scrawl-canvas
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<h1 id="tracer-factory">Tracer factory</h1>
<p>The Scrawl-canvas particle physics engine is a simple system designed to allow developers a way to add particle-based effects to their canvas animation scenes. The physics engine is built on top of the following components:</p>
<ul>
<li><a href="./particle.html">Particle objects</a>, which represent a 3-dimensional coordinate - based on a Scrawl-canvas <a href="./vector.html">Vector object</a> - and include a history of recent positions which we can use to determine how to display that particle on screen.</li>
<li><a href="./particleHistory.html">History arrays</a> which can be pooled (reused) to cut down on Array creation and distruction during the animation.</li>
<li><a href="./particleForce.html">Force objects</a> which define the general and occasional forces to be applied to each particle in the system as the animation progresses - a <strong>gravity</strong> force object is pre-defined by Scrawl-canvas.</li>
<li><a href="./particleSpring.html">Spring objects</a> used to define a constraint (connection) between two particles in a system.</li>
<li><a href="./particleWorld.html">World objects</a> where we can store attributes and values used by various objects; these attributes can be set up so that they will be inherited by clones of the World object. We can also influence the speed of the physics animation here.</li>
</ul>
<p>We do not have to handle particle generation and manipulation ourselves. Instead, Scrawl-canvas gives us three dedicated <strong>entitys</strong> which we use to add particle animation effects to the canvas scene. These entitys are:</p>
<ul>
<li><a href="./tracer.html">Tracer</a> - this entity generates a single non-recycled (in other words: long lasting) particle with a history, which we can use to display trace effects in the animation.</li>
<li><a href="./emitter.html">Emitter</a> - an entity which generates a stream of short-lived, recycled particles, each with its own history. Emitters are highly versatile entitys which can generate a wide range of effects.
= <a href="./net.html">Net</a> - a (generally) larger entity which uses both forces and springs to manage the animation of its non-recycled particles. Note that other artefacts can use Net particles as a reference for their own positioning.</li>
</ul>
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<h4 id="demos">Demos:</h4>
<ul>
<li><a href="../../demo/particles-011.html">particles-011</a> - Tracer entity: basic functionality</li>
<li><a href="../../demo/particles-012.html">particles-012</a> - Use Net entity particles as reference coordinates for other artefacts</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, tween, artefact, group } <span class="hljs-keyword">from</span> <span class="hljs-string">'../core/library.js'</span>;
<span class="hljs-keyword">import</span> { pushUnique, mergeOver, λ<span class="hljs-literal">null</span>, isa_fn, isa_obj, xta, Ωempty } <span class="hljs-keyword">from</span> <span class="hljs-string">'../core/utilities.js'</span>;
<span class="hljs-keyword">import</span> { currentGroup } <span class="hljs-keyword">from</span> <span class="hljs-string">'../core/document.js'</span>;
<span class="hljs-keyword">import</span> { makeParticle } <span class="hljs-keyword">from</span> <span class="hljs-string">'./particle.js'</span>;
<span class="hljs-keyword">import</span> { requestVector, releaseVector } <span class="hljs-keyword">from</span> <span class="hljs-string">'./vector.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> entityMix <span class="hljs-keyword">from</span> <span class="hljs-string">'../mixin/entity.js'</span>;</pre></div></div>
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<h4 id="tracer-constructor">Tracer constructor</h4>
</div>
<div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> <span class="hljs-title class_">Tracer</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_">makeName</span>(items.<span class="hljs-property">name</span>);
<span class="hljs-variable language_">this</span>.<span class="hljs-title function_">register</span>();
<span class="hljs-variable language_">this</span>.<span class="hljs-title function_">initializePositions</span>();
<span class="hljs-variable language_">this</span>.<span class="hljs-title function_">set</span>(<span class="hljs-variable language_">this</span>.<span class="hljs-property">defs</span>);</pre></div></div>
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<p>The entity has a hit zone which can be used for drag-and-drop, and other user interactions. Thus the <code>onXYZ</code> UI functions remain relevant.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-variable language_">this</span>.<span class="hljs-property">onEnter</span> = λ<span class="hljs-literal">null</span>;
<span class="hljs-variable language_">this</span>.<span class="hljs-property">onLeave</span> = λ<span class="hljs-literal">null</span>;
<span class="hljs-variable language_">this</span>.<span class="hljs-property">onDown</span> = λ<span class="hljs-literal">null</span>;
<span class="hljs-variable language_">this</span>.<span class="hljs-property">onUp</span> = λ<span class="hljs-literal">null</span>;</pre></div></div>
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<p>As part of its <code>stamp</code> functionality the Tracer entity will invoke the <code>stampAction</code> function. If not supplied, the entity will not display anything on the canvas.</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-variable language_">this</span>.<span class="hljs-property">stampAction</span> = λ<span class="hljs-literal">null</span>;</pre></div></div>
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<p>Tracer entitys use just one Particle, which gets initialized here and stored in the <code>trace</code> attribute</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-variable language_">this</span>.<span class="hljs-property">trace</span> = <span class="hljs-title function_">makeParticle</span>(items);
<span class="hljs-keyword">if</span> (!items.<span class="hljs-property">group</span>) items.<span class="hljs-property">group</span> = currentGroup;
<span class="hljs-variable language_">this</span>.<span class="hljs-title function_">set</span>(items);
<span class="hljs-keyword">if</span> (<span class="hljs-variable language_">this</span>.<span class="hljs-property">purge</span>) <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">purgeArtefact</span>(<span class="hljs-variable language_">this</span>.<span class="hljs-property">purge</span>);
<span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>;
};</pre></div></div>
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<h4 id="tracer-prototype">Tracer 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_">Tracer</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">'Tracer'</span>;
P.<span class="hljs-property">lib</span> = <span class="hljs-string">'entity'</span>;
P.<span class="hljs-property">isArtefact</span> = <span class="hljs-literal">true</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_">entityMix</span>(P);</pre></div></div>
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<h4 id="tracer-attributes">Tracer 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/position.html">position mixin</a>: <strong>group, visibility, order, calculateOrder, stampOrder, start, <em>startX</em>, <em>startY</em>, handle, <em>handleX</em>, <em>handleY</em>, offset, <em>offsetX</em>, <em>offsetY</em>, dimensions, <em>width</em>, <em>height</em>, pivoted, mimicked, lockTo, <em>lockXTo</em>, <em>lockYTo</em>, scale, roll, noUserInteraction, noPositionDependencies, noCanvasEngineUpdates, noFilters, noPathUpdates, purge, bringToFrontOnDrag</strong>.</li>
<li>Attributes defined in the <a href="../mixin/delta.html">delta mixin</a>: <strong>delta, noDeltaUpdates</strong>.</li>
<li>Attributes defined in the <a href="../mixin/pivot.html">pivot mixin</a>: <strong>pivot, pivotCorner, addPivotHandle, addPivotOffset, addPivotRotation</strong>.</li>
<li>Attributes defined in the <a href="../mixin/mimic.html">mimic mixin</a>: <strong>mimic, useMimicDimensions, useMimicScale, useMimicStart, useMimicHandle, useMimicOffset, useMimicRotation, useMimicFlip, addOwnDimensionsToMimic, addOwnScaleToMimic, addOwnStartToMimic, addOwnHandleToMimic, addOwnOffsetToMimic, addOwnRotationToMimic</strong>.</li>
<li>Attributes defined in the <a href="../mixin/path.html">path mixin</a>: <strong>path, pathPosition, addPathHandle, addPathOffset, addPathRotation, constantPathSpeed</strong>.</li>
<li>Attributes defined in the <a href="../mixin/entity.html">entity mixin</a>: <strong>method, pathObject, winding, flipReverse, flipUpend, scaleOutline, lockFillStyleToEntity, lockStrokeStyleToEntity, onEnter, onLeave, onDown, onUp, <em>fillStyle, strokeStyle, globalAlpha, globalCompositeOperation, lineWidth, lineCap, lineJoin, lineDash, lineDashOffset, miterLimit, shadowOffsetX, shadowOffsetY, shadowBlur, shadowColor, filter</em></strong>.</li>
<li>Attributes defined in the <a href="../mixin/anchor.html">anchor mixin</a>: <strong>anchor</strong>.</li>
<li>Attributes defined in the <a href="../mixin/filter.html">filter mixin</a>: <strong>filters, isStencil</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>Note that Tracer entitys, unlike Emitters or Nets, do not need or use World objects; they are not affected by Forces or springs. They are - effectively - entitys that record their location coordinate, with the ability to remember a history of its recent locations.</p>
<p><strong>artefact</strong> - In theory, any Scrawl-canvas object whose <code>isArtefact</code> flag is set to <code>true</code> can be assigned to this attribute. However this has not been tested on non-entity artefacts. For now, stick to Scrawl-canvas entity objects.</p>
<ul>
<li>Can be set using the String name of an artefact object, or the artefact object itself.</li>
</ul>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attr">artefact</span>: <span class="hljs-literal">null</span>,</pre></div></div>
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<p><strong>historyLength</strong> - positive integer Number - every Particle will keep a record of its recent state, in a set of ParticleHistory arrays stored in the Particle’s <code>history</code> Array. The Emitter entity will set the maximum permitted length of the history array whenever it generates a new Particle. </p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attr">historyLength</span>: <span class="hljs-number">1</span>,</pre></div></div>
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<p>Note that the <strong>hitRadius</strong> attribute is tied directly to the <strong>width</strong> and <strong>height</strong> attributes (which are effectively meaningless for this entity)</p>
<ul>
<li>This attribute is absolute - unlike other Scrawl-canvas radius attributes it cannot be set using a percentage String value</li>
</ul>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attr">hitRadius</span>: <span class="hljs-number">10</span>,</pre></div></div>
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<p>We can tell the entity to display its hit zone by setting the <code>showHitRadius</code> flag. The hit zone outline color attribute <code>hitRadiusColor</code> accepts any valid CSS color String value</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-attr">showHitRadius</span>: <span class="hljs-literal">false</span>,
<span class="hljs-attr">hitRadiusColor</span>: <span class="hljs-string">'#000000'</span>,</pre></div></div>
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<h5 id="not-defined-in-the-defs-object-but-set-up-in-the-constructor-and-setters">Not defined in the defs object, but set up in the constructor and setters</h5>
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<p><strong>trace</strong> - the entity’s Particle object</p>
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<p><strong>stampAction</strong> - define all major rendering actions in this function. The function receives the following arguments: <code>(artefact, trace, host)</code> - where <code>artefact</code> is the Tracer entity’s artefact object (if any has been defined/set); <code>trace</code> is the entity’s Particle object whose history needs to be rendered onto the canvas; and <code>host</code> is the Cell wrapper on which we will draw our graphics</p>
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<div class="content"><div class='highlight'><pre>};
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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<li id="section-18">
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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">packetExclusions</span> = <span class="hljs-title function_">pushUnique</span>(P.<span class="hljs-property">packetExclusions</span>, []);
P.<span class="hljs-property">packetExclusionsByRegex</span> = <span class="hljs-title function_">pushUnique</span>(P.<span class="hljs-property">packetExclusionsByRegex</span>, []);
P.<span class="hljs-property">packetCoordinates</span> = <span class="hljs-title function_">pushUnique</span>(P.<span class="hljs-property">packetCoordinates</span>, []);
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">'artefact'</span>, <span class="hljs-string">'particle'</span>]);
P.<span class="hljs-property">packetFunctions</span> = <span class="hljs-title function_">pushUnique</span>(P.<span class="hljs-property">packetFunctions</span>, [<span class="hljs-string">'stampAction'</span>]);
P.<span class="hljs-property">finalizePacketOut</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">copy, items</span>) {
<span class="hljs-keyword">return</span> copy;
};</pre></div></div>
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<h4 id="clone-management">Clone management</h4>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">postCloneAction</span> = <span class="hljs-keyword">function</span>(<span class="hljs-params">clone, items</span>) {
clone.<span class="hljs-property">trace</span> = <span class="hljs-title function_">makeParticle</span>({
<span class="hljs-attr">name</span>: clone.<span class="hljs-property">name</span>,
<span class="hljs-attr">historyLength</span>: items.<span class="hljs-property">historyLength</span> || <span class="hljs-variable language_">this</span>.<span class="hljs-property">historyLength</span> || <span class="hljs-number">1</span>,
});
<span class="hljs-keyword">return</span> clone;
};</pre></div></div>
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<li id="section-20">
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<h4 id="kill-management">Kill management</h4>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">factoryKill</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">killArtefact</span>) {
<span class="hljs-keyword">if</span> (killArtefact) <span class="hljs-variable language_">this</span>.<span class="hljs-property">artefact</span>.<span class="hljs-title function_">kill</span>();
<span class="hljs-variable language_">this</span>.<span class="hljs-property">trace</span>.<span class="hljs-title function_">kill</span>();
};</pre></div></div>
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<h4 id="get-set-deltaset">Get, Set, deltaSet</h4>
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<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>;
S.<span class="hljs-property">stampAction</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-keyword">if</span> (<span class="hljs-title function_">isa_fn</span>(item)) <span class="hljs-variable language_">this</span>.<span class="hljs-property">stampAction</span> = item;
};
S.<span class="hljs-property">artefact</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">item</span>) {
<span class="hljs-keyword">let</span> art;
<span class="hljs-keyword">if</span> (item.<span class="hljs-property">substring</span>) art = artefact[item];
<span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (<span class="hljs-title function_">isa_obj</span>(item) && item.<span class="hljs-property">isArtefact</span>) art = item;
<span class="hljs-keyword">if</span> (art) {
<span class="hljs-variable language_">this</span>.<span class="hljs-property">artefact</span> = art;
<span class="hljs-variable language_">this</span>.<span class="hljs-property">dirtyFilterIdentifier</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>regularStamp</code> - overwriters the functionality defined in the entity.js mixin</p>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">regularStamp</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params"></span>) {
<span class="hljs-keyword">let</span> {artefact, trace, stampAction, showHitRadius, hitRadius, hitRadiusColor, currentStampPosition} = <span class="hljs-variable language_">this</span>;
<span class="hljs-keyword">let</span> host = <span class="hljs-variable language_">this</span>.<span class="hljs-property">currentHost</span>;
trace.<span class="hljs-title function_">set</span>({
<span class="hljs-attr">position</span>: currentStampPosition,
});
trace.<span class="hljs-title function_">manageHistory</span>(<span class="hljs-number">0</span>, host);
stampAction.<span class="hljs-title function_">call</span>(<span class="hljs-variable language_">this</span>, artefact, trace, host);
<span class="hljs-keyword">if</span> (showHitRadius) {
<span class="hljs-keyword">let</span> engine = host.<span class="hljs-property">engine</span>;
engine.<span class="hljs-title function_">save</span>();
engine.<span class="hljs-property">lineWidth</span> = <span class="hljs-number">1</span>;
engine.<span class="hljs-property">strokeStyle</span> = hitRadiusColor;
engine.<span class="hljs-title function_">setTransform</span>(<span class="hljs-number">1</span>, <span class="hljs-number">0</span>, <span class="hljs-number">0</span>, <span class="hljs-number">1</span>, <span class="hljs-number">0</span>, <span class="hljs-number">0</span>);
engine.<span class="hljs-title function_">beginPath</span>();
engine.<span class="hljs-title function_">arc</span>(currentStampPosition[<span class="hljs-number">0</span>], currentStampPosition[<span class="hljs-number">1</span>], hitRadius, <span class="hljs-number">0</span>, <span class="hljs-title class_">Math</span>.<span class="hljs-property">PI</span> * <span class="hljs-number">2</span>);
engine.<span class="hljs-title function_">stroke</span>();
engine.<span class="hljs-title function_">restore</span>();
}
};</pre></div></div>
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<p><code>checkHit</code> - overwrites the function defined in mixin/position.js</p>
<ul>
<li>The Tracer entity’s hit area is a circle centred on the entity’s rotation/reflection (start) position or, where the entity’s position is determined by reference (pivot, mimic, path, etc), the reference’s current position.</li>
<li>Tracer entitys can be dragged and dropped around a canvas display like any other Scrawl-canvas artefact.</li>
</ul>
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<div class="content"><div class='highlight'><pre>P.<span class="hljs-property">checkHit</span> = <span class="hljs-keyword">function</span> (<span class="hljs-params">items = [], mycell</span>) {
<span class="hljs-keyword">if</span> (<span class="hljs-variable language_">this</span>.<span class="hljs-property">noUserInteraction</span>) <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
<span class="hljs-keyword">let</span> tests = (!<span class="hljs-title class_">Array</span>.<span class="hljs-title function_">isArray</span>(items)) ? [items] : items;
<span class="hljs-keyword">let</span> currentStampPosition = <span class="hljs-variable language_">this</span>.<span class="hljs-property">currentStampPosition</span>,
res = <span class="hljs-literal">false</span>,
tx, ty;
<span class="hljs-keyword">if</span> (tests.<span class="hljs-title function_">some</span>(<span class="hljs-function"><span class="hljs-params">test</span> =></span> {
<span class="hljs-keyword">if</span> (<span class="hljs-title class_">Array</span>.<span class="hljs-title function_">isArray</span>(test)) {
tx = test[<span class="hljs-number">0</span>];
ty = test[<span class="hljs-number">1</span>];
}
<span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (<span class="hljs-title function_">xta</span>(test, test.<span class="hljs-property">x</span>, test.<span class="hljs-property">y</span>)) {
tx = test.<span class="hljs-property">x</span>;
ty = test.<span class="hljs-property">y</span>;
}
<span class="hljs-keyword">else</span> <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
<span class="hljs-keyword">if</span> (!tx.<span class="hljs-property">toFixed</span> || !ty.<span class="hljs-property">toFixed</span> || <span class="hljs-built_in">isNaN</span>(tx) || <span class="hljs-built_in">isNaN</span>(ty)) <span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
<span class="hljs-keyword">let</span> v = <span class="hljs-title function_">requestVector</span>(currentStampPosition).<span class="hljs-title function_">vectorSubtract</span>(test);
<span class="hljs-keyword">if</span> (v.<span class="hljs-title function_">getMagnitude</span>() < <span class="hljs-variable language_">this</span>.<span class="hljs-property">hitRadius</span>) res = <span class="hljs-literal">true</span>;
<span class="hljs-title function_">releaseVector</span>(v);
<span class="hljs-keyword">return</span> res;
}, <span class="hljs-variable language_">this</span>)) {
<span class="hljs-keyword">let</span> r = <span class="hljs-variable language_">this</span>.<span class="hljs-title function_">checkHitReturn</span>(tx, ty, mycell);
<span class="hljs-keyword">return</span> r;
}
<span class="hljs-keyword">return</span> <span class="hljs-literal">false</span>;
};</pre></div></div>
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<h4 id="factory">Factory</h4>
<pre><code>
</code></pre>
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<div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> makeTracer = <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_">Tracer</span>(items);
};
constructors.<span class="hljs-property">Tracer</span> = <span class="hljs-title class_">Tracer</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> {
makeTracer,
};</pre></div></div>
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