Remove a bad assert from tooltip implementation (#127629)

Fixes https://github.com/flutter/flutter/issues/127575

The `_handleMouseEnter` and `_handleMouseExit` calls are balanced, but the tooltip could be dismissed by an external `PointerDown` event interacting with a different UI component so the ` assert(_activeHoveringPointerDevices.isNotEmpty);` does not really make sense.

packages/flutter/lib/src/material/tooltip.dart

@@ -425,6 +425,10 @@ class TooltipState extends State<Tooltip> with SingleTickerProviderStateMixin {
   TapGestureRecognizer? _tapRecognizer;
 
   // The ids of mouse devices that are keeping the tooltip from being dismissed.
+  //
+  // Device ids are added to this set in _handleMouseEnter, and removed in
+  // _handleMouseExit. The set is cleared in _handleTapToDismiss, typically when
+  // a PointerDown event interacts with some other UI component.
   final Set<int> _activeHoveringPointerDevices = <int>{};
   AnimationStatus _animationStatus = AnimationStatus.dismissed;
   void _handleStatusChanged(AnimationStatus status) {
@@ -469,18 +473,14 @@ class TooltipState extends State<Tooltip> with SingleTickerProviderStateMixin {
       'timer must not be active when the tooltip is fading out',
     );
     switch (_controller.status) {
-      case AnimationStatus.dismissed:
+      case AnimationStatus.dismissed when withDelay.inMicroseconds > 0:
-        if (withDelay.inMicroseconds > 0) {
+        _timer ??= Timer(withDelay, show);
-          _timer ??= Timer(withDelay, show);
-        } else {
-          show();
-        }
       // If the tooltip is already fading in or fully visible, skip the
       // animation and show the tooltip immediately.
+      case AnimationStatus.dismissed:
       case AnimationStatus.forward:
       case AnimationStatus.reverse:
       case AnimationStatus.completed:
-        // Fade in if needed and schedule to hide.
         show();
     }
   }
@@ -646,10 +646,9 @@ class TooltipState extends State<Tooltip> with SingleTickerProviderStateMixin {
   }
 
   void _handleMouseExit(PointerExitEvent event) {
-    if (!mounted) {
+    if (!mounted || _activeHoveringPointerDevices.isEmpty) {
       return;
     }
-    assert(_activeHoveringPointerDevices.isNotEmpty);
     _activeHoveringPointerDevices.remove(event.device);
     if (_activeHoveringPointerDevices.isEmpty) {
       _scheduleDismissTooltip(withDelay: _hoverShowDuration);
@@ -699,45 +698,36 @@ class TooltipState extends State<Tooltip> with SingleTickerProviderStateMixin {
 
   // https://material.io/components/tooltips#specs
   double _getDefaultTooltipHeight() {
-    final ThemeData theme = Theme.of(context);
+    return switch (Theme.of(context).platform) {
-    switch (theme.platform) {
+      TargetPlatform.macOS ||
-      case TargetPlatform.macOS:
+      TargetPlatform.linux ||
-      case TargetPlatform.linux:
+      TargetPlatform.windows => 24.0,
-      case TargetPlatform.windows:
+      TargetPlatform.android ||
-        return 24.0;
+      TargetPlatform.fuchsia ||
-      case TargetPlatform.android:
+      TargetPlatform.iOS     => 32.0,
-      case TargetPlatform.fuchsia:
+    };
-      case TargetPlatform.iOS:
-        return 32.0;
-    }
   }
 
   EdgeInsets _getDefaultPadding() {
-    final ThemeData theme = Theme.of(context);
+    return switch (Theme.of(context).platform) {
-    switch (theme.platform) {
+      TargetPlatform.macOS ||
-      case TargetPlatform.macOS:
+      TargetPlatform.linux ||
-      case TargetPlatform.linux:
+      TargetPlatform.windows => const EdgeInsets.symmetric(horizontal: 8.0, vertical: 4.0),
-      case TargetPlatform.windows:
+      TargetPlatform.android ||
-        return const EdgeInsets.symmetric(horizontal: 8.0, vertical: 4.0);
+      TargetPlatform.fuchsia ||
-      case TargetPlatform.android:
+      TargetPlatform.iOS     => const EdgeInsets.symmetric(horizontal: 16.0, vertical: 4.0),
-      case TargetPlatform.fuchsia:
+    };
-      case TargetPlatform.iOS:
-        return const EdgeInsets.symmetric(horizontal: 16.0, vertical: 4.0);
-    }
   }
 
   double _getDefaultFontSize() {
-    final ThemeData theme = Theme.of(context);
+    return switch (Theme.of(context).platform) {
-    switch (theme.platform) {
+      TargetPlatform.macOS ||
-      case TargetPlatform.macOS:
+      TargetPlatform.linux ||
-      case TargetPlatform.linux:
+      TargetPlatform.windows => 12.0,
-      case TargetPlatform.windows:
+      TargetPlatform.android ||
-        return 12.0;
+      TargetPlatform.fuchsia ||
-      case TargetPlatform.android:
+      TargetPlatform.iOS     => 14.0,
-      case TargetPlatform.fuchsia:
+    };
-      case TargetPlatform.iOS:
-        return 14.0;
-    }
   }
 
   void _createNewEntry() {

packages/flutter/test/material/tooltip_test.dart

@@ -1993,7 +1993,7 @@ void main() {
     }
   });
 
-  testWidgets('Tooltip trigger mode ignores mouse events', (WidgetTester tester) async {
+  testWidgetsWithLeakTracking('Tooltip trigger mode ignores mouse events', (WidgetTester tester) async {
     await tester.pumpWidget(
       const MaterialApp(
         home: Tooltip(
@@ -2021,7 +2021,7 @@ void main() {
     expect(find.text(tooltipText), findsOneWidget);
   });
 
-  testWidgets('Tooltip does not block other mouse regions', (WidgetTester tester) async {
+  testWidgetsWithLeakTracking('Tooltip does not block other mouse regions', (WidgetTester tester) async {
     bool entered = false;
 
     await tester.pumpWidget(
@@ -2046,7 +2046,7 @@ void main() {
     expect(entered, isTrue);
   });
 
-  testWidgets('Does not rebuild on mouse connect/disconnect', (WidgetTester tester) async {
+  testWidgetsWithLeakTracking('Does not rebuild on mouse connect/disconnect', (WidgetTester tester) async {
     // Regression test for https://github.com/flutter/flutter/issues/117627
     int buildCount = 0;
     await tester.pumpWidget(
@@ -2100,6 +2100,165 @@ void main() {
     await _testGestureTap(tester, textSpan);
     expect(isTapped, isTrue);
   });
+
+  testWidgetsWithLeakTracking('Hold mouse button down and hover over the Tooltip widget', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const MaterialApp(
+        home: Center(
+          child: SizedBox.square(
+            dimension: 10.0,
+            child: Tooltip(
+              message: tooltipText,
+              waitDuration: Duration(seconds: 1),
+              triggerMode: TooltipTriggerMode.longPress,
+              child: SizedBox.expand(),
+            ),
+          ),
+        ),
+      ),
+    );
+
+    final TestGesture mouseGesture = await tester.startGesture(Offset.zero, kind: PointerDeviceKind.mouse);
+    addTearDown(mouseGesture.removePointer);
+    await mouseGesture.moveTo(tester.getCenter(find.byTooltip(tooltipText)));
+    await tester.pump(const Duration(seconds: 1));
+    expect(
+      find.text(tooltipText), findsOneWidget, reason: 'Tooltip should be visible when hovered.');
+
+    await mouseGesture.up();
+    await tester.pump(const Duration(days: 10));
+    await tester.pumpAndSettle();
+    expect(
+      find.text(tooltipText),
+      findsOneWidget,
+      reason: 'Tooltip should be visible even when there is a PointerUp when hovered.',
+    );
+
+    await mouseGesture.moveTo(Offset.zero);
+    await tester.pump(const Duration(seconds: 1));
+    await tester.pumpAndSettle();
+    expect(
+      find.text(tooltipText),
+      findsNothing,
+      reason: 'Tooltip should be dismissed with no hovering mouse cursor.' ,
+    );
+  });
+
+  testWidgetsWithLeakTracking('Hovered text should dismiss when clicked outside', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const MaterialApp(
+        home: Center(
+          child: SizedBox.square(
+            dimension: 10.0,
+            child: Tooltip(
+              message: tooltipText,
+              waitDuration: Duration(seconds: 1),
+              triggerMode: TooltipTriggerMode.longPress,
+              child: SizedBox.expand(),
+            ),
+          ),
+        ),
+      ),
+    );
+
+    // Avoid using startGesture here to avoid the PointDown event from also being
+    // interpreted as a PointHover event by the Tooltip.
+    final TestGesture mouseGesture1 = await tester.createGesture(kind: PointerDeviceKind.mouse);
+    addTearDown(mouseGesture1.removePointer);
+    await mouseGesture1.moveTo(tester.getCenter(find.byTooltip(tooltipText)));
+    await tester.pump(const Duration(seconds: 1));
+    expect(find.text(tooltipText), findsOneWidget, reason: 'Tooltip should be visible when hovered.');
+
+    // Tapping on the Tooltip widget should dismiss the tooltip, since the
+    // trigger mode is longPress.
+    await tester.tap(find.byTooltip(tooltipText));
+    await tester.pump();
+    await tester.pumpAndSettle();
+    expect(find.text(tooltipText), findsNothing);
+    await mouseGesture1.removePointer();
+
+    final TestGesture mouseGesture2 = await tester.createGesture(kind: PointerDeviceKind.mouse);
+    addTearDown(mouseGesture2.removePointer);
+    await mouseGesture2.moveTo(tester.getCenter(find.byTooltip(tooltipText)));
+    await tester.pump(const Duration(seconds: 1));
+    expect(find.text(tooltipText), findsOneWidget, reason: 'Tooltip should be visible when hovered.');
+
+    await tester.tapAt(Offset.zero);
+    await tester.pump();
+    await tester.pumpAndSettle();
+    expect(find.text(tooltipText), findsNothing, reason: 'Tapping outside of the Tooltip widget should dismiss the tooltip.');
+  });
+
+  testWidgetsWithLeakTracking('Mouse tap and hover over the Tooltip widget', (WidgetTester tester) async {
+    // Regression test for https://github.com/flutter/flutter/issues/127575 .
+    await tester.pumpWidget(
+      const MaterialApp(
+        home: Center(
+          child: SizedBox.square(
+            dimension: 10.0,
+            child: Tooltip(
+              message: tooltipText,
+              waitDuration: Duration(seconds: 1),
+              triggerMode: TooltipTriggerMode.longPress,
+              child: SizedBox.expand(),
+            ),
+          ),
+        ),
+      ),
+    );
+
+    // The PointDown event is also interpreted as a PointHover event by the
+    // Tooltip. This should be pretty rare but since it's more of a tap event
+    // than a hover event, the tooltip shouldn't show unless the triggerMode
+    // is set to tap.
+    final TestGesture mouseGesture1 = await tester.startGesture(
+      tester.getCenter(find.byTooltip(tooltipText)),
+      kind: PointerDeviceKind.mouse,
+    );
+    addTearDown(mouseGesture1.removePointer);
+    await tester.pump(const Duration(seconds: 1));
+    expect(
+      find.text(tooltipText),
+      findsNothing,
+      reason: 'Tooltip should NOT be visible when hovered and tapped, when trigger mode is not tap',
+    );
+    await mouseGesture1.up();
+    await mouseGesture1.removePointer();
+    await tester.pump(const Duration(days: 10));
+    await tester.pumpAndSettle();
+
+    await tester.pumpWidget(
+      const MaterialApp(
+        home: Center(
+          child: SizedBox.square(
+            dimension: 10.0,
+            child: Tooltip(
+              message: tooltipText,
+              waitDuration: Duration(seconds: 1),
+              triggerMode: TooltipTriggerMode.tap,
+              child: SizedBox.expand(),
+            ),
+          ),
+        ),
+      ),
+    );
+
+    final TestGesture mouseGesture2 = await tester.startGesture(
+      tester.getCenter(find.byTooltip(tooltipText)),
+      kind: PointerDeviceKind.mouse,
+    );
+    addTearDown(mouseGesture2.removePointer);
+    // The tap should be ignored, since Tooltip does not track "trigger gestures"
+    // for mouse devices.
+    await tester.pump(const Duration(milliseconds: 100));
+    await mouseGesture2.up();
+    await tester.pump(const Duration(seconds: 1));
+    expect(
+      find.text(tooltipText),
+      findsNothing,
+      reason: 'Tooltip should NOT be visible when hovered and tapped, when trigger mode is tap',
+    );
+  });
 }
 
 Future<void> setWidgetForTooltipMode(