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[dygraphs.git] / plugins / grid.js
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1/**
2 * @license
3 * Copyright 2012 Dan Vanderkam (danvdk@gmail.com)
4 * MIT-licensed (http://opensource.org/licenses/MIT)
5 */
6
7Dygraph.Plugins.Grid = (function() {
8
9/*
10
11Current bits of jankiness:
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12- Direct layout access
13- Direct area access
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14
15*/
16
17"use strict";
18
19
20/**
21 * Draws the gridlines, i.e. the gray horizontal & vertical lines running the
22 * length of the chart.
23 *
24 * @constructor
25 */
26var grid = function() {
27};
28
29grid.prototype.toString = function() {
30 return "Gridline Plugin";
31};
32
33grid.prototype.activate = function(g) {
34 return {
98eb4713 35 willDrawChart: this.willDrawChart
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36 };
37};
38
98eb4713 39grid.prototype.willDrawChart = function(e) {
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40 // Draw the new X/Y grid. Lines appear crisper when pixels are rounded to
41 // half-integers. This prevents them from drawing in two rows/cols.
42 var g = e.dygraph;
43 var ctx = e.drawingContext;
44 var layout = g.layout_;
45 var area = e.dygraph.plotter_.area;
46
47 function halfUp(x) { return Math.round(x) + 0.5; }
48 function halfDown(y){ return Math.round(y) - 0.5; }
49
50 var x, y, i, ticks;
51 if (g.getOption('drawYGrid')) {
52 ticks = layout.yticks;
53 ctx.save();
54 ctx.strokeStyle = g.getOption('gridLineColor');
55 ctx.lineWidth = g.getOption('gridLineWidth');
56 for (i = 0; i < ticks.length; i++) {
57 // TODO(danvk): allow secondary axes to draw a grid, too.
58 if (ticks[i][0] !== 0) continue;
59 x = halfUp(area.x);
60 y = halfDown(area.y + ticks[i][1] * area.h);
61 ctx.beginPath();
62 ctx.moveTo(x, y);
63 ctx.lineTo(x + area.w, y);
64 ctx.closePath();
65 ctx.stroke();
66 }
67 ctx.restore();
68 }
69
70 if (g.getOption('drawXGrid')) {
71 ticks = layout.xticks;
72 ctx.save();
73 ctx.strokeStyle = g.getOption('gridLineColor');
74 ctx.lineWidth = g.getOption('gridLineWidth');
75 for (i = 0; i < ticks.length; i++) {
76 x = halfUp(area.x + ticks[i][0] * area.w);
77 y = halfDown(area.y + area.h);
78 ctx.beginPath();
79 ctx.moveTo(x, y);
80 ctx.lineTo(x, area.y);
81 ctx.closePath();
82 ctx.stroke();
83 }
84 ctx.restore();
85 }
86}
87
88grid.prototype.destroy = function() {
89};
90
91return grid;
92
93})();