scrawl-canvas

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class="sswrap "> <a class="ss" href="#section-1">§</a> </div> <h1 id="demo-canvas-056">Demo Canvas 056</h1> <p>Seeded random number generator; point on path</p> </div> </li> <li id="section-2"> <div class="annotation"> <div class="sswrap "> <a class="ss" href="#section-2">§</a> </div> <p><a href="../../demo/canvas-056.html">Run code</a></p> </div> <div class="content"><div class='highlight'><pre><span class="hljs-keyword">import</span> * <span class="hljs-keyword">as</span> scrawl <span class="hljs-keyword">from</span> <span class="hljs-string">'../source/scrawl.js'</span> <span class="hljs-keyword">import</span> { reportSpeed } <span class="hljs-keyword">from</span> <span class="hljs-string">'./utilities.js'</span>;</pre></div></div> </li> <li id="section-3"> <div class="annotation"> <div class="sswrap "> <a class="ss" href="#section-3">§</a> </div> <h4 id="scene-setup">Scene setup</h4> </div> <div class="content"><div class='highlight'><pre><span class="hljs-keyword">let</span> canvas = scrawl.<span class="hljs-property">library</span>.<span class="hljs-property">artefact</span>.<span class="hljs-property">mycanvas</span>;</pre></div></div> </li> <li id="section-4"> <div class="annotation"> <div class="sswrap "> <a class="ss" href="#section-4">§</a> </div> <p>Magic numbers</p> </div> <div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> noOfPins = <span class="hljs-number">16</span>, angleAddition = <span class="hljs-number">90</span>, pinRotationAngle = <span class="hljs-number">360</span> / noOfPins;;</pre></div></div> </li> <li id="section-5"> <div class="annotation"> <div class="sswrap "> <a class="ss" href="#section-5">§</a> </div> <p>User-updatable values</p> </div> <div class="content"><div class='highlight'><pre><span class="hljs-keyword">let</span> densityValue = <span class="hljs-number">600</span>, lengthValue = <span class="hljs-number">20</span>, rotationValue = <span class="hljs-number">360</span>, pathrollValue = <span class="hljs-literal">false</span>;</pre></div></div> </li> <li id="section-6"> <div class="annotation"> <div class="sswrap "> <a class="ss" href="#section-6">§</a> </div> <p>We use a Polyline entity as the guide along which we shall calculate the hairs for our Shape entity. The Polyline’s pins are a set of Wheel entitys which the user can drag around the canvas to reshape the Polyline</p> </div> <div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> firstPins = scrawl.<span class="hljs-title function_">makeGroup</span>({ <span class="hljs-attr">name</span>: <span class="hljs-string">'first-pins'</span>, <span class="hljs-attr">host</span>: canvas.<span class="hljs-property">base</span>.<span class="hljs-property">name</span>, }); <span class="hljs-keyword">const</span> coord = scrawl.<span class="hljs-title function_">requestCoordinate</span>(); <span class="hljs-keyword">for</span> (<span class="hljs-keyword">let</span> i = <span class="hljs-number">0</span>; i < noOfPins; i++) { coord.<span class="hljs-title function_">setFromArray</span>([<span class="hljs-number">0</span>, <span class="hljs-number">200</span>]).<span class="hljs-title function_">rotate</span>(i * pinRotationAngle).<span class="hljs-title function_">add</span>([<span class="hljs-number">300</span>, <span class="hljs-number">300</span>]); scrawl.<span class="hljs-title function_">makeWheel</span>({ <span class="hljs-attr">name</span>: <span class="hljs-string">`pin-1-<span class="hljs-subst">${i}</span>`</span>, <span class="hljs-attr">group</span>: <span class="hljs-string">'first-pins'</span>,</pre></div></div> </li> <li id="section-7"> <div class="annotation"> <div class="sswrap "> <a class="ss" href="#section-7">§</a> </div> <p>@ts-expect-error</p> </div> <div class="content"><div class='highlight'><pre> <span class="hljs-attr">start</span>: [...coord], <span class="hljs-attr">handle</span>: [<span class="hljs-string">'center'</span>, <span class="hljs-string">'center'</span>], <span class="hljs-attr">radius</span>: <span class="hljs-number">10</span>, <span class="hljs-attr">fillStyle</span>: <span class="hljs-string">'red'</span>, <span class="hljs-attr">method</span>: <span class="hljs-string">'fillThenDraw'</span>, }); } scrawl.<span class="hljs-title function_">releaseCoordinate</span>(coord); <span class="hljs-keyword">const</span> firstOutline = scrawl.<span class="hljs-title function_">makePolyline</span>({ <span class="hljs-attr">name</span>: <span class="hljs-string">'first-outline'</span>, <span class="hljs-attr">pins</span>: firstPins.<span class="hljs-title function_">get</span>(<span class="hljs-string">'artefacts'</span>), <span class="hljs-attr">mapToPins</span>: <span class="hljs-literal">true</span>, <span class="hljs-attr">tension</span>: <span class="hljs-number">0.25</span>, <span class="hljs-attr">strokeStyle</span>: <span class="hljs-string">'green'</span>, <span class="hljs-attr">method</span>: <span class="hljs-string">'draw'</span>, <span class="hljs-attr">closed</span>: <span class="hljs-literal">true</span>, <span class="hljs-attr">useAsPath</span>: <span class="hljs-literal">true</span>, <span class="hljs-attr">constantPathSpeed</span>: <span class="hljs-literal">true</span>, });</pre></div></div> </li> <li id="section-8"> <div class="annotation"> <div class="sswrap "> <a class="ss" href="#section-8">§</a> </div> <p>The Shape entity starts with a minimal pathDefinition value. Note that the Shape’s start and handle attributes are centered; this entity does not pivot or mimic to the Polyline entity which is why their borders are often misaligned.</p> </div> <div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> secondOutline = scrawl.<span class="hljs-title function_">makeShape</span>({ <span class="hljs-attr">name</span>: <span class="hljs-string">'second-outline'</span>, <span class="hljs-attr">pathDefinition</span>: <span class="hljs-string">'m0,0'</span>, <span class="hljs-attr">start</span>: [<span class="hljs-string">'center'</span>, <span class="hljs-string">'center'</span>], <span class="hljs-attr">handle</span>: [<span class="hljs-string">'center'</span>, <span class="hljs-string">'center'</span>], <span class="hljs-attr">lineWidth</span>: <span class="hljs-number">4</span>, <span class="hljs-attr">lineCap</span>: <span class="hljs-string">'round'</span>, <span class="hljs-attr">strokeStyle</span>: <span class="hljs-string">'darkslategray'</span>, <span class="hljs-attr">method</span>: <span class="hljs-string">'draw'</span>, });</pre></div></div> </li> <li id="section-9"> <div class="annotation"> <div class="sswrap "> <a class="ss" href="#section-9">§</a> </div> <p>We recalculate the Shape entity’s pathDefinition value each time the user updates a control or drags one of the Polyline entity’s pins. </p> </div> <div class="content"><div class='highlight'><pre><span class="hljs-keyword">let</span> currentOutline = <span class="hljs-string">''</span>; <span class="hljs-keyword">const</span> checkOutlines = <span class="hljs-keyword">function</span> (<span class="hljs-params"></span>) { <span class="hljs-keyword">let</span> outline = firstOutline.<span class="hljs-title function_">get</span>(<span class="hljs-string">'pathDefinition'</span>); <span class="hljs-keyword">if</span> (outline !== currentOutline) { currentOutline = outline;</pre></div></div> </li> <li id="section-10"> <div class="annotation"> <div class="sswrap "> <a class="ss" href="#section-10">§</a> </div> <p>Rotations are calculated with the help of a pool Coordinate object</p> </div> <div class="content"><div class='highlight'><pre> <span class="hljs-keyword">const</span> coord = scrawl.<span class="hljs-title function_">requestCoordinate</span>();</pre></div></div> </li> <li id="section-11"> <div class="annotation"> <div class="sswrap "> <a class="ss" href="#section-11">§</a> </div> <p>Get the number generator</p> </div> <div class="content"><div class='highlight'><pre> <span class="hljs-keyword">const</span> numberGenerator = scrawl.<span class="hljs-title function_">seededRandomNumberGenerator</span>(<span class="hljs-string">'hello-world'</span>); <span class="hljs-keyword">let</span> pos, x, y, a, dx, dy; <span class="hljs-keyword">let</span> line = <span class="hljs-string">''</span>; <span class="hljs-keyword">for</span> (<span class="hljs-keyword">let</span> i = <span class="hljs-number">0</span>; i < densityValue; i++) {</pre></div></div> </li> <li id="section-12"> <div class="annotation"> <div class="sswrap "> <a class="ss" href="#section-12">§</a> </div> <p><strong>getPathPositionData</strong> returns an Object with attributes <code>x</code>, <code>y</code>, <code>angle</code>.</p> <ul> <li>The first argument is a float Number value between <code>0</code> and <code>1</code>, representing the relative position of the required point along the path.</li> <li>The second argument is a boolean which, when set to true, will return the <code>constant speed</code> coordinate rather than the <code>natural speed</code> coordinate.</li> </ul> </div> <div class="content"><div class='highlight'><pre> pos = firstOutline.<span class="hljs-title function_">getPathPositionData</span>(i / densityValue, <span class="hljs-literal">true</span>); x = pos.<span class="hljs-property">x</span>; y = pos.<span class="hljs-property">y</span>; <span class="hljs-keyword">if</span> (pathrollValue) { a = pos.<span class="hljs-property">angle</span> + <span class="hljs-number">90</span>; coord.<span class="hljs-title function_">set</span>(<span class="hljs-number">0</span>, numberGenerator.<span class="hljs-title function_">random</span>() * lengthValue).<span class="hljs-title function_">rotate</span>(a + (numberGenerator.<span class="hljs-title function_">random</span>() * rotationValue)).<span class="hljs-title function_">add</span>([x, y]); } <span class="hljs-keyword">else</span> { coord.<span class="hljs-title function_">set</span>(<span class="hljs-number">0</span>, numberGenerator.<span class="hljs-title function_">random</span>() * lengthValue).<span class="hljs-title function_">rotate</span>(numberGenerator.<span class="hljs-title function_">random</span>() * rotationValue).<span class="hljs-title function_">add</span>([x, y]); } [dx, dy] = coord; line += <span class="hljs-string">`M<span class="hljs-subst">${x}</span>,<span class="hljs-subst">${y}</span>L<span class="hljs-subst">${dx}</span>,<span class="hljs-subst">${dy}</span>`</span>; }</pre></div></div> </li> <li id="section-13"> <div class="annotation"> <div class="sswrap "> <a class="ss" href="#section-13">§</a> </div> <p>Return the Coordinate object back to the pool - failure to do this leads to memory leaks!</p> </div> <div class="content"><div class='highlight'><pre> scrawl.<span class="hljs-title function_">releaseCoordinate</span>(coord); secondOutline.<span class="hljs-title function_">set</span>({ <span class="hljs-attr">pathDefinition</span>: line, }); } };</pre></div></div> </li> <li id="section-14"> <div class="annotation"> <div class="sswrap "> <a class="ss" href="#section-14">§</a> </div> <h4 id="scene-animation">Scene animation</h4> <p>Function to display frames-per-second data, and other information relevant to the demo</p> </div> <div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> report = <span class="hljs-title function_">reportSpeed</span>(<span class="hljs-string">'#reportmessage'</span>, <span class="hljs-keyword">function</span> (<span class="hljs-params"></span>) {</pre></div></div> </li> <li id="section-15"> <div class="annotation"> <div class="sswrap "> <a class="ss" href="#section-15">§</a> </div> <p>@ts-expect-error</p> </div> <div class="content"><div class='highlight'><pre> <span class="hljs-keyword">return</span> <span class="hljs-string">` Rotation: <span class="hljs-subst">${rotation.value}</span>; Length: <span class="hljs-subst">${length.value}</span>; Density: <span class="hljs-subst">${density.value}</span>`</span>; });</pre></div></div> </li> <li id="section-16"> <div class="annotation"> <div class="sswrap "> <a class="ss" href="#section-16">§</a> </div> <p>Create the Display cycle animation</p> </div> <div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> animation = scrawl.<span class="hljs-title function_">makeRender</span>({ <span class="hljs-attr">name</span>: <span class="hljs-string">"demo-animation"</span>, <span class="hljs-attr">target</span>: canvas, <span class="hljs-attr">commence</span>: checkOutlines, <span class="hljs-attr">afterShow</span>: report, }); scrawl.<span class="hljs-title function_">makeDragZone</span>({ <span class="hljs-attr">zone</span>: canvas, <span class="hljs-attr">collisionGroup</span>: <span class="hljs-string">'first-pins'</span>, <span class="hljs-attr">endOn</span>: [<span class="hljs-string">'up'</span>, <span class="hljs-string">'leave'</span>], <span class="hljs-attr">preventTouchDefaultWhenDragging</span>: <span class="hljs-literal">true</span>, });</pre></div></div> </li> <li id="section-17"> <div class="annotation"> <div class="sswrap "> <a class="ss" href="#section-17">§</a> </div> <h4 id="development-and-testing">Development and testing</h4> </div> <div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> rotation = <span class="hljs-variable language_">document</span>.<span class="hljs-title function_">querySelector</span>(<span class="hljs-string">'#rotation'</span>); <span class="hljs-keyword">const</span> length = <span class="hljs-variable language_">document</span>.<span class="hljs-title function_">querySelector</span>(<span class="hljs-string">'#length'</span>); <span class="hljs-keyword">const</span> density = <span class="hljs-variable language_">document</span>.<span class="hljs-title function_">querySelector</span>(<span class="hljs-string">'#density'</span>); <span class="hljs-keyword">const</span> pathRotation = <span class="hljs-variable language_">document</span>.<span class="hljs-title function_">querySelector</span>(<span class="hljs-string"