Make non-interactive tooltips not interactable (#8362)

Fixes two bugs around tooltips:
- During sizing pass tooltips would render at a different size, at which
point they might overlap the interacted widget causing the hover state
to change and the tooltip to never be shown
- Fix: During sizing pass make the area `interactable: false` so events
pass through
- When hovering close to the boarder of a widget (in the area where
`interact_radius` takes effect), there could be a feedback loop where
the tooltip is shown one frame and hidden the next.
- Fix: Always make tooltips `interactable: false` when they don't have
interactive contents

This PR changes the behavior of `Area::interactable` to it's original
behavior: Now interactions will pass through the area background _and_
it's containing widgets. It worked this way initially but got changed in
#4026

---------

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/egui_tests/tests/regression_tests.rs

@@ -1,15 +1,15 @@
 use std::sync::Arc;
 
-use egui::ScrollArea;
 use egui::accesskit::Role;
 #[cfg(debug_assertions)]
 use egui::epaint::Shape;
 use egui::style::ScrollAnimation;
 use egui::text::{LayoutJob, TextWrapping};
 use egui::{
-    Align, Button, Color32, FontFamily, FontId, Image, Label, Layout, RichText, Sense, TextBuffer,
-    TextFormat, TextWrapMode, Ui, include_image, vec2,
+    Align, Button, Color32, FontFamily, FontId, Image, Label, Layout, Rect, RichText, Sense,
+    TextBuffer, TextFormat, TextWrapMode, Ui, Vec2, include_image, vec2,
 };
+use egui::{Pos2, ScrollArea};
 use egui_kittest::Harness;
 use egui_kittest::kittest::{NodeT as _, Queryable as _};
 
@@ -481,3 +481,81 @@ fn animated_scroll_beats_sticky_bottom() {
         "animated explicit scroll should leave the sticky bottom"
     );
 }
+
+/// Tests that tooltips are shown correctly for buttons that are only shown on hover.
+///
+/// Basically, this tests that a tooltip overlapping the mouse cursor does not interfere with a
+/// buttons hover state.
+#[test]
+fn tooltip_should_work_for_hover_button() {
+    let button_rect = Rect::from_min_size(Pos2::new(4.0, 4.0), Vec2::new(80.0, 20.0));
+    let mut harness = Harness::builder().with_size((320.0, 80.0)).build_ui(|ui| {
+        if ui.rect_contains_pointer(button_rect) {
+            ui.button("A tooltip should be shown")
+                .on_hover_text("My tooltip");
+        }
+    });
+
+    harness.hover_at(button_rect.center());
+
+    harness.run();
+
+    harness.snapshot("test_tooltip_hover_regression");
+}
+
+/// Ensure that hovering close to a widget doesn't cause a tooltip feedback loop (due to a
+/// difference between `hovered` and `contains_pointer` caused by the interact radius).
+#[test]
+fn tooltip_covering_button_should_not_cause_feedback_loop() {
+    let mut harness = Harness::builder().with_size((200.0, 30.0)).build_ui(|ui| {
+        ui.button("A tooltip should be shown")
+            .on_hover_text("This tooltip is larger than the button");
+    });
+
+    harness.hover_at(
+        harness
+            .get_by_label("A tooltip should be shown")
+            .rect()
+            .left_center()
+            - Vec2::X,
+    );
+
+    harness.run();
+
+    harness.snapshot("tooltip_covering_button_should_not_cause_feedback_loop");
+}
+
+/// Tests that a tooltip closes when the pointer moves onto a neighboring widget,
+/// so that the neighbor can show its own tooltip.
+///
+/// The two buttons are only `item_spacing.y` (3 pt) apart, which is less than the
+/// hit-test `interact_radius` (5 pt), so the first button is still close enough to
+/// interact with when the pointer is on the second one.
+#[test]
+fn tooltip_should_hand_over_to_neighboring_widget() {
+    let mut harness = Harness::builder().with_size((300.0, 200.0)).build_ui(|ui| {
+        ui.button("Button A").on_hover_text("Tooltip A");
+        ui.button("Button B").on_hover_text("Tooltip B");
+    });
+
+    let a_rect = harness.get_by_label("Button A").rect();
+    let b_rect = harness.get_by_label("Button B").rect();
+
+    harness.hover_at(a_rect.center_bottom() - Vec2::Y);
+    harness.run();
+    assert!(
+        harness.query_by_label("Tooltip A").is_some(),
+        "Tooltip A should be shown when hovering Button A"
+    );
+
+    harness.hover_at(b_rect.center_top() + Vec2::Y);
+    harness.run();
+    assert!(
+        harness.query_by_label("Tooltip B").is_some(),
+        "Tooltip B should be shown when hovering Button B"
+    );
+    assert!(
+        harness.query_by_label("Tooltip A").is_none(),
+        "Tooltip A should be hidden when hovering Button B"
+    );
+}

tests/egui_tests/tests/snapshots/test_tooltip_hover_regression.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:59bef0e3593896985988c03171c710d8ed31ed8bb89c7a3f63c060c573e4fb74
+size 6510

tests/egui_tests/tests/snapshots/tooltip_covering_button_should_not_cause_feedback_loop.png

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:ed2f80921ab864b0df3303834a8ab943a3aa5e10456896991c2dca81be0c4968
+size 3968