Merge pull request #2607 from abarth/rotated_box

Add RotatedBox which applies a rotation before layout

packages/flutter/lib/rendering.dart

@@ -26,6 +26,7 @@ export 'src/rendering/overflow.dart';
 export 'src/rendering/paragraph.dart';
 export 'src/rendering/performance_overlay.dart';
 export 'src/rendering/proxy_box.dart';
+export 'src/rendering/rotated_box.dart';
 export 'src/rendering/semantics.dart';
 export 'src/rendering/shifted_box.dart';
 export 'src/rendering/stack.dart';

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

@@ -154,6 +154,16 @@ class BoxConstraints extends Constraints {
                               maxHeight: height == null ? maxHeight : height.clamp(minHeight, maxHeight));
   }
 
+  /// A box constraints with the width and height constraints flipped.
+  BoxConstraints get flipped {
+    return new BoxConstraints(
+      minWidth: minHeight,
+      maxWidth: maxHeight,
+      minHeight: minWidth,
+      maxHeight: maxWidth
+    );
+  }
+
   /// Returns box constraints with the same width constraints but with
   /// unconstrainted height.
   BoxConstraints widthConstraints() => new BoxConstraints(minWidth: minWidth, maxWidth: maxWidth);

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

@@ -0,0 +1,110 @@
+// Copyright 2016 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:math' as math;
+
+import 'package:flutter/gestures.dart';
+import 'package:vector_math/vector_math_64.dart';
+
+import 'box.dart';
+import 'object.dart';
+
+const double _kQuarterTurnsInRadians = math.PI / 2.0;
+
+/// Rotates its child by a integral number of quarter turns.
+///
+/// Unlike [RenderTransform], which applies a transform just prior to painting,
+/// this object applies its rotation prior to layout, which means the entire
+/// rotated box consumes only as much space as required by the rotated child.
+class RenderRotatedBox extends RenderBox with RenderObjectWithChildMixin<RenderBox> {
+  RenderRotatedBox({
+    int quarterTurns,
+    RenderBox child
+  }) : _quarterTurns = quarterTurns {
+    assert(quarterTurns != null);
+    this.child = child;
+  }
+
+  /// The number of clockwise quarter turns the child should be rotated.
+  int get quarterTurns => _quarterTurns;
+  int _quarterTurns;
+  void set quarterTurns(int value) {
+    assert(value != null);
+    if (_quarterTurns == value)
+      return;
+    _quarterTurns = value;
+    markNeedsLayout();
+  }
+
+  bool get _isVertical => quarterTurns % 2 == 1;
+
+  double getMinIntrinsicWidth(BoxConstraints constraints) {
+    assert(constraints.debugAssertIsNormalized);
+    if (child != null)
+      return _isVertical ? child.getMinIntrinsicHeight(constraints.flipped) : child.getMinIntrinsicWidth(constraints);
+    return super.getMinIntrinsicWidth(constraints);
+  }
+
+  double getMaxIntrinsicWidth(BoxConstraints constraints) {
+    assert(constraints.debugAssertIsNormalized);
+    if (child != null)
+      return _isVertical ? child.getMaxIntrinsicHeight(constraints.flipped) : child.getMaxIntrinsicWidth(constraints);
+    return super.getMaxIntrinsicWidth(constraints);
+  }
+
+  double getMinIntrinsicHeight(BoxConstraints constraints) {
+    assert(constraints.debugAssertIsNormalized);
+    if (child != null)
+      return _isVertical ? child.getMinIntrinsicWidth(constraints.flipped) : child.getMinIntrinsicHeight(constraints);
+    return super.getMinIntrinsicHeight(constraints);
+  }
+
+  double getMaxIntrinsicHeight(BoxConstraints constraints) {
+    assert(constraints.debugAssertIsNormalized);
+    if (child != null)
+      return _isVertical ? child.getMaxIntrinsicWidth(constraints.flipped) : child.getMaxIntrinsicHeight(constraints);
+    return super.getMaxIntrinsicHeight(constraints);
+  }
+
+  Matrix4 _paintTransform;
+
+  void performLayout() {
+    _paintTransform = null;
+    if (child != null) {
+      child.layout(_isVertical ? constraints.flipped : constraints, parentUsesSize: true);
+      size = _isVertical ? new Size(child.size.height, child.size.width) : child.size;
+      _paintTransform = new Matrix4.identity()
+        ..translate(size.width / 2.0, size.height / 2.0)
+        ..rotateZ(_kQuarterTurnsInRadians * (quarterTurns % 4))
+        ..translate(-child.size.width / 2.0, -child.size.height / 2.0);
+    } else {
+      performResize();
+    }
+  }
+
+  bool hitTestChildren(HitTestResult result, { Point position }) {
+    assert(_paintTransform != null || needsLayout || child == null);
+    if (child == null || _paintTransform == null)
+      return false;
+    Matrix4 inverse = new Matrix4.inverted(_paintTransform);
+    Vector3 position3 = new Vector3(position.x, position.y, 0.0);
+    Vector3 transformed3 = inverse.transform3(position3);
+    return child.hitTest(result, position: new Point(transformed3.x, transformed3.y));
+  }
+
+  void _paintChild(PaintingContext context, Offset offset) {
+    context.paintChild(child, offset);
+  }
+
+  void paint(PaintingContext context, Offset offset) {
+    if (child != null)
+      context.pushTransform(needsCompositing, offset, _paintTransform, _paintChild);
+  }
+
+  void applyPaintTransform(RenderBox child, Matrix4 transform) {
+    if (_paintTransform != null)
+      transform.multiply(_paintTransform);
+    super.applyPaintTransform(child, transform);
+  }
+}

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

@@ -320,6 +320,27 @@ class FractionalTranslation extends OneChildRenderObjectWidget {
   }
 }
 
+/// Rotates its child by a integral number of quarter turns.
+///
+/// Unlike [Transform], which applies a transform just prior to painting,
+/// this object applies its rotation prior to layout, which means the entire
+/// rotated box consumes only as much space as required by the rotated child.
+class RotatedBox extends OneChildRenderObjectWidget {
+  RotatedBox({ Key key, this.quarterTurns, Widget child })
+    : super(key: key, child: child) {
+    assert(quarterTurns != null);
+  }
+
+  /// The number of clockwise quarter turns the child should be rotated.
+  final int quarterTurns;
+
+  RenderRotatedBox createRenderObject(BuildContext context) => new RenderRotatedBox(quarterTurns: quarterTurns);
+
+  void updateRenderObject(BuildContext context, RenderRotatedBox renderObject) {
+    renderObject.quarterTurns = quarterTurns;
+  }
+}
+
 /// Insets its child by the given padding.
 ///
 /// When passing layout constraints to its child, padding shrinks the

packages/flutter/test/widget/rotated_box_test.dart

@@ -0,0 +1,58 @@
+// 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 'package:flutter_test/flutter_test.dart';
+import 'package:flutter/material.dart';
+import 'package:test/test.dart';
+
+void main() {
+  test('Rotated box control test', () {
+    testWidgets((WidgetTester tester) {
+      List<String> log = <String>[];
+      Key rotatedBoxKey = new UniqueKey();
+
+      tester.pumpWidget(
+        new Center(
+          child: new RotatedBox(
+            key: rotatedBoxKey,
+            quarterTurns: 1,
+            child: new Row(
+              justifyContent: FlexJustifyContent.collapse,
+              children: <Widget>[
+                new GestureDetector(
+                  onTap: () { log.add('left'); },
+                  child: new Container(
+                    width: 100.0,
+                    height: 40.0,
+                    decoration: new BoxDecoration(backgroundColor: Colors.blue[500])
+                  )
+                ),
+                new GestureDetector(
+                  onTap: () { log.add('right'); },
+                  child: new Container(
+                    width: 75.0,
+                    height: 65.0,
+                    decoration: new BoxDecoration(backgroundColor: Colors.blue[500])
+                  )
+                ),
+              ]
+            )
+          )
+        )
+      );
+
+      RenderBox box = tester.findElementByKey(rotatedBoxKey).renderObject;
+      expect(box.size.width, equals(65.0));
+      expect(box.size.height, equals(175.0));
+
+      tester.tapAt(new Point(420.0, 280.0));
+      expect(log, equals(['left']));
+      log.clear();
+
+      tester.tapAt(new Point(380.0, 320.0));
+      expect(log, equals(['right']));
+      log.clear();
+    });
+  });
+}