Update scale API and add example

examples/widgets/scale.dart

+// Copyright 2015 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:math' as math;
+
+import 'package:sky/rendering.dart';
+import 'package:sky/theme/colors.dart' as colors;
+import 'package:sky/widgets.dart';
+
+class ScaleApp extends App {
+
+  Point _startingFocalPoint;
+
+  Offset _previousOffset;
+  Offset _offset;
+
+  double _previousZoom;
+  double _zoom;
+
+  void initState() {
+    _offset = Offset.zero;
+    _zoom = 1.0;
+  }
+
+  void _handleScaleStart(Point focalPoint) {
+    setState(() {
+      _startingFocalPoint = focalPoint;
+      _previousOffset = _offset;
+      _previousZoom = _zoom;
+    });
+  }
+
+  void _handleScaleUpdate(double scale, Point focalPoint) {
+    setState(() {
+      _zoom = _previousZoom * scale;
+      _offset = _previousOffset + (focalPoint - _startingFocalPoint) / _zoom;
+    });
+  }
+
+  void callback(PaintingCanvas canvas, Size size) {
+    Point center = size.center(Point.origin) + _offset * _zoom;
+    double radius = size.width / 2.0 * _zoom;
+    Gradient gradient = new RadialGradient(
+      center: center, radius: radius,
+      colors: [colors.Blue[200], colors.Blue[800]]
+    );
+    Paint paint = new Paint()
+      ..shader = gradient.createShader();
+    canvas.drawCircle(center, radius, paint);
+  }
+
+  Widget build() {
+    return new Theme(
+      data: new ThemeData.dark(),
+      child: new Scaffold(
+        toolbar: new ToolBar(
+            center: new Text('Scale Demo')),
+        body: new Material(
+          type: MaterialType.canvas,
+          child: new GestureDetector(
+            onScaleStart: _handleScaleStart,
+            onScaleUpdate: _handleScaleUpdate,
+            child: new CustomPaint(callback: callback)
+          )
+        )
+      )
+    );
+  }
+}
+
+void main() => runApp(new ScaleApp());

packages/flutter/lib/gestures/constants.dart

@@ -18,7 +18,7 @@ const double kTouchSlop = 8.0;  // Logical pixels
 const double kDoubleTapTouchSlop = kTouchSlop;  // Logical pixels
 const double kPagingTouchSlop = kTouchSlop * 2.0;  // Logical pixels
 const double kPanSlop = kTouchSlop * 2.0;  // Logical pixels
-const double kPinchSlop = kTouchSlop;  // Logical pixels
+const double kScaleSlop = kTouchSlop;  // Logical pixels
 const double kDoubleTapSlop = 100.0;  // Logical pixels
 const double kWindowTouchSlop = 16.0;  // Logical pixels
 const double kMinFlingVelocity = 50.0;  // Logical pixels / second

packages/flutter/lib/gestures/drag.dart

@@ -100,7 +100,6 @@ abstract class _DragGestureRecognizer<T extends dynamic> extends GestureRecogniz
       sky.Offset velocity = sky.Offset.zero;
       if (_isFlingGesture(gestureVelocity))
         velocity = new sky.Offset(gestureVelocity.x, gestureVelocity.y);
-      resolve(GestureDisposition.accepted);
       onEnd(velocity);
     }
     _velocityTracker.reset();

packages/flutter/lib/gestures/pinch.dart → packages/flutter/lib/gestures/scale.dart

@@ -9,37 +9,37 @@ import 'package:sky/gestures/arena.dart';
 import 'package:sky/gestures/recognizer.dart';
 import 'package:sky/gestures/constants.dart';
 
-enum PinchState {
+enum ScaleState {
   ready,
   possible,
-  started,
-  ended
+  accepted,
+  started
 }
 
-typedef void GesturePinchStartCallback();
-typedef void GesturePinchUpdateCallback(double scale);
-typedef void GesturePinchEndCallback();
+typedef void GestureScaleStartCallback(sky.Point focalPoint);
+typedef void GestureScaleUpdateCallback(double scale, sky.Point focalPoint);
+typedef void GestureScaleEndCallback();
 
-class PinchGestureRecognizer extends GestureRecognizer {
-  PinchGestureRecognizer({ PointerRouter router, this.onStart, this.onUpdate, this.onEnd })
+class ScaleGestureRecognizer extends GestureRecognizer {
+  ScaleGestureRecognizer({ PointerRouter router, this.onStart, this.onUpdate, this.onEnd })
     : super(router: router);
 
-  GesturePinchStartCallback onStart;
-  GesturePinchUpdateCallback onUpdate;
-  GesturePinchEndCallback onEnd;
+  GestureScaleStartCallback onStart;
+  GestureScaleUpdateCallback onUpdate;
+  GestureScaleEndCallback onEnd;
 
-  PinchState _state = PinchState.ready;
+  ScaleState _state = ScaleState.ready;
 
   double _initialSpan;
   double _currentSpan;
   Map<int, sky.Point> _pointerLocations;
 
-  double get _scaleFactor => _initialSpan > 0 ? _currentSpan / _initialSpan : 1.0;
+  double get _scaleFactor => _initialSpan > 0.0 ? _currentSpan / _initialSpan : 1.0;
 
   void addPointer(sky.PointerEvent event) {
     startTrackingPointer(event.pointer);
-    if (_state == PinchState.ready) {
-      _state = PinchState.possible;
+    if (_state == ScaleState.ready) {
+      _state = ScaleState.possible;
       _initialSpan = 0.0;
       _currentSpan = 0.0;
       _pointerLocations = new Map<int, sky.Point>();
@@ -47,7 +47,7 @@ class PinchGestureRecognizer extends GestureRecognizer {
   }
 
   void handleEvent(sky.PointerEvent event) {
-    assert(_state != PinchState.ready);
+    assert(_state != ScaleState.ready);
     bool configChanged = false;
     switch(event.type) {
       case 'pointerup':
@@ -63,6 +63,12 @@ class PinchGestureRecognizer extends GestureRecognizer {
         break;
     }
 
+    _update(configChanged);
+
+    stopTrackingIfPointerNoLongerDown(event);
+  }
+
+  void _update(bool configChanged) {
     int count = _pointerLocations.keys.length;
 
     // Compute the focal point
@@ -79,58 +85,53 @@ class PinchGestureRecognizer extends GestureRecognizer {
 
     if (configChanged) {
       _initialSpan = _currentSpan;
-      if (_state == PinchState.started) {
-        _state = PinchState.ended;
+      if (_state == ScaleState.started) {
         if (onEnd != null)
           onEnd();
+        _state = ScaleState.accepted;
       }
     }
 
-    if (_state == PinchState.ready)
-      _state = PinchState.possible;
+    if (_state == ScaleState.ready)
+      _state = ScaleState.possible;
 
-    if (_state == PinchState.possible &&
-        (_currentSpan - _initialSpan).abs() > kPinchSlop) {
+    if (_state == ScaleState.possible &&
+        (_currentSpan - _initialSpan).abs() > kScaleSlop) {
       resolve(GestureDisposition.accepted);
     }
 
-    if (_state == PinchState.ended && _currentSpan != _initialSpan) {
-      _state = PinchState.started;
+    if (_state == ScaleState.accepted && !configChanged) {
+      _state = ScaleState.started;
       if (onStart != null)
-        onStart();
+        onStart(focalPoint);
     }
 
-    if (_state == PinchState.started && onUpdate != null)
-      onUpdate(_scaleFactor);
-
-    stopTrackingIfPointerNoLongerDown(event);
+    if (_state == ScaleState.started && onUpdate != null)
+      onUpdate(_scaleFactor, focalPoint);
   }
 
   void acceptGesture(int pointer) {
-    if (_state != PinchState.started) {
-      _state = PinchState.started;
-      if (onStart != null)
-        onStart();
-      if (onUpdate != null)
-        onUpdate(_scaleFactor);
+    if (_state != ScaleState.accepted) {
+      _state = ScaleState.accepted;
+      _update(false);
     }
   }
 
   void didStopTrackingLastPointer(int pointer) {
     switch(_state) {
-      case PinchState.possible:
+      case ScaleState.possible:
         resolve(GestureDisposition.rejected);
         break;
-      case PinchState.ready:
-        assert(false);
+      case ScaleState.ready:
+        assert(false);  // We should have not seen a pointer yet
         break;
-      case PinchState.started:
-        assert(false);
+      case ScaleState.accepted:
         break;
-      case PinchState.ended:
+      case ScaleState.started:
+        assert(false);  // We should be in the accepted state when user is done
         break;
     }
-    _state = PinchState.ready;
+    _state = ScaleState.ready;
   }
 
   void dispose() {

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

@@ -6,7 +6,7 @@ import 'dart:sky' as sky;
 
 import 'package:sky/gestures/drag.dart';
 import 'package:sky/gestures/long_press.dart';
-import 'package:sky/gestures/pinch.dart';
+import 'package:sky/gestures/scale.dart';
 import 'package:sky/gestures/recognizer.dart';
 import 'package:sky/gestures/show_press.dart';
 import 'package:sky/gestures/tap.dart';
@@ -29,9 +29,9 @@ class GestureDetector extends StatefulComponent {
     this.onPanStart,
     this.onPanUpdate,
     this.onPanEnd,
-    this.onPinchStart,
-    this.onPinchUpdate,
-    this.onPinchEnd
+    this.onScaleStart,
+    this.onScaleUpdate,
+    this.onScaleEnd
   }) : super(key: key);
 
   Widget child;
@@ -51,9 +51,9 @@ class GestureDetector extends StatefulComponent {
   GesturePanUpdateCallback onPanUpdate;
   GesturePanEndCallback onPanEnd;
 
-  GesturePinchStartCallback onPinchStart;
-  GesturePinchUpdateCallback onPinchUpdate;
-  GesturePinchEndCallback onPinchEnd;
+  GestureScaleStartCallback onScaleStart;
+  GestureScaleUpdateCallback onScaleUpdate;
+  GestureScaleEndCallback onScaleEnd;
 
   void syncConstructorArguments(GestureDetector source) {
     child = source.child;
@@ -69,9 +69,9 @@ class GestureDetector extends StatefulComponent {
     onPanStart = source.onPanStart;
     onPanUpdate = source.onPanUpdate;
     onPanEnd = source.onPanEnd;
-    onPinchStart = source.onPinchStart;
-    onPinchUpdate = source.onPinchUpdate;
-    onPinchEnd = source.onPinchEnd;
+    onScaleStart = source.onScaleStart;
+    onScaleUpdate = source.onScaleUpdate;
+    onScaleEnd = source.onScaleEnd;
     _syncGestureListeners();
   }
 
@@ -114,16 +114,18 @@ class GestureDetector extends StatefulComponent {
 
   PanGestureRecognizer _pan;
   PanGestureRecognizer _ensurePan() {
+    assert(_scale == null);  // Scale is a superset of pan; just use scale
     if (_pan == null)
       _pan = new PanGestureRecognizer(router: _router);
     return _pan;
   }
 
-  PinchGestureRecognizer _pinch;
-  PinchGestureRecognizer _ensurePinch() {
-    if (_pinch == null)
-      _pinch = new PinchGestureRecognizer(router: _router);
-    return _pinch;
+  ScaleGestureRecognizer _scale;
+  ScaleGestureRecognizer _ensureScale() {
+    assert(_pan == null);  // Scale is a superset of pan; just use scale
+    if (_scale == null)
+      _scale = new ScaleGestureRecognizer(router: _router);
+    return _scale;
   }
 
   void didMount() {
@@ -139,7 +141,7 @@ class GestureDetector extends StatefulComponent {
     _verticalDrag = _ensureDisposed(_verticalDrag);
     _horizontalDrag = _ensureDisposed(_horizontalDrag);
     _pan = _ensureDisposed(_pan);
-    _pinch = _ensureDisposed(_pinch);
+    _scale = _ensureDisposed(_scale);
   }
 
   void _syncGestureListeners() {
@@ -149,7 +151,7 @@ class GestureDetector extends StatefulComponent {
     _syncVerticalDrag();
     _syncHorizontalDrag();
     _syncPan();
-    _syncPinch();
+    _syncScale();
   }
 
   void _syncTap() {
@@ -206,14 +208,14 @@ class GestureDetector extends StatefulComponent {
     }
   }
 
-  void _syncPinch() {
-    if (onPinchStart == null && onPinchUpdate == null && onPinchEnd == null) {
-      _pinch = _ensureDisposed(_pan);
+  void _syncScale() {
+    if (onScaleStart == null && onScaleUpdate == null && onScaleEnd == null) {
+      _scale = _ensureDisposed(_pan);
     } else {
-      _ensurePinch()
-        ..onStart = onPinchStart
-        ..onUpdate = onPinchUpdate
-        ..onEnd = onPinchEnd;
+      _ensureScale()
+        ..onStart = onScaleStart
+        ..onUpdate = onScaleUpdate
+        ..onEnd = onScaleEnd;
     }
   }
 
@@ -235,8 +237,8 @@ class GestureDetector extends StatefulComponent {
       _horizontalDrag.addPointer(event);
     if (_pan != null)
       _pan.addPointer(event);
-    if (_pinch != null)
-      _pinch.addPointer(event);
+    if (_scale != null)
+      _scale.addPointer(event);
     return EventDisposition.processed;
   }