Move Rectangle and Point into dart:math.

sdk/lib/math/rectangle.dart

+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+part of dart.math;
+
+/**
+ * A base class for representing two-dimensional axis-aligned rectangles.
+ */
+abstract class _RectangleBase<T extends num> {
+  const _RectangleBase();
+
+  /** The x-coordinate of the left edge. */
+  T get left;
+  /** The y-coordinate of the top edge. */
+  T get top;
+  /** The `width` of the rectangle. */
+  T get width;
+  /** The `height` of the rectangle. */
+  T get height;
+
+  /** The x-coordinate of the right edge. */
+  T get right => left + width;
+  /** The y-coordinate of the bottom edge. */
+  T get bottom => top + height;
+
+  String toString() {
+    return 'Rectangle ($left, $top) $width x $height';
+  }
+
+  bool operator ==(other) {
+    if (other is !Rectangle) return false;
+    return left == other.left && top == other.top && width == other.width &&
+        height == other.height;
+  }
+
+  int get hashCode => _JenkinsSmiHash.hash4(left.hashCode, top.hashCode,
+      width.hashCode, height.hashCode);
+
+  /**
+   * Computes the intersection of `this` and [other].
+   *
+   * The intersection of two axis-aligned rectangles, if any, is always another
+   * axis-aligned rectangle.
+   *
+   * Returns the intersection of this and `other`, or `null` if they don't
+   * intersect.
+   */
+  Rectangle<T> intersection(Rectangle<T> other) {
+    var x0 = max(left, other.left);
+    var x1 = min(left + width, other.left + other.width);
+
+    if (x0 <= x1) {
+      var y0 = max(top, other.top);
+      var y1 = min(top + height, other.top + other.height);
+
+      if (y0 <= y1) {
+        return new Rectangle<T>(x0, y0, x1 - x0, y1 - y0);
+      }
+    }
+    return null;
+  }
+
+
+  /**
+   * Returns true if `this` intersects [other].
+   */
+  bool intersects(Rectangle<num> other) {
+    return (left <= other.left + other.width &&
+        other.left <= left + width &&
+        top <= other.top + other.height &&
+        other.top <= top + height);
+  }
+
+  /**
+   * Returns a new rectangle which completely contains `this` and [other].
+   */
+  Rectangle<T> boundingBox(Rectangle<T> other) {
+    var right = max(this.left + this.width, other.left + other.width);
+    var bottom = max(this.top + this.height, other.top + other.height);
+
+    var left = min(this.left, other.left);
+    var top = min(this.top, other.top);
+
+    return new Rectangle<T>(left, top, right - left, bottom - top);
+  }
+
+  /**
+   * Tests whether `this` entirely contains [another].
+   */
+  bool contains(Rectangle<num> another) {
+    return left <= another.left &&
+           left + width >= another.left + another.width &&
+           top <= another.top &&
+           top + height >= another.top + another.height;
+  }
+
+  /**
+   * Tests whether [another] is inside or along the edges of `this`.
+   */
+  bool containsPoint(Point<num> another) {
+    return another.x >= left &&
+           another.x <= left + width &&
+           another.y >= top &&
+           another.y <= top + height;
+  }
+
+  Point<T> get topLeft => new Point<T>(this.left, this.top);
+  Point<T> get topRight => new Point<T>(this.left + this.width, this.top);
+  Point<T> get bottomRight => new Point<T>(this.left + this.width,
+      this.top + this.height);
+  Point<T> get bottomLeft => new Point<T>(this.left,
+      this.top + this.height);
+}
+
+
+/**
+ * A class for representing two-dimensional rectangles whose properties are
+ * immutable.
+ */
+class Rectangle<T extends num> extends _RectangleBase<T> {
+  final T left;
+  final T top;
+  final T width;
+  final T height;
+
+  const Rectangle(this.left, this.top, this.width, this.height);
+
+  factory Rectangle.fromPoints(Point<T> a, Point<T> b) {
+    T left = min(a.x, b.x);
+    T width = max(a.x, b.x) - left;
+    T top = min(a.y, b.y);
+    T height = max(a.y, b.y) - top;
+    return new Rectangle<T>(left, top, width, height);
+  }
+}
+
+/**
+ * A class for representing two-dimensional axis-aligned rectangles with mutable
+ * properties.
+ */
+class MutableRectangle<T extends num>  extends _RectangleBase<T>
+    implements Rectangle<T> {
+  T left;
+  T top;
+  T width;
+  T height;
+
+  MutableRectangle(this.left, this.top, this.width, this.height);
+
+  factory MutableRectangle.fromPoints(Point<T> a, Point<T> b) {
+    T left = min(a.x, b.x);
+    T width = max(a.x, b.x) - left;
+    T top = min(a.y, b.y);
+    T height = max(a.y, b.y) - top;
+    return new MutableRectangle<T>(left, top, width, height);
+  }
+}

[siva, 2013/10/08 22:05:30]

Wouldn't it make more sense to call the classes :

ImmutableRectangle
Rectangle

Currently Rectangle does not seem to convey the fact that it is immutable.

[Emily Fortuna, 2013/10/08 22:20:27]

We convey immutability that in the documentation. And we have the immutable
version simply called "Rectangle" to encourage users to use that one, as it is
more performant, which would generally be more desirable if you're in the
dart:math class.