From: Jonathan Gray <jsg@jsg.id.au>
Subject: Re: fail early in mesa/eglInitialize when on wayland
To: Landry Breuil <landry@openbsd.org>
Cc: tech@openbsd.org, matthieu@openbsd.org
Date: Tue, 11 Nov 2025 17:16:48 +1100

On Sat, Nov 01, 2025 at 06:33:19PM +0100, Landry Breuil wrote:
> hi,
> 
> currently mesa isnt built with wayland support (which is a topic in itself).
> When running on wayland, starting any gtk+4 app will crash early when
> initializing, because we end up taking a libxcb codepath, eg run gtk+4-demo:
> 
> Program terminated with signal SIGSEGV, Segmentation fault.
> #0  0x00000316d2ae48aa in XGetXCBConnection () from /usr/X11R6/lib/libX11-xcb.so.2.0
> [Current thread is 1 (process 381892)]
> (gdb) bt
> #0  0x00000316d2ae48aa in XGetXCBConnection () from /usr/X11R6/lib/libX11-xcb.so.2.0
> #1  0x00000316849f7ff4 in dri2_get_xcb_connection (disp=0x31632dbc5a0, dri2_dpy=0x3161541bcc0) at /usr/xenocara/lib/mesa/mk/libEGL/../../src/egl/drivers/dri2/platform_x11.c:1720
> #2  0x00000316849f7ad8 in dri2_initialize_x11_dri3 (disp=0x31632dbc5a0) at /usr/xenocara/lib/mesa/mk/libEGL/../../src/egl/drivers/dri2/platform_x11.c:1926
> #3  dri2_initialize_x11 (disp=0x31632dbc5a0) at /usr/xenocara/lib/mesa/mk/libEGL/../../src/egl/drivers/dri2/platform_x11.c:2095
> #4  0x00000316849e3ee5 in dri2_initialize (disp=0x31632dbc5a0) at /usr/xenocara/lib/mesa/mk/libEGL/../../src/egl/drivers/dri2/egl_dri2.c:891
> #5  0x00000316849e79b1 in eglInitialize (dpy=<optimized out>, major=0x7eac247c3468, minor=0x7eac247c346c) at /usr/xenocara/lib/mesa/mk/libEGL/../../src/egl/main/eglapi.c:705
> #6  0x000003163bf7675e in gdk_display_init_egl () from /usr/local/lib/libgtk-4.so.5.5
> #7  0x000003163bf0c073 in gdk_wayland_display_init_gl () from /usr/local/lib/libgtk-4.so.5.5
> #8  0x000003163bf76399 in gdk_display_prepare_gl () from /usr/local/lib/libgtk-4.so.5.5
> #9  0x000003163bfe1217 in get_renderer_for_gl () from /usr/local/lib/libgtk-4.so.5.5
> #10 0x000003163bfe0880 in gsk_renderer_new_for_surface_full () from /usr/local/lib/libgtk-4.so.5.5
> #11 0x000003163bd2b543 in gtk_window_realize () from /usr/local/lib/libgtk-4.so.5.5
> 
> it can also be seen with /usr/local/lib/firefox/glxtest -w, which also calls
> eglIinitialize:
> https://searchfox.org/firefox-main/source/toolkit/xre/glxtest/glxtest.cpp#612
> 
> looking at the code, display->Platform is X11, since wayland support isnt
> builtin:
> 
> #4  0x00000316849e3ee5 in dri2_initialize (disp=0x31632dbc5a0) at /usr/xenocara/lib/mesa/mk/libEGL/../../src/egl/drivers/dri2/egl_dri2.c:891
> (gdb) p disp->Platform
> $3 = _EGL_PLATFORM_X11
> 
> so, i think we should fail early if we know we're on wayland. maybe the test
> should be !!getenv(DISPLAY) to negate the condition, but i've stolen it from
> https://github.com/openbsd/xenocara/blob/master/lib/mesa/src/vulkan/device-select-layer/device_select_layer.c#L149
> and in my limited testing, now i can run gtk4-demo or d-spy from within wayland,
> and glxtest doesnt crash when firefox starts:
> 
> $/usr/local/lib/firefox/glxtest
> WARNING
> libEGL initialize failed
> VENDOR
> AMD
> RENDERER
> AMD Radeon Vega 10 Graphics (radeonsi, raven, ACO, DRM 3.61, 7.8)
> VERSION
> 4.6 (Compatibility Profile) Mesa 25.0.7
> TFP
> TRUE
> MESA_VENDOR_ID
> 0x1002
> MESA_DEVICE_ID
> 0x15d8
> MESA_ACCELERATED
> TRUE
> MESA_VRAM
> 2048MB
> DRI_DRIVER
> radeonsi
> TEST_TYPE
> GLX
> 
> $/usr/local/lib/firefox/glxtest -w
> WARNING
> libEGL initialize failed
> ERROR
> EGL test failed
> TEST_TYPE
> EGL
> 
> so, how about the following diff, for now ?
> 
> Landry

How about this instead?  Works with glxtest -w running on wayland.

Index: lib/mesa/src/egl/main/egldisplay.c
===================================================================
RCS file: /cvs/xenocara/lib/mesa/src/egl/main/egldisplay.c,v
diff -u -p -U5 -r1.12 egldisplay.c
--- lib/mesa/src/egl/main/egldisplay.c	2 Apr 2024 10:42:16 -0000	1.12
+++ lib/mesa/src/egl/main/egldisplay.c	11 Nov 2025 06:06:46 -0000
@@ -139,10 +139,13 @@ _eglNativePlatformDetectNativeDisplay(vo
 #ifdef HAVE_WAYLAND_PLATFORM
       /* wl_display is a wl_proxy, which is a wl_object.
        * wl_object's first element points to the interfacetype. */
       if (first_pointer == &wl_display_interface)
          return _EGL_PLATFORM_WAYLAND;
+#else
+      if (getenv("WAYLAND_DISPLAY") || getenv("WAYLAND_SOCKET"))
+         return _EGL_PLATFORM_WAYLAND;
 #endif
 
 #ifdef HAVE_DRM_PLATFORM
       /* gbm has a pointer to its constructor as first element. */
       if (first_pointer == gbm_create_device)