xvfb: probe host DRI paths so GLX is advertised on non-EL distros (#78)

Xvfb's bundled libGLdispatch is hardcoded to look for DRI drivers under
/usr/lib64/dri (the AlmaLinux 8 layout). On Debian/Ubuntu they live in
/usr/lib/x86_64-linux-gnu/dri, so the GL provider fails to load and the
server brings up without the GLX extension — which silently breaks any
GLX client (raylib/GLFW). Set LIBGL_DRIVERS_PATH from the wrapper to a
list of standard distro paths so the host's swrast driver is found.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

xvfb/pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "xvfb"
-version = "1.20.11"
+version = "1.20.11.post1"
 description = "Xvfb (X virtual framebuffer) headless X server"
 requires-python = ">=3.8"
 

xvfb/xvfb/__init__.py

@@ -10,12 +10,30 @@ XVFB_BIN = os.path.join(BIN_DIR, "Xvfb")
 XKBCOMP_BIN = os.path.join(BIN_DIR, "xkbcomp")
 
 
+# Common host paths where Mesa DRI drivers (e.g. swrast_dri.so) live. Xvfb
+# was built on AlmaLinux 8 with /usr/lib64/dri baked in; on other distros
+# (Debian/Ubuntu in particular) the drivers are elsewhere, and without them
+# Xvfb fails to bring up a GL provider and silently disables the GLX
+# extension. Probing the standard locations lets the host's drivers be
+# found regardless of distro.
+_DRI_PATHS = (
+  "/usr/lib64/dri",
+  "/usr/lib/x86_64-linux-gnu/dri",
+  "/usr/lib/aarch64-linux-gnu/dri",
+  "/usr/lib/dri",
+)
+
+
 def _run_xvfb():
   # The bundled Xvfb has its compile-time XkbBinDirectory blanked out so it
   # invokes xkbcomp via PATH lookup; prepend our bin dir so the bundled
   # xkbcomp wins. -xkbdir points the server at the bundled keymap data.
   env = os.environ.copy()
   env["PATH"] = BIN_DIR + os.pathsep + env.get("PATH", "")
+  if "LIBGL_DRIVERS_PATH" not in env:
+    found = [p for p in _DRI_PATHS if os.path.isdir(p)]
+    if found:
+      env["LIBGL_DRIVERS_PATH"] = os.pathsep.join(found)
   args = sys.argv[1:]
   if not any(a == "-xkbdir" for a in args):
     args = ["-xkbdir", XKB_DIR] + args