winit: Allow moving the cursor

It is not necessary to set the cursor position on winit since the
windowing system already updates the position on its own. Instead, doing
this makes the cursor (almost) stuck and unmovable. Thus, this commit
just removes that code from the winit backend.

Fixes: https://github.com/Smithay/smithay/issues/241
Signed-off-by: Uli Schlachter <psychon@znc.in>

src/backend/winit.rs

@@ -251,14 +251,13 @@ impl CursorBackend for WinitGraphicsBackend {
     type CursorFormat = CursorIcon;
     type Error = ();
 
-    fn set_cursor_position(&self, x: u32, y: u32) -> ::std::result::Result<(), ()> {
-        debug!(self.logger, "Setting cursor position to {:?}", (x, y));
-        self.window
-            .window()
-            .set_cursor_position(LogicalPosition::new(x as f64, y as f64))
-            .map_err(|err| {
-                debug!(self.logger, "{}", err);
-            })
+    fn set_cursor_position(&self, _x: u32, _y: u32) -> ::std::result::Result<(), ()> {
+        // With other backends, we read events from input devices and then have to position the
+        // mouse cursor on screen accordingly. Here, there is already a windowing system that deals
+        // with the position on screen. If we "force" out idea of the cursor position here, that
+        // breaks and e.g. the cursor on X11 becomes stuck and cannot move. (Us forcing a cursor
+        // position generates a mouse move event and thus we force the same cursor position again.)
+        Ok(())
     }
 
     fn set_cursor_representation(