Fix tooltip so only one shows at a time when hovering (#90457)

In the process of fixing #90044, I realized that it's also possible for hovered tooltips to show more than one at a time if the widgets are nested, so this PR is a fix that prevents more than one tooltip from showing at a time with hovered tooltips.

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

@@ -194,18 +194,41 @@ class Tooltip extends StatefulWidget {
   ///  * [Feedback], for providing platform-specific feedback to certain actions.
   final bool? enableFeedback;
 
-  static final Set<_TooltipState> _openedToolTips = <_TooltipState>{};
+  static final List<_TooltipState> _openedTooltips = <_TooltipState>[];
+
+  // Causes any current tooltips to be concealed. Only called for mouse hover enter
+  // detections. Won't conceal the supplied tooltip.
+  static void _concealOtherTooltips(_TooltipState current) {
+    if (_openedTooltips.isNotEmpty) {
+      // Avoid concurrent modification.
+      final List<_TooltipState> openedTooltips = _openedTooltips.toList();
+      for (final _TooltipState state in openedTooltips) {
+        if (state == current) {
+          continue;
+        }
+        state._concealTooltip();
+      }
+    }
+  }
+
+  // Causes the most recently concealed tooltip to be revealed. Only called for mouse
+  // hover exit detections.
+  static void _revealLastTooltip() {
+    if (_openedTooltips.isNotEmpty) {
+      _openedTooltips.last._revealTooltip();
+    }
+  }
 
   /// Dismiss all of the tooltips that are currently shown on the screen.
   ///
   /// This method returns true if it successfully dismisses the tooltips. It
   /// returns false if there is no tooltip shown on the screen.
   static bool dismissAllToolTips() {
-    if (_openedToolTips.isNotEmpty) {
+    if (_openedTooltips.isNotEmpty) {
       // Avoid concurrent modification.
-      final List<_TooltipState> openedToolTips = List<_TooltipState>.from(_openedToolTips);
-      for (final _TooltipState state in openedToolTips) {
-        state._hideTooltip(immediately: true);
+      final List<_TooltipState> openedTooltips = _openedTooltips.toList();
+      for (final _TooltipState state in openedTooltips) {
+        state._dismissTooltip(immediately: true);
       }
       return true;
     }
@@ -255,7 +278,7 @@ class _TooltipState extends State<Tooltip> with SingleTickerProviderStateMixin {
   late bool excludeFromSemantics;
   late AnimationController _controller;
   OverlayEntry? _entry;
-  Timer? _hideTimer;
+  Timer? _dismissTimer;
   Timer? _showTimer;
   late Duration showDuration;
   late Duration hoverShowDuration;
@@ -264,10 +287,14 @@ class _TooltipState extends State<Tooltip> with SingleTickerProviderStateMixin {
   bool _pressActivated = false;
   late TooltipTriggerMode triggerMode;
   late bool enableFeedback;
+  late bool _isConcealed;
+  late bool _forceRemoval;
 
   @override
   void initState() {
     super.initState();
+    _isConcealed = false;
+    _forceRemoval = false;
     _mouseIsConnected = RendererBinding.instance!.mouseTracker.mouseIsConnected;
     _controller = AnimationController(
       duration: _fadeInDuration,
@@ -333,29 +360,34 @@ class _TooltipState extends State<Tooltip> with SingleTickerProviderStateMixin {
   }
 
   void _handleStatusChanged(AnimationStatus status) {
-    if (status == AnimationStatus.dismissed) {
-      _hideTooltip(immediately: true);
+    // If this tip is concealed, don't remove it, even if it is dismissed, so that we can
+    // reveal it later, unless it has explicitly been hidden with _dismissTooltip.
+    if (status == AnimationStatus.dismissed && (_forceRemoval || !_isConcealed)) {
+      _removeEntry();
     }
   }
 
-  void _hideTooltip({ bool immediately = false }) {
+  void _dismissTooltip({ bool immediately = false }) {
     _showTimer?.cancel();
     _showTimer = null;
     if (immediately) {
       _removeEntry();
       return;
     }
+    // So it will be removed when it's done reversing, regardless of whether it is
+    // still concealed or not.
+    _forceRemoval = true;
     if (_pressActivated) {
-      _hideTimer ??= Timer(showDuration, _controller.reverse);
+      _dismissTimer ??= Timer(showDuration, _controller.reverse);
     } else {
-      _hideTimer ??= Timer(hoverShowDuration, _controller.reverse);
+      _dismissTimer ??= Timer(hoverShowDuration, _controller.reverse);
     }
     _pressActivated = false;
   }
 
   void _showTooltip({ bool immediately = false }) {
-    _hideTimer?.cancel();
-    _hideTimer = null;
+    _dismissTimer?.cancel();
+    _dismissTimer = null;
     if (immediately) {
       ensureTooltipVisible();
       return;
@@ -363,17 +395,61 @@ class _TooltipState extends State<Tooltip> with SingleTickerProviderStateMixin {
     _showTimer ??= Timer(waitDuration, ensureTooltipVisible);
   }
 
+  void _concealTooltip() {
+    if (_isConcealed || _forceRemoval) {
+      // Already concealed, or it's being removed.
+      return;
+    }
+    _isConcealed = true;
+    _dismissTimer?.cancel();
+    _dismissTimer = null;
+    _showTimer?.cancel();
+    _showTimer = null;
+    if (_entry!= null) {
+      _entry!.remove();
+    }
+    _controller.reverse();
+  }
+
+  void _revealTooltip() {
+    if (!_isConcealed) {
+      // Already uncovered.
+      return;
+    }
+    _isConcealed = false;
+    _dismissTimer?.cancel();
+    _dismissTimer = null;
+    _showTimer?.cancel();
+    _showTimer = null;
+    if (!_entry!.mounted) {
+      final OverlayState overlayState = Overlay.of(
+        context,
+        debugRequiredFor: widget,
+      )!;
+      overlayState.insert(_entry!);
+    }
+    SemanticsService.tooltip(widget.message);
+    _controller.forward();
+  }
+
   /// Shows the tooltip if it is not already visible.
   ///
-  /// Returns `false` when the tooltip was already visible or if the context has
-  /// become null.
+  /// Returns `false` when the tooltip was already visible.
   bool ensureTooltipVisible() {
     _showTimer?.cancel();
     _showTimer = null;
+    _forceRemoval = false;
+    if (_isConcealed) {
+      if (_mouseIsConnected) {
+        Tooltip._concealOtherTooltips(this);
+      }
+      _revealTooltip();
+      return true;
+    }
     if (_entry != null) {
       // Stop trying to hide, if we were.
-      _hideTimer?.cancel();
-      _hideTimer = null;
+      _dismissTimer?.cancel();
+      _dismissTimer = null;
       _controller.forward();
       return false; // Already visible.
     }
@@ -382,6 +458,17 @@ class _TooltipState extends State<Tooltip> with SingleTickerProviderStateMixin {
     return true;
   }
 
+  static final Set<_TooltipState> _mouseIn = <_TooltipState>{};
+
+  void _handleMouseEnter() {
+    _showTooltip();
+  }
+
+  void _handleMouseExit({bool immediately = false}) {
+    // If the tip is currently covered, we can just remove it without waiting.
+    _dismissTooltip(immediately: _isConcealed || immediately);
+  }
+
   void _createNewEntry() {
     final OverlayState overlayState = Overlay.of(
       context,
@@ -404,8 +491,8 @@ class _TooltipState extends State<Tooltip> with SingleTickerProviderStateMixin {
         height: height,
         padding: padding,
         margin: margin,
-        onEnter: _mouseIsConnected ? (PointerEnterEvent event) => _showTooltip() : null,
-        onExit: _mouseIsConnected ? (PointerExitEvent event) => _hideTooltip() : null,
+        onEnter: _mouseIsConnected ? (_) => _handleMouseEnter() : null,
+        onExit: _mouseIsConnected ? (_) => _handleMouseExit() : null,
         decoration: decoration,
         textStyle: textStyle,
         animation: CurvedAnimation(
@@ -418,19 +505,34 @@ class _TooltipState extends State<Tooltip> with SingleTickerProviderStateMixin {
       ),
     );
     _entry = OverlayEntry(builder: (BuildContext context) => overlay);
+    _isConcealed = false;
     overlayState.insert(_entry!);
     SemanticsService.tooltip(widget.message);
-    Tooltip._openedToolTips.add(this);
+    if (_mouseIsConnected) {
+      // Hovered tooltips shouldn't show more than one at once. For example, a chip with
+      // a delete icon shouldn't show both the delete icon tooltip and the chip tooltip
+      // at the same time.
+      Tooltip._concealOtherTooltips(this);
+    }
+    assert(!Tooltip._openedTooltips.contains(this));
+    Tooltip._openedTooltips.add(this);
   }
 
   void _removeEntry() {
-    Tooltip._openedToolTips.remove(this);
-    _hideTimer?.cancel();
-    _hideTimer = null;
+    Tooltip._openedTooltips.remove(this);
+    _mouseIn.remove(this);
+    _dismissTimer?.cancel();
+    _dismissTimer = null;
     _showTimer?.cancel();
     _showTimer = null;
-    _entry?.remove();
+    if (!_isConcealed) {
+      _entry?.remove();
+    }
+    _isConcealed = false;
     _entry = null;
+    if (_mouseIsConnected) {
+      Tooltip._revealLastTooltip();
+    }
   }
 
   void _handlePointerEvent(PointerEvent event) {
@@ -438,16 +540,16 @@ class _TooltipState extends State<Tooltip> with SingleTickerProviderStateMixin {
       return;
     }
     if (event is PointerUpEvent || event is PointerCancelEvent) {
-      _hideTooltip();
+      _handleMouseExit();
     } else if (event is PointerDownEvent) {
-      _hideTooltip(immediately: true);
+      _handleMouseExit(immediately: true);
     }
   }
 
   @override
   void deactivate() {
     if (_entry != null) {
-      _hideTooltip(immediately: true);
+      _dismissTooltip(immediately: true);
     }
     _showTimer?.cancel();
     super.deactivate();
@@ -535,8 +637,8 @@ class _TooltipState extends State<Tooltip> with SingleTickerProviderStateMixin {
     // Only check for hovering if there is a mouse connected.
     if (_mouseIsConnected) {
       result = MouseRegion(
-        onEnter: (PointerEnterEvent event) => _showTooltip(),
-        onExit: (PointerExitEvent event) => _hideTooltip(),
+        onEnter: (_) => _handleMouseEnter(),
+        onExit: (_) => _handleMouseExit(),
         child: result,
       );
     }

packages/flutter/test/material/tooltip_test.dart

@@ -919,8 +919,7 @@ void main() {
     const Duration waitDuration = Duration.zero;
     TestGesture? gesture = await tester.createGesture(kind: PointerDeviceKind.mouse);
     addTearDown(() async {
-      if (gesture != null)
-        return gesture.removePointer();
+      gesture?.removePointer();
     });
     await gesture.addPointer();
     await gesture.moveTo(const Offset(1.0, 1.0));
@@ -970,6 +969,70 @@ void main() {
     expect(find.text(tooltipText), findsNothing);
   });
 
+  testWidgets('Tooltip should not show more than one tooltip when hovered', (WidgetTester tester) async {
+    const Duration waitDuration = Duration(milliseconds: 500);
+    final UniqueKey innerKey = UniqueKey();
+    final UniqueKey outerKey = UniqueKey();
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Center(
+          child: Tooltip(
+            message: 'Outer',
+            child: Container(
+              key: outerKey,
+              width: 100,
+              height: 100,
+              alignment: Alignment.centerRight,
+              child: Tooltip(
+                message: 'Inner',
+                child: SizedBox(
+                  key: innerKey,
+                  width: 25,
+                  height: 100,
+                ),
+              ),
+            ),
+          ),
+        ),
+      ),
+    );
+
+    TestGesture? gesture = await tester.createGesture(kind: PointerDeviceKind.mouse);
+    addTearDown(() async { gesture?.removePointer(); });
+
+    // Both the inner and outer containers have tooltips associated with them, but only
+    // the currently hovered one should appear, even though the pointer is inside both.
+    final Finder outer = find.byKey(outerKey);
+    final Finder inner = find.byKey(innerKey);
+    await gesture.moveTo(Offset.zero);
+    await tester.pump();
+    await gesture.moveTo(tester.getCenter(outer));
+    await tester.pump();
+    await gesture.moveTo(tester.getCenter(inner));
+    await tester.pump();
+
+    // Wait for it to appear.
+    await tester.pump(waitDuration);
+
+    expect(find.text('Outer'), findsNothing);
+    expect(find.text('Inner'), findsOneWidget);
+    await gesture.moveTo(tester.getCenter(outer));
+    await tester.pump();
+    // Wait for it to switch.
+    await tester.pump(waitDuration);
+    expect(find.text('Outer'), findsOneWidget);
+    expect(find.text('Inner'), findsNothing);
+
+    await gesture.moveTo(Offset.zero);
+
+    // Wait for all tooltips to disappear.
+    await tester.pumpAndSettle();
+    await gesture.removePointer();
+    gesture = null;
+    expect(find.text('Outer'), findsNothing);
+    expect(find.text('Inner'), findsNothing);
+  });
+
   testWidgets('Tooltip can be dismissed by escape key', (WidgetTester tester) async {
     const Duration waitDuration = Duration.zero;
     TestGesture? gesture = await tester.createGesture(kind: PointerDeviceKind.mouse);