Add some more dartdoc to widgets

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

@@ -1101,9 +1101,18 @@ typedef void PointerMoveEventListener(PointerMoveEvent event);
 typedef void PointerUpEventListener(PointerUpEvent event);
 typedef void PointerCancelEventListener(PointerCancelEvent event);
 
+/// How to behave during hit tests.
 enum HitTestBehavior {
+  /// Consider this target hit if, and only if, its child was hit.
   deferToChild,
+
+  /// Consider this target hit whenever the position being hit tested is within its bounds.
   opaque,
+
+  /// Never consider this target hit but always add the target to the event path anyway.
+  ///
+  /// Translucent targets both receive events at a given location and permit
+  /// targets visually behind them to also receive events.
   translucent,
 }
 

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

@@ -9,6 +9,7 @@ import 'framework.dart';
 
 import 'package:vector_math/vector_math_64.dart';
 
+/// An animated value that interpolates [BoxConstraint]s.
 class AnimatedBoxConstraintsValue extends AnimatedValue<BoxConstraints> {
   AnimatedBoxConstraintsValue(BoxConstraints begin, { BoxConstraints end, Curve curve, Curve reverseCurve })
     : super(begin, end: end, curve: curve, reverseCurve: reverseCurve);
@@ -16,6 +17,7 @@ class AnimatedBoxConstraintsValue extends AnimatedValue<BoxConstraints> {
   BoxConstraints lerp(double t) => BoxConstraints.lerp(begin, end, t);
 }
 
+/// An animated value that interpolates [Decoration]s.
 class AnimatedDecorationValue extends AnimatedValue<Decoration> {
   AnimatedDecorationValue(Decoration begin, { Decoration end, Curve curve, Curve reverseCurve })
     : super(begin, end: end, curve: curve, reverseCurve: reverseCurve);
@@ -29,6 +31,7 @@ class AnimatedDecorationValue extends AnimatedValue<Decoration> {
   }
 }
 
+/// An animated value that interpolates [EdgeDims].
 class AnimatedEdgeDimsValue extends AnimatedValue<EdgeDims> {
   AnimatedEdgeDimsValue(EdgeDims begin, { EdgeDims end, Curve curve, Curve reverseCurve })
     : super(begin, end: end, curve: curve, reverseCurve: reverseCurve);
@@ -36,6 +39,9 @@ class AnimatedEdgeDimsValue extends AnimatedValue<EdgeDims> {
   EdgeDims lerp(double t) => EdgeDims.lerp(begin, end, t);
 }
 
+/// An animated value that interpolates [Matrix4]s.
+///
+/// Currently this class works only for translations.
 class AnimatedMatrix4Value extends AnimatedValue<Matrix4> {
   AnimatedMatrix4Value(Matrix4 begin, { Matrix4 end, Curve curve, Curve reverseCurve })
     : super(begin, end: end, curve: curve, reverseCurve: reverseCurve);
@@ -50,6 +56,12 @@ class AnimatedMatrix4Value extends AnimatedValue<Matrix4> {
   }
 }
 
+/// A container that gradually changes its values over a period of time.
+///
+/// This class is useful for generating simple implicit transitions between
+/// different parameters to [Container]. For more complex animations, you'll
+/// likely want to use a subclass of [Transition] or control a [Performance]
+/// yourself.
 class AnimatedContainer extends StatefulComponent {
   AnimatedContainer({
     Key key,
@@ -73,16 +85,34 @@ class AnimatedContainer extends StatefulComponent {
 
   final Widget child;
 
+  /// Additional constraints to apply to the child.
   final BoxConstraints constraints;
+
+  /// The decoration to paint behind the child.
   final Decoration decoration;
+
+  /// The decoration to paint in front of the child.
   final Decoration foregroundDecoration;
+
+  /// Empty space to surround the decoration.
   final EdgeDims margin;
+
+  /// Empty space to inscribe inside the decoration.
   final EdgeDims padding;
+
+  /// The tranformation matrix to apply before painting the container.
   final Matrix4 transform;
+
+  /// If non-null, requires the decoration to have this width.
   final double width;
+
+  /// If non-null, requires the decoration to have this height.
   final double height;
 
+  /// The curve to apply when animating the parameters of this container.
   final Curve curve;
+
+  /// The duration over which to animate the parameters of this container.
   final Duration duration;
 
   _AnimatedContainerState createState() => new _AnimatedContainerState();

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

@@ -786,14 +786,33 @@ class Container extends StatelessComponent {
     assert(decoration == null || decoration.debugAssertValid());
   }
 
+  /// The child to contain in the container.
+  ///
+  /// If null, the container will expand to fill all available space in its parent.
   final Widget child;
+
+  /// Additional constraints to apply to the child.
   final BoxConstraints constraints;
+
+  /// The decoration to paint behind the child.
   final Decoration decoration;
+
+  /// The decoration to paint in front of the child.
   final Decoration foregroundDecoration;
+
+  /// Empty space to surround the decoration.
   final EdgeDims margin;
+
+  /// Empty space to inscribe inside the decoration.
   final EdgeDims padding;
+
+  /// The tranformation matrix to apply before painting the container.
   final Matrix4 transform;
+
+  /// If non-null, requires the decoration to have this width.
   final double width;
+
+  /// If non-null, requires the decoration to have this height.
   final double height;
 
   EdgeDims get _paddingIncludingDecoration {

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

@@ -9,6 +9,7 @@ import 'package:flutter/scheduler.dart';
 
 import 'framework.dart';
 
+/// The glue that binds the widget framework to the Flutter engine.
 class WidgetFlutterBinding extends FlutterBinding {
 
   WidgetFlutterBinding() {
@@ -22,6 +23,7 @@ class WidgetFlutterBinding extends FlutterBinding {
     assert(FlutterBinding.instance is WidgetFlutterBinding);
   }
 
+  /// The one static instance of this class.
   static WidgetFlutterBinding get instance => FlutterBinding.instance;
 
   void beginFrame() {
@@ -83,11 +85,13 @@ class WidgetFlutterBinding extends FlutterBinding {
   }
 }
 
+/// Inflate the given widget and attach it to the screen.
 void runApp(Widget app) {
   WidgetFlutterBinding.ensureInitialized();
   WidgetFlutterBinding.instance._runApp(app);
 }
 
+/// Print a string representation of the currently running app.
 void debugDumpApp() {
   assert(WidgetFlutterBinding.instance != null);
   assert(WidgetFlutterBinding.instance.renderViewElement != null);

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

@@ -12,8 +12,9 @@ import 'package:flutter/rendering.dart';
 import 'basic.dart';
 import 'framework.dart';
 
-const _kCursorBlinkHalfPeriod = 500; // milliseconds
+const Duration _kCursorBlinkHalfPeriod = const Duration(milliseconds: 500);
 
+/// A range of characters in a string of tet.
 class TextRange {
   const TextRange({ this.start, this.end });
   const TextRange.collapsed(int position)
@@ -173,7 +174,7 @@ class EditableTextState extends State<EditableText> {
   /// The cursor blink interval (the amount of time the cursor is in the "on"
   /// state or the "off" state). A complete cursor blink period is twice this
   /// value (half on, half off).
-  Duration get cursorBlinkInterval => new Duration(milliseconds: _kCursorBlinkHalfPeriod);
+  Duration get cursorBlinkInterval => _kCursorBlinkHalfPeriod;
 
   void _cursorTick(Timer timer) {
     setState(() {
@@ -183,10 +184,7 @@ class EditableTextState extends State<EditableText> {
 
   void _startCursorTimer() {
     _showCursor = true;
-    _cursorTimer = new Timer.periodic(
-      new Duration(milliseconds: _kCursorBlinkHalfPeriod),
-      _cursorTick
-    );
+    _cursorTimer = new Timer.periodic(_kCursorBlinkHalfPeriod, _cursorTick);
   }
 
   void dispose() {

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

@@ -27,6 +27,11 @@ export 'package:flutter/gestures.dart' show
   GestureScaleUpdateCallback,
   GestureScaleEndCallback;
 
+/// A widget that detects gestures.
+///
+/// Attempts to recognize gestures that coorespond to its non-null callbacks.
+///
+/// See http://flutter.io/gestures/ for additional information.
 class GestureDetector extends StatefulComponent {
   const GestureDetector({
     Key key,
@@ -109,6 +114,7 @@ class GestureDetector extends StatefulComponent {
   final GestureScaleUpdateCallback onScaleUpdate;
   final GestureScaleEndCallback onScaleEnd;
 
+  /// How this gesture detector should behave during hit testing.
   final HitTestBehavior behavior;
 
   _GestureDetectorState createState() => new _GestureDetectorState();

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

@@ -4,7 +4,7 @@
 
 import 'framework.dart';
 
-// Superclass for locale-specific data provided by the application.
+/// Superclass for locale-specific data provided by the application.
 class LocaleQueryData { }
 
 class LocaleQuery<T extends LocaleQueryData> extends InheritedWidget {

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

@@ -5,14 +5,23 @@
 import 'basic.dart';
 import 'framework.dart';
 
-enum Orientation { portrait, landscape }
+/// Whether in portrait or landscape.
+enum Orientation {
+  /// Taller than wide.
+  portrait,
 
-class MediaQueryData {
+  /// Wider than tall.
+  landscape
+}
 
+/// The result of a media query.
+class MediaQueryData {
   const MediaQueryData({ this.size });
 
+  /// The size of the media (e.g, the size of the screen).
   final Size size;
 
+  /// The orientation of the media (e.g., whether the device is in landscape or portrait mode).
   Orientation get orientation {
     return size.width > size.height ? Orientation.landscape : Orientation.portrait;
   }
@@ -29,6 +38,7 @@ class MediaQueryData {
   String toString() => '$runtimeType($size, $orientation)';
 }
 
+/// Establishes a subtree in which media queries resolve to the given data.
 class MediaQuery extends InheritedWidget {
   MediaQuery({
     Key key,
@@ -39,8 +49,10 @@ class MediaQuery extends InheritedWidget {
     assert(data != null);
   }
 
+  /// The result of media queries in this subtree.
   final MediaQueryData data;
 
+  /// Queries the current media for the given context.
   static MediaQueryData of(BuildContext context) {
     MediaQuery query = context.inheritFromWidgetOfType(MediaQuery);
     return query == null ? null : query.data;

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

@@ -12,18 +12,22 @@ import 'basic.dart';
 import 'framework.dart';
 import 'overlay.dart';
 
-class MimicableKey {
-  MimicableKey._(this._state);
+/// An opaque reference to a widget that can be mimicked.
+class MimicableHandle {
+  MimicableHandle._(this._state);
 
   final MimicableState _state;
 
+  /// The size and position of the original widget in global coordinates.
   Rect get globalBounds => _state._globalBounds;
 
+  /// Stop the mimicking process, restoring the widget to its original location in the tree.
   void stopMimic() {
     _state._stopMimic();
   }
 }
 
+/// An overlay entry that is mimicking another widget.
 class MimicOverlayEntry {
   MimicOverlayEntry._(this._key) {
     _overlayEntry = new OverlayEntry(builder: _build);
@@ -32,7 +36,7 @@ class MimicOverlayEntry {
 
   Rect _initialGlobalBounds;
 
-  MimicableKey _key;
+  MimicableHandle _key;
   OverlayEntry _overlayEntry;
 
   // Animation state
@@ -40,6 +44,12 @@ class MimicOverlayEntry {
   Curve _curve;
   Performance _performance;
 
+  /// Animate the entry to the location of the widget that has the given target key.
+  ///
+  /// The animation will take place over the given duration and will apply the
+  /// given curve.
+  ///
+  /// Currently we don't support calling this function more than once per overlay entry.
   Future animateTo({
     GlobalKey targetKey,
     Duration duration,
@@ -59,10 +69,18 @@ class MimicOverlayEntry {
     return _performance.play();
   }
 
+  /// Cause the overlay entry to rebuild during the next pipeline flush.
+  ///
+  /// You need to call this function if you rebuild the widget that this entry
+  /// is mimicking in order for the overlay entry to pick up the changes that
+  /// you've made to the [Mimicable].
   void markNeedsBuild() {
    _overlayEntry?.markNeedsBuild();
  }
 
+  /// Remove this entry from the overlay and restore the widget to its original place in the tree.
+  ///
+  /// Once removed, the overlay entry cannot be used further.
   void dispose() {
     _targetKey = null;
     _curve = null;
@@ -106,10 +124,12 @@ class MimicOverlayEntry {
   }
 }
 
+/// A widget that copies the appearance of another widget.
 class Mimic extends StatelessComponent {
   Mimic({ Key key, this.original }) : super(key: key);
 
-  final MimicableKey original;
+  /// A handle to the widget that this widget should copy.
+  final MimicableHandle original;
 
   Widget build(BuildContext context) {
     if (original != null && original._state._beingMimicked)
@@ -118,6 +138,7 @@ class Mimic extends StatelessComponent {
   }
 }
 
+/// A widget that can be copied by a [Mimic].
 class Mimicable extends StatefulComponent {
   Mimicable({ Key key, this.child }) : super(key: key);
 
@@ -130,15 +151,26 @@ class MimicableState extends State<Mimicable> {
   Size _size;
   bool _beingMimicked = false;
 
-  MimicableKey startMimic() {
+  /// Start the mimicking process.
+  ///
+  /// The child of this object will no longer be built at this location in the
+  /// tree.  Instead, this widget will build a transparent placeholder with the
+  /// same dimensions as the widget had when the mimicking process started.
+  MimicableHandle startMimic() {
     assert(!_beingMimicked);
     assert(_size != null);
     setState(() {
       _beingMimicked = true;
     });
-    return new MimicableKey._(this);
+    return new MimicableHandle._(this);
   }
 
+  /// Mimic this object in the enclosing overlay.
+  ///
+  /// The child of this object will no longer be built at this location in the
+  /// tree.  Instead, (1) this widget will build a transparent placeholder with
+  /// the same dimensions as the widget had when the mimicking process started
+  /// and (2) the child will be placed in the enclosing overlay.
   MimicOverlayEntry liftToOverlay() {
     OverlayState overlay = Overlay.of(context);
     assert(overlay != null); // You need an overlay to lift into.

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

@@ -9,6 +9,7 @@ import 'framework.dart';
 import 'navigator.dart';
 import 'transitions.dart';
 
+/// Prevents the user from interacting with widgets behind itself.
 class ModalBarrier extends StatelessComponent {
   ModalBarrier({
     Key key,
@@ -16,7 +17,10 @@ class ModalBarrier extends StatelessComponent {
     this.dismissable: true
   }) : super(key: key);
 
+  /// If non-null, fill the barrier with this color.
   final Color color;
+
+  /// Whether touching the barrier will pop the current route off the [Navigator].
   final bool dismissable;
 
   Widget build(BuildContext context) {
@@ -38,6 +42,7 @@ class ModalBarrier extends StatelessComponent {
   }
 }
 
+/// Prevents the user from interacting with widgets behind itself.
 class AnimatedModalBarrier extends StatelessComponent {
   AnimatedModalBarrier({
     Key key,
@@ -46,8 +51,15 @@ class AnimatedModalBarrier extends StatelessComponent {
     this.dismissable: true
   }) : super(key: key);
 
+  /// If non-null, fill the barrier with this color.
+  ///
+  /// The barrier will animate this color according to the given [performance].
   final AnimatedColorValue color;
+
+  /// The performance to use when animating the given [color].
   final PerformanceView performance;
+
+  /// Whether touching the barrier will pop the current route off the [Navigator].
   final bool dismissable;
 
   Widget build(BuildContext context) {

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

@@ -5,14 +5,20 @@
 import 'basic.dart';
 import 'framework.dart';
 
+/// A place in the overlay that can contain a widget.
 class OverlayEntry {
   OverlayEntry({
     this.builder,
     bool opaque: false
   }) : _opaque = opaque;
 
+  /// This entry will include the widget built by this builder in the overlay at the entry's position.
   final WidgetBuilder builder;
 
+  /// Whether this entry occludes the entire overlay.
+  ///
+  /// If an entry claims to be opaque, the overlay will skip building all the
+  /// entries below that entry for efficiency.
   bool get opaque => _opaque;
   bool _opaque;
   void set opaque (bool value) {
@@ -24,12 +30,15 @@ class OverlayEntry {
 
   OverlayState _state;
 
-  /// Remove the entry from the overlay.
+  /// Remove this entry from the overlay.
   void remove() {
     _state?._remove(this);
     _state = null;
   }
 
+  /// Cause this entry to rebuild during the next pipeline flush.
+  ///
+  /// You need to call this function if the output of [builder] has changed.
   void markNeedsBuild() {
     // TODO(ianh): find a way to make this not rebuild the entire overlay
     _state?.setState(() {});
@@ -38,19 +47,23 @@ class OverlayEntry {
   String toString() => '$runtimeType@$hashCode(opaque: $opaque)';
 }
 
+/// A [Stack] of entries that can be managed independently.
 class Overlay extends StatefulComponent {
   Overlay({
     Key key,
     this.initialEntries
   }) : super(key: key);
 
+  /// The entries to include in the overlay initially.
   final List<OverlayEntry> initialEntries;
 
+  /// The closest enclosing overlay of the given context.
   static OverlayState of(BuildContext context) => context.ancestorStateOfType(OverlayState);
 
   OverlayState createState() => new OverlayState();
 }
 
+/// The current state of an [Overlay].
 class OverlayState extends State<Overlay> {
   final List<OverlayEntry> _entries = new List<OverlayEntry>();
 
@@ -59,6 +72,10 @@ class OverlayState extends State<Overlay> {
     insertAll(config.initialEntries);
   }
 
+  /// Insert the given entry into the overlay.
+  ///
+  /// If [above] is non-null, the entry is inserted just above [above].
+  /// Otherwise, the entry is inserted on top.
   void insert(OverlayEntry entry, { OverlayEntry above }) {
     assert(entry._state == null);
     assert(above == null || (above._state == this && _entries.contains(above)));
@@ -69,6 +86,10 @@ class OverlayState extends State<Overlay> {
     });
   }
 
+  /// Insert all the entries in the given iterable.
+  ///
+  /// If [above] is non-null, the entries are inserted just above [above].
+  /// Otherwise, the entries are inserted on top.
   void insertAll(Iterable<OverlayEntry> entries, { OverlayEntry above }) {
     assert(above == null || (above._state == this && _entries.contains(above)));
     for (OverlayEntry entry in entries) {
@@ -87,12 +108,14 @@ class OverlayState extends State<Overlay> {
     });
   }
 
+  /// (DEBUG ONLY) Check whether a given entry is visible (i.e., not behind an opaque entry).
+  ///
+  /// This is an O(N) algorithm, and should not be necessary except for debug asserts.
+  /// To avoid people depending on it, we only implement it in checked mode.
   bool debugIsVisible(OverlayEntry entry) {
     bool result = false;
     assert(_entries.contains(entry));
     assert(() {
-      // This is an O(N) algorithm, and should not be necessary except for debug asserts.
-      // To avoid people depending on it, we only implement it in checked mode.
       for (int i = _entries.length - 1; i > 0; i -= 1) {
         OverlayEntry candidate = _entries[i];
         if (candidate == entry) {

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

@@ -28,7 +28,7 @@ abstract class PageRoute<T> extends ModalRoute<T> {
     return performance;
   }
 
-  // Subclasses can override this method to customize way heroes are inserted
+  /// Subclasses can override this method to customize way heroes are inserted
   void insertHeroOverlayEntry(OverlayEntry entry, Object tag, OverlayState overlay) {
     overlay.insert(entry);
   }

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

@@ -5,6 +5,7 @@
 import 'basic.dart';
 import 'framework.dart';
 
+/// A widget whose child can be mutated.
 class Placeholder extends StatefulComponent {
   Placeholder({ Key key }) : super(key: key);
 
@@ -12,6 +13,9 @@ class Placeholder extends StatefulComponent {
 }
 
 class PlaceholderState extends State<Placeholder> {
+  /// The child that this widget builds.
+  ///
+  /// Mutating this field will cause this widget to rebuild with the new child.
   Widget get child => _child;
   Widget _child;
   void set child(Widget child) {

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

@@ -17,9 +17,12 @@ import 'pages.dart';
 
 const _kTransparent = const Color(0x00000000);
 
+/// A route that displays widgets in the [Navigator]'s [Overlay].
 abstract class OverlayRoute<T> extends Route<T> {
+  /// Subclasses should override this getter to return the builders for the overlay.
   List<WidgetBuilder> get builders;
 
+  /// The entries this route has placed in the overlay.
   List<OverlayEntry> get overlayEntries => _overlayEntries;
   final List<OverlayEntry> _overlayEntries = <OverlayEntry>[];
 
@@ -30,7 +33,7 @@ abstract class OverlayRoute<T> extends Route<T> {
     navigator.overlay?.insertAll(_overlayEntries, above: insertionPoint);
   }
 
-  // Subclasses shouldn't call this if they want to delay the finished() call.
+  /// Subclasses shouldn't call this if they want to delay the finished() call.
   bool didPop(T result) {
     finished();
     return true;

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

@@ -36,6 +36,7 @@ enum StatisticsOption {
   visualizeEngineStatistics,
 }
 
+/// Displays performance statistics.
 class StatisticsOverlay extends LeafRenderObjectWidget {
 
   /// Create a statistics overlay that only displays specific statistics. The

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

@@ -5,11 +5,16 @@
 import 'package:flutter/services.dart';
 import 'package:flutter/widgets.dart';
 
+/// Controls the description of this app in the operating system.
 class Title extends StatelessComponent {
   Title({ this.title, this.child, this.color });
 
   final Widget child;
+
+  /// A one-line description of this app for use in the window manager.
   final String title;
+
+  /// A color that the window manager should use to identify this app.
   final Color color;
 
   Widget build(BuildContext context) {

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

@@ -4,6 +4,7 @@
 
 import 'framework.dart';
 
+/// A widget that has exactly one inflated instance in the tree.
 abstract class UniqueComponent<T extends State> extends StatefulComponent {
   UniqueComponent({ GlobalKey key }) : super(key: key) {
     assert(key != null);
@@ -11,6 +12,7 @@ abstract class UniqueComponent<T extends State> extends StatefulComponent {
 
   T createState();
 
+  /// The state for the unique inflated instance of this widget.
   T get currentState {
     GlobalKey globalKey = key;
     return globalKey.currentState;