iOS tap handling on CupertinoTextField (#24034)

packages/flutter/lib/src/cupertino/text_field.dart

 // Copyright 2018 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
+import 'dart:async';
 
+import 'package:flutter/gestures.dart' show kDoubleTapTimeout, kDoubleTapSlop;
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
@@ -418,6 +420,13 @@ class _CupertinoTextFieldState extends State<CupertinoTextField> with AutomaticK
   FocusNode _focusNode;
   FocusNode get _effectiveFocusNode => widget.focusNode ?? (_focusNode ??= FocusNode());
 
+  // Is shortly after a previous single tap when not null.
+  Timer _doubleTapTimer;
+  Offset _lastTapOffset;
+  // True if second tap down of a double tap is detected. Used to discard
+  // subsequent tap up / tap hold of the same tap.
+  bool _isDoubleTap = false;
+
   @override
   void initState() {
     super.initState();
@@ -447,6 +456,7 @@ class _CupertinoTextFieldState extends State<CupertinoTextField> with AutomaticK
   void dispose() {
     _focusNode?.dispose();
     _controller?.removeListener(updateKeepAlive);
+    _doubleTapTimer?.cancel();
     super.dispose();
   }
 
@@ -456,17 +466,54 @@ class _CupertinoTextFieldState extends State<CupertinoTextField> with AutomaticK
 
   RenderEditable get _renderEditable => _editableTextKey.currentState.renderEditable;
 
+  // The down handler is force-run on success of a single tap and optimistically
+  // run before a long press success.
   void _handleTapDown(TapDownDetails details) {
     _renderEditable.handleTapDown(details);
+    // This isn't detected as a double tap gesture in the gesture recognizer
+    // because it's 2 single taps, each of which may do different things depending
+    // on whether it's a single tap, the first tap of a double tap, the second
+    // tap held down, a clean double tap etc.
+    if (_doubleTapTimer != null && _isWithinDoubleTapTolerance(details.globalPosition)) {
+      // If there was already a previous tap, the second down hold/tap is a
+      // double tap.
+      _renderEditable.selectWord(cause: SelectionChangedCause.doubleTap);
+      _doubleTapTimer.cancel();
+      _doubleTapTimeout();
+      _isDoubleTap = true;
+    }
   }
 
-  void _handleTap() {
-    _renderEditable.handleTap();
+  void _handleTapUp(TapUpDetails details) {
+    if (!_isDoubleTap) {
+      _renderEditable.selectWordEdge(cause: SelectionChangedCause.tap);
+      _lastTapOffset = details.globalPosition;
+      _doubleTapTimer = Timer(kDoubleTapTimeout, _doubleTapTimeout);
       _requestKeyboard();
     }
+    _isDoubleTap = false;
+  }
 
   void _handleLongPress() {
-    _renderEditable.handleLongPress();
+    if (!_isDoubleTap) {
+      _renderEditable.selectPosition(cause: SelectionChangedCause.longPress);
+    }
+    _isDoubleTap = false;
+  }
+
+  void _doubleTapTimeout() {
+    _doubleTapTimer = null;
+    _lastTapOffset = null;
+  }
+
+  bool _isWithinDoubleTapTolerance(Offset secondTapOffset) {
+    assert(secondTapOffset != null);
+    if (_lastTapOffset == null) {
+      return false;
+    }
+
+    final Offset difference = secondTapOffset - _lastTapOffset;
+    return difference.distance <= kDoubleTapSlop;
   }
 
   @override
@@ -648,7 +695,7 @@ class _CupertinoTextFieldState extends State<CupertinoTextField> with AutomaticK
             child: GestureDetector(
               behavior: HitTestBehavior.translucent,
               onTapDown: _handleTapDown,
-              onTap: _handleTap,
+              onTapUp: _handleTapUp,
               onLongPress: _handleLongPress,
               excludeFromSemantics: true,
               child: _addTextDependentAttachments(paddedEditable),

packages/flutter/lib/src/rendering/editable.dart

@@ -32,6 +32,10 @@ enum SelectionChangedCause {
   /// of the cursor) to change.
   tap,
 
+  /// The user tapped twice in quick succession on the text and that caused
+  /// the selection (or the location of the cursor) to change.
+  doubleTap,
+
   /// The user long-pressed the text and that caused the selection (or the
   /// location of the cursor) to change.
   longPress,
@@ -190,7 +194,7 @@ class RenderEditable extends RenderBox {
 
   /// If true [handleEvent] does nothing and it's assumed that this
   /// renderer will be notified of input gestures via [handleTapDown],
-  /// [handleTap], and [handleLongPress].
+  /// [handleTap], [handleDoubleTap], and [handleLongPress].
   ///
   /// The default value of this property is false.
   bool ignorePointer;
@@ -1081,18 +1085,23 @@ class RenderEditable extends RenderBox {
   /// When [ignorePointer] is true, an ancestor widget must respond to tap
   /// events by calling this method.
   void handleTap() {
-    _layoutText(constraints.maxWidth);
-    assert(_lastTapDownPosition != null);
-    if (onSelectionChanged != null) {
-      final TextPosition position = _textPainter.getPositionForOffset(globalToLocal(_lastTapDownPosition));
-      onSelectionChanged(TextSelection.fromPosition(position), this, SelectionChangedCause.tap);
-    }
+    selectPosition(cause: SelectionChangedCause.tap);
   }
   void _handleTap() {
     assert(!ignorePointer);
     handleTap();
   }
 
+  /// If [ignorePointer] is false (the default) then this method is called by
+  /// the internal gesture recognizer's [DoubleTapGestureRecognizer.onDoubleTap]
+  /// callback.
+  ///
+  /// When [ignorePointer] is true, an ancestor widget must respond to double
+  /// tap events by calling this method.
+  void handleDoubleTap() {
+    selectWord(cause: SelectionChangedCause.doubleTap);
+  }
+
   /// If [ignorePointer] is false (the default) then this method is called by
   /// the internal gesture recognizer's [LongPressRecognizer.onLongPress]
   /// callback.
@@ -1100,16 +1109,57 @@ class RenderEditable extends RenderBox {
   /// When [ignorePointer] is true, an ancestor widget must respond to long
   /// press events by calling this method.
   void handleLongPress() {
+    selectWord(cause: SelectionChangedCause.longPress);
+  }
+  void _handleLongPress() {
+    assert(!ignorePointer);
+    handleLongPress();
+  }
+
+  /// Move selection to the location of the last tap down.
+  void selectPosition({@required SelectionChangedCause cause}) {
+    assert(cause != null);
     _layoutText(constraints.maxWidth);
     assert(_lastTapDownPosition != null);
     if (onSelectionChanged != null) {
       final TextPosition position = _textPainter.getPositionForOffset(globalToLocal(_lastTapDownPosition));
-      onSelectionChanged(_selectWordAtOffset(position), this, SelectionChangedCause.longPress);
+      onSelectionChanged(TextSelection.fromPosition(position), this, cause);
+    }
+  }
+
+  /// Select a word around the location of the last tap down.
+  void selectWord({@required SelectionChangedCause cause}) {
+    assert(cause != null);
+    _layoutText(constraints.maxWidth);
+    assert(_lastTapDownPosition != null);
+    if (onSelectionChanged != null) {
+      final TextPosition position = _textPainter.getPositionForOffset(globalToLocal(_lastTapDownPosition));
+      onSelectionChanged(_selectWordAtOffset(position), this, cause);
+    }
+  }
+
+  /// Move the selection to the beginning or end of a word.
+  void selectWordEdge({@required SelectionChangedCause cause}) {
+    assert(cause != null);
+    _layoutText(constraints.maxWidth);
+    assert(_lastTapDownPosition != null);
+    if (onSelectionChanged != null) {
+      final TextPosition position = _textPainter.getPositionForOffset(globalToLocal(_lastTapDownPosition));
+      final TextRange word = _textPainter.getWordBoundary(position);
+      if (position.offset - word.start <= 1) {
+        onSelectionChanged(
+          TextSelection.collapsed(offset: word.start, affinity: TextAffinity.downstream),
+          this,
+          cause,
+        );
+      } else {
+        onSelectionChanged(
+          TextSelection.collapsed(offset: word.end, affinity: TextAffinity.upstream),
+          this,
+          cause,
+        );
       }
     }
-  void _handleLongPress() {
-    assert(!ignorePointer);
-    handleLongPress();
   }
 
   TextSelection _selectWordAtOffset(TextPosition position) {

packages/flutter/lib/src/widgets/editable_text.dart

@@ -740,7 +740,7 @@ class EditableTextState extends State<EditableText> with AutomaticKeepAliveClien
       final bool longPress = cause == SelectionChangedCause.longPress;
       if (cause != SelectionChangedCause.keyboard && (_value.text.isNotEmpty || longPress))
         _selectionOverlay.showHandles();
-      if (longPress)
+      if (longPress || cause == SelectionChangedCause.doubleTap)
         _selectionOverlay.showToolbar();
       if (widget.onSelectionChanged != null)
         widget.onSelectionChanged(selection, cause);