Return Err instead of panic on surfaceless GLX contexts

Co-authored-by: Marijn Suijten <marijns95@gmail.com>

CHANGELOG.md

@@ -1,8 +1,9 @@
 # Unreleased
 
-- Fix crash when creating OpenGLES context without explicit version
-- Add `buffer_age` method on `WindowedContext`
+- Fix crash when creating OpenGLES context without explicit version.
+- Add `buffer_age` method on `WindowedContext`.
 - On Android, switched from `StaticStructGenerator` to `StructGenerator`, fixing some compilation errors.
+- Return an `Err` instead of panicking when surfaceless GLX context creation fails on Linux.
 
 # Version 0.28.0 (2021-12-02)
 

glutin/src/platform_impl/unix/x11.rs

@@ -264,7 +264,11 @@ impl Context {
                 // Prototype::Glx(ctx) =>
                 // X11Context::Glx(ctx.finish_surfaceless(xwin)?),
                 Prototype::Egl(ctx) => X11Context::Egl(ctx.finish_surfaceless()?),
-                _ => unimplemented!(),
+                _ => {
+                    return Err(CreationError::NotSupported(
+                        "Surfaceless GLX context not implemented".to_string(),
+                    ))
+                }
             };
 
             let context = Context::Surfaceless(ContextInner { context });