GLFW backend links with X11 on linux since 1.92.3-docking

[ramenguy99]

Version/Branch of Dear ImGui:

Version 1.92.3+, Branch: docking

Back-ends:

imgui_impl_glfw.cpp

Compiler, OS:

Linux + Any compiler

Full config/build information:

No response

Details:

Since commit 6b2cdf2 the GLFW backend uses X11 functions directly (e.g. XFlush in ImGui_ImplGlfw_SetWindowFloating). This is a breaking change for some builds because this means that executables and dynamic libraries now need this symbol at link or load time respectively.

GLFW internally loads these function at initialization time with dlopen and calls them through function pointers. This is also potentially bad because the versions of these functions used by GLFW are potentially not the same as those linked at build time or loaded at load time (though I don't really know in which realistic scenario this could actually happen).

The best solution in my opinion would be to use the function pointers loaded by GLFW or expose this functionality in GLFW directly, but there does not seem to be a straight forward way to do this without changes to GLFW (as far as I know).

A workaround would be to put these behind a build flag / define to allow existing code that cannot link with X11 at build or load time to keep working.

[ocornut]

A change to GLFW would take a long time to spread and we try to support older versions anyhow. However I suppose if a GLFW release supported it we could fallback to use GLFW function, lifting the linking constraint if you update GLFW.

Do you feel is it is a big problem to add linking to x11 lib from your app?

I’d be open to other solutions.

[ramenguy99]

My usecase is maybe a bit unusual, I am building python wheels that have to be as portable as possible (building on manylinux and musllinux ideally working on wayland only systems) so the runtime loading approach of GLFW works quite well because the wheels have little to no link-time dependency. Linking to X11 would break this level of portability.

I also don't see any good solution other than modifying GLFW or making this functionality optional in ImGui.

Edit: another solution that just came to mind would be to replicate GLFW dynamic loading approach to load function pointers at runtime, it's a bit redundant to reload the function pointers and requires some extra boilerplate code in the backend, but this would revert the change in linking behaviour.

[ocornut]

dynamic loading approach to load function pointers at runtime

That'd be preferable if it is not too much boilerplate, but I will also work toward adding explicit opt-out define.

cc @Ikos3k

[ocornut]

Does this patch works for you?

imgui-5db80b2-Backends GLFW add support for IMGUI_IMPL_GLFW_DISABLE_X11, IMGUI_IMPL_GLFW_DISABLE_WAYLAND.patch