canvas/lib/context2d.js

Canvas graphics API backed by Cairo

'use strict';

/*!
 * Canvas - Context2d
 * Copyright (c) 2010 LearnBoost <tj@learnboost.com>
 * MIT Licensed
 */

/**
 * Module dependencies.
 */

const bindings = require('./bindings')
const parseFont = require('./parse-font')
const Context2d = module.exports = bindings.CanvasRenderingContext2d
const CanvasGradient = bindings.CanvasGradient
const CanvasPattern = bindings.CanvasPattern
const ImageData = bindings.ImageData
const DOMMatrix = require('./DOMMatrix').DOMMatrix

/**
 * Text baselines.
 */

var baselines = ['alphabetic', 'top', 'bottom', 'middle', 'ideographic', 'hanging'];

/**
 * Create a pattern from `Image` or `Canvas`.
 *
 * @param {Image|Canvas} image
 * @param {String} repetition
 * @return {CanvasPattern}
 * @api public
 */

Context2d.prototype.createPattern = function(image, repetition){
  return new CanvasPattern(image, repetition || 'repeat');
};

/**
 * Create a linear gradient at the given point `(x0, y0)` and `(x1, y1)`.
 *
 * @param {Number} x0
 * @param {Number} y0
 * @param {Number} x1
 * @param {Number} y1
 * @return {CanvasGradient}
 * @api public
 */

Context2d.prototype.createLinearGradient = function(x0, y0, x1, y1){
  return new CanvasGradient(x0, y0, x1, y1);
};

/**
 * Create a radial gradient at the given point `(x0, y0)` and `(x1, y1)`
 * and radius `r0` and `r1`.
 *
 * @param {Number} x0
 * @param {Number} y0
 * @param {Number} r0
 * @param {Number} x1
 * @param {Number} y1
 * @param {Number} r1
 * @return {CanvasGradient}
 * @api public
 */

Context2d.prototype.createRadialGradient = function(x0, y0, r0, x1, y1, r1){
  return new CanvasGradient(x0, y0, r0, x1, y1, r1);
};

/**
 * Reset transform matrix to identity, then apply the given args.
 *
 * @param {...}
 * @api public
 */

Context2d.prototype.setTransform = function(){
  this.resetTransform();
  this.transform.apply(this, arguments);
};

Object.defineProperty(Context2d.prototype, 'currentTransform', {
  get: function () {
    var values = new Float64Array(6)
    this._getMatrix(values)
    return new DOMMatrix(values)
  },
  set: function (m) {
    if (!(m instanceof DOMMatrix)) {
      throw new TypeError('Expected DOMMatrix')
    }
    this.setTransform(m.a, m.b, m.c, m.d, m.e, m.f)
  },
  configurable: true
})

/**
 * Set the fill style with the given css color string.
 *
 * @api public
 */

Context2d.prototype.__defineSetter__('fillStyle', function(val){
  if (val instanceof CanvasGradient
    || val instanceof CanvasPattern) {
    this.lastFillStyle = val;
    this._setFillPattern(val);
  } else {
    this.lastFillStyle = undefined;
    this._setFillColor(String(val));
  }
});

/**
 * Get previous fill style.
 *
 * @return {CanvasGradient|String}
 * @api public
 */

Context2d.prototype.__defineGetter__('fillStyle', function(){
  return this.lastFillStyle || this.fillColor;
});

/**
 * Set the stroke style with the given css color string.
 *
 * @api public
 */

Context2d.prototype.__defineSetter__('strokeStyle', function(val){
  if (val instanceof CanvasGradient
    || val instanceof CanvasPattern) {
    this.lastStrokeStyle = val;
    this._setStrokePattern(val);
  } else {
    this._setStrokeColor(String(val));
  }
});

/**
 * Get previous stroke style.
 *
 * @return {CanvasGradient|String}
 * @api public
 */

Context2d.prototype.__defineGetter__('strokeStyle', function(){
  return this.lastStrokeStyle || this.strokeColor;
});

/**
 * Set font.
 *
 * @see exports.parseFont()
 * @api public
 */

Context2d.prototype.__defineSetter__('font', function(val){
  if (!val) return;
  if ('string' == typeof val) {
    var font;
    if (font = parseFont(val)) {
      this.lastFontString = val;
      this._setFont(
          font.weight
        , font.style
        , font.size
        , font.unit
        , font.family);
    }
  }
});

/**
 * Get the current font.
 *
 * @api public
 */

Context2d.prototype.__defineGetter__('font', function(){
  return this.lastFontString || '10px sans-serif';
});

/**
 * Set text baseline.
 *
 * @api public
 */

Context2d.prototype.__defineSetter__('textBaseline', function(val){
  if (!val) return;
  var n = baselines.indexOf(val);
  if (~n) {
    this.lastBaseline = val;
    this._setTextBaseline(n);
  }
});

/**
 * Get the current baseline setting.
 *
 * @api public
 */

Context2d.prototype.__defineGetter__('textBaseline', function(){
  return this.lastBaseline || 'alphabetic';
});

/**
 * Set text alignment.
 *
 * @api public
 */

Context2d.prototype.__defineSetter__('textAlign', function(val){
  switch (val) {
    case 'center':
      this._setTextAlignment(0);
      this.lastTextAlignment = val;
      break;
    case 'left':
    case 'start':
      this._setTextAlignment(-1);
      this.lastTextAlignment = val;
      break;
    case 'right':
    case 'end':
      this._setTextAlignment(1);
      this.lastTextAlignment = val;
      break;
  }
});

/**
 * Get the current font.
 *
 * @see exports.parseFont()
 * @api public
 */

Context2d.prototype.__defineGetter__('textAlign', function(){
  return this.lastTextAlignment || 'start';
});

/**
 * Create `ImageData` with the given dimensions or
 * `ImageData` instance for dimensions.
 *
 * @param {Number|ImageData} width
 * @param {Number} height
 * @return {ImageData}
 * @api public
 */

Context2d.prototype.createImageData = function (width, height) {
  if (typeof width === 'object') {
    height = width.height
    width = width.width
  }
  var Bpp = this.canvas.stride / this.canvas.width;
  var nBytes = Bpp * width * height
  var arr;
  if (this.pixelFormat === "RGB16_565") {
    arr = new Uint16Array(nBytes / 2);
  } else {
    arr = new Uint8ClampedArray(nBytes);
  }
  return new ImageData(arr, width, height);
}