Allow the user to force X11 under Wayland

Use forced backend over the env variables. 

Signed-off-by: John Nunley <dev@notgull.net>
Fixes: #3057

CHANGELOG.md

@@ -19,6 +19,7 @@ And please only add new entries to the top of this list, right below the `# Unre
 - On Web, remove any fullscreen requests from the queue when an external fullscreen activation was detected.
 - On Wayland, fix `TouchPhase::Canceled` being sent for moved events.
 - Mark `startup_notify` unsafe functions as safe.
+- Fix a bug where Wayland would be chosen on Linux even if the user specified `with_x11`. (#3058)
 
 # 0.29.1-beta
 

src/platform_impl/linux/mod.rs

@@ -716,21 +716,34 @@ impl<T: 'static> EventLoop<T> {
         }
 
         // NOTE: Wayland first because of X11 could be present under wayland as well.
+        let backend = match (
+            attributes.forced_backend,
+            env::var("WAYLAND_DISPLAY").is_ok(),
+            env::var("DISPLAY").is_ok(),
+        ) {
+            // User is forcing a backend.
+            (Some(backend), _, _) => backend,
+            // Wayland is present.
             #[cfg(wayland_platform)]
-        if attributes.forced_backend == Some(Backend::Wayland)
-            || env::var("WAYLAND_DISPLAY").is_ok()
-        {
-            return EventLoop::new_wayland_any_thread().map_err(Into::into);
-        }
-
+            (None, true, _) => Backend::Wayland,
+            // X11 is present.
             #[cfg(x11_platform)]
-        if attributes.forced_backend == Some(Backend::X) || env::var("DISPLAY").is_ok() {
-            return Ok(EventLoop::new_x11_any_thread().unwrap());
-        }
-
-        Err(EventLoopError::Os(os_error!(OsError::Misc(
+            (None, _, true) => Backend::X,
+            // No backend is present.
+            _ => {
+                return Err(EventLoopError::Os(os_error!(OsError::Misc(
                     "neither WAYLAND_DISPLAY nor DISPLAY is set."
-        ))))
+                ))));
+            }
+        };
+
+        // Create the display based on the backend.
+        match backend {
+            #[cfg(wayland_platform)]
+            Backend::Wayland => EventLoop::new_wayland_any_thread().map_err(Into::into),
+            #[cfg(x11_platform)]
+            Backend::X => Ok(EventLoop::new_x11_any_thread().unwrap()),
+        }
     }
 
     #[cfg(wayland_platform)]