Split layout2.dart into several files

sky/sdk/lib/framework/rendering/render_flex.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:sky' as sky;
+import 'render_node.dart';
+import 'render_box.dart';
+import 'render_node.dart';
+
+class FlexBoxParentData extends BoxParentData with ContainerParentDataMixin<RenderBox> {
+  int flex;
+  void merge(FlexBoxParentData other) {
+    if (other.flex != null)
+      flex = other.flex;
+    super.merge(other);
+  }
+}
+
+enum FlexDirection { Horizontal, Vertical }
+
+class RenderFlex extends RenderBox with ContainerRenderNodeMixin<RenderBox, FlexBoxParentData>,
+                                        RenderBoxContainerDefaultsMixin<RenderBox, FlexBoxParentData> {
+  // lays out RenderBox children using flexible layout
+
+  RenderFlex({
+    FlexDirection direction: FlexDirection.Horizontal
+  }) : _direction = direction;
+
+  FlexDirection _direction;
+  FlexDirection get direction => _direction;
+  void set direction (FlexDirection value) {
+    if (_direction != value) {
+      _direction = value;
+      markNeedsLayout();
+    }
+  }
+
+  void setParentData(RenderBox child) {
+    if (child.parentData is! FlexBoxParentData)
+      child.parentData = new FlexBoxParentData();
+  }
+
+  bool get sizedByParent => true;
+  void performResize() {
+    size = constraints.constrain(new sky.Size(constraints.maxWidth, constraints.maxHeight));
+    assert(size.height < double.INFINITY);
+    assert(size.width < double.INFINITY);
+  }
+
+  int _getFlex(RenderBox child) {
+    assert(child.parentData is FlexBoxParentData);
+    return child.parentData.flex != null ? child.parentData.flex : 0;
+  }
+
+  void performLayout() {
+    // Based on http://www.w3.org/TR/css-flexbox-1/ Section 9.7 Resolving Flexible Lengths
+    // Steps 1-3. Determine used flex factor, size inflexible items, calculate free space
+    int totalFlex = 0;
+    assert(constraints != null);
+    double freeSpace = (_direction == FlexDirection.Horizontal) ? constraints.maxWidth : constraints.maxHeight;
+    RenderBox child = firstChild;
+    while (child != null) {
+      int flex = _getFlex(child);
+      if (flex > 0) {
+        totalFlex += child.parentData.flex;
+      } else {
+        BoxConstraints innerConstraints = new BoxConstraints(maxHeight: constraints.maxHeight,
+                                                             maxWidth: constraints.maxWidth);
+        child.layout(innerConstraints, parentUsesSize: true);
+        freeSpace -= (_direction == FlexDirection.Horizontal) ? child.size.width : child.size.height;
+      }
+      child = child.parentData.nextSibling;
+    }
+
+    // Steps 4-5. Distribute remaining space to flexible children.
+    double spacePerFlex = totalFlex > 0 ? (freeSpace / totalFlex) : 0.0;
+    double usedSpace = 0.0;
+    child = firstChild;
+    while (child != null) {
+      int flex = _getFlex(child);
+      if (flex > 0) {
+        double spaceForChild = spacePerFlex * flex;
+        BoxConstraints innerConstraints;
+        switch (_direction) {
+          case FlexDirection.Horizontal:
+            innerConstraints = new BoxConstraints(maxHeight: constraints.maxHeight,
+                                                  minWidth: spaceForChild,
+                                                  maxWidth: spaceForChild);
+            break;
+          case FlexDirection.Vertical:
+            innerConstraints = new BoxConstraints(minHeight: spaceForChild,
+                                                  maxHeight: spaceForChild,
+                                                  maxWidth: constraints.maxWidth);
+            break;
+        }
+        child.layout(innerConstraints, parentUsesSize: true);
+      }
+
+      // For now, center the flex items in the cross direction
+      switch (_direction) {
+        case FlexDirection.Horizontal:
+          child.parentData.position = new sky.Point(usedSpace, size.height / 2.0 - child.size.height / 2.0);
+          usedSpace += child.size.width;
+          break;
+        case FlexDirection.Vertical:
+          child.parentData.position = new sky.Point(size.width / 2.0 - child.size.width / 2.0, usedSpace);
+          usedSpace += child.size.height;
+          break;
+      }
+      child = child.parentData.nextSibling;
+    }
+  }
+
+  void hitTestChildren(HitTestResult result, { sky.Point position }) {
+    defaultHitTestChildren(result, position: position);
+  }
+
+  void paint(RenderNodeDisplayList canvas) {
+    defaultPaint(canvas);
+  }
+}