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deathkiller / jazz2-native

🎮 · Jazz² Resurrection: Native C++ reimplementation of Jazz Jackrabbit 2
https://deat.tk/jazz2/
GNU General Public License v3.0
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Fix linkage against modern GLVND OpenGL implementation on GNU/Linux. #58

Closed vanfanel closed 6 months ago

vanfanel commented 6 months ago

Modern Wayland-based GNU/Linux systems don't need to support legacy X11-based GLX OpenGL implementation: for full OpenGL, there's GLVND which MESA is commonly built with.

This allows jazz2-native to build on lightweight Wayland-based GNU/Linux systems that have no X11/GLX libs, but simply modern GLVND on KMS/DRM (=no desktop enviroment) or Wayland.

This does not break X11/GLX compatibility: on legacy X11-based systems, GLX is still used.

deathkiller commented 6 months ago

Thanks!

deathkiller commented 6 months ago

According to https://cmake.org/cmake/help/latest/policy/CMP0072.html, CMake should handle this automatically. Is it broken?

EDIT: I changed the target from OpenGL::GL to OpenGL::OpenGL which should work equally as your pull request if I'm not mistaken.

vanfanel commented 6 months ago

@deathkiller Sadly, even if I greatly prefer your way (in fact yout way is the correct way!), that doesn't work. First problem is that doing find_package(OpenGL REQUIRED) on a system without GLX, fails:


CMake Error at /usr/local/lib/python3.11/dist-packages/cmake/data/share/cmake-3.29/Modules/FindPackageHandleStandardArgs.cmake:230 (message):                                                                                                                                 
  Could NOT find OpenGL (missing: OPENGL_glx_LIBRARY)                                                                                  
Call Stack (most recent call first):                                                                                                   
  /usr/local/lib/python3.11/dist-packages/cmake/data/share/cmake-3.29/Modules/FindPackageHandleStandardArgs.cmake:600 (_FPHSA_FAILURE_MESSAGE)                                                                                                                                
  /usr/local/lib/python3.11/dist-packages/cmake/data/share/cmake-3.29/Modules/FindOpenGL.cmake:579 (FIND_PACKAGE_HANDLE_STANDARD_ARGS) 
  cmake/ncine_imported_targets.cmake:210 (find_package)                                                                                
  CMakeLists.txt:73 (include)

...and since that fails, then OPENGL_FOUND is never set true, and thus this is never true and GL linkage fails:

https://github.com/deathkiller/jazz2-native/blob/0493e28689a2c0aeeea7bca0a72c7472302148b8/cmake/ncine_extra_sources.cmake#L28

I am using latest stable CMAKE here:

root@debian:~/src/j2/jazz2-native/b4# cmake --version
cmake version 3.29.3

...so it may be broken indeed. Maybe it's a CMake or MESA problem?

deathkiller commented 6 months ago

I think it's because the line here - https://github.com/Kitware/CMake/blob/master/Modules/FindOpenGL.cmake#L474, but I don't know why it's done like this. I tried to set OPENGL_USE_OPENGL in the latest commit, so the whole condition should be false and OPENGL_glx_LIBRARY should be skipped. Let me know if it's any better.

vanfanel commented 6 months ago

@deathkiller Yes, that works. Thanks a lot. I had already opened a thread in https://discourse.cmake.org/t/gnu-linux-debian-12-cmake-fails-to-find-opengl-when-mesa-has-been-built-without-glx-support/10901 so I will add your findings there.

Really, thanks for going WAY out of your way and investigating this with me! :)

deathkiller commented 6 months ago

Great! Now, I'm not sure if I should prefer old OpenGL::GL target or new OpenGL::OpenGL target in official releases. Do you think there will be some compatibility problems with the new one?

vanfanel commented 6 months ago

Great! Now, I'm not sure if I should prefer old OpenGL::GL target or new OpenGL::OpenGL target in official releases. Do you think there will be some compatibility problems with the new one?

There should be no problems with the OpenGL::OpenGL target, every major distro has moved to GLVND years ago anyway or has both GLX and GLVND. GLX is a legacy thing by now, bound to the dying X11 Xorg server. I wouldn't worry about it for a moment.