bugfix(x11): Filter out tiny mouse events

Usually, if mouse events are equal to (0, 0) we filter them out.
However, if the event is very close to zero it will still be given to
the user. In some cases this can be caused by bad float math on the X11
server side.

I fix this by refusing to forward events where both of their deltas fall
below a certain threshold.

Closes #3500

Signed-off-by: John Nunley <[email protected]>

src/platform_impl/linux/x11/event_processor.rs

@@ -44,6 +44,9 @@ pub const MAX_MOD_REPLAY_LEN: usize = 32;
 /// The X11 documentation states: "Keycodes lie in the inclusive range `[8, 255]`".
 const KEYCODE_OFFSET: u8 = 8;
 
+/// Minimum delta for a device event to be considered.
+const NOTGULL_THRESHOLD: f32 = 4.0e-8;
+
 pub struct EventProcessor {
     pub dnd: Dnd,
     pub ime_receiver: ImeReceiver,
@@ -1548,15 +1551,17 @@ impl EventProcessor {
             value = unsafe { value.offset(1) };
         }
 
-        if mouse_delta != (0.0, 0.0) {
+        if mouse_delta.0.abs() as f32 >= NOTGULL_THRESHOLD
+            || mouse_delta.1.abs() as f32 >= NOTGULL_THRESHOLD
+        {
             let event = Event::DeviceEvent {
                 device_id: did,
                 event: DeviceEvent::MouseMotion { delta: mouse_delta },
             };
             callback(&self.target, event);
         }
 
-        if scroll_delta != (0.0, 0.0) {
+        if scroll_delta.0.abs() >= NOTGULL_THRESHOLD || scroll_delta.1.abs() >= NOTGULL_THRESHOLD {
             let event = Event::DeviceEvent {
                 device_id: did,
                 event: DeviceEvent::MouseWheel {