better comment egui/src/data/input.rs

Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

egui/src/data/input.rs

@@ -177,9 +177,12 @@ pub enum Event {
     /// The mouse or touch moved to a new place.
     PointerMoved(Pos2),
 
-    /// The mouse delta from winit::DeviceEvent. MouseDelta and PointerMoved can be emmited simultaneously.
-    /// If MouseDelta accumulated value is zero per frame, then `old_pos-new_pos` will be used as fallback.
-    /// For now it used in situations when we need delta but mouse pointer is on screen edge.
+    /// Mouse movement in unspecified units.
+    ///
+    /// Both [`Self::MouseDelta`] and [`Self::PointerMoved`] can both be emitted for the same movement,
+    /// but when a pointer is grabbed or at the edge of the screen, only [`Self::MouseDelta`] is emitted.
+    ///
+    /// Some integrations do not emit any [`Self::MouseDelta`]. In these cases the change in [`Self::PointerMoved`]  will be used for [`PointerState::delta`].
     MouseDelta(Vec2),
 
     /// A mouse button was pressed or released (or a touch started or stopped).