A proof of concept for annular sector layout.

Could be useful for watch faces. :-)
Includes some minor fixes to layout2.dart.
Includes adding a very basic path API.

R=abarth@chromium.org

Review URL: https://codereview.chromium.org/1152383002

examples/raw/sector-layout.dart

@@ -0,0 +1,377 @@
+// 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:math' as math;
+import 'dart:sky' as sky;
+import 'package:sky/framework/layout2.dart';
+
+const double kTwoPi = 2 * math.PI;
+
+double deg(double radians) => radians * 180.0 / math.PI;
+
+class SectorConstraints {
+  const SectorConstraints({
+    this.minDeltaRadius: 0.0,
+    this.maxDeltaRadius: double.INFINITY,
+    this.minDeltaTheta: 0.0,
+    this.maxDeltaTheta: kTwoPi});
+
+  const SectorConstraints.tight({ double deltaRadius: 0.0, double deltaTheta: 0.0 })
+    : minDeltaRadius = deltaRadius,
+      maxDeltaRadius = deltaRadius,
+      minDeltaTheta = deltaTheta,
+      maxDeltaTheta = deltaTheta;
+
+  final double minDeltaRadius;
+  final double maxDeltaRadius;
+  final double minDeltaTheta;
+  final double maxDeltaTheta;
+
+  double constrainDeltaRadius(double deltaRadius) {
+    return clamp(min: minDeltaRadius, max: maxDeltaRadius, value: deltaRadius);
+  }
+
+  double constrainDeltaTheta(double deltaTheta) {
+    return clamp(min: minDeltaTheta, max: maxDeltaTheta, value: deltaTheta);
+  }
+}
+
+class SectorDimensions {
+  const SectorDimensions({ this.deltaRadius: 0.0, this.deltaTheta: 0.0 });
+
+  factory SectorDimensions.withConstraints(
+    SectorConstraints constraints,
+    { double deltaRadius: 0.0, double deltaTheta: 0.0 }
+  ) {
+    return new SectorDimensions(
+      deltaRadius: constraints.constrainDeltaRadius(deltaRadius),
+      deltaTheta: constraints.constrainDeltaTheta(deltaTheta)
+    );
+  }
+
+  final double deltaRadius;
+  final double deltaTheta;
+}
+
+class SectorParentData extends ParentData {
+  double radius = 0.0;
+  double theta = 0.0;
+}
+
+abstract class RenderSector extends RenderNode {
+
+  void setParentData(RenderNode child) {
+    if (child.parentData is! SectorParentData)
+      child.parentData = new SectorParentData();
+  }
+
+  SectorDimensions getIntrinsicDimensions(SectorConstraints constraints, double radius) {
+    return new SectorDimensions.withConstraints(constraints);
+  }
+
+  void layout(SectorConstraints constraints, double radius, { RenderNode relayoutSubtreeRoot }) {
+    deltaRadius = constraints.constrainDeltaRadius(0.0);
+    deltaTheta = constraints.constrainDeltaTheta(0.0);
+    layoutDone();
+  }
+
+  double deltaRadius;
+  double deltaTheta;
+}
+
+class RenderDecoratedSector extends RenderSector {
+  BoxDecoration _decoration;
+
+  RenderDecoratedSector(BoxDecoration decoration) : _decoration = decoration;
+
+  void setBoxDecoration(BoxDecoration decoration) {
+    if (_decoration == decoration)
+      return;
+    _decoration = decoration;
+    markNeedsPaint();
+  }
+
+  // origin must be set to the center of the circle
+  void paint(RenderNodeDisplayList canvas) {
+    assert(deltaRadius != null);
+    assert(deltaTheta != null);
+    assert(parentData is SectorParentData);
+
+    if (_decoration == null)
+      return;
+
+    if (_decoration.backgroundColor != null) {
+      sky.Paint paint = new sky.Paint()..color = _decoration.backgroundColor;
+      sky.Path path = new sky.Path();
+      double outerRadiusOver2 = (parentData.radius + deltaRadius) / 2.0;
+      sky.Rect outerBounds = new sky.Rect()..setLTRB(-outerRadiusOver2, -outerRadiusOver2, outerRadiusOver2, outerRadiusOver2);
+      path.arcTo(outerBounds, deg(parentData.theta), deg(deltaTheta), true);
+      double innerRadiusOver2 = parentData.radius / 2.0;
+      sky.Rect innerBounds = new sky.Rect()..setLTRB(-innerRadiusOver2, -innerRadiusOver2, innerRadiusOver2, innerRadiusOver2);
+      path.arcTo(innerBounds, deg(parentData.theta + deltaTheta), deg(-deltaTheta), false);
+      path.close();
+      canvas.drawPath(path, paint);
+    }
+  }
+}
+
+class SectorChildListParentData extends SectorParentData with ContainerParentDataMixin<RenderSector> { }
+
+class RenderSectorRing extends RenderDecoratedSector with ContainerRenderNodeMixin<RenderSector, SectorChildListParentData> {
+  // lays out RenderSector children in a ring
+
+  RenderSectorRing({
+    BoxDecoration decoration,
+    double deltaRadius: double.INFINITY,
+    double padding: 0.0
+  }) : super(decoration), _padding = padding, _desiredDeltaRadius = deltaRadius;
+
+  double _desiredDeltaRadius;
+  double get desiredDeltaRadius => _desiredDeltaRadius;
+  void set desiredDeltaRadius(double value) {
+    assert(value != null);
+    if (_desiredDeltaRadius != value) {
+      _desiredDeltaRadius = value;
+      markNeedsLayout();
+    }
+  }
+
+  double _padding;
+  double get padding => _padding;
+  void set padding(double value) {
+    assert(value != null);
+    if (_padding != value) {
+      _padding = value;
+      markNeedsLayout();
+    }
+  }
+
+  void setParentData(RenderNode child) {
+    if (child.parentData is! SectorChildListParentData)
+      child.parentData = new SectorChildListParentData();
+  }
+
+  SectorDimensions getIntrinsicDimensions(SectorConstraints constraints, double radius) {
+    double outerDeltaRadius = constraints.constrainDeltaRadius(desiredDeltaRadius);
+    double innerDeltaRadius = outerDeltaRadius - padding * 2.0;
+    double childRadius = radius + padding;
+    double paddingTheta = math.atan(padding / (radius + outerDeltaRadius));
+    double innerTheta = paddingTheta; // increments with each child
+    double remainingTheta = constraints.maxDeltaTheta - (innerTheta + paddingTheta);
+    RenderSector child = firstChild;
+    while (child != null) {
+      SectorConstraints innerConstraints = new SectorConstraints(
+        maxDeltaRadius: innerDeltaRadius,
+        maxDeltaTheta: remainingTheta
+      );
+      SectorDimensions childDimensions = child.getIntrinsicDimensions(innerConstraints, childRadius);
+      innerTheta += childDimensions.deltaTheta;
+      remainingTheta -= childDimensions.deltaTheta;
+      assert(child.parentData is SectorChildListParentData);
+      child = child.parentData.nextSibling;
+      if (child != null) {
+        innerTheta += paddingTheta;
+        remainingTheta -= paddingTheta;
+      }
+    }
+    return new SectorDimensions.withConstraints(constraints,
+                                                deltaRadius: outerDeltaRadius,
+                                                deltaTheta: innerTheta);
+  }
+
+  SectorConstraints _constraints;
+  void layout(SectorConstraints constraints, double radius, { RenderNode relayoutSubtreeRoot }) {
+    if (relayoutSubtreeRoot != null)
+      saveRelayoutSubtreeRoot(relayoutSubtreeRoot);
+    relayoutSubtreeRoot = relayoutSubtreeRoot == null ? this : relayoutSubtreeRoot;
+    deltaRadius = constraints.constrainDeltaRadius(desiredDeltaRadius);
+    assert(deltaRadius < double.INFINITY);
+    _constraints = constraints;
+    internalLayout(radius, relayoutSubtreeRoot);
+  }
+
+  void relayout() {
+    assert(parentData is SectorParentData);
+    internalLayout(parentData.radius, this);
+  }
+
+  void internalLayout(double radius, RenderNode relayoutSubtreeRoot) {
+    double innerDeltaRadius = deltaRadius - padding * 2.0;
+    double childRadius = radius + padding;
+    double paddingTheta = math.atan(padding / (radius + deltaRadius));
+    double innerTheta = paddingTheta; // increments with each child
+    double remainingTheta = _constraints.maxDeltaTheta - (innerTheta + paddingTheta);
+    RenderSector child = firstChild;
+    while (child != null) {
+      SectorConstraints innerConstraints = new SectorConstraints(
+        maxDeltaRadius: innerDeltaRadius,
+        maxDeltaTheta: remainingTheta
+      );
+      child.layout(innerConstraints, childRadius, relayoutSubtreeRoot: relayoutSubtreeRoot);
+      assert(child.parentData is SectorParentData);
+      child.parentData.theta = innerTheta;
+      child.parentData.radius = childRadius;
+      innerTheta += child.deltaTheta;
+      remainingTheta -= child.deltaTheta;
+      assert(child.parentData is SectorChildListParentData);
+      child = child.parentData.nextSibling;
+      if (child != null) {
+        innerTheta += paddingTheta;
+        remainingTheta -= paddingTheta;
+      }
+    }
+    deltaTheta = innerTheta;
+  }
+
+  // TODO(ianh): hit testing et al is pending on adam's patch
+
+  // paint origin is 0,0 of our circle
+  // each sector then knows how to paint itself at its location
+  void paint(RenderNodeDisplayList canvas) {
+    super.paint(canvas);
+    RenderSector child = firstChild;
+    while (child != null) {
+      assert(child.parentData is SectorChildListParentData);
+      canvas.paintChild(child, 0.0, 0.0);
+      child = child.parentData.nextSibling;
+    }
+  }
+
+}
+
+class RenderBoxToRenderSectorAdapter extends RenderBox {
+
+  RenderBoxToRenderSectorAdapter({ double innerRadius: 0.0, RenderSector child }) :
+    _innerRadius = innerRadius {
+    _child = child;
+    adoptChild(_child);
+  }
+
+  double _innerRadius;
+  double get innerRadius => _innerRadius;
+  void set innerRadius(double value) {
+    _innerRadius = value;
+    markNeedsLayout();
+  }
+
+  RenderSector _child;
+  RenderSector get child => _child;
+  void set child(RenderSector value) {
+    if (_child != null)
+      dropChild(_child);
+    _child = value;
+    adoptChild(_child);
+    markNeedsLayout();
+  }
+
+  void setParentData(RenderNode child) {
+    if (child.parentData is! SectorParentData)
+      child.parentData = new SectorParentData();
+  }
+
+  BoxDimensions getIntrinsicDimensions(BoxConstraints constraints) {
+    if (child == null)
+      return new BoxDimensions.withConstraints(constraints, width: 0.0, height: 0.0);
+    assert(child is RenderSector);
+    assert(child.parentData is SectorParentData);
+    assert(!constraints.isInfinite);
+    double maxChildDeltaRadius = math.max(constraints.maxWidth, constraints.maxHeight) / 2.0 - innerRadius;
+    SectorDimensions childDimensions = child.getIntrinsicDimensions(new SectorConstraints(maxDeltaRadius: maxChildDeltaRadius), innerRadius);
+    double dimension = (innerRadius + childDimensions.deltaRadius) * 2.0;
+    return new BoxDimensions.withConstraints(constraints, width: dimension, height: dimension);
+  }
+
+  void layout(BoxConstraints constraints, { RenderNode relayoutSubtreeRoot }) {
+    if (relayoutSubtreeRoot != null)
+      saveRelayoutSubtreeRoot(relayoutSubtreeRoot);
+    relayoutSubtreeRoot = relayoutSubtreeRoot == null ? this : relayoutSubtreeRoot;
+    BoxDimensions ourDimensions;
+    if (child == null) {
+      ourDimensions = new BoxDimensions.withConstraints(constraints, width: 0.0, height: 0.0);
+    } else {
+      assert(child is RenderSector);
+      assert(child.parentData is SectorParentData);
+      assert(!constraints.isInfinite);
+      double maxChildDeltaRadius = math.min(constraints.maxWidth, constraints.maxHeight) / 2.0 - innerRadius;
+      child.layout(new SectorConstraints(maxDeltaRadius: maxChildDeltaRadius), innerRadius, relayoutSubtreeRoot: relayoutSubtreeRoot);
+      double dimension = (innerRadius + child.deltaRadius) * 2.0;
+      ourDimensions = new BoxDimensions.withConstraints(constraints, width: dimension, height: dimension);
+    }
+    width = ourDimensions.width;
+    height = ourDimensions.height;
+    print("adapter is: ${width}x${height}");
+    layoutDone();
+  }
+
+  double width;
+  double height;
+
+  // TODO(ianh): hit testing et al is pending on adam's patch
+
+  // paint origin is 0,0 of our circle
+  void paint(RenderNodeDisplayList canvas) {
+    super.paint(canvas);
+    if (child != null) {
+      print("painting child at ${width/2.0},${height/2.0}");
+      sky.Paint paint;
+      paint = new sky.Paint()..color = 0xFF474700;
+      canvas.drawRect(new sky.Rect()..setLTRB(0.0, 0.0, width, height), paint);
+      paint = new sky.Paint()..color = 0xFFF7F700;
+      canvas.drawRect(new sky.Rect()..setLTRB(10.0, 10.0, width-10.0, height-10.0), paint);
+      paint = new sky.Paint()..color = 0xFFFFFFFF;
+      canvas.drawRect(new sky.Rect()..setLTRB(width/2.0-5.0, height/2.0-5.0, width/2.0+5.0, height/2.0+5.0), paint);
+      canvas.paintChild(child, width/2.0, height/2.0);
+    }
+  }
+  
+}
+
+class RenderSolidColor extends RenderDecoratedSector {
+  final int backgroundColor;
+
+  RenderSolidColor(int backgroundColor)
+      : super(new BoxDecoration(backgroundColor: backgroundColor)),
+        backgroundColor = backgroundColor;
+
+  SectorDimensions getIntrinsicDimensions(SectorConstraints constraints, double radius) {
+    return new SectorDimensions.withConstraints(constraints, deltaTheta: 1.0); // 1.0 radians
+  }
+
+  void layout(SectorConstraints constraints, double radius, { RenderNode relayoutSubtreeRoot }) {
+    deltaRadius = constraints.constrainDeltaRadius(constraints.maxDeltaRadius);
+    deltaTheta = constraints.constrainDeltaTheta(1.0); // 1.0 radians
+    layoutDone();
+  }
+}
+
+RenderView renderView;
+
+void beginFrame(double timeStamp) {
+  RenderNode.flushLayout();
+
+  renderView.paintFrame();
+}
+
+bool handleEvent(sky.Event event) {
+  if (event is! sky.PointerEvent)
+    return false;
+  return renderView.handlePointer(event, x: event.x, y: event.y);
+}
+
+void main() {
+  print("test...");
+  sky.view.setEventCallback(handleEvent);
+  sky.view.setBeginFrameCallback(beginFrame);
+
+  var rootCircle = new RenderSectorRing(padding: 10.0);
+  rootCircle.add(new RenderSolidColor(0xFF00FF00));
+  rootCircle.add(new RenderSolidColor(0xFF0000FF));
+
+  var root = new RenderBoxToRenderSectorAdapter(innerRadius: 50.0, child: rootCircle);
+  renderView = new RenderView(root: root);
+  renderView.layout(newWidth: sky.view.width, newHeight: sky.view.height);
+
+  sky.view.scheduleFrame();
+  print("window is ${sky.view.width}x${sky.view.height}");
+}