall procedure did not complete successfully.

  * The installation package was faulty and references files it does not
  provide.



-- Generating done
CMake Generate step failed.  Build files cannot be regenerated correctly.

Any ideas from either of those?

[sbc100]

I think you need to make sure sdl2 is built before you can run that test. We should probably add an embuilder command in there to fix that.