PopupMenu shouldn't use CustomPaint

Align is now powerful enough to do all the work we need to do here.

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

@@ -5,13 +5,11 @@
 import 'dart:async';
 
 import 'package:flutter/animation.dart';
-import 'package:flutter/painting.dart';
 import 'package:flutter/widgets.dart';
 
 import 'ink_well.dart';
+import 'material.dart';
 import 'popup_menu_item.dart';
-import 'shadows.dart';
-import 'theme.dart';
 
 const Duration _kMenuDuration = const Duration(milliseconds: 300);
 const double _kMenuCloseIntervalEnd = 2.0 / 3.0;
@@ -21,38 +19,6 @@ const double _kMenuMaxWidth = 5.0 * _kMenuWidthStep;
 const double _kMenuHorizontalPadding = 16.0;
 const double _kMenuVerticalPadding = 8.0;
 
-class _PopupMenuPainter extends CustomPainter {
-  const _PopupMenuPainter({
-    this.color,
-    this.elevation,
-    this.width,
-    this.height
-  });
-
-  final Color color;
-  final int elevation;
-  final double width;
-  final double height;
-
-  void paint(Canvas canvas, Size size) {
-    double widthValue = width * size.width;
-    double heightValue = height * size.height;
-    final BoxPainter painter = new BoxPainter(new BoxDecoration(
-      backgroundColor: color,
-      borderRadius: 2.0,
-      boxShadow: elevationToShadow[elevation]
-    ));
-    painter.paint(canvas, new Rect.fromLTWH(size.width - widthValue, 0.0, widthValue, heightValue));
-  }
-
-  bool shouldRepaint(_PopupMenuPainter oldPainter) {
-    return oldPainter.color != color
-        || oldPainter.elevation != elevation
-        || oldPainter.width != width
-        || oldPainter.height != height;
-  }
-}
-
 class _PopupMenu<T> extends StatelessComponent {
   _PopupMenu({
     Key key,
@@ -88,25 +54,26 @@ class _PopupMenu<T> extends StatelessComponent {
       builder: (BuildContext context) {
         return new Opacity(
           opacity: opacity.value,
-          child: new CustomPaint(
-            painter: new _PopupMenuPainter(
-              color: Theme.of(context).canvasColor,
-              elevation: route.elevation,
-              width: width.value,
-              height: height.value
-            ),
-            child: new ConstrainedBox(
-              constraints: new BoxConstraints(
-                minWidth: _kMenuMinWidth,
-                maxWidth: _kMenuMaxWidth
-              ),
-              child: new IntrinsicWidth(
-                stepWidth: _kMenuWidthStep,
-                child: new Block(
-                  children,
-                  padding: const EdgeDims.symmetric(
-                    horizontal: _kMenuHorizontalPadding,
-                    vertical: _kMenuVerticalPadding
+          child: new Material(
+            type: MaterialType.card,
+            elevation: route.elevation,
+            child: new Align(
+              alignment: const FractionalOffset(1.0, 0.0),
+              widthFactor: width.value,
+              heightFactor: height.value,
+              child: new ConstrainedBox(
+                constraints: new BoxConstraints(
+                  minWidth: _kMenuMinWidth,
+                  maxWidth: _kMenuMaxWidth
+                ),
+                child: new IntrinsicWidth(
+                  stepWidth: _kMenuWidthStep,
+                  child: new Block(
+                    children,
+                    padding: const EdgeDims.symmetric(
+                      horizontal: _kMenuHorizontalPadding,
+                      vertical: _kMenuVerticalPadding
+                    )
                   )
                 )
               )

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

@@ -162,8 +162,8 @@ class RenderFractionallySizedBox extends RenderProxyBox {
     double widthFactor,
     double heightFactor
   }) : _widthFactor = widthFactor, _heightFactor = heightFactor, super(child) {
-    assert(_widthFactor == null || _widthFactor > 0.0);
-    assert(_heightFactor == null || _heightFactor > 0.0);
+    assert(_widthFactor == null || _widthFactor >= 0.0);
+    assert(_heightFactor == null || _heightFactor >= 0.0);
   }
 
   /// The multiple to apply to the incoming maximum width constraint to use as
@@ -172,7 +172,7 @@ class RenderFractionallySizedBox extends RenderProxyBox {
   double get widthFactor => _widthFactor;
   double _widthFactor;
   void set widthFactor (double value) {
-    assert(value == null || value > 0.0);
+    assert(value == null || value >= 0.0);
     if (_widthFactor == value)
       return;
     _widthFactor = value;
@@ -185,7 +185,7 @@ class RenderFractionallySizedBox extends RenderProxyBox {
   double get heightFactor => _heightFactor;
   double _heightFactor;
   void set heightFactor (double value) {
-    assert(value == null || value > 0.0);
+    assert(value == null || value >= 0.0);
     if (_heightFactor == value)
       return;
     _heightFactor = value;
@@ -193,11 +193,25 @@ class RenderFractionallySizedBox extends RenderProxyBox {
   }
 
   BoxConstraints _getInnerConstraints(BoxConstraints constraints) {
+    double minWidth = constraints.minWidth;
+    double maxWidth = constraints.maxWidth;
+    if (_widthFactor != null) {
+      double width = maxWidth * _widthFactor;
+      minWidth = width;
+      maxWidth = width;
+    }
+    double minHeight = constraints.minHeight;
+    double maxHeight = constraints.maxHeight;
+    if (_heightFactor != null) {
+      double height = maxHeight * _heightFactor;
+      minHeight = height;
+      maxHeight = height;
+    }
     return new BoxConstraints(
-      minWidth: _widthFactor == null ? constraints.minWidth : constraints.maxWidth * _widthFactor,
-      maxWidth: _widthFactor == null ? constraints.maxWidth : constraints.maxWidth * _widthFactor,
-      minHeight: _heightFactor == null ? constraints.minHeight : constraints.maxHeight * _heightFactor,
-      maxHeight: _heightFactor == null ? constraints.maxHeight : constraints.maxHeight * _heightFactor
+      minWidth: minWidth,
+      maxWidth: maxWidth,
+      minHeight: minHeight,
+      maxHeight: maxHeight
     );
   }