Fix style of disabled widgets (#4163)

* Broke in https://github.com/emilk/egui/pull/4026/files

The `Response::sense` for `enabled: false` widgets was wrong, leading to
the wrong widget style.

crates/egui/src/context.rs

@@ -1018,12 +1018,7 @@ impl Context {
     ///
     /// If the widget already exists, its state (sense, Rect, etc) will be updated.
     #[allow(clippy::too_many_arguments)]
-    pub(crate) fn create_widget(&self, mut w: WidgetRect) -> Response {
-        if !w.enabled {
-            w.sense.click = false;
-            w.sense.drag = false;
-        }
-
+    pub(crate) fn create_widget(&self, w: WidgetRect) -> Response {
         // Remember this widget
         self.write(|ctx| {
             let viewport = ctx.viewport();
@@ -1130,7 +1125,8 @@ impl Context {
             let input = &viewport.input;
             let memory = &mut ctx.memory;
 
-            if sense.click
+            if enabled
+                && sense.click
                 && memory.has_focus(id)
                 && (input.key_pressed(Key::Space) || input.key_pressed(Key::Enter))
             {
@@ -1139,7 +1135,10 @@ impl Context {
             }
 
             #[cfg(feature = "accesskit")]
-            if sense.click && input.has_accesskit_action_request(id, accesskit::Action::Default) {
+            if enabled
+                && sense.click
+                && input.has_accesskit_action_request(id, accesskit::Action::Default)
+            {
                 res.clicked[PointerButton::Primary as usize] = true;
             }
 
@@ -1159,7 +1158,7 @@ impl Context {
 
             for pointer_event in &input.pointer.pointer_events {
                 if let PointerEvent::Released { click, button } = pointer_event {
-                    if sense.click && clicked {
+                    if enabled && sense.click && clicked {
                         if let Some(click) = click {
                             res.clicked[*button as usize] = true;
                             res.double_clicked[*button as usize] = click.is_double();

crates/egui/src/hit_test.rs

@@ -78,6 +78,16 @@ pub fn hit_test(
         let top_layer = closest_hit.layer_id;
         close.retain(|w| w.layer_id == top_layer);
 
+        // If the widget is disabled, treat it as if it isn't sensing anything.
+        // This simplifies the code in `hit_test_on_close` so it doesn't have to check
+        // the `enabled` flag everywhere:
+        for w in &mut close {
+            if !w.enabled {
+                w.sense.click = false;
+                w.sense.drag = false;
+            }
+        }
+
         let pos_in_layer = pos_in_layers.get(&top_layer).copied().unwrap_or(pos);
         let hits = hit_test_on_close(&close, pos_in_layer);
 

crates/egui/src/interaction.rs

@@ -161,18 +161,20 @@ pub(crate) fn interact(
     if dragged.is_none() {
         // Check if we started dragging something new:
         if let Some(widget) = interaction.potential_drag_id.and_then(|id| widgets.get(id)) {
-            let is_dragged = if widget.sense.click && widget.sense.drag {
-                // This widget is sensitive to both clicks and drags.
-                // When the mouse first is pressed, it could be either,
-                // so we postpone the decision until we know.
-                input.pointer.is_decidedly_dragging()
-            } else {
-                // This widget is just sensitive to drags, so we can mark it as dragged right away:
-                widget.sense.drag
-            };
+            if widget.enabled {
+                let is_dragged = if widget.sense.click && widget.sense.drag {
+                    // This widget is sensitive to both clicks and drags.
+                    // When the mouse first is pressed, it could be either,
+                    // so we postpone the decision until we know.
+                    input.pointer.is_decidedly_dragging()
+                } else {
+                    // This widget is just sensitive to drags, so we can mark it as dragged right away:
+                    widget.sense.drag
+                };
 
-            if is_dragged {
-                dragged = Some(widget.id);
+                if is_dragged {
+                    dragged = Some(widget.id);
+                }
             }
         }
     }

crates/egui/src/response.rs

@@ -42,6 +42,13 @@ pub struct Response {
     pub interact_rect: Rect,
 
     /// The senses (click and/or drag) that the widget was interested in (if any).
+    ///
+    /// Note: if [`Self::enabled`] is `false`, then
+    /// the widget _effectively_ doesn't sense anything,
+    /// but can still have the same `Sense`.
+    /// This is because the sense informs the styling of the widget,
+    /// but we don't want to change the style when a widget is disabled
+    /// (that is handled by the `Painter` directly).
     pub sense: Sense,
 
     /// Was the widget enabled?

crates/egui/src/widget_rect.rs

@@ -29,6 +29,13 @@ pub struct WidgetRect {
     pub interact_rect: Rect,
 
     /// How the widget responds to interaction.
+    ///
+    /// Note: if [`Self::enabled`] is `false`, then
+    /// the widget _effectively_ doesn't sense anything,
+    /// but can still have the same `Sense`.
+    /// This is because the sense informs the styling of the widget,
+    /// but we don't want to change the style when a widget is disabled
+    /// (that is handled by the `Painter` directly).
     pub sense: Sense,
 
     /// Is the widget enabled?