Give the CustomPaint and SizeObserver callbacks better names

The style we use for callbacks in widgets is "onFoo". These classes were using
an order naming convention and just called their callbacks "callback".

examples/game/lib/main.dart

@@ -159,7 +159,7 @@ class TextureButtonState extends State<TextureButton> {
         width: config.width,
         height: config.height,
         child: new CustomPaint(
-          callback: paintCallback,
+          onPaint: paintCallback,
           token: new _TextureButtonToken(
             _highlight,
             config.texture,

examples/rendering/baseline.dart

@@ -37,7 +37,7 @@ RenderBox getBox(double lh) {
           padding: new EdgeDims.all(10.0),
           child: new RenderCustomPaint(
             child: paragraph,
-            callback: (canvas, size) {
+            onPaint: (canvas, size) {
               double baseline = paragraph.getDistanceToBaseline(TextBaseline.alphabetic);
               double w = paragraph.getMaxIntrinsicWidth(new BoxConstraints.loose(size));
               double h = paragraph.getMaxIntrinsicHeight(new BoxConstraints.loose(size));

examples/stocks/lib/stock_arrow.dart

@@ -25,7 +25,7 @@ class StockArrow extends StatelessComponent {
     // TODO(jackson): This should change colors with the theme
     Color color = _colorForPercentChange(percentChange);
     const double kSize = 40.0;
-    var arrow = new CustomPaint(callback: (ui.Canvas canvas, Size size) {
+    var arrow = new CustomPaint(onPaint: (ui.Canvas canvas, Size size) {
       Paint paint = new Paint()..color = color;
       paint.strokeWidth = 1.0;
       const double padding = 2.0;

examples/widgets/card_collection.dart

@@ -337,7 +337,7 @@ class CardCollectionState extends State<CardCollection> {
       ]);
 
     Widget body = new SizeObserver(
-      callback: _updateCardCollectionSize,
+      onSizeChanged: _updateCardCollectionSize,
       child: new Container(
         padding: const EdgeDims.symmetric(vertical: 12.0, horizontal: 8.0),
         decoration: new BoxDecoration(backgroundColor: Theme.of(context).primarySwatch[50]),

examples/widgets/overlay_geometry.dart

@@ -58,7 +58,7 @@ class Marker extends StatelessComponent {
         child: new Container(
           width: size,
           height: size,
-          child: new CustomPaint(callback: paintMarker)
+          child: new CustomPaint(onPaint: paintMarker)
         )
       )
     );

examples/widgets/pageable_list.dart

@@ -136,7 +136,7 @@ class PageableListAppState extends State<PageableListApp> {
           : pageSize.width
     );
     return new SizeObserver(
-      callback: updatePageSize,
+      onSizeChanged: updatePageSize,
       child: list
     );
   }

examples/widgets/scale.dart

@@ -63,7 +63,7 @@ class ScaleAppState extends State<ScaleApp> {
         body: new GestureDetector(
           onScaleStart: _handleScaleStart,
           onScaleUpdate: _handleScaleUpdate,
-          child: new CustomPaint(callback: paint, token: "$_zoom $_offset")
+          child: new CustomPaint(onPaint: paint, token: "$_zoom $_offset")
         )
       )
     );

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

@@ -116,7 +116,7 @@ class _InputState extends ScrollableState<Input> {
 
     return new Listener(
       child: new SizeObserver(
-        callback: _handleContainerSizeChanged,
+        onSizeChanged: _handleContainerSizeChanged,
         child: new Container(
           child: new Stack(textChildren),
           padding: _kTextfieldPadding,

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

@@ -75,7 +75,7 @@ class PopupMenu extends StatelessComponent {
         variables: <AnimatedValue<double>>[width, height],
         builder: (BuildContext context) {
           return new CustomPaint(
-            callback: (ui.Canvas canvas, Size size) {
+            onPaint: (ui.Canvas canvas, Size size) {
               double widthValue = width.value * size.width;
               double heightValue = height.value * size.height;
               painter.paint(canvas, new Rect.fromLTWH(size.width - widthValue, 0.0, widthValue, heightValue));

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

@@ -107,7 +107,7 @@ class LinearProgressIndicator extends ProgressIndicator {
       ),
       child: new CustomPaint(
         token: _getCustomPaintToken(performanceValue),
-        callback: (Canvas canvas, Size size) {
+        onPaint: (Canvas canvas, Size size) {
           _paint(context, performanceValue, canvas, size);
         }
       )
@@ -157,7 +157,7 @@ class CircularProgressIndicator extends ProgressIndicator {
       ),
       child: new CustomPaint(
         token: _getCustomPaintToken(performanceValue),
-        callback: (Canvas canvas, Size size) {
+        onPaint: (Canvas canvas, Size size) {
           _paint(context, performanceValue, canvas, size);
         }
       )

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

@@ -45,7 +45,7 @@ class Radio extends StatelessComponent {
         width: kDiameter,
         height: kDiameter,
         child: new CustomPaint(
-          callback: (Canvas canvas, Size size) {
+          onPaint: (Canvas canvas, Size size) {
 
             // Draw the outer circle
             Paint paint = new Paint()

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

@@ -545,7 +545,7 @@ class _TabBarState extends ScrollableState<TabBar> {
 
     if (config.isScrollable) {
       content = new SizeObserver(
-        callback: _handleViewportSizeChanged,
+        onSizeChanged: _handleViewportSizeChanged,
         child: new Viewport(
           scrollDirection: ScrollDirection.horizontal,
           scrollOffset: new Offset(scrollOffset, 0.0),

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

@@ -962,33 +962,33 @@ class RenderTransform extends RenderProxyBox {
 /// Called when a size changes
 typedef void SizeChangedCallback(Size newSize);
 
-/// Calls [callback] whenever the child's layout size changes
+/// Calls [onSizeChanged] whenever the child's layout size changes
 ///
 /// Note: Size observer calls its callback during layout, which means you cannot
 /// dirty layout information during the callback.
 class RenderSizeObserver extends RenderProxyBox {
   RenderSizeObserver({
-    this.callback,
+    this.onSizeChanged,
     RenderBox child
   }) : super(child) {
-    assert(callback != null);
+    assert(onSizeChanged != null);
   }
 
   /// The callback to call whenever the child's layout size changes
-  SizeChangedCallback callback;
+  SizeChangedCallback onSizeChanged;
 
   void performLayout() {
     Size oldSize = hasSize ? size : null;
     super.performLayout();
     if (oldSize != size)
-      callback(size);
+      onSizeChanged(size);
   }
 }
 
 /// Called when its time to paint into the given canvas
 typedef void CustomPaintCallback(PaintingCanvas canvas, Size size);
 
-/// Delegates its painting to [callback]
+/// Delegates its painting to [onPaint]
 ///
 /// When asked to paint, custom paint first calls its callback with the current
 /// canvas and then paints its children. The coodinate system of the canvas
@@ -1003,36 +1003,36 @@ typedef void CustomPaintCallback(PaintingCanvas canvas, Size size);
 class RenderCustomPaint extends RenderProxyBox {
 
   RenderCustomPaint({
-    CustomPaintCallback callback,
+    CustomPaintCallback onPaint,
     RenderBox child
   }) : super(child) {
-    assert(callback != null);
-    _callback = callback;
+    assert(onPaint != null);
+    _onPaint = onPaint;
   }
 
   /// The callback to which this render object delegates its painting
   ///
   /// The callback must be non-null whenever the render object is attached to
   /// the render tree.
-  CustomPaintCallback get callback => _callback;
-  CustomPaintCallback _callback;
-  void set callback (CustomPaintCallback newCallback) {
+  CustomPaintCallback get onPaint => _onPaint;
+  CustomPaintCallback _onPaint;
+  void set onPaint (CustomPaintCallback newCallback) {
     assert(newCallback != null || !attached);
-    if (_callback == newCallback)
+    if (_onPaint == newCallback)
       return;
-    _callback = newCallback;
+    _onPaint = newCallback;
     markNeedsPaint();
   }
 
   void attach() {
-    assert(_callback != null);
+    assert(_onPaint != null);
     super.attach();
   }
 
   void paint(PaintingContext context, Offset offset) {
-    assert(_callback != null);
+    assert(_onPaint != null);
     context.canvas.translate(offset.dx, offset.dy);
-    _callback(context.canvas, size);
+    _onPaint(context.canvas, size);
     // TODO(abarth): We should translate back before calling super because in
     // the future, super.paint might switch our compositing layer.
     super.paint(context, Offset.zero);

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

@@ -134,24 +134,24 @@ class DecoratedBox extends OneChildRenderObjectWidget {
 }
 
 class CustomPaint extends OneChildRenderObjectWidget {
-  CustomPaint({ Key key, this.callback, this.token, Widget child })
+  CustomPaint({ Key key, this.onPaint, this.token, Widget child })
     : super(key: key, child: child) {
-    assert(callback != null);
+    assert(onPaint != null);
   }
 
-  final CustomPaintCallback callback;
+  final CustomPaintCallback onPaint;
   final Object token; // set this to be repainted automatically when the token changes
 
-  RenderCustomPaint createRenderObject() => new RenderCustomPaint(callback: callback);
+  RenderCustomPaint createRenderObject() => new RenderCustomPaint(onPaint: onPaint);
 
   void updateRenderObject(RenderCustomPaint renderObject, CustomPaint oldWidget) {
     if (oldWidget != null && oldWidget.token != token)
       renderObject.markNeedsPaint();
-    renderObject.callback = callback;
+    renderObject.onPaint = onPaint;
   }
 
   void didUnmountRenderObject(RenderCustomPaint renderObject) {
-    renderObject.callback = null;
+    renderObject.onPaint = null;
   }
 }
 
@@ -428,21 +428,21 @@ class Viewport extends OneChildRenderObjectWidget {
 }
 
 class SizeObserver extends OneChildRenderObjectWidget {
-  SizeObserver({ Key key, this.callback, Widget child })
+  SizeObserver({ Key key, this.onSizeChanged, Widget child })
     : super(key: key, child: child) {
-    assert(callback != null);
+    assert(onSizeChanged != null);
   }
 
-  final SizeChangedCallback callback;
+  final SizeChangedCallback onSizeChanged;
 
-  RenderSizeObserver createRenderObject() => new RenderSizeObserver(callback: callback);
+  RenderSizeObserver createRenderObject() => new RenderSizeObserver(onSizeChanged: onSizeChanged);
 
   void updateRenderObject(RenderSizeObserver renderObject, SizeObserver oldWidget) {
-    renderObject.callback = callback;
+    renderObject.onSizeChanged = onSizeChanged;
   }
 
   void didUnmountRenderObject(RenderSizeObserver renderObject) {
-    renderObject.callback = null;
+    renderObject.onSizeChanged = null;
   }
 }
 

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

@@ -251,7 +251,7 @@ class _DismissableState extends State<Dismissable> {
       onVerticalDragUpdate: _directionIsYAxis ? _handleDragUpdate : null,
       onVerticalDragEnd: _directionIsYAxis ? _handleDragEnd : null,
       child: new SizeObserver(
-        callback: _handleSizeChanged,
+        onSizeChanged: _handleSizeChanged,
         child: new FadeTransition(
           performance: _fadePerformance.view,
           opacity: new AnimatedValue<double>(1.0, end: 0.0),

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

@@ -81,7 +81,7 @@ class MimicableState extends State<Mimicable> {
       );
     }
     return new SizeObserver(
-      callback: _handleSizeChanged,
+      onSizeChanged: _handleSizeChanged,
       child: config.child
     );
   }

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

@@ -54,11 +54,11 @@ class NavigatorState extends State<Navigator> {
     _insertRoute(route);
   }
 
-  void pushState(State owner, Function callback) {
+  void pushState(State owner, StateRouteCallback onPop) {
     push(new StateRoute(
       route: currentRoute,
       owner: owner,
-      callback: callback
+      onPop: onPop
     ));
   }
 
@@ -318,11 +318,11 @@ class PageRoute extends PerformanceRoute {
 }
 
 class StateRoute extends Route {
-  StateRoute({ this.route, this.owner, this.callback });
+  StateRoute({ this.route, this.owner, this.onPop });
 
   Route route;
   State owner;
-  StateRouteCallback callback;
+  StateRouteCallback onPop;
 
   bool get hasContent => false;
   bool get modal => false;
@@ -330,8 +330,8 @@ class StateRoute extends Route {
 
   void didPop([dynamic result]) {
     assert(result == null);
-    if (callback != null)
-      callback(this);
+    if (onPop != null)
+      onPop(this);
     super.didPop(result);
   }
 

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

@@ -362,12 +362,12 @@ class ScrollableViewportState extends ScrollableState<ScrollableViewport> {
 
   Widget buildContent(BuildContext context) {
     return new SizeObserver(
-      callback: _handleViewportSizeChanged,
+      onSizeChanged: _handleViewportSizeChanged,
       child: new Viewport(
         scrollOffset: scrollOffsetVector,
         scrollDirection: config.scrollDirection,
         child: new SizeObserver(
-          callback: _handleChildSizeChanged,
+          onSizeChanged: _handleChildSizeChanged,
           child: config.child
         )
       )
@@ -596,7 +596,7 @@ abstract class ScrollableWidgetListState<T extends ScrollableWidgetList> extends
     }
 
     return new SizeObserver(
-      callback: _handleSizeChanged,
+      onSizeChanged: _handleSizeChanged,
       child: new Container(
         padding: _crossAxisPadding,
         child: new HomogeneousViewport(
@@ -820,7 +820,7 @@ class ScrollableMixedWidgetListState extends ScrollableState<ScrollableMixedWidg
 
   Widget buildContent(BuildContext context) {
     return new SizeObserver(
-      callback: _handleSizeChanged,
+      onSizeChanged: _handleSizeChanged,
       child: new MixedViewport(
         startOffset: scrollOffset,
         builder: config.builder,

packages/unit/test/widget/fractionally_sized_box_test.dart

@@ -19,7 +19,7 @@ void main() {
             width: 0.5,
             height: 0.25,
             child: new SizeObserver(
-              callback: (Size size) {
+              onSizeChanged: (Size size) {
                 detectedSize = size;
               },
               child: new Container(

packages/unit/test/widget/size_observer_test.dart

@@ -11,7 +11,7 @@ void main() {
       List<Size> results = <Size>[];
       tester.pumpWidget(new Center(
         child: new SizeObserver(
-          callback: (Size size) { results.add(size); },
+          onSizeChanged: (Size size) { results.add(size); },
           child: new Container(width:0.0, height:0.0)
         )
       ));
@@ -20,7 +20,7 @@ void main() {
       expect(results, equals([Size.zero]));
       tester.pumpWidget(new Center(
         child: new SizeObserver(
-          callback: (Size size) { results.add(size); },
+          onSizeChanged: (Size size) { results.add(size); },
           child: new Container(width:100.0, height:0.0)
         )
       ));
@@ -29,7 +29,7 @@ void main() {
       expect(results, equals([Size.zero, const Size(100.0, 0.0)]));
       tester.pumpWidget(new Center(
         child: new SizeObserver(
-          callback: (Size size) { results.add(size); },
+          onSizeChanged: (Size size) { results.add(size); },
           child: new Container(width:0.0, height:0.0)
         )
       ));
@@ -38,7 +38,7 @@ void main() {
       expect(results, equals([Size.zero, const Size(100.0, 0.0), Size.zero]));
       tester.pumpWidget(new Center(
         child: new SizeObserver(
-          callback: (Size size) { results.add(size); },
+          onSizeChanged: (Size size) { results.add(size); },
           child: new Container(width:0.0, height:0.0)
         )
       ));

packages/unit/test/widget/stack_test.dart

@@ -139,7 +139,7 @@ void main() {
       Widget buildFrame(int index) {
         itemsPainted = <int>[];
         List<Widget> items = new List<Widget>.generate(itemCount, (i) {
-          return new CustomPaint(child: new Text('$i'), callback: (_, __) { itemsPainted.add(i); });
+          return new CustomPaint(child: new Text('$i'), onPaint: (_, __) { itemsPainted.add(i); });
         });
         return new Center(child: new IndexedStack(items, index: index));
       }