Say position-only, and stop falsifying the cursor

`is_momentary` becomes `position_only` on both the sense and the cursor,
inverted so it reads as what it tests.

A widget the cursor has left was being handed a blanked cursor so its
press senses would not match. `should_run` now skips non-position senses
when the pointer is not inside, which is the same rule without lying
about the input: the widget still gets the real cursor with its hover
ending.

`consumes` loses its `momentary` argument, since the cursor answers that
itself.

src/default/sense.rs

@@ -41,14 +41,15 @@ impl Event for CursorSenses {
 
 impl CursorSenses {
     /// Whether a widget with these senses stops the input reaching the layer
-    /// below it. Where the cursor rests stops at the top layer that is under
-    /// it; something happening to the cursor stops only at a widget that
-    /// answers to that, so a click-only child does not swallow a scroll.
-    fn consumes(&self, cursor: &CursorState, hover: ActivationState, momentary: bool) -> bool {
-        if !momentary {
+    /// below it. A cursor that is only somewhere stops at the first layer it
+    /// is over. A cursor doing something -- a press, a scroll -- stops only
+    /// where something answers to it, so a button drawn over a list does not
+    /// swallow the list's scrolling.
+    fn consumes(&self, cursor: &CursorState, hover: ActivationState) -> bool {
+        if cursor.position_only() {
             return true;
         }
-        should_run(self, cursor, hover).is_some_and(|sense| sense.is_momentary())
+        should_run(self, cursor, hover).is_some_and(|sense| !sense.position_only())
     }
 }
 
@@ -66,10 +67,10 @@ impl CursorSense {
         matches!(self, CursorSense::Pressing(CursorButton::Left))
     }
 
-    /// Whether this sense is about something happening to the cursor, rather
-    /// than about where it rests.
-    fn is_momentary(&self) -> bool {
-        !matches!(self, Self::HoverStart | Self::Hovering | Self::HoverEnd)
+    /// False if the sense is a button or a scroll, true if it is only about
+    /// where the cursor is.
+    fn position_only(&self) -> bool {
+        matches!(self, Self::HoverStart | Self::Hovering | Self::HoverEnd)
     }
 }
 
@@ -115,9 +116,10 @@ impl CursorButtons {
 }
 
 impl CursorState {
-    /// Whether anything is happening to the cursor beyond where it rests.
-    pub fn has_momentary_input(&self) -> bool {
-        self.scroll_delta != Vec2::ZERO || self.buttons.iter().any(|(_, state)| !state.is_off())
+    /// True if the cursor is only reporting where it is: no button and no
+    /// scroll this frame.
+    pub fn position_only(&self) -> bool {
+        self.scroll_delta == Vec2::ZERO && self.buttons.iter().all(|(_, state)| state.is_off())
     }
 
     pub fn end_frame(&mut self) {
@@ -188,7 +190,6 @@ impl SensorUi for UiRenderState {
         // state like thing, but local to render state, and is passed to UiRsc events so you can
         // update it there?
         let mut active = std::mem::take(&mut rsc.events_mut().get_type::<CursorSense>().active);
-        let momentary = cursor.has_momentary_input();
         for layer in self.layers.indices().rev() {
             let mut consumed = false;
             for (id, sensor) in active.get_mut(&layer).into_flat_iter() {
@@ -199,22 +200,13 @@ impl SensorUi for UiRenderState {
                 if sensor.hover == ActivationState::Off {
                     continue;
                 }
-                // A widget the cursor has left still hears its hover ending,
-                // but a press or a scroll landing elsewhere is not its input.
-                let cursor = match in_shape {
-                    true => cursor.clone(),
-                    false => CursorState {
-                        pos: cursor.pos,
-                        exists: cursor.exists,
-                        ..Default::default()
-                    },
-                };
-                consumed = consumed
-                    || rsc
-                        .events_mut()
-                        .get_type::<CursorSense>()
-                        .registered(*id)
-                        .any(|senses| senses.consumes(&cursor, sensor.hover, momentary));
+                consumed |= rsc
+                    .events_mut()
+                    .get_type::<CursorSense>()
+                    .registered(*id)
+                    .any(|senses| senses.consumes(&cursor, sensor.hover));
+
+                let cursor = cursor.clone();
 
                 let data = CursorData {
                     pos: cursor.pos - region.top_left,
@@ -243,6 +235,11 @@ pub fn should_run(
     hover: ActivationState,
 ) -> Option<CursorSense> {
     for sense in senses.iter() {
+        // A widget the cursor is no longer inside senses only its position:
+        // the press that ended its hover landed on something else.
+        if !hover.is_on() && !sense.position_only() {
+            continue;
+        }
         if match sense {
             CursorSense::PressStart(button) => cursor.buttons.select(button).is_start(),
             CursorSense::Pressing(button) => cursor.buttons.select(button).is_on(),

tests/pointer_routing.rs

@@ -126,8 +126,8 @@ fn full(ui: &mut Ui) -> StrongWidget<Rect> {
 
 #[test]
 fn hover_stops_at_the_topmost_widget() {
-    let mut ui = Ui::new();
-    let (bottom, middle, top) = (full(&mut ui), full(&mut ui), full(&mut ui));
+    let ui = &mut Ui::new();
+    let (bottom, middle, top) = (full(ui), full(ui), full(ui));
     let bottom_hover = ui.listen(&bottom, CursorSense::HoverStart);
     let middle_hover = ui.listen(&middle, CursorSense::HoverStart);
     let top_hover = ui.listen(&top, CursorSense::HoverStart);
@@ -147,8 +147,8 @@ fn hover_stops_at_the_topmost_widget() {
 
 #[test]
 fn a_scroll_passes_through_every_widget_that_does_not_want_it() {
-    let mut ui = Ui::new();
-    let (list, button, overlay) = (full(&mut ui), full(&mut ui), full(&mut ui));
+    let ui = &mut Ui::new();
+    let (list, button, overlay) = (full(ui), full(ui), full(ui));
     let scrolled = ui.listen(&list, CursorSense::Scroll);
     let clicked = ui.listen(&button, CursorSense::click());
     let overlay_clicked = ui.listen(&overlay, CursorSense::click());
@@ -169,8 +169,8 @@ fn a_scroll_passes_through_every_widget_that_does_not_want_it() {
 
 #[test]
 fn only_the_topmost_listener_takes_a_press() {
-    let mut ui = Ui::new();
-    let (below, above) = (full(&mut ui), full(&mut ui));
+    let ui = &mut Ui::new();
+    let (below, above) = (full(ui), full(ui));
     let below_clicked = ui.listen(&below, CursorSense::click());
     let above_clicked = ui.listen(&above, CursorSense::click());
     ui.stack(vec![below.any(), above.any()]);
@@ -185,11 +185,11 @@ fn only_the_topmost_listener_takes_a_press() {
 
 #[test]
 fn a_press_beside_the_button_reaches_the_layer_below() {
-    let mut ui = Ui::new();
-    let list = full(&mut ui);
+    let ui = &mut Ui::new();
+    let list = full(ui);
     // The row above the list covers it, but only its left half is the button.
-    let button = full(&mut ui);
-    let gap = full(&mut ui);
+    let button = full(ui);
+    let gap = full(ui);
     let list_clicked = ui.listen(&list, CursorSense::click());
     let button_clicked = ui.listen(&button, CursorSense::click());
     let row = ui.rsc.ui.widgets.add_strong(Span {
@@ -218,8 +218,8 @@ fn a_press_beside_the_button_reaches_the_layer_below() {
 
 #[test]
 fn leaving_a_widget_still_ends_its_hover() {
-    let mut ui = Ui::new();
-    let widget = full(&mut ui);
+    let ui = &mut Ui::new();
+    let widget = full(ui);
     let hover = ui.listen(&widget, CursorSense::HoverStart | CursorSense::HoverEnd);
     ui.stack(vec![widget.any()]);