px-vis-canvas.html

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you may not use this file except in compliance with the License.
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    http://www.apache.org/licenses/LICENSE-2.0

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<link rel="import" href="../polymer/polymer.html"/>
<link rel="import" href="px-vis-behavior-common.html" />
<link rel="import" href="px-vis-behavior-d3.html" />
<link rel="import" href="css/px-vis-styles.html">

<!--

### Usage

    <px-vis-canvas
        canvas-context="{{canvasContext}}"
        width="[[width]]"
        height="[[height]]"
        margin="[[margin]]"
        offset="[[offset]]">
    </px-vis-canvas>

@element px-vis-canvas
@blurb Element which creates a canvas element
@homepage index.html
@demo demo.html
-->

<dom-module id="px-vis-canvas">

    <template>
      <style include="px-vis-styles"></style>

      <canvas
        id="chartCanvas"
        width="[[width]]"
        height="[[height]]">
      </canvas>
    </template>
</dom-module>

<script>

  Polymer({

    is: 'px-vis-canvas',

    /****** EVENTS ******/
    /**
     * Fired once d3 canvas context has been configured.
     *
     * Uses the px-vis-behavior-chart behavior, for listening and setting property, locally or globally.
     * Detail includes:
     *
     * ```
     * { 'data': canvasContext }
     * ```
     *
     * @event px-vis-canvas-context-updated
     */

    behaviors: [
      PxVisBehavior.observerCheck,
      PxVisBehavior.sizing,
      PxVisBehavior.commonMethods,
      PxVisBehaviorD3.canvasContext
    ],

    /**
     * Properties block, expose attribute values to the DOM via 'reflect'
     *
     * @property properties
     * @type Object
     */
    properties: {
      /**
       * The canvas element
       *
       *
       */
      _canvas:{
        type:Object
      }
    },

    observers: [
      '_setCanvas(width,height,margin,offset.*)'
    ],

    /**
    * when attached, re-fire set properties for precipitation pattern, as well as the svg element that's inside px-svg.
    *
    * @method attached
    */
    attached: function(){
      if(this._doesObjHaveValues(this.canvasContext)){
        this.fire('px-vis-canvas-context-updated',{ 'data': this.canvasContext, 'dataVar': 'canvasContext', 'method': 'set' });
      }
    },
    detached: function() {
      if(this.canvasContext) {
        this.canvasContext.pxClearCanvas();
      }
    },
    /**
     * Configures the canvas and context
     *
     */
    _setCanvas: function(){
     if(this.hasUndefinedArguments(arguments)) {
       return;
     }

      if(this.width && this.height && this._doesObjHaveValues(this.margin)) {
        if(this.canvasContext) {
          this._reCenterCanvas();
        } else {
          this._createCanvaContext();
        }
      }
    },

    _reCenterCanvas: function() {
      this.canvasContext.setTransform(1, 0, 0, 1, 0, 0);
      this.canvasContext.translate(this.margin.left + this.offset[0], this.margin.top + this.offset[1]);
      this.canvasContext._translation = [this.margin.left + this.offset[0], this.margin.top + this.offset[1]];

      this.fire('px-vis-canvas-context-updated',{ 'data': this.canvasContext, 'dataVar': 'canvasContext', 'method': 'set' });
    },

    _createCanvaContext: function() {
      var context;

      this._canvas = this.$.chartCanvas;

      context = this._canvas.getContext("2d");

      //reset translation so subsequent calls do not keep shifting canvas drawings
      context.setTransform(1, 0, 0, 1, 0, 0);
      context.translate(this.margin.left + this.offset[0], this.margin.top + this.offset[1]);

      context._translation = [this.margin.left + this.offset[0], this.margin.top + this.offset[1]];

      context.pxClearCanvas = function() {
        this.save()
        this.setTransform(1, 0, 0, 1, 0, 0);
        this.clearRect(0,0, this.canvas.width, this.canvas.height);
        this.restore();
      }.bind(context);

      this.set('canvasContext',context);
      this.fire('px-vis-canvas-context-updated',{ 'data': context, 'dataVar': 'canvasContext', 'method': 'set' });
    }
  });
</script>