Merge pull request #1371 from Hixie/fab-snack

Make the FAB move up when a Snack Bar slides in.

examples/stocks/lib/stock_home.dart

@@ -236,7 +236,6 @@ class StockHomeState extends State<StockHome> {
     if (_snackBarStatus == AnimationStatus.dismissed)
       return null;
     return new SnackBar(
-      transitionKey: snackBarKey,
       showing: _isSnackBarShowing,
       content: new Text("Stock purchased!"),
       actions: [new SnackBarAction(label: "UNDO", onPressed: _handleUndo)],

packages/flutter/lib/src/fn3/basic.dart

@@ -211,7 +211,9 @@ class SizedBox extends OneChildRenderObjectWidget {
   final double width;
   final double height;
 
-  RenderConstrainedBox createRenderObject() => new RenderConstrainedBox(additionalConstraints: _additionalConstraints);
+  RenderConstrainedBox createRenderObject() => new RenderConstrainedBox(
+    additionalConstraints: _additionalConstraints
+  );
 
   BoxConstraints get _additionalConstraints {
     BoxConstraints result = const BoxConstraints();
@@ -227,6 +229,24 @@ class SizedBox extends OneChildRenderObjectWidget {
   }
 }
 
+class OverflowBox extends OneChildRenderObjectWidget {
+  OverflowBox({ Key key, this.width, this.height, Widget child })
+    : super(key: key, child: child);
+
+  final double width;
+  final double height;
+
+  RenderOverflowBox createRenderObject() => new RenderOverflowBox(
+    innerWidth: width,
+    innerHeight: height
+  );
+
+  void updateRenderObject(RenderOverflowBox renderObject, OverflowBox oldWidget) {
+    renderObject.innerWidth = width;
+    renderObject.innerHeight = height;
+  }
+}
+
 class ConstrainedBox extends OneChildRenderObjectWidget {
   ConstrainedBox({ Key key, this.constraints, Widget child })
     : super(key: key, child: child) {

packages/flutter/lib/src/fn3/scaffold.dart

@@ -102,6 +102,7 @@ class RenderScaffold extends RenderBox {
   void performLayout() {
     double bodyHeight = size.height;
     double bodyPosition = 0.0;
+    double fabOffset = 0.0;
     if (_slots[ScaffoldSlots.statusBar] != null) {
       RenderBox statusBar = _slots[ScaffoldSlots.statusBar];
       statusBar.layout(new BoxConstraints.tight(new Size(size.width, kStatusBarHeight)));
@@ -127,18 +128,20 @@ class RenderScaffold extends RenderBox {
     if (_slots[ScaffoldSlots.snackBar] != null) {
       RenderBox snackBar = _slots[ScaffoldSlots.snackBar];
       // TODO(jackson): On tablet/desktop, minWidth = 288, maxWidth = 568
-      snackBar.layout(new BoxConstraints(minWidth: size.width, maxWidth: size.width, minHeight: 0.0, maxHeight: size.height),
-                      parentUsesSize: true);
+      snackBar.layout(
+        new BoxConstraints(minWidth: size.width, maxWidth: size.width, minHeight: 0.0, maxHeight: bodyHeight),
+        parentUsesSize: true
+      );
       assert(snackBar.parentData is BoxParentData);
-      // Position it off-screen. SnackBar slides in with an animation.
-      snackBar.parentData.position = new Point(0.0, size.height);
+      snackBar.parentData.position = new Point(0.0, bodyPosition + bodyHeight - snackBar.size.height);
+      fabOffset += snackBar.size.height;
     }
     if (_slots[ScaffoldSlots.floatingActionButton] != null) {
       RenderBox floatingActionButton = _slots[ScaffoldSlots.floatingActionButton];
       Size area = new Size(size.width - kButtonX, size.height - kButtonY);
       floatingActionButton.layout(new BoxConstraints.loose(area), parentUsesSize: true);
       assert(floatingActionButton.parentData is BoxParentData);
-      floatingActionButton.parentData.position = (area - floatingActionButton.size).toPoint();
+      floatingActionButton.parentData.position = (area - floatingActionButton.size).toPoint() + new Offset(0.0, -fabOffset);
     }
     if (_slots[ScaffoldSlots.drawer] != null) {
       RenderBox drawer = _slots[ScaffoldSlots.drawer];

packages/flutter/lib/src/fn3/snack_bar.dart

@@ -17,7 +17,10 @@ import 'package:sky/src/fn3/transitions.dart';
 typedef void SnackBarDismissedCallback();
 
 const Duration _kSlideInDuration = const Duration(milliseconds: 200);
-// TODO(ianh): factor out some of the constants below
+const double kSnackHeight = 52.0;
+const double kSideMargins = 24.0;
+const double kVerticalPadding = 14.0;
+const Color kSnackBackground = const Color(0xFF323232);
 
 class SnackBarAction extends StatelessComponent {
   SnackBarAction({Key key, this.label, this.onPressed }) : super(key: key) {
@@ -31,8 +34,8 @@ class SnackBarAction extends StatelessComponent {
     return new GestureDetector(
       onTap: onPressed,
       child: new Container(
-        margin: const EdgeDims.only(left: 24.0),
-        padding: const EdgeDims.only(top: 14.0, bottom: 14.0),
+        margin: const EdgeDims.only(left: kSideMargins),
+        padding: const EdgeDims.symmetric(vertical: kVerticalPadding),
         child: new Text(label)
       )
     );
@@ -42,7 +45,6 @@ class SnackBarAction extends StatelessComponent {
 class SnackBar extends AnimatedComponent {
   SnackBar({
     Key key,
-    this.transitionKey,
     this.content,
     this.actions,
     bool showing,
@@ -51,7 +53,6 @@ class SnackBar extends AnimatedComponent {
     assert(content != null);
   }
 
-  final Key transitionKey;
   final Widget content;
   final List<SnackBarAction> actions;
   final SnackBarDismissedCallback onDismissed;
@@ -69,7 +70,7 @@ class SnackBarState extends AnimatedState<SnackBar> {
     List<Widget> children = [
       new Flexible(
         child: new Container(
-          margin: const EdgeDims.symmetric(vertical: 14.0),
+          margin: const EdgeDims.symmetric(vertical: kVerticalPadding),
           child: new DefaultTextStyle(
             style: Typography.white.subhead,
             child: config.content
@@ -79,24 +80,28 @@ class SnackBarState extends AnimatedState<SnackBar> {
     ];
     if (config.actions != null)
       children.addAll(config.actions);
-    return new SlideTransition(
-      key: config.transitionKey,
+    return new SquashTransition(
       performance: performance.view,
-      position: new AnimatedValue<Point>(
-        Point.origin,
-        end: const Point(0.0, -52.0),
+      height: new AnimatedValue<double>(
+        0.0,
+        end: kSnackHeight,
         curve: easeIn,
         reverseCurve: easeOut
       ),
-      child: new Material(
-        level: 2,
-        color: const Color(0xFF323232),
-        type: MaterialType.canvas,
-        child: new Container(
-          margin: const EdgeDims.symmetric(horizontal: 24.0),
-          child: new DefaultTextStyle(
-            style: new TextStyle(color: Theme.of(context).accentColor),
-            child: new Row(children)
+      child: new ClipRect(
+        child: new OverflowBox(
+          height: kSnackHeight,
+          child: new Material(
+            level: 2,
+            color: kSnackBackground,
+            type: MaterialType.canvas,
+            child: new Container(
+              margin: const EdgeDims.symmetric(horizontal: kSideMargins),
+              child: new DefaultTextStyle(
+                style: new TextStyle(color: Theme.of(context).accentColor),
+                child: new Row(children)
+              )
+            )
           )
         )
       )

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

@@ -83,7 +83,7 @@ class RenderProxyBox extends RenderBox with RenderObjectWithChildMixin<RenderBox
 
 /// A render object that imposes additional constraints on its child
 ///
-/// A render constrainted box proxies most functions in the render box protocol
+/// A render constrained box proxies most functions in the render box protocol
 /// to its child, except that when laying out its child, it tightens the
 /// constraints provided by its parent by enforcing the [additionalConstraints]
 /// as well.
@@ -94,7 +94,7 @@ class RenderConstrainedBox extends RenderProxyBox {
   RenderConstrainedBox({
     RenderBox child,
     BoxConstraints additionalConstraints
-  }) : super(child), _additionalConstraints = additionalConstraints {
+  }) : _additionalConstraints = additionalConstraints, super(child) {
     assert(additionalConstraints != null);
   }
 
@@ -145,6 +145,99 @@ class RenderConstrainedBox extends RenderProxyBox {
   String debugDescribeSettings(String prefix) => '${super.debugDescribeSettings(prefix)}${prefix}additionalConstraints: ${additionalConstraints}\n';
 }
 
+/// A render object that imposes different constraints on its child than it gets
+/// from its parent, possibly allowing the child to overflow the parent.
+///
+/// A render overflow box proxies most functions in the render box protocol to
+/// its child, except that when laying out its child, it passes constraints
+/// based on the innerWidth and innerHeight fields instead of just passing the
+/// parent's constraints in. It then sizes itself based on the parent's
+/// constraints' maxWidth and maxHeight, ignoring the child's dimensions.
+///
+/// For example, if you wanted a box to always render 50x50, regardless of where
+/// it was rendered, you would wrap it in a RenderOverflow with innerWidth and
+/// innerHeight members set to 50.0. Generally speaking, to avoid confusing
+/// behaviour around hit testing, a RenderOverflowBox should usually be wrapped
+/// in a RenderClipRect.
+///
+/// The child is positioned at the top left of the box. To position a smaller
+/// child inside a larger parent, use [RenderPositionedBox] and
+/// [RenderConstrainedBox] rather than RenderOverflowBox.
+///
+/// If you pass null for innerWidth or innerHeight, the constraints from the
+/// parent are passed instead.
+class RenderOverflowBox extends RenderProxyBox {
+  RenderOverflowBox({
+    RenderBox child,
+    double innerWidth,
+    double innerHeight
+  }) : _innerWidth = innerWidth, _innerHeight = innerHeight, super(child);
+
+  /// The tight width constraint to give the child. Set this to null (the
+  /// default) to use the constraints from the parent instead.
+  double get innerWidth => _innerWidth;
+  double _innerWidth;
+  void set innerWidth (double value) {
+    if (_innerWidth == value)
+      return;
+    _innerWidth = value;
+    markNeedsLayout();
+  }
+
+  /// The tight height constraint to give the child. Set this to null (the
+  /// default) to use the constraints from the parent instead.
+  double get innerHeight => _innerHeight;
+  double _innerHeight;
+  void set innerHeight (double value) {
+    if (_innerHeight == value)
+      return;
+    _innerHeight = value;
+    markNeedsLayout();
+  }
+
+  BoxConstraints childConstraints(BoxConstraints constraints) {
+    return new BoxConstraints(
+      minWidth: _innerWidth ?? constraints.minWidth,
+      maxWidth: _innerWidth ?? constraints.maxWidth,
+      minHeight: _innerHeight ?? constraints.minHeight,
+      maxHeight: _innerHeight ?? constraints.maxHeight
+    );
+  }
+
+  double getMinIntrinsicWidth(BoxConstraints constraints) {
+    return constraints.constrainWidth();
+  }
+
+  double getMaxIntrinsicWidth(BoxConstraints constraints) {
+    return constraints.constrainWidth();
+  }
+
+  double getMinIntrinsicHeight(BoxConstraints constraints) {
+    return constraints.constrainHeight();
+  }
+
+  double getMaxIntrinsicHeight(BoxConstraints constraints) {
+    return constraints.constrainHeight();
+  }
+
+  bool get sizedByParent => true;
+
+  void performResize() {
+    size = constraints.biggest;
+  }
+
+  void performLayout() {
+    if (child != null)
+      child.layout(childConstraints(constraints));
+  }
+
+  String debugDescribeSettings(String prefix) {
+    return '${super.debugDescribeSettings(prefix)}' + 
+           '${prefix}innerWidth: ${innerWidth ?? "use parent width constraints"}\n' +
+           '${prefix}innerHeight: ${innerHeight ?? "use parent height constraints"}\n';
+  }
+}
+
 /// Forces child to layout at a specific aspect ratio
 ///
 /// The width of this render object is the largest width permited by the layout