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<h1 id="conicgradient-factory">ConicGradient factory</h1>
<p>Scrawl-canvas ConicGradient objects implement the Canvas API’s <a href="https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/createConicGradient">createConicGradient</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>ConicGradients fully participate in the Scrawl-canvas packet system, thus can be saved, restored, cloned, killed, etc.</li>
<li>ConicGradients can be animated in a variety of ways; the can act as target objects for Scrawl-canvas Tweens.</li>
</ul>
<p>ConicGradients 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> ConicGradients 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> ConicGradients display their entire color range on the entity, move with the entity and even rotate with the entity.</li>
</ul>
<p><strong>TO NOTE: <em>this is an experimental technology; most browsers do not (yet) support conic gradients for canvases, only in CSS.</em></strong> In these browsers, the gradient will return a solid, transparent color. To see the effect, enable the appropriate flags in the browser:</p>
<ul>
<li>Chrome browsers< - from version 86: this feature is behind the #new-canvas-2d-api preferences. To change preferences in Chrome, visit chrome://flags</li>
<li>Firefox browsers - From version 86: this feature is behind the canvas.createConicGradient.enabled preferences. To change preferences in Firefox, visit about:config</li>
<li>Other browsers - currently no signals about support. See the MDN createConicGradient() page for further details</li>
</ul>
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<h4 id="demos">Demos:</h4>
<ul>
<li><a href="../../demo/canvas-049.html">Canvas-049</a> - Conic gradients</li>
</ul>
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<h4 id="imports">Imports</h4>
</div>
<div class="content"><div class='highlight'><pre><span class="hljs-keyword">import</span> { constructors, radian } <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="conicgradient-constructor">ConicGradient constructor</h4>
</div>
<div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> <span class="hljs-title class_">ConicGradient</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="conicgradient-prototype">ConicGradient prototype</h4>
</div>
<div class="content"><div class='highlight'><pre><span class="hljs-keyword">let</span> P = <span class="hljs-title class_">ConicGradient</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">'ConicGradient'</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="conicgradient-attributes">ConicGradient 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>ConicGradients calculate their gradients as a sweep of color around the <code>start</code> (<code>startX</code> and <code>startY</code>) coordinate. The <strong>startAngle</strong> attribute - measured in degrees, not radians - represents the angle at which the color stop 0 occurs.</p>
<ul>
<li>The sweep of colors is, by default, clockwise around the start coordinate; to reverse this, swap the gradient’s <code>paletteStart</code> and <code>paletteEnd</code> attributes.</li>
</ul>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attr">angle</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>
<p>No additional getter/setter functionality required</p>
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<h4 id="prototype-functions">Prototype functions</h4>
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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>
</div>
<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">if</span> (!engine.<span class="hljs-property">createConicGradient</span>) <span class="hljs-keyword">return</span> <span class="hljs-string">'rgba(0,0,0,0)'</span>;
<span class="hljs-keyword">let</span> gradient = engine.<span class="hljs-title function_">createConicGradient</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>
</div>
<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>,
angle = <span class="hljs-variable language_">this</span>.<span class="hljs-property">angle</span> * radian;
<span class="hljs-keyword">let</span> sx = currentStart[<span class="hljs-number">0</span>] + x,
sy = currentStart[<span class="hljs-number">1</span>] + y;
gradientArgs.<span class="hljs-property">length</span> = <span class="hljs-number">0</span>;
gradientArgs.<span class="hljs-title function_">push</span>(angle, sx, sy);
};</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_">makeConicGradient</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">angle</span>: <span class="hljs-number">90</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>
</div>
<div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> makeConicGradient = <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_">ConicGradient</span>(items);
};
constructors.<span class="hljs-property">ConicGradient</span> = <span class="hljs-title class_">ConicGradient</span>;</pre></div></div>
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<h4 id="exports">Exports</h4>
</div>
<div class="content"><div class='highlight'><pre><span class="hljs-keyword">export</span> {
makeConicGradient,
};</pre></div></div>
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