Let PressSource represent a mouse without a button

Author: dhardy

crates/kas-core/src/event/cx/press.rs

@@ -64,9 +64,9 @@ impl GrabMode {
 
 /// Source of a [`Press`] event
 ///
-/// This identifies the source of a click, touch or similar event, including
-/// which mouse button is pressed and whether this is a double-click (see
-/// [`Self::repetitions`]).
+/// This identifies the source of a click, touch or pointer motion. It
+/// identifies which mouse button is pressed (if any) and whether this is a
+/// double-click (see [`Self::repetitions`]).
 ///
 /// This may be used to track a click/touch, but note that identifiers may be
 /// re-used after the event completes, thus an [`Event::PressStart`] with
@@ -80,10 +80,11 @@ impl PressSource {
     const FLAG_TOUCH: u64 = 1 << 63;
 
     /// Construct a mouse source
-    pub(crate) fn mouse(button: MouseButton, repetitions: u32) -> Self {
+    pub(crate) fn mouse(button: Option<MouseButton>, repetitions: u32) -> Self {
         let r = (repetitions as u64) << 32;
         debug_assert!(r & Self::FLAG_TOUCH == 0);
-        let b = button as u8;
+        // Note: MouseButton::try_from_u8 returns None on u8::MAX
+        let b = button.map(|b| b as u8).unwrap_or(u8::MAX);
         Self(r | b as u64)
     }
 
@@ -120,8 +121,8 @@ impl PressSource {
 
     /// Identify the mouse button used
     ///
-    /// This always returns `Some(_)` for mouse events and `None` for touch
-    /// events.
+    /// This returns `Some(button)` for mouse events with a button. It returns
+    /// `None` for touch events and mouse events without a button (e.g. motion).
     pub fn mouse_button(self) -> Option<MouseButton> {
         if self.is_mouse() {
             let b = self.0 as u8;
@@ -134,29 +135,19 @@ impl PressSource {
     /// Returns true if this represents the left mouse button or a touch event
     #[inline]
     pub fn is_primary(self) -> bool {
-        match self.mouse_button() {
-            None => true,
-            Some(MouseButton::Left) => true,
-            Some(_) => false,
-        }
+        self.is_touch() || self.mouse_button() == Some(MouseButton::Left)
     }
 
     /// Returns true if this represents the right mouse button
     #[inline]
     pub fn is_secondary(self) -> bool {
-        match self.mouse_button() {
-            Some(MouseButton::Right) => true,
-            None | Some(_) => false,
-        }
+        self.mouse_button() == Some(MouseButton::Right)
     }
 
     /// Returns true if this represents the middle mouse button
     #[inline]
     pub fn is_tertiary(self) -> bool {
-        match self.mouse_button() {
-            Some(MouseButton::Middle) => true,
-            None | Some(_) => false,
-        }
+        self.mouse_button() == Some(MouseButton::Middle)
     }
 
     /// The `repetitions` value
@@ -325,7 +316,7 @@ impl GrabBuilder {
         } else if let Some(finger_id) = source.finger_id() {
             cx.touch.start_grab(finger_id, id.clone(), position, mode)
         } else {
-            unreachable!()
+            false
         };
 
         if success {

crates/kas-core/src/event/cx/press/mouse.rs

@@ -21,8 +21,6 @@ use winit::event::{ElementState, MouseButton, MouseScrollDelta};
 // TODO: this should be configurable or derived from the system
 const DOUBLE_CLICK_TIMEOUT: Duration = Duration::from_secs(1);
 
-const FAKE_MOUSE_BUTTON: MouseButton = MouseButton::Button32;
-
 #[derive(Clone, Debug)]
 struct PanDetails {
     c0: DVec2,
@@ -69,7 +67,7 @@ pub(crate) struct Mouse {
     pub(super) over: Option<Id>, // widget under the mouse
     pub(super) icon: CursorIcon, // non-grab icon
     old_icon: CursorIcon,        // last icon set (grab or non-grab)
-    last_click_button: MouseButton,
+    last_click_button: Option<MouseButton>,
     last_click_repetitions: u32,
     last_click_timeout: Instant,
     last_pin: Option<(Id, DVec2)>,
@@ -85,7 +83,7 @@ impl Default for Mouse {
             over: None,
             icon: CursorIcon::Default,
             old_icon: CursorIcon::Default,
-            last_click_button: FAKE_MOUSE_BUTTON,
+            last_click_button: None,
             last_click_repetitions: 0,
             last_click_timeout: Instant::now(),
             last_pin: None,
@@ -287,7 +285,7 @@ impl<'a> EventCx<'a> {
             } else {
                 last_pin = None;
                 let press = Press {
-                    source: PressSource::mouse(grab.button, grab.repetitions),
+                    source: PressSource::mouse(Some(grab.button), grab.repetitions),
                     id: self.mouse.over.clone(),
                     coord: self.mouse.last_position.cast_nearest(),
                 };
@@ -349,7 +347,7 @@ impl<'a> EventCx<'a> {
             self.mouse.samples.push_delta(delta);
         }
         self.mouse.last_position = position;
-        self.mouse.last_click_button = FAKE_MOUSE_BUTTON;
+        self.mouse.last_click_button = None;
 
         self.set_over(window.re(), id.clone());
 
@@ -359,7 +357,7 @@ impl<'a> EventCx<'a> {
                 GrabDetails::Grab => {
                     let target = grab.start_id.clone();
                     let press = Press {
-                        source: PressSource::mouse(grab.button, grab.repetitions),
+                        source: PressSource::mouse(Some(grab.button), grab.repetitions),
                         id,
                         coord,
                     };
@@ -380,7 +378,7 @@ impl<'a> EventCx<'a> {
             .map(|state| state.desc.id.clone())
         {
             let press = Press {
-                source: PressSource::mouse(FAKE_MOUSE_BUTTON, 0),
+                source: PressSource::mouse(None, 0),
                 id,
                 coord,
             };
@@ -397,7 +395,7 @@ impl<'a> EventCx<'a> {
 
     /// Handle mouse cursor leaving the app.
     pub(in crate::event::cx) fn handle_cursor_left(&mut self, window: Node<'_>) {
-        self.mouse.last_click_button = FAKE_MOUSE_BUTTON;
+        self.mouse.last_click_button = None;
 
         if self.mouse.grab.is_none() {
             self.set_over(window, None);
@@ -410,7 +408,7 @@ impl<'a> EventCx<'a> {
         window: Node<'_>,
         delta: MouseScrollDelta,
     ) {
-        self.mouse.last_click_button = FAKE_MOUSE_BUTTON;
+        self.mouse.last_click_button = None;
 
         let event = Event::Scroll(match delta {
             MouseScrollDelta::LineDelta(x, y) => ScrollDelta::Lines(x, y),
@@ -432,8 +430,8 @@ impl<'a> EventCx<'a> {
     ) {
         if state == ElementState::Pressed {
             let now = Instant::now();
-            if button != self.mouse.last_click_button || self.mouse.last_click_timeout < now {
-                self.mouse.last_click_button = button;
+            if Some(button) != self.mouse.last_click_button || self.mouse.last_click_timeout < now {
+                self.mouse.last_click_button = Some(button);
                 self.mouse.last_click_repetitions = 0;
             }
             self.mouse.last_click_repetitions += 1;
@@ -466,7 +464,7 @@ impl<'a> EventCx<'a> {
                     self.set_nav_focus(id, FocusSource::Pointer);
                 }
 
-                let source = PressSource::mouse(button, self.mouse.last_click_repetitions);
+                let source = PressSource::mouse(Some(button), self.mouse.last_click_repetitions);
                 let press = PressStart {
                     source,
                     id: Some(id.clone()),