gecko-dev/toolkit/modules/Geometry.jsm

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

var EXPORTED_SYMBOLS = ["Point", "Rect"];

/**
 * Simple Point class.
 *
 * Any method that takes an x and y may also take a point.
 */
function Point(x, y) {
  this.set(x, y);
}

Point.prototype = {
  clone: function clone() {
    return new Point(this.x, this.y);
  },

  set: function set(x, y) {
    this.x = x;
    this.y = y;
    return this;
  },

  equals: function equals(x, y) {
    return this.x == x && this.y == y;
  },

  toString: function toString() {
    return "(" + this.x + "," + this.y + ")";
  },

  map: function map(f) {
    this.x = f.call(this, this.x);
    this.y = f.call(this, this.y);
    return this;
  },

  add: function add(x, y) {
    this.x += x;
    this.y += y;
    return this;
  },

  subtract: function subtract(x, y) {
    this.x -= x;
    this.y -= y;
    return this;
  },

  scale: function scale(s) {
    this.x *= s;
    this.y *= s;
    return this;
  },

  isZero() {
    return this.x == 0 && this.y == 0;
  },
};

(function() {
  function takePointOrArgs(f) {
    return function(arg1, arg2) {
      if (arg2 === undefined) {
        return f.call(this, arg1.x, arg1.y);
      }
      return f.call(this, arg1, arg2);
    };
  }

  for (let f of ["add", "subtract", "equals", "set"]) {
    Point.prototype[f] = takePointOrArgs(Point.prototype[f]);
  }
})();

/**
 * Rect is a simple data structure for representation of a rectangle supporting
 * many basic geometric operations.
 *
 * NOTE: Since its operations are closed, rectangles may be empty and will report
 * non-positive widths and heights in that case.
 */

function Rect(x, y, w, h) {
  this.left = x;
  this.top = y;
  this.right = x + w;
  this.bottom = y + h;
}

Rect.fromRect = function fromRect(r) {
  return new Rect(r.left, r.top, r.right - r.left, r.bottom - r.top);
};

Rect.prototype = {
  get x() {
    return this.left;
  },
  get y() {
    return this.top;
  },
  get width() {
    return this.right - this.left;
  },
  get height() {
    return this.bottom - this.top;
  },
  set x(v) {
    let diff = this.left - v;
    this.left = v;
    this.right -= diff;
  },
  set y(v) {
    let diff = this.top - v;
    this.top = v;
    this.bottom -= diff;
  },
  set width(v) {
    this.right = this.left + v;
  },
  set height(v) {
    this.bottom = this.top + v;
  },

  isEmpty: function isEmpty() {
    return this.left >= this.right || this.top >= this.bottom;
  },

  setRect(x, y, w, h) {
    this.left = x;
    this.top = y;
    this.right = x + w;
    this.bottom = y + h;

    return this;
  },

  setBounds(l, t, r, b) {
    this.top = t;
    this.left = l;
    this.bottom = b;
    this.right = r;

    return this;
  },

  equals: function equals(other) {
    return (
      other != null &&
      ((this.isEmpty() && other.isEmpty()) ||
        (this.top == other.top &&
          this.left == other.left &&
          this.bottom == other.bottom &&
          this.right == other.right))
    );
  },

  clone: function clone() {
    return new Rect(
      this.left,
      this.top,
      this.right - this.left,
      this.bottom - this.top
    );
  },

  center: function center() {
    if (this.isEmpty()) {
      throw new Error("Empty rectangles do not have centers");
    }
    return new Point(
      this.left + (this.right - this.left) / 2,
      this.top + (this.bottom - this.top) / 2
    );
  },

  copyFrom(other) {
    this.top = other.top;
    this.left = other.left;
    this.bottom = other.bottom;
    this.right = other.right;

    return this;
  },

  translate(x, y) {
    this.left += x;
    this.right += x;
    this.top += y;
    this.bottom += y;

    return this;
  },

  toString() {
    return (
      "[" + this.x + "," + this.y + "," + this.width + "," + this.height + "]"
    );
  },

  /** return a new rect that is the union of that one and this one */
  union(other) {
    return this.clone().expandToContain(other);
  },

  contains(other) {
    if (other.isEmpty()) {
      return true;
    }
    if (this.isEmpty()) {
      return false;
    }

    return (
      other.left >= this.left &&
      other.right <= this.right &&
      other.top >= this.top &&
      other.bottom <= this.bottom
    );
  },

  intersect(other) {
    return this.clone().restrictTo(other);
  },

  intersects(other) {
    if (this.isEmpty() || other.isEmpty()) {
      return false;
    }

    let x1 = Math.max(this.left, other.left);
    let x2 = Math.min(this.right, other.right);
    let y1 = Math.max(this.top, other.top);
    let y2 = Math.min(this.bottom, other.bottom);
    return x1 < x2 && y1 < y2;
  },

  /** Restrict area of this rectangle to the intersection of both rectangles. */
  restrictTo: function restrictTo(other) {
    if (this.isEmpty() || other.isEmpty()) {
      return this.setRect(0, 0, 0, 0);
    }

    let x1 = Math.max(this.left, other.left);
    let x2 = Math.min(this.right, other.right);
    let y1 = Math.max(this.top, other.top);
    let y2 = Math.min(this.bottom, other.bottom);
    // If width or height is 0, the intersection was empty.
    return this.setRect(x1, y1, Math.max(0, x2 - x1), Math.max(0, y2 - y1));
  },

  /** Expand this rectangle to the union of both rectangles. */
  expandToContain: function expandToContain(other) {
    if (this.isEmpty()) {
      return this.copyFrom(other);
    }
    if (other.isEmpty()) {
      return this;
    }

    let l = Math.min(this.left, other.left);
    let r = Math.max(this.right, other.right);
    let t = Math.min(this.top, other.top);
    let b = Math.max(this.bottom, other.bottom);
    return this.setRect(l, t, r - l, b - t);
  },

  /**
   * Expands to the smallest rectangle that contains original rectangle and is bounded
   * by lines with integer coefficients.
   */
  expandToIntegers: function round() {
    this.left = Math.floor(this.left);
    this.top = Math.floor(this.top);
    this.right = Math.ceil(this.right);
    this.bottom = Math.ceil(this.bottom);
    return this;
  },

  scale: function scale(xscl, yscl) {
    this.left *= xscl;
    this.right *= xscl;
    this.top *= yscl;
    this.bottom *= yscl;
    return this;
  },

  map: function map(f) {
    this.left = f.call(this, this.left);
    this.top = f.call(this, this.top);
    this.right = f.call(this, this.right);
    this.bottom = f.call(this, this.bottom);
    return this;
  },

  /** Ensure this rectangle is inside the other, if possible. Preserves w, h. */
  translateInside: function translateInside(other) {
    let offsetX = 0;
    if (this.left <= other.left) {
      offsetX = other.left - this.left;
    } else if (this.right > other.right) {
      offsetX = other.right - this.right;
    }

    let offsetY = 0;
    if (this.top <= other.top) {
      offsetY = other.top - this.top;
    } else if (this.bottom > other.bottom) {
      offsetY = other.bottom - this.bottom;
    }

    return this.translate(offsetX, offsetY);
  },

  /** Subtract other area from this. Returns array of rects whose union is this-other. */
  subtract: function subtract(other) {
    let r = new Rect(0, 0, 0, 0);
    let result = [];
    other = other.intersect(this);
    if (other.isEmpty()) {
      return [this.clone()];
    }

    // left strip
    r.setBounds(this.left, this.top, other.left, this.bottom);
    if (!r.isEmpty()) {
      result.push(r.clone());
    }
    // inside strip
    r.setBounds(other.left, this.top, other.right, other.top);
    if (!r.isEmpty()) {
      result.push(r.clone());
    }
    r.setBounds(other.left, other.bottom, other.right, this.bottom);
    if (!r.isEmpty()) {
      result.push(r.clone());
    }
    // right strip
    r.setBounds(other.right, this.top, this.right, this.bottom);
    if (!r.isEmpty()) {
      result.push(r.clone());
    }

    return result;
  },

  /**
   * Blends two rectangles together.
   * @param rect Rectangle to blend this one with
   * @param scalar Ratio from 0 (returns a clone of this rect) to 1 (clone of rect).
   * @return New blended rectangle.
   */
  blend: function blend(rect, scalar) {
    return new Rect(
      this.left + (rect.left - this.left) * scalar,
      this.top + (rect.top - this.top) * scalar,
      this.width + (rect.width - this.width) * scalar,
      this.height + (rect.height - this.height) * scalar
    );
  },

  /**
   * Grows or shrinks the rectangle while keeping the center point.
   * Accepts single multipler, or separate for both axes.
   */
  inflate: function inflate(xscl, yscl) {
    let xAdj = (this.width * xscl - this.width) / 2;
    let s = arguments.length > 1 ? yscl : xscl;
    let yAdj = (this.height * s - this.height) / 2;
    this.left -= xAdj;
    this.right += xAdj;
    this.top -= yAdj;
    this.bottom += yAdj;
    return this;
  },

  /**
   * Grows or shrinks the rectangle by fixed amount while keeping the center point.
   * Accepts single fixed amount
   */
  inflateFixed: function inflateFixed(fixed) {
    this.left -= fixed;
    this.right += fixed;
    this.top -= fixed;
    this.bottom += fixed;
    return this;
  },
};