Adding horizontal and vertical scale parameter to ScaleUpdateDetails. (#27752)

packages/flutter/lib/src/gestures/scale.dart

@@ -49,30 +49,67 @@ class ScaleStartDetails {
 class ScaleUpdateDetails {
   /// Creates details for [GestureScaleUpdateCallback].
   ///
-  /// The [focalPoint], [scale], [rotation] arguments must not be null. The [scale]
+  /// The [focalPoint], [scale], [horizontalScale], [verticalScale], [rotation]
+  /// arguments must not be null. The [scale], [horizontalScale], and [verticalScale]
   /// argument must be greater than or equal to zero.
   ScaleUpdateDetails({
     this.focalPoint = Offset.zero,
     this.scale = 1.0,
+    this.horizontalScale = 1.0,
+    this.verticalScale = 1.0,
     this.rotation = 0.0,
   }) : assert(focalPoint != null),
        assert(scale != null && scale >= 0.0),
+       assert(horizontalScale != null && horizontalScale >= 0.0),
+       assert(verticalScale != null && verticalScale >= 0.0),
        assert(rotation != null);
 
-  /// The focal point of the pointers in contact with the screen. Reported in
-  /// global coordinates.
+  /// The focal point of the pointers in contact with the screen.
+  ///
+  /// Reported in global coordinates.
   final Offset focalPoint;
 
-  /// The scale implied by the pointers in contact with the screen. A value
-  /// greater than or equal to zero.
+  /// The scale implied by the average distance between the pointers in contact
+  /// with the screen.
+  ///
+  /// This value must be greater than or equal to zero.
+  ///
+  /// See also:
+  ///
+  ///  * [horizontalScale], which is the scale along the horizontal axis.
+  ///  * [verticalScale], which is the scale along the vertical axis.
   final double scale;
 
+  /// The scale implied by the average distance along the horizontal axis
+  /// between the pointers in contact with the screen.
+  ///
+  /// This value must be greater than or equal to zero.
+  ///
+  /// See also:
+  ///
+  ///  * [scale], which is the general scale implied by the pointers.
+  ///  * [verticalScale], which is the scale along the vertical axis.
+  final double horizontalScale;
+
+  /// The scale implied by the average distance along the vertical axis
+  /// between the pointers in contact with the screen.
+  ///
+  /// This value must be greater than or equal to zero.
+  ///
+  /// See also:
+  ///
+  ///  * [scale], which is the general scale implied by the pointers.
+  ///  * [horizontalScale], which is the scale along the horizontal axis.
+  final double verticalScale;
+
   /// The angle implied by the first two pointers to enter in contact with
-  /// the screen. Expressed in radians.
+  /// the screen.
+  ///
+  /// Expressed in radians.
   final double rotation;
 
   @override
-  String toString() => 'ScaleUpdateDetails(focalPoint: $focalPoint, scale: $scale, rotation: $rotation)';
+  String toString() => 'ScaleUpdateDetails(focalPoint: $focalPoint, scale: $scale, horizontalScale: $horizontalScale, verticalScale: $verticalScale, rotation: $rotation)';
 }
 
 /// Details for [GestureScaleEndCallback].
@@ -165,6 +202,10 @@ class ScaleGestureRecognizer extends OneSequenceGestureRecognizer {
   Offset _currentFocalPoint;
   double _initialSpan;
   double _currentSpan;
+  double _initialHorizontalSpan;
+  double _currentHorizontalSpan;
+  double _initialVerticalSpan;
+  double _currentVerticalSpan;
   _LineBetweenPointers _initialLine;
   _LineBetweenPointers _currentLine;
   Map<int, Offset> _pointerLocations;
@@ -173,6 +214,10 @@ class ScaleGestureRecognizer extends OneSequenceGestureRecognizer {
 
   double get _scaleFactor => _initialSpan > 0.0 ? _currentSpan / _initialSpan : 1.0;
 
+  double get _horizontalScaleFactor => _initialHorizontalSpan > 0.0 ? _currentHorizontalSpan / _initialHorizontalSpan : 1.0;
+
+  double get _verticalScaleFactor => _initialVerticalSpan > 0.0 ? _currentVerticalSpan / _initialVerticalSpan : 1.0;
+
   double _computeRotationFactor() {
     if (_initialLine == null || _currentLine == null) {
       return 0.0;
@@ -201,6 +246,10 @@ class ScaleGestureRecognizer extends OneSequenceGestureRecognizer {
       _state = _ScaleState.possible;
       _initialSpan = 0.0;
       _currentSpan = 0.0;
+      _initialHorizontalSpan = 0.0;
+      _currentHorizontalSpan = 0.0;
+      _initialVerticalSpan = 0.0;
+      _currentVerticalSpan = 0.0;
       _pointerLocations = <int, Offset>{};
       _pointerQueue = <int>[];
     }
@@ -246,11 +295,20 @@ class ScaleGestureRecognizer extends OneSequenceGestureRecognizer {
       focalPoint += _pointerLocations[pointer];
     _currentFocalPoint = count > 0 ? focalPoint / count.toDouble() : Offset.zero;
 
-    // Span is the average deviation from focal point
+    // Span is the average deviation from focal point. Horizontal and vertical
+    // spans are the average deviations from the focal point's horizontal and
+    // vertical coordinates, respectively.
     double totalDeviation = 0.0;
-    for (int pointer in _pointerLocations.keys)
+    double totalHorizontalDeviation = 0.0;
+    double totalVerticalDeviation = 0.0;
+    for (int pointer in _pointerLocations.keys) {
       totalDeviation += (_currentFocalPoint - _pointerLocations[pointer]).distance;
+      totalHorizontalDeviation += (_currentFocalPoint.dx - _pointerLocations[pointer].dx).abs();
+      totalVerticalDeviation += (_currentFocalPoint.dy - _pointerLocations[pointer].dy).abs();
+    }
     _currentSpan = count > 0 ? totalDeviation / count : 0.0;
+    _currentHorizontalSpan = count > 0 ? totalHorizontalDeviation / count : 0.0;
+    _currentVerticalSpan = count > 0 ? totalVerticalDeviation / count : 0.0;
   }
 
   /// Updates [_initialLine] and [_currentLine] accordingly to the situation of
@@ -269,7 +327,7 @@ class ScaleGestureRecognizer extends OneSequenceGestureRecognizer {
         pointerStartId: _pointerQueue[0],
         pointerStartLocation: _pointerLocations[_pointerQueue[0]],
         pointerEndId: _pointerQueue[1],
-        pointerEndLocation: _pointerLocations[ _pointerQueue[1]]
+        pointerEndLocation: _pointerLocations[_pointerQueue[1]]
       );
     } else {
       /// A new rotation process is on the way, set the [_initialLine]
@@ -277,7 +335,7 @@ class ScaleGestureRecognizer extends OneSequenceGestureRecognizer {
         pointerStartId: _pointerQueue[0],
         pointerStartLocation: _pointerLocations[_pointerQueue[0]],
         pointerEndId: _pointerQueue[1],
-        pointerEndLocation: _pointerLocations[ _pointerQueue[1]]
+        pointerEndLocation: _pointerLocations[_pointerQueue[1]]
       );
       _currentLine = null;
     }
@@ -287,6 +345,8 @@ class ScaleGestureRecognizer extends OneSequenceGestureRecognizer {
     _initialFocalPoint = _currentFocalPoint;
     _initialSpan = _currentSpan;
     _initialLine = _currentLine;
+    _initialHorizontalSpan = _currentHorizontalSpan;
+    _initialVerticalSpan = _currentVerticalSpan;
     if (_state == _ScaleState.started) {
       if (onEnd != null) {
         final VelocityTracker tracker = _velocityTrackers[pointer];
@@ -327,7 +387,15 @@ class ScaleGestureRecognizer extends OneSequenceGestureRecognizer {
     }
 
     if (_state == _ScaleState.started && onUpdate != null)
-      invokeCallback<void>('onUpdate', () => onUpdate(ScaleUpdateDetails(scale: _scaleFactor, focalPoint: _currentFocalPoint, rotation: _computeRotationFactor())));
+      invokeCallback<void>('onUpdate', () {
+        onUpdate(ScaleUpdateDetails(
+          scale: _scaleFactor,
+          horizontalScale: _horizontalScaleFactor,
+          verticalScale: _verticalScaleFactor,
+          focalPoint: _currentFocalPoint,
+          rotation: _computeRotationFactor(),
+        ));
+      });
   }
 
   void _dispatchOnStartCallbackIfNeeded() {

packages/flutter/test/gestures/scale_test.dart

@@ -24,8 +24,12 @@ void main() {
     };
 
     double updatedScale;
+    double updatedHorizontalScale;
+    double updatedVerticalScale;
     scale.onUpdate = (ScaleUpdateDetails details) {
       updatedScale = details.scale;
+      updatedHorizontalScale = details.horizontalScale;
+      updatedVerticalScale = details.verticalScale;
       updatedFocalPoint = details.focalPoint;
     };
 
@@ -91,18 +95,35 @@ void main() {
     expect(updatedFocalPoint, const Offset(10.0, 20.0));
     updatedFocalPoint = null;
     expect(updatedScale, 2.0);
+    expect(updatedHorizontalScale, 2.0);
+    expect(updatedVerticalScale, 2.0);
     updatedScale = null;
+    updatedHorizontalScale = null;
+    updatedVerticalScale = null;
     expect(didEndScale, isFalse);
     expect(didTap, isFalse);
 
     // Zoom out
     tester.route(pointer2.move(const Offset(15.0, 25.0)));
     expect(updatedFocalPoint, const Offset(17.5, 27.5));
-    updatedFocalPoint = null;
     expect(updatedScale, 0.5);
-    updatedScale = null;
+    expect(updatedHorizontalScale, 0.5);
+    expect(updatedVerticalScale, 0.5);
     expect(didTap, isFalse);
 
+    // Horizontal scaling
+    tester.route(pointer2.move(const Offset(0.0, 20.0)));
+    expect(updatedHorizontalScale, 2.0);
+    expect(updatedVerticalScale, 1.0);
+
+    // Vertical scaling
+    tester.route(pointer2.move(const Offset(10.0, 10.0)));
+    expect(updatedHorizontalScale, 1.0);
+    expect(updatedVerticalScale, 2.0);
+    tester.route(pointer2.move(const Offset(15.0, 25.0)));
+    updatedFocalPoint = null;
+    updatedScale = null;
+
     // Three-finger scaling
     final TestPointer pointer3 = TestPointer(3);
     final PointerDownEvent down3 = pointer3.down(const Offset(25.0, 35.0));