1 | /* Flot plugin for drawing all elements of a plot on the canvas. |
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2 | |
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3 | Copyright (c) 2007-2013 IOLA and Ole Laursen. |
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4 | Licensed under the MIT license. |
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5 | |
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6 | Flot normally produces certain elements, like axis labels and the legend, using |
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7 | HTML elements. This permits greater interactivity and customization, and often |
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8 | looks better, due to cross-browser canvas text inconsistencies and limitations. |
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9 | |
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10 | It can also be desirable to render the plot entirely in canvas, particularly |
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11 | if the goal is to save it as an image, or if Flot is being used in a context |
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12 | where the HTML DOM does not exist, as is the case within Node.js. This plugin |
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13 | switches out Flot's standard drawing operations for canvas-only replacements. |
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14 | |
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15 | Currently the plugin supports only axis labels, but it will eventually allow |
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16 | every element of the plot to be rendered directly to canvas. |
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17 | |
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18 | The plugin supports these options: |
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19 | |
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20 | { |
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21 | canvas: boolean |
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22 | } |
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23 | |
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24 | The "canvas" option controls whether full canvas drawing is enabled, making it |
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25 | possible to toggle on and off. This is useful when a plot uses HTML text in the |
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26 | browser, but needs to redraw with canvas text when exporting as an image. |
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27 | |
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28 | */ |
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29 | |
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30 | (function($) { |
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31 | |
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32 | var options = { |
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33 | canvas: true |
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34 | }; |
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35 | |
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36 | var render, getTextInfo, addText; |
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37 | |
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38 | // Cache the prototype hasOwnProperty for faster access |
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39 | |
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40 | var hasOwnProperty = Object.prototype.hasOwnProperty; |
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41 | |
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42 | function init(plot, classes) { |
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43 | |
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44 | var Canvas = classes.Canvas; |
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45 | |
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46 | // We only want to replace the functions once; the second time around |
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47 | // we would just get our new function back. This whole replacing of |
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48 | // prototype functions is a disaster, and needs to be changed ASAP. |
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49 | |
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50 | if (render == null) { |
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51 | getTextInfo = Canvas.prototype.getTextInfo, |
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52 | addText = Canvas.prototype.addText, |
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53 | render = Canvas.prototype.render; |
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54 | } |
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55 | |
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56 | // Finishes rendering the canvas, including overlaid text |
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57 | |
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58 | Canvas.prototype.render = function() { |
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59 | |
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60 | if (!plot.getOptions().canvas) { |
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61 | return render.call(this); |
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62 | } |
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63 | |
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64 | var context = this.context, |
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65 | cache = this._textCache; |
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66 | |
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67 | // For each text layer, render elements marked as active |
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68 | |
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69 | context.save(); |
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70 | context.textBaseline = "middle"; |
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71 | |
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72 | for (var layerKey in cache) { |
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73 | if (hasOwnProperty.call(cache, layerKey)) { |
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74 | var layerCache = cache[layerKey]; |
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75 | for (var styleKey in layerCache) { |
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76 | if (hasOwnProperty.call(layerCache, styleKey)) { |
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77 | var styleCache = layerCache[styleKey], |
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78 | updateStyles = true; |
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79 | for (var key in styleCache) { |
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80 | if (hasOwnProperty.call(styleCache, key)) { |
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81 | |
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82 | var info = styleCache[key], |
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83 | positions = info.positions, |
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84 | lines = info.lines; |
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85 | |
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86 | // Since every element at this level of the cache have the |
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87 | // same font and fill styles, we can just change them once |
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88 | // using the values from the first element. |
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89 | |
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90 | if (updateStyles) { |
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91 | context.fillStyle = info.font.color; |
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92 | context.font = info.font.definition; |
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93 | updateStyles = false; |
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94 | } |
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95 | |
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96 | for (var i = 0, position; position = positions[i]; i++) { |
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97 | if (position.active) { |
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98 | for (var j = 0, line; line = position.lines[j]; j++) { |
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99 | context.fillText(lines[j].text, line[0], line[1]); |
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100 | } |
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101 | } else { |
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102 | positions.splice(i--, 1); |
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103 | } |
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104 | } |
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105 | |
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106 | if (positions.length == 0) { |
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107 | delete styleCache[key]; |
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108 | } |
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109 | } |
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110 | } |
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111 | } |
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112 | } |
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113 | } |
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114 | } |
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115 | |
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116 | context.restore(); |
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117 | }; |
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118 | |
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119 | // Creates (if necessary) and returns a text info object. |
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120 | // |
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121 | // When the canvas option is set, the object looks like this: |
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122 | // |
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123 | // { |
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124 | // width: Width of the text's bounding box. |
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125 | // height: Height of the text's bounding box. |
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126 | // positions: Array of positions at which this text is drawn. |
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127 | // lines: [{ |
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128 | // height: Height of this line. |
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129 | // widths: Width of this line. |
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130 | // text: Text on this line. |
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131 | // }], |
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132 | // font: { |
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133 | // definition: Canvas font property string. |
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134 | // color: Color of the text. |
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135 | // }, |
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136 | // } |
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137 | // |
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138 | // The positions array contains objects that look like this: |
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139 | // |
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140 | // { |
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141 | // active: Flag indicating whether the text should be visible. |
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142 | // lines: Array of [x, y] coordinates at which to draw the line. |
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143 | // x: X coordinate at which to draw the text. |
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144 | // y: Y coordinate at which to draw the text. |
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145 | // } |
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146 | |
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147 | Canvas.prototype.getTextInfo = function(layer, text, font, angle, width) { |
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148 | |
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149 | if (!plot.getOptions().canvas) { |
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150 | return getTextInfo.call(this, layer, text, font, angle, width); |
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151 | } |
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152 | |
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153 | var textStyle, layerCache, styleCache, info; |
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154 | |
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155 | // Cast the value to a string, in case we were given a number |
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156 | |
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157 | text = "" + text; |
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158 | |
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159 | // If the font is a font-spec object, generate a CSS definition |
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160 | |
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161 | if (typeof font === "object") { |
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162 | textStyle = font.style + " " + font.variant + " " + font.weight + " " + font.size + "px " + font.family; |
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163 | } else { |
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164 | textStyle = font; |
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165 | } |
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166 | |
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167 | // Retrieve (or create) the cache for the text's layer and styles |
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168 | |
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169 | layerCache = this._textCache[layer]; |
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170 | |
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171 | if (layerCache == null) { |
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172 | layerCache = this._textCache[layer] = {}; |
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173 | } |
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174 | |
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175 | styleCache = layerCache[textStyle]; |
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176 | |
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177 | if (styleCache == null) { |
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178 | styleCache = layerCache[textStyle] = {}; |
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179 | } |
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180 | |
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181 | info = styleCache[text]; |
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182 | |
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183 | if (info == null) { |
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184 | |
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185 | var context = this.context; |
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186 | |
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187 | // If the font was provided as CSS, create a div with those |
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188 | // classes and examine it to generate a canvas font spec. |
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189 | |
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190 | if (typeof font !== "object") { |
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191 | |
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192 | var element = $("<div> </div>") |
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193 | .css("position", "absolute") |
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194 | .addClass(typeof font === "string" ? font : null) |
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195 | .appendTo(this.getTextLayer(layer)); |
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196 | |
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197 | font = { |
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198 | lineHeight: element.height(), |
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199 | style: element.css("font-style"), |
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200 | variant: element.css("font-variant"), |
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201 | weight: element.css("font-weight"), |
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202 | family: element.css("font-family"), |
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203 | color: element.css("color") |
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204 | }; |
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205 | |
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206 | // Setting line-height to 1, without units, sets it equal |
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207 | // to the font-size, even if the font-size is abstract, |
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208 | // like 'smaller'. This enables us to read the real size |
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209 | // via the element's height, working around browsers that |
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210 | // return the literal 'smaller' value. |
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211 | |
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212 | font.size = element.css("line-height", 1).height(); |
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213 | |
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214 | element.remove(); |
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215 | } |
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216 | |
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217 | textStyle = font.style + " " + font.variant + " " + font.weight + " " + font.size + "px " + font.family; |
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218 | |
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219 | // Create a new info object, initializing the dimensions to |
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220 | // zero so we can count them up line-by-line. |
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221 | |
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222 | info = styleCache[text] = { |
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223 | width: 0, |
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224 | height: 0, |
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225 | positions: [], |
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226 | lines: [], |
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227 | font: { |
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228 | definition: textStyle, |
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229 | color: font.color |
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230 | } |
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231 | }; |
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232 | |
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233 | context.save(); |
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234 | context.font = textStyle; |
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235 | |
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236 | // Canvas can't handle multi-line strings; break on various |
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237 | // newlines, including HTML brs, to build a list of lines. |
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238 | // Note that we could split directly on regexps, but IE < 9 is |
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239 | // broken; revisit when we drop IE 7/8 support. |
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240 | |
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241 | var lines = (text + "").replace(/<br ?\/?>|\r\n|\r/g, "\n").split("\n"); |
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242 | |
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243 | for (var i = 0; i < lines.length; ++i) { |
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244 | |
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245 | var lineText = lines[i], |
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246 | measured = context.measureText(lineText); |
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247 | |
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248 | info.width = Math.max(measured.width, info.width); |
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249 | info.height += font.lineHeight; |
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250 | |
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251 | info.lines.push({ |
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252 | text: lineText, |
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253 | width: measured.width, |
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254 | height: font.lineHeight |
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255 | }); |
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256 | } |
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257 | |
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258 | context.restore(); |
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259 | } |
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260 | |
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261 | return info; |
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262 | }; |
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263 | |
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264 | // Adds a text string to the canvas text overlay. |
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265 | |
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266 | Canvas.prototype.addText = function(layer, x, y, text, font, angle, width, halign, valign) { |
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267 | |
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268 | if (!plot.getOptions().canvas) { |
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269 | return addText.call(this, layer, x, y, text, font, angle, width, halign, valign); |
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270 | } |
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271 | |
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272 | var info = this.getTextInfo(layer, text, font, angle, width), |
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273 | positions = info.positions, |
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274 | lines = info.lines; |
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275 | |
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276 | // Text is drawn with baseline 'middle', which we need to account |
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277 | // for by adding half a line's height to the y position. |
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278 | |
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279 | y += info.height / lines.length / 2; |
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280 | |
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281 | // Tweak the initial y-position to match vertical alignment |
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282 | |
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283 | if (valign == "middle") { |
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284 | y = Math.round(y - info.height / 2); |
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285 | } else if (valign == "bottom") { |
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286 | y = Math.round(y - info.height); |
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287 | } else { |
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288 | y = Math.round(y); |
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289 | } |
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290 | |
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291 | // FIXME: LEGACY BROWSER FIX |
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292 | // AFFECTS: Opera < 12.00 |
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293 | |
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294 | // Offset the y coordinate, since Opera is off pretty |
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295 | // consistently compared to the other browsers. |
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296 | |
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297 | if (!!(window.opera && window.opera.version().split(".")[0] < 12)) { |
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298 | y -= 2; |
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299 | } |
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300 | |
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301 | // Determine whether this text already exists at this position. |
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302 | // If so, mark it for inclusion in the next render pass. |
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303 | |
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304 | for (var i = 0, position; position = positions[i]; i++) { |
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305 | if (position.x == x && position.y == y) { |
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306 | position.active = true; |
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307 | return; |
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308 | } |
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309 | } |
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310 | |
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311 | // If the text doesn't exist at this position, create a new entry |
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312 | |
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313 | position = { |
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314 | active: true, |
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315 | lines: [], |
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316 | x: x, |
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317 | y: y |
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318 | }; |
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319 | |
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320 | positions.push(position); |
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321 | |
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322 | // Fill in the x & y positions of each line, adjusting them |
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323 | // individually for horizontal alignment. |
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324 | |
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325 | for (var i = 0, line; line = lines[i]; i++) { |
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326 | if (halign == "center") { |
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327 | position.lines.push([Math.round(x - line.width / 2), y]); |
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328 | } else if (halign == "right") { |
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329 | position.lines.push([Math.round(x - line.width), y]); |
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330 | } else { |
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331 | position.lines.push([Math.round(x), y]); |
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332 | } |
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333 | y += line.height; |
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334 | } |
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335 | }; |
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336 | } |
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337 | |
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338 | $.plot.plugins.push({ |
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339 | init: init, |
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340 | options: options, |
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341 | name: "canvas", |
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342 | version: "1.0" |
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343 | }); |
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344 | |
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345 | })(jQuery); |
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