Mark extensible enums in winit-core as #[non_exhaustive]

Event, input source, error, data transfer, native key, IME request,
scroll delta and fullscreen enums can now gain variants without a
breaking change. Backends and examples get wildcard arms where they
matched exhaustively; unknown IME requests are reported as
ImeRequestError::NotSupported and unknown fullscreen modes behave
like Fullscreen::Borderless(None).

winit-wayland/src/dnd.rs

@@ -85,6 +85,7 @@ impl DataSourceHandler for WinitState {
                 },
             },
             SendData::Bytes(binary) => Cursor::new(binary),
+            _ => return,
         };
 
         let _ = self.loop_handle.insert_source(fd, move |_, file, _| {

winit-wayland/src/event_loop/mod.rs

@@ -694,7 +694,7 @@ impl RootActiveEventLoop for ActiveEventLoop {
     ) -> Result<CoreCustomCursor, RequestError> {
         let cursor_image = match cursor {
             CustomCursorSource::Image(cursor_image) => cursor_image,
-            CustomCursorSource::Animation { .. } | CustomCursorSource::Url { .. } => {
+            _ => {
                 return Err(NotSupportedError::new("unsupported cursor kind").into());
             },
         };

winit-wayland/src/window/mod.rs

@@ -453,9 +453,6 @@ impl CoreWindow for Window {
 
     fn set_fullscreen(&self, fullscreen: Option<Fullscreen>) {
         match fullscreen {
-            Some(Fullscreen::Exclusive(..)) => {
-                warn!("`Fullscreen::Exclusive` is ignored on Wayland");
-            },
             Some(Fullscreen::Borderless(monitor)) => {
                 let output = monitor.as_ref().and_then(|monitor| {
                     monitor.cast_ref::<output::MonitorHandle>().map(|handle| &handle.proxy)
@@ -463,6 +460,9 @@ impl CoreWindow for Window {
 
                 self.window.set_fullscreen(output)
             },
+            Some(_) => {
+                warn!("this fullscreen mode is ignored on Wayland");
+            },
             None => self.window.unset_fullscreen(),
         }
     }

winit-wayland/src/window/state.rs

@@ -1269,6 +1269,7 @@ impl WindowState {
                 self.text_input_state = None;
                 true
             },
+            _ => return Err(ImeRequestError::NotSupported),
         };
 
         // Only one input method may be active per (seat, surface),