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<h1 id="coordinate-factory">Coordinate factory</h1>
<p>Scrawl-canvas uses Coordinate Arrays extensively throughout the code base - in particular to hold artefact coordinate [x, y] and dimensional [w, h] data. The Coordinate factory does not care whether these values are presented as Numbers or Strings (or a mixture of both) - it leaves such functionality to other mixins (in particular the <a href="../mixin/position.html">position</a>, <a href="../mixin/dom.html">dom</a> and <a href="../mixin/entity.html">entity</a> mixins) and factories.</p>
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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> { xt, isa_number } <span class="hljs-keyword">from</span> <span class="hljs-string">'../core/utilities.js'</span>;</pre></div></div>
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<h4 id="coordinate-constructor">Coordinate constructor</h4>
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<div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> <span class="hljs-title class_">Coordinate</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">items, y</span>) {
<span class="hljs-keyword">let</span> coords = [<span class="hljs-number">0</span>, <span class="hljs-number">0</span>];
<span class="hljs-title class_">Object</span>.<span class="hljs-title function_">setPrototypeOf</span>(coords, <span class="hljs-title class_">Coordinate</span>.<span class="hljs-property"><span class="hljs-keyword">prototype</span></span>);
<span class="hljs-keyword">if</span> (items) coords.<span class="hljs-title function_">set</span>(items, y);
<span class="hljs-keyword">return</span> coords;
};</pre></div></div>
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<h4 id="coordinate-prototype">Coordinate 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_">Coordinate</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_">Array</span>.<span class="hljs-property"><span class="hljs-keyword">prototype</span></span>);
P.<span class="hljs-property">constructor</span> = <span class="hljs-title class_">Coordinate</span>;
P.<span class="hljs-property">type</span> = <span class="hljs-string">'Coordinate'</span>;</pre></div></div>
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<h4 id="mixins">Mixins</h4>
<p>Coordinate Arrays do not use mixins - they are regular Javascript Arrays. As such, they do not possess packet, clone or kill functionality.</p>
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<h4 id="coordinate-attributes">Coordinate attributes</h4>
<p>There are no attributes. The constructor returns an Array containing two members, whose prototype object includes functions for manipulating those members in various ways.</p>
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<h4 id="get-set-deltaset">Get, Set, deltaSet</h4>
<p>The Array members can be set using a <code>set</code> function, which is overloaded as follows:</p>
<ul>
<li><code>mycoordinate.set(Coordinate)</code> - use another Coordinate Array to set this Coordinate members’ values</li>
<li><code>mycoordinate.set(Array)</code> - - use a Javascript Array to set this Coordinate members’ values</li>
<li><code>mycoordinate.set(Quaternion)</code> - use a Quaternion object (specifically, its <strong>v</strong> Vector object attribute) to set this Coordinate members’ values</li>
<li><code>mycoordinate.set(Vector)</code> - use a Vector object to set this Coordinate members’ values</li>
<li><code>mycoordinate.set(a:Number|String, b:Number|String)</code> - supply two arguments to the function</li>
</ul>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">set</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">items, y</span>) {
<span class="hljs-keyword">if</span> (<span class="hljs-title function_">xt</span>(items)) {
<span class="hljs-keyword">if</span> (items.<span class="hljs-property">type</span> === <span class="hljs-string">'Coordinate'</span>) <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">setFromArray</span>(items);
<span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (items.<span class="hljs-property">type</span> === <span class="hljs-string">'Vector'</span>) <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">setFromVector</span>(items);
<span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (items.<span class="hljs-property">type</span> === <span class="hljs-string">'Quaternion'</span>) <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">setFromVector</span>(items.<span class="hljs-property">v</span>);
<span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (<span class="hljs-title class_">Array</span>.<span class="hljs-title function_">isArray</span>(items)) <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">setFromArray</span>(items);
<span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (<span class="hljs-title function_">xt</span>(y)) <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">setFromArray</span>([items, y]);
}
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>;
};
P.<span class="hljs-property">setFromArray</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-variable language_">this</span>[<span class="hljs-number">0</span>] = item[<span class="hljs-number">0</span>];
<span class="hljs-variable language_">this</span>[<span class="hljs-number">1</span>] = item[<span class="hljs-number">1</span>];
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>;
};
P.<span class="hljs-property">setFromVector</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-variable language_">this</span>[<span class="hljs-number">0</span>] = item.<span class="hljs-property">x</span>;
<span class="hljs-variable language_">this</span>[<span class="hljs-number">1</span>] = item.<span class="hljs-property">y</span>;
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>;
};</pre></div></div>
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<h4 id="prototype-functions">Prototype functions</h4>
<p>Set the Coordinate array to <code>[0, 0]</code></p>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">zero</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params"></span>) {
<span class="hljs-variable language_">this</span>[<span class="hljs-number">0</span>] = <span class="hljs-number">0</span>;
<span class="hljs-variable language_">this</span>[<span class="hljs-number">1</span>] = <span class="hljs-number">0</span>;
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>;
};</pre></div></div>
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<p>Add a Vector object’s <strong>x</strong> and <strong>y</strong> attributes to the Coordinate members’ values</p>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">vectorAdd</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-variable language_">this</span>[<span class="hljs-number">0</span>] += item.<span class="hljs-property">x</span>;
<span class="hljs-variable language_">this</span>[<span class="hljs-number">1</span>] += item.<span class="hljs-property">y</span>;
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>;
};</pre></div></div>
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<p>Subtract a Vector object’s <strong>x</strong> and <strong>y</strong> attributes from the Coordinate members’ values</p>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">vectorSubtract</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-variable language_">this</span>[<span class="hljs-number">0</span>] -= item.<span class="hljs-property">x</span>;
<span class="hljs-variable language_">this</span>[<span class="hljs-number">1</span>] -= item.<span class="hljs-property">y</span>;
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>;
};</pre></div></div>
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<p>Array addition - argument is a <code>[Number, Number]</code> Array</p>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">add</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-variable language_">this</span>[<span class="hljs-number">0</span>] += item[<span class="hljs-number">0</span>];
<span class="hljs-variable language_">this</span>[<span class="hljs-number">1</span>] += item[<span class="hljs-number">1</span>];
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>;
};</pre></div></div>
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<p>Array subtraction - argument is a <code>[Number, Number]</code> Array</p>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">subtract</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-variable language_">this</span>[<span class="hljs-number">0</span>] -= item[<span class="hljs-number">0</span>];
<span class="hljs-variable language_">this</span>[<span class="hljs-number">1</span>] -= item[<span class="hljs-number">1</span>];
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>;
};</pre></div></div>
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<p>Array multiplication - argument is a <code>[Number, Number]</code> Array</p>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">multiply</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-variable language_">this</span>[<span class="hljs-number">0</span>] *= item[<span class="hljs-number">0</span>];
<span class="hljs-variable language_">this</span>[<span class="hljs-number">1</span>] *= item[<span class="hljs-number">1</span>];
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>;
};</pre></div></div>
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<p>Array division - argument is a <code>[Number, Number]</code> Array</p>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">divide</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-keyword">let</span> [x, y] = item;
<span class="hljs-keyword">if</span> (x && y) {
<span class="hljs-variable language_">this</span>[<span class="hljs-number">0</span>] /= x;
<span class="hljs-variable language_">this</span>[<span class="hljs-number">1</span>] /= y;
}
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>;
};</pre></div></div>
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<p>Multiply both Coordinate Array members by the argument Number</p>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">scalarMultiply</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-variable language_">this</span>[<span class="hljs-number">0</span>] *= item;
<span class="hljs-variable language_">this</span>[<span class="hljs-number">1</span>] *= item;
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>;
};</pre></div></div>
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<p>Divide both Coordinate Array members by the argument Number</p>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">scalarDivide</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-keyword">if</span> (item && item.<span class="hljs-property">toFixed</span>) {
<span class="hljs-variable language_">this</span>[<span class="hljs-number">0</span>] /= item;
<span class="hljs-variable language_">this</span>[<span class="hljs-number">1</span>] /= item;
}
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>;
};</pre></div></div>
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<p>Get the Array’s <strong>magnitude</strong> value (treating the Coordinate as if it was a 2D vector)</p>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">getMagnitude</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params"></span>) {
<span class="hljs-keyword">return</span> <span class="hljs-title class_">Math</span>.<span class="hljs-title function_">hypot</span>(<span class="hljs-variable language_">this</span>[<span class="hljs-number">0</span>], <span class="hljs-variable language_">this</span>[<span class="hljs-number">1</span>]);
};</pre></div></div>
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<p>Rotate the Coordinate by the argument number (treating the Coordinate as if it was a 2D vector) - the argument represents degrees, not radians</p>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">rotate</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">angle</span>) {
<span class="hljs-keyword">let</span> x = <span class="hljs-variable language_">this</span>[<span class="hljs-number">0</span>],
y = <span class="hljs-variable language_">this</span>[<span class="hljs-number">1</span>],
r0, r1;
r0 = <span class="hljs-title class_">Math</span>.<span class="hljs-title function_">atan2</span>(y, x);
r0 += (angle * <span class="hljs-number">0.01745329251</span>);
r1 = <span class="hljs-title class_">Math</span>.<span class="hljs-title function_">hypot</span>(x, y);
<span class="hljs-variable language_">this</span>[<span class="hljs-number">0</span>] = r1 * <span class="hljs-title class_">Math</span>.<span class="hljs-title function_">cos</span>(r0);
<span class="hljs-variable language_">this</span>[<span class="hljs-number">1</span>] = r1 * <span class="hljs-title class_">Math</span>.<span class="hljs-title function_">sin</span>(r0);
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>;
};</pre></div></div>
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<p>Reverse the numerical sign on each of the Array’s members</p>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">reverse</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params"></span>) {
<span class="hljs-variable language_">this</span>[<span class="hljs-number">0</span>] = -<span class="hljs-variable language_">this</span>[<span class="hljs-number">0</span>];
<span class="hljs-variable language_">this</span>[<span class="hljs-number">1</span>] = -<span class="hljs-variable language_">this</span>[<span class="hljs-number">1</span>];
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>;
};</pre></div></div>
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<p>Get the Array’s <strong>dot product</strong> value (treating the Coordinate as if it was a 2D vector)</p>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">getDotProduct</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">coord</span>) {
<span class="hljs-keyword">return</span> (<span class="hljs-variable language_">this</span>[<span class="hljs-number">0</span>] * coord[<span class="hljs-number">0</span>]) + (<span class="hljs-variable language_">this</span>[<span class="hljs-number">1</span>] * coord[<span class="hljs-number">1</span>]);
};</pre></div></div>
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<p><strong>Normalize</strong> the Array’s members (treating the Coordinate as if it was a 2D vector)</p>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">normalize</span> = <span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) {
<span class="hljs-keyword">let</span> val = <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">getMagnitude</span>();
<span class="hljs-keyword">if</span> (val > <span class="hljs-number">0</span>) {
<span class="hljs-variable language_">this</span>[<span class="hljs-number">0</span>] /= val;
<span class="hljs-variable language_">this</span>[<span class="hljs-number">1</span>] /= val;
}
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>;
};</pre></div></div>
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<h4 id="coordinate-pool">Coordinate pool</h4>
<p>An attempt to reuse coordinates rather than constantly creating and deleting them</p>
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<div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> coordinatePool = [];</pre></div></div>
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<p><code>exported function</code> - retrieve a Coordinate from the coordinate pool</p>
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<div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> requestCoordinate = <span class="hljs-keyword">function</span> (<span class="hljs-params">items, y</span>) {
<span class="hljs-keyword">if</span> (!coordinatePool.<span class="hljs-property">length</span>) coordinatePool.<span class="hljs-title function_">push</span>(<span class="hljs-keyword">new</span> <span class="hljs-title class_">Coordinate</span>());
<span class="hljs-keyword">let</span> c = coordinatePool.<span class="hljs-title function_">shift</span>();
c.<span class="hljs-title function_">set</span>(items, y);
<span class="hljs-keyword">return</span> c
};</pre></div></div>
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<p><code>exported function</code> - return a Coordinate to the coordinate pool. Failing to return Coordinates to the pool may lead to more inefficient code and possible memory leaks.</p>
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<div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> releaseCoordinate = <span class="hljs-keyword">function</span> (<span class="hljs-params">coordinate</span>) {
<span class="hljs-keyword">if</span> (coordinate && coordinate.<span class="hljs-property">type</span> === <span class="hljs-string">'Coordinate'</span>) coordinatePool.<span class="hljs-title function_">push</span>(coordinate.<span class="hljs-title function_">zero</span>());
};</pre></div></div>
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<h4 id="factory">Factory</h4>
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<div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> makeCoordinate = <span class="hljs-keyword">function</span> (<span class="hljs-params">items, y</span>) {
<span class="hljs-keyword">return</span> <span class="hljs-keyword">new</span> <span class="hljs-title class_">Coordinate</span>(items, y);
};
constructors.<span class="hljs-property">Coordinate</span> = <span class="hljs-title class_">Coordinate</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> {
makeCoordinate,
requestCoordinate,
releaseCoordinate,
};</pre></div></div>
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