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<h1 id="radialgradient-factory">RadialGradient factory</h1>
<p>Scrawl-canvas RadialGradient objects implement the Canvas API’s <a href="https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/createRadialGradient">createRadialGradient</a> method. The resulting <a href="https://developer.mozilla.org/en-US/docs/Web/API/CanvasGradient">CanvasGradient</a> object can be used by any Scrawl-canvas entity as its <code>fillStyle</code> or <code>strokeStyle</code>.</p>
<ul>
<li>Most gradient-related functionality has been coded up in the <a href="../mixin/styles.html">styles mixin</a>, and is documented there.</li>
<li>RadialGradients fully participate in the Scrawl-canvas packet system, thus can be saved, restored, cloned, killed, etc.</li>
<li>RadialGradients can be animated in a variety of ways; the can act as target objects for Scrawl-canvas Tweens.</li>
</ul>
<p>RadialGradients can be applied to an entity in two different ways, depending on the entity’s <code>lockFillStyleToEntity</code> and <code>lockStrokeStyleToEntity</code> attribute flags:</p>
<ul>
<li><strong>Cell-locked</strong> RadialGradients will cover the entire Cell; an entity moved from one part of the display to another will show different parts of the gradient</li>
<li><strong>Entity-locked</strong> RadialGradients display their entire color range on the entity, move with the entity and even rotate with the entity.</li>
</ul>
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<h4 id="demos">Demos:</h4>
<ul>
<li><a href="../../demo/canvas-004.html">Canvas-004</a> - Radial gradients</li>
<li><a href="../../demo/canvas-005.html">Canvas-005</a> - Cell-locked, and Entity-locked, gradients; animating gradients by delta, and by tween</li>
</ul>
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<h4 id="imports">Imports</h4>
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<div class="content"><div class='highlight'><pre><span class="hljs-keyword">import</span> { constructors } <span class="hljs-keyword">from</span> <span class="hljs-string">'../core/library.js'</span>;
<span class="hljs-keyword">import</span> { mergeOver, addStrings, isa_number, pushUnique, Ωempty } <span class="hljs-keyword">from</span> <span class="hljs-string">'../core/utilities.js'</span>;
<span class="hljs-keyword">import</span> baseMix <span class="hljs-keyword">from</span> <span class="hljs-string">'../mixin/base.js'</span>;
<span class="hljs-keyword">import</span> stylesMix <span class="hljs-keyword">from</span> <span class="hljs-string">'../mixin/styles.js'</span>;</pre></div></div>
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<h4 id="radialgradient-constructor">RadialGradient constructor</h4>
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<div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> <span class="hljs-title class_">RadialGradient</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">items = Ωempty</span>) {
<span class="hljs-variable language_">this</span>.<span class="hljs-title function_">stylesInit</span>(items);
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>;
};</pre></div></div>
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<h4 id="radialgradient-prototype">RadialGradient prototype</h4>
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<div class="content"><div class='highlight'><pre><span class="hljs-keyword">let</span> P = <span class="hljs-title class_">RadialGradient</span>.<span class="hljs-property"><span class="hljs-keyword">prototype</span></span> = <span class="hljs-title class_">Object</span>.<span class="hljs-title function_">create</span>(<span class="hljs-title class_">Object</span>.<span class="hljs-property"><span class="hljs-keyword">prototype</span></span>);
P.<span class="hljs-property">type</span> = <span class="hljs-string">'RadialGradient'</span>;
P.<span class="hljs-property">lib</span> = <span class="hljs-string">'styles'</span>;
P.<span class="hljs-property">isArtefact</span> = <span class="hljs-literal">false</span>;
P.<span class="hljs-property">isAsset</span> = <span class="hljs-literal">false</span>;</pre></div></div>
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<h4 id="mixins">Mixins</h4>
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<div class="content"><div class='highlight'><pre>P = <span class="hljs-title function_">baseMix</span>(P);
P = <span class="hljs-title function_">stylesMix</span>(P);</pre></div></div>
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<h4 id="radialgradient-attributes">RadialGradient attributes</h4>
<ul>
<li>Attributes defined in the <a href="../mixin/base.html">base mixin</a>: <strong>name</strong>.</li>
<li>Attributes defined in the <a href="../mixin/styles.html">styles mixin</a>: <strong>start, end, palette, paletteStart, paletteEnd, cyclePalette</strong>.</li>
<li>Attributes defined in the <a href="./palette.html">Palette factory</a>: <strong>colors, cyclic</strong>.</li>
</ul>
</div>
<div class="content"><div class='highlight'><pre><span class="hljs-keyword">let</span> defaultAttributes = {</pre></div></div>
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<p>RadialGradients calculate their gradients spanning between two circles, whose sizes are determined by the <code>startRadius</code> and <code>endRadius</code> attributes. Values can be:</p>
<ul>
<li><strong>Absolute</strong> - Numbers, measured in pixels.</li>
<li><strong>Relative</strong> - String% - as a percentage of the containing Cell’s <code>width</code></li>
</ul>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attr">startRadius</span>: <span class="hljs-number">0</span>,
<span class="hljs-attr">endRadius</span>: <span class="hljs-number">0</span>,
};
P.<span class="hljs-property">defs</span> = <span class="hljs-title function_">mergeOver</span>(P.<span class="hljs-property">defs</span>, defaultAttributes);</pre></div></div>
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<p>In addition to the attributes defined in the <strong>base</strong> and <strong>styles</strong> mixins, Gradients also pass through Palette attributes to their Palette object. </p>
<p>Attributes from <strong>base</strong> mixin:</p>
<ul>
<li><code>name</code></li>
</ul>
<p>Attributes from <strong>styles</strong> mixin:</p>
<ul>
<li><code>start</code></li>
<li><code>startX</code></li>
<li><code>startY</code></li>
<li><code>end</code></li>
<li><code>endX</code></li>
<li><code>endY</code></li>
<li><code>palette</code></li>
<li><code>paletteStart</code></li>
<li><code>paletteEnd</code></li>
<li><code>cyclePalette</code></li>
</ul>
<p>Attributes from the <strong>palette</strong> factory:</p>
<ul>
<li><code>colors</code> </li>
<li><code>cyclic</code></li>
</ul>
</div>
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<h4 id="packet-management">Packet management</h4>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">packetObjects</span> = <span class="hljs-title function_">pushUnique</span>(P.<span class="hljs-property">packetObjects</span>, [<span class="hljs-string">'palette'</span>]);</pre></div></div>
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<h4 id="clone-management">Clone management</h4>
<p>No additional clone functionality required</p>
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<h4 id="kill-management">Kill management</h4>
<p>No additional kill functionality required</p>
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<h4 id="get-set-deltaset">Get, Set, deltaSet</h4>
</div>
<div class="content"><div class='highlight'><pre><span class="hljs-keyword">let</span> G = P.<span class="hljs-property">getters</span>,
S = P.<span class="hljs-property">setters</span>,
D = P.<span class="hljs-property">deltaSetters</span>;</pre></div></div>
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<p>The getter functions <code>myradialgradient.get('startRadius')</code> and <code>myradialgradient.get('endRadius')</code> return the current radius values as Numbers, measuring pixels</p>
</div>
<div class="content"><div class='highlight'><pre>G.<span class="hljs-property">startRadius</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>.<span class="hljs-property">currentStartRadius</span>;
};
G.<span class="hljs-property">endRadius</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>.<span class="hljs-property">currentEndRadius</span>;
};</pre></div></div>
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<p>Both <code>startRadius</code> and <code>endRadius</code> attributes can be set and deltaSet</p>
</div>
<div class="content"><div class='highlight'><pre>S.<span class="hljs-property">startRadius</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-variable language_">this</span>.<span class="hljs-property">startRadius</span> = item;
<span class="hljs-variable language_">this</span>.<span class="hljs-property">dirtyStyle</span> = <span class="hljs-literal">true</span>;
};
S.<span class="hljs-property">endRadius</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-variable language_">this</span>.<span class="hljs-property">endRadius</span> = item;
<span class="hljs-variable language_">this</span>.<span class="hljs-property">dirtyStyle</span> = <span class="hljs-literal">true</span>;
};
D.<span class="hljs-property">startRadius</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-variable language_">this</span>.<span class="hljs-property">startRadius</span> = <span class="hljs-title function_">addStrings</span>(<span class="hljs-variable language_">this</span>.<span class="hljs-property">startRadius</span>, item);
<span class="hljs-variable language_">this</span>.<span class="hljs-property">dirtyStyle</span> = <span class="hljs-literal">true</span>;
};
D.<span class="hljs-property">endRadius</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-variable language_">this</span>.<span class="hljs-property">endRadius</span> = <span class="hljs-title function_">addStrings</span>(<span class="hljs-variable language_">this</span>.<span class="hljs-property">endRadius</span>, item);
<span class="hljs-variable language_">this</span>.<span class="hljs-property">dirtyStyle</span> = <span class="hljs-literal">true</span>;
};</pre></div></div>
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<h4 id="prototype-functions">Prototype functions</h4>
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<p><code>cleanRadius</code> - internal function to calculate the current radius values (in px) of the start and end radii</p>
</div>
<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">cleanRadius</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">width</span>) {
<span class="hljs-keyword">const</span> <span class="hljs-title function_">convertLength</span> = (<span class="hljs-params">val, len</span>) => {
<span class="hljs-keyword">if</span> (<span class="hljs-title function_">isa_number</span>(val)) <span class="hljs-keyword">return</span> val;
<span class="hljs-keyword">else</span> {
<span class="hljs-keyword">switch</span>(val){
<span class="hljs-keyword">case</span> <span class="hljs-string">'top'</span> :
<span class="hljs-keyword">case</span> <span class="hljs-string">'left'</span> :
<span class="hljs-keyword">return</span> <span class="hljs-number">0</span>;
<span class="hljs-keyword">case</span> <span class="hljs-string">'bottom'</span> :
<span class="hljs-keyword">case</span> <span class="hljs-string">'right'</span> :
<span class="hljs-keyword">return</span> len;
<span class="hljs-keyword">case</span> <span class="hljs-string">'center'</span> :
<span class="hljs-keyword">return</span> len / <span class="hljs-number">2</span>;
<span class="hljs-keyword">default</span> :
val = <span class="hljs-built_in">parseFloat</span>(val);
<span class="hljs-keyword">if</span> (!<span class="hljs-title function_">isa_number</span>(val)) <span class="hljs-keyword">return</span> <span class="hljs-number">0</span>;
<span class="hljs-keyword">return</span> ( val / <span class="hljs-number">100</span>) * len;
}
}
};
<span class="hljs-variable language_">this</span>.<span class="hljs-property">currentStartRadius</span> = (width) ? <span class="hljs-title function_">convertLength</span>(<span class="hljs-variable language_">this</span>.<span class="hljs-property">startRadius</span>, width) : <span class="hljs-variable language_">this</span>.<span class="hljs-property">defs</span>.<span class="hljs-property">startRadius</span>;
<span class="hljs-variable language_">this</span>.<span class="hljs-property">currentEndRadius</span> = (width) ? <span class="hljs-title function_">convertLength</span>(<span class="hljs-variable language_">this</span>.<span class="hljs-property">endRadius</span>, width) : <span class="hljs-variable language_">this</span>.<span class="hljs-property">defs</span>.<span class="hljs-property">endRadius</span>;
};</pre></div></div>
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<p><code>buildStyle</code> - internal function: creates the radial gradient on the Cell’s CanvasRenderingContext2D engine, and then adds the color stops to it.</p>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">buildStyle</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">cell</span>) {
<span class="hljs-keyword">if</span> (cell) {
<span class="hljs-keyword">let</span> engine = cell.<span class="hljs-property">engine</span>;
<span class="hljs-keyword">if</span> (engine) {
<span class="hljs-keyword">let</span> gradient = engine.<span class="hljs-title function_">createRadialGradient</span>(...<span class="hljs-variable language_">this</span>.<span class="hljs-property">gradientArgs</span>);
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">addStopsToGradient</span>(gradient, <span class="hljs-variable language_">this</span>.<span class="hljs-property">paletteStart</span>, <span class="hljs-variable language_">this</span>.<span class="hljs-property">paletteEnd</span>, <span class="hljs-variable language_">this</span>.<span class="hljs-property">cyclePalette</span>);
}
}
<span class="hljs-keyword">return</span> <span class="hljs-string">'rgba(0,0,0,0)'</span>;
};</pre></div></div>
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<p><code>updateGradientArgs</code> - internal function</p>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">updateGradientArgs</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">x, y</span>) {
<span class="hljs-keyword">let</span> gradientArgs = <span class="hljs-variable language_">this</span>.<span class="hljs-property">gradientArgs</span>,
currentStart = <span class="hljs-variable language_">this</span>.<span class="hljs-property">currentStart</span>,
currentEnd = <span class="hljs-variable language_">this</span>.<span class="hljs-property">currentEnd</span>,
sr = <span class="hljs-variable language_">this</span>.<span class="hljs-property">currentStartRadius</span>,
er = <span class="hljs-variable language_">this</span>.<span class="hljs-property">currentEndRadius</span>;
<span class="hljs-keyword">let</span> sx = currentStart[<span class="hljs-number">0</span>] + x,
sy = currentStart[<span class="hljs-number">1</span>] + y,
ex = currentEnd[<span class="hljs-number">0</span>] + x,
ey = currentEnd[<span class="hljs-number">1</span>] + y;</pre></div></div>
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<p>check to correct situation where coordinates represent a ‘0 x 0’ box - which will cause errors in some browsers</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">if</span> (sx === ex && sy === ey && sr === er) er++;
gradientArgs.<span class="hljs-property">length</span> = <span class="hljs-number">0</span>;
gradientArgs.<span class="hljs-title function_">push</span>(sx, sy, sr, ex, ey, er);
};</pre></div></div>
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<h4 id="factory">Factory</h4>
<pre><code><span class="hljs-keyword">let</span> graddy = scrawl.<span class="hljs-title function_">makeRadialGradient</span>({
<span class="hljs-attr">name</span>: <span class="hljs-string">'mygradient'</span>,
<span class="hljs-attr">startX</span>: <span class="hljs-string">'50%'</span>,
<span class="hljs-attr">startY</span>: <span class="hljs-string">'50%'</span>,
<span class="hljs-attr">endX</span>: <span class="hljs-string">'50%'</span>,
<span class="hljs-attr">endY</span>: <span class="hljs-string">'50%'</span>,
<span class="hljs-attr">endRadius</span>: <span class="hljs-number">300</span>,
});
scrawl.<span class="hljs-title function_">makeBlock</span>({
<span class="hljs-attr">name</span>: <span class="hljs-string">'myblock'</span>,
<span class="hljs-attr">width</span>: <span class="hljs-string">'90%'</span>,
<span class="hljs-attr">height</span>: <span class="hljs-string">'90%'</span>,
<span class="hljs-attr">startX</span>: <span class="hljs-string">'5%'</span>,
<span class="hljs-attr">startY</span>: <span class="hljs-string">'5%'</span>,
<span class="hljs-attr">fillStyle</span>: graddy,
<span class="hljs-attr">strokeStyle</span>: <span class="hljs-string">'coral'</span>,
<span class="hljs-attr">lineWidth</span>: <span class="hljs-number">2</span>,
<span class="hljs-attr">method</span>: <span class="hljs-string">'fillAndDraw'</span>,
});
</code></pre>
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<div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> makeRadialGradient = <span class="hljs-keyword">function</span> (<span class="hljs-params">items</span>) {
<span class="hljs-keyword">if</span> (!items) <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
<span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">RadialGradient</span>(items);
};
constructors.<span class="hljs-property">RadialGradient</span> = <span class="hljs-title class_">RadialGradient</span>;</pre></div></div>
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<h4 id="exports">Exports</h4>
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<div class="content"><div class='highlight'><pre><span class="hljs-keyword">export</span> {
makeRadialGradient,
};</pre></div></div>
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