scrawl-canvas
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<h1 id="dom-management">DOM management</h1>
<p>Core DOM element discovery and management functionality, and the Scrawl-canvas <strong>Display cycle</strong>.</p>
<p>Scrawl-canvas breaks down the display cycle into three parts: <strong>clear</strong>; <strong>compile</strong>; and <strong>show</strong>. These can be triggered either as a single, combined <strong>render</strong> operation, or separately as-and-when needed.</p>
<p>The order in which DOM stack and canvas elements are processed during the display cycle can be changed by setting that element’s controller’s <strong>order</strong> attribute to a higher or lower integer value; elements are processed (in batches) from lowest to highest order value</p>
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<h4 id="imports">Imports</h4>
</div>
<div class="content"><div class='highlight'><pre><span class="hljs-keyword">import</span> { isa_canvas, generateUniqueString, isa_dom, pushUnique, removeItem, xt, Ωempty } <span class="hljs-keyword">from</span> <span class="hljs-string">"./utilities.js"</span>;
<span class="hljs-keyword">import</span> { artefact, canvas, group, stack, css, xcss } <span class="hljs-keyword">from</span> <span class="hljs-string">"./library.js"</span>;
<span class="hljs-keyword">import</span> { getPixelRatio, getIgnorePixelRatio } <span class="hljs-keyword">from</span> <span class="hljs-string">"./events.js"</span>;
<span class="hljs-keyword">import</span> { makeStack } <span class="hljs-keyword">from</span> <span class="hljs-string">"../factory/stack.js"</span>;
<span class="hljs-keyword">import</span> { makeElement } <span class="hljs-keyword">from</span> <span class="hljs-string">"../factory/element.js"</span>;
<span class="hljs-keyword">import</span> { makeCanvas } <span class="hljs-keyword">from</span> <span class="hljs-string">"../factory/canvas.js"</span>;</pre></div></div>
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<h4 id="root-elements">Root elements</h4>
<p><code>Exported array and function</code> (to modules). Root elements are the boxes whose dimensions define the dimensions and positioning of all that they contain. All <canvas> elements are root elements. Scrawl-canvas also allows other DOM elements (typically <div> elements) to be defined as root elements called <strong>stacks</strong>, whose child elements can then be positioned and dimensioned just like entity objects in a canvas.</p>
<p>Stacks can be nested within each other, and canvases can also be nested inside a stack. (Nothing can nest inside a canvas element). Only the top level stack will be included in the rootElements array.</p>
<p>The Scrawl-canvas <strong>Display cycle</strong> can start at the rootElements array, with each member of the array processed in turn.</p>
<p>The <strong>rootElements</strong> array keeps track of all ‘root’ stack artefacts, and also includes all canvas artefacts, whether they’re part of a stack or not. <strong>setRootElementSort</strong> forces the root</p>
</div>
<div class="content"><div class='highlight'><pre><span class="hljs-keyword">let</span> rootElements = [],
setRootElementsSort = <span class="hljs-function">() =></span> {rootElementsSort = <span class="hljs-literal">true</span>};</pre></div></div>
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<p>Local variables</p>
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<div class="content"><div class='highlight'><pre><span class="hljs-keyword">let</span> rootElements_sorted = [],
rootElementsSort = <span class="hljs-literal">true</span>;</pre></div></div>
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<p>Scrawl-canvas rootElements sorter uses a ‘bucket sort’ algorithm</p>
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<div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> sortRootElements = <span class="hljs-keyword">function</span> (<span class="hljs-params"></span>) {
<span class="hljs-keyword">let</span> floor = <span class="hljs-title class_">Math</span>.<span class="hljs-property">floor</span>;
<span class="hljs-keyword">if</span> (rootElementsSort) {
rootElementsSort = <span class="hljs-literal">false</span>;
<span class="hljs-keyword">let</span> buckets = [],
art, order, i, iz, item;
<span class="hljs-keyword">for</span> (i = <span class="hljs-number">0</span>, iz = rootElements.<span class="hljs-property">length</span>; i < iz; i++) {
item = rootElements[i];
art = artefact[item];
<span class="hljs-keyword">if</span> (art) {
order = <span class="hljs-title function_">floor</span>(art.<span class="hljs-property">order</span>) || <span class="hljs-number">0</span>;
<span class="hljs-keyword">if</span> (!buckets[order]) buckets[order] = [];
buckets[order].<span class="hljs-title function_">push</span>(art.<span class="hljs-property">name</span>);
}
}
rootElements_sorted = buckets.<span class="hljs-title function_">reduce</span>(<span class="hljs-function">(<span class="hljs-params">a, v</span>) =></span> a.<span class="hljs-title function_">concat</span>(v), []);
}
};</pre></div></div>
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<h4 id="stack-discovery">Stack discovery</h4>
<p><code>Exported function</code> (to modules). Parse the DOM, looking for all elements that have been given a <strong>data-stack</strong> attribute; then create <strong>Stack</strong> artefact wrappers for each of them. </p>
<p>This function will also create wrappers for all <strong>direct child elements</strong> (one level down) within the stack, and create appropriate wrappers (Stack, Canvas, Element) for them.</p>
</div>
<div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> getStacks = <span class="hljs-keyword">function</span> (<span class="hljs-params">query = <span class="hljs-string">'[data-scrawl-stack]'</span></span>) {
<span class="hljs-variable language_">document</span>.<span class="hljs-title function_">querySelectorAll</span>(query).<span class="hljs-title function_">forEach</span>(<span class="hljs-function"><span class="hljs-params">el</span> =></span> <span class="hljs-title function_">addInitialStackElement</span>(el));
};</pre></div></div>
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<p>Create a <strong>stack</strong> artefact wrapper for a given stack element.</p>
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<div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> addInitialStackElement = <span class="hljs-keyword">function</span> (<span class="hljs-params">el</span>) {
<span class="hljs-keyword">let</span> mygroup = el.<span class="hljs-title function_">getAttribute</span>(<span class="hljs-string">'data-scrawl-group'</span>),
myname = el.<span class="hljs-property">id</span> || el.<span class="hljs-title function_">getAttribute</span>(<span class="hljs-string">'name'</span>),
position = <span class="hljs-string">'absolute'</span>;
<span class="hljs-keyword">if</span> (!mygroup) {
el.<span class="hljs-title function_">setAttribute</span>(<span class="hljs-string">'data-scrawl-group'</span>, <span class="hljs-string">'root'</span>);
mygroup = <span class="hljs-string">'root'</span>;
position = <span class="hljs-string">'relative'</span>;
}
<span class="hljs-keyword">if</span> (!myname) {
myname = <span class="hljs-title function_">generateUniqueString</span>();
el.<span class="hljs-property">id</span> = myname;
}
<span class="hljs-keyword">let</span> mystack = <span class="hljs-title function_">makeStack</span>({
<span class="hljs-attr">name</span>: myname,
<span class="hljs-attr">domElement</span>: el,
<span class="hljs-attr">group</span>: mygroup,
<span class="hljs-attr">host</span>: mygroup,
<span class="hljs-attr">position</span>: position,
<span class="hljs-attr">setInitialDimensions</span>: <span class="hljs-literal">true</span>
});
<span class="hljs-title function_">processNewStackChildren</span>(el, myname);
<span class="hljs-keyword">return</span> mystack;
};</pre></div></div>
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<p>Helper function for addInitialStackElement()</p>
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<div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> processNewStackChildren = <span class="hljs-keyword">function</span> (<span class="hljs-params">el, name</span>) {
<span class="hljs-keyword">let</span> hostDims = el.<span class="hljs-title function_">getBoundingClientRect</span>(),
y = <span class="hljs-number">0</span>;</pre></div></div>
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<p>Only go down one level of hierarchy here; stacks don’t do hierarchies, only interested in knowing about immediate child elements</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-title class_">Array</span>.<span class="hljs-title function_">from</span>(el.<span class="hljs-property">children</span>).<span class="hljs-title function_">forEach</span>(<span class="hljs-function"><span class="hljs-params">child</span> =></span> {
<span class="hljs-keyword">if</span> (child.<span class="hljs-title function_">getAttribute</span>(<span class="hljs-string">'data-scrawl-stack'</span>) == <span class="hljs-literal">null</span> && !<span class="hljs-title function_">isa_canvas</span>(child) && child.<span class="hljs-property">tagName</span> !== <span class="hljs-string">'SCRIPT'</span>) {
<span class="hljs-keyword">let</span> dims = child.<span class="hljs-title function_">getBoundingClientRect</span>(),
computed = <span class="hljs-variable language_">window</span>.<span class="hljs-title function_">getComputedStyle</span>(child);
<span class="hljs-keyword">let</span> yHeight = <span class="hljs-built_in">parseFloat</span>(computed.<span class="hljs-property">marginTop</span>) + <span class="hljs-built_in">parseFloat</span>(computed.<span class="hljs-property">borderTopWidth</span>) + <span class="hljs-built_in">parseFloat</span>(computed.<span class="hljs-property">paddingTop</span>) + <span class="hljs-built_in">parseFloat</span>(computed.<span class="hljs-property">paddingBottom</span>) + <span class="hljs-built_in">parseFloat</span>(computed.<span class="hljs-property">borderBottomWidth</span>) + <span class="hljs-built_in">parseFloat</span>(computed.<span class="hljs-property">marginBottom</span>);
y = (!y) ? dims.<span class="hljs-property">top</span> - hostDims.<span class="hljs-property">top</span> : y;
<span class="hljs-keyword">let</span> args = {
<span class="hljs-attr">name</span>: child.<span class="hljs-property">id</span> || child.<span class="hljs-title function_">getAttribute</span>(<span class="hljs-string">'name'</span>),
<span class="hljs-attr">domElement</span>: child,
<span class="hljs-attr">group</span>: name,
<span class="hljs-attr">host</span>: name,
<span class="hljs-attr">position</span>: <span class="hljs-string">'absolute'</span>,
<span class="hljs-attr">width</span>: dims.<span class="hljs-property">width</span>,
<span class="hljs-attr">height</span>: dims.<span class="hljs-property">height</span>,
<span class="hljs-attr">startX</span>: dims.<span class="hljs-property">left</span> - hostDims.<span class="hljs-property">left</span>,
<span class="hljs-attr">startY</span>: y,
<span class="hljs-attr">classes</span>: (child.<span class="hljs-property">className</span>) ? child.<span class="hljs-property">className</span> : <span class="hljs-string">''</span>,
};
y += yHeight + dims.<span class="hljs-property">height</span>;
<span class="hljs-title function_">makeElement</span>(args);
}</pre></div></div>
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<p>No need to worry about processing child stacks - they’ll already be in the list of stacks to be processed</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">else</span> child.<span class="hljs-title function_">setAttribute</span>(<span class="hljs-string">'data-scrawl-group'</span>, name);
});
};</pre></div></div>
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<p><code>Exported function</code> (to modules and scrawl object). Use <strong>addStack</strong> to add a Scrawl-canvas stack element to a web page, or transform an existing element into a stack element. The items argument can include </p>
<ul>
<li><strong>element</strong> - the DOM element to be the stack - if not present, will autogenerate a div element</li>
<li><strong>host</strong> - the host element, either as the DOM element itself, or some sort of CSS search string; if not present, will create the stack at the stack element’s current place or, failing all else, add the stack to the end of the document body</li>
<li><strong>name</strong> - String identifier for the stack; if not included the function will attempt to use the element’s existing id or name attribute or, failing that, generate a random name for the stack.</li>
<li>any other regular stack attribute</li>
</ul>
</div>
<div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> addStack = <span class="hljs-keyword">function</span> (<span class="hljs-params">items = Ωempty</span>) {</pre></div></div>
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<p>define variables</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">let</span> el, host, hostinscrawl, mystack, mygroup, name,
position = <span class="hljs-string">'absolute'</span>,
newElement = <span class="hljs-literal">false</span>;</pre></div></div>
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<p>get, or generate a new, stack-to-be element</p>
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<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">if</span> (items.<span class="hljs-property">element</span> && items.<span class="hljs-property">element</span>.<span class="hljs-property">substring</span>) el = <span class="hljs-variable language_">document</span>.<span class="hljs-title function_">querySelector</span>(items.<span class="hljs-property">element</span>);
<span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (<span class="hljs-title function_">isa_dom</span>(items.<span class="hljs-property">element</span>)) el = items.<span class="hljs-property">element</span>;
<span class="hljs-keyword">else</span> {
newElement = <span class="hljs-literal">true</span>;
el = <span class="hljs-variable language_">document</span>.<span class="hljs-title function_">createElement</span>(<span class="hljs-string">'div'</span>);
}</pre></div></div>
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<li id="section-14">
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<p>get element’s host (parent-to-be) element</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">if</span> (items.<span class="hljs-property">host</span> && items.<span class="hljs-property">host</span>.<span class="hljs-property">substring</span>) {
host = <span class="hljs-variable language_">document</span>.<span class="hljs-title function_">querySelector</span>(items.<span class="hljs-property">host</span>);
<span class="hljs-keyword">if</span> (!host) host = <span class="hljs-variable language_">document</span>.<span class="hljs-property">body</span>;
}
<span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (<span class="hljs-title function_">isa_dom</span>(items.<span class="hljs-property">host</span>)) host = items.<span class="hljs-property">host</span>;
<span class="hljs-keyword">else</span> <span class="hljs-keyword">if</span> (<span class="hljs-title function_">xt</span>(el.<span class="hljs-property">parentElement</span>)) host = el.<span class="hljs-property">parentElement</span>;
<span class="hljs-keyword">else</span> host = <span class="hljs-variable language_">document</span>.<span class="hljs-property">body</span>;</pre></div></div>
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<li id="section-15">
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<p>if dimensions have been set in the argument, apply them to the stack-to-be element</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">if</span> (<span class="hljs-title function_">xt</span>(items.<span class="hljs-property">width</span>)) el.<span class="hljs-property">style</span>.<span class="hljs-property">width</span> = (items.<span class="hljs-property">width</span>.<span class="hljs-property">toFixed</span>) ? <span class="hljs-string">`<span class="hljs-subst">${items.width}</span>px`</span> : items.<span class="hljs-property">width</span>;
<span class="hljs-keyword">if</span> (<span class="hljs-title function_">xt</span>(items.<span class="hljs-property">height</span>)) el.<span class="hljs-property">style</span>.<span class="hljs-property">height</span> = (items.<span class="hljs-property">height</span>.<span class="hljs-property">toFixed</span>) ? <span class="hljs-string">`<span class="hljs-subst">${items.height}</span>px`</span> : items.<span class="hljs-property">height</span>;</pre></div></div>
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<li id="section-16">
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<p>make sure the stack-to-be element has an id attribute</p>
</div>
<div class="content"><div class='highlight'><pre> name = items.<span class="hljs-property">name</span> || el.<span class="hljs-property">id</span> || el.<span class="hljs-title function_">getAttribute</span>(<span class="hljs-string">'name'</span>) || <span class="hljs-string">''</span>;
<span class="hljs-keyword">if</span> (!name) name = <span class="hljs-title function_">generateUniqueString</span>();
el.<span class="hljs-property">id</span> = name;</pre></div></div>
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<li id="section-17">
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<p>set the ‘data-scrawl-stack’ attribute on the stack-to-be element</p>
</div>
<div class="content"><div class='highlight'><pre> el.<span class="hljs-title function_">setAttribute</span>(<span class="hljs-string">'data-scrawl-stack'</span>, <span class="hljs-string">'data-scrawl-stack'</span>);</pre></div></div>
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<li id="section-18">
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<p>determine whether the parent element is already known to Scrawl-canvas - affects the stack-to-be element’s group </p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">if</span> (host && host.<span class="hljs-title function_">getAttribute</span>(<span class="hljs-string">'data-scrawl-stack'</span>) != <span class="hljs-literal">null</span>) {
hostinscrawl = artefact[host.<span class="hljs-property">id</span>];
mygroup = (hostinscrawl) ? hostinscrawl.<span class="hljs-property">name</span> : <span class="hljs-string">'root'</span>;
}
<span class="hljs-keyword">else</span> mygroup = <span class="hljs-string">'root'</span>;</pre></div></div>
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<p>set the ‘data-scrawl-group’ attribute on the stack-to-be element</p>
</div>
<div class="content"><div class='highlight'><pre> el.<span class="hljs-title function_">setAttribute</span>(<span class="hljs-string">'data-scrawl-group'</span>, mygroup);</pre></div></div>
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<p>determine what the stack-to-be element’s position style attribute will be</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">if</span> (mygroup === <span class="hljs-string">'root'</span>) position = <span class="hljs-string">'relative'</span>;</pre></div></div>
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<li id="section-21">
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<p>add (or move) the stack-to-be element to/in the DOM</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">if</span> (!el.<span class="hljs-property">parentElement</span> || host.<span class="hljs-property">id</span> !== el.<span class="hljs-property">parentElement</span>.<span class="hljs-property">id</span>) host.<span class="hljs-title function_">appendChild</span>(el);</pre></div></div>
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<li id="section-22">
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<p>create the Scrawl-canvas Stack artefact</p>
</div>
<div class="content"><div class='highlight'><pre> mystack = <span class="hljs-title function_">makeStack</span>({
<span class="hljs-attr">name</span>: name,
<span class="hljs-attr">domElement</span>: el,
<span class="hljs-attr">group</span>: mygroup,
<span class="hljs-attr">host</span>: mygroup,
<span class="hljs-attr">position</span>: position,
<span class="hljs-attr">setInitialDimensions</span>: <span class="hljs-literal">true</span>
});
<span class="hljs-title function_">processNewStackChildren</span>(el, name);</pre></div></div>
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<li id="section-23">
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<p>in case any of the child elements were already a Scrawl-canvas stack, un-root them (if required)</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-title class_">Array</span>.<span class="hljs-title function_">from</span>(el.<span class="hljs-property">childNodes</span>).<span class="hljs-title function_">forEach</span>(<span class="hljs-function"><span class="hljs-params">child</span> =></span> {
<span class="hljs-keyword">if</span> (child.<span class="hljs-property">id</span> && rootElements.<span class="hljs-title function_">indexOf</span>(child.<span class="hljs-property">id</span>) >= <span class="hljs-number">0</span>) <span class="hljs-title function_">removeItem</span>(rootElements, child.<span class="hljs-property">id</span>);
});</pre></div></div>
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<p>set the new Stack’s remaining attributes, clearing out any attributes already handled</p>
</div>
<div class="content"><div class='highlight'><pre> <span class="hljs-keyword">delete</span> items.<span class="hljs-property">name</span>;
<span class="hljs-keyword">delete</span> items.<span class="hljs-property">element</span>;
<span class="hljs-keyword">delete</span> items.<span class="hljs-property">host</span>;
<span class="hljs-keyword">delete</span> items.<span class="hljs-property">width</span>;
<span class="hljs-keyword">delete</span> items.<span class="hljs-property">height</span>;
mystack.<span class="hljs-title function_">set</span>(items);</pre></div></div>
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<p>tidy up and complete</p>
</div>
<div class="content"><div class='highlight'><pre> rootElementsSort = <span class="hljs-literal">true</span>;
<span class="hljs-keyword">return</span> mystack;
};</pre></div></div>
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<li id="section-26">
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<h4 id="canvas-discovery">Canvas discovery</h4>
<p><code>Exported function</code> (to modules). Parse the DOM, looking for <canvas> elements; then create <strong>Canvas</strong> artefact and <strong>Cell</strong> asset wrappers for each canvas found. Canvas elements do not need to be part of a stack and can appear anywhere in the HTML body.</p>
</div>
<div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> getCanvases = <span class="hljs-keyword">function</span> (<span class="hljs-params">query = <span class="hljs-string">'[data-scrawl-canvas]'</span></span>) {
<span class="hljs-keyword">let</span> item;
<span class="hljs-variable language_">document</span>.<span class="hljs-title function_">querySelectorAll</span>(query).<span class="hljs-title function_">forEach</span>(<span class="hljs-function">(<span class="hljs-params">el, index</span>) =></span> {
item = <span class="hljs-title function_">addInitialCanvasElement</span>(el);
<span class="hljs-keyword">if</span> (!index) <span class="hljs-title function_">setCurrentCanvas</span>(item);
});
};</pre></div></div>
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<li id="section-27">
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<p>Create a <strong>canvas</strong> artefact wrapper for a given canvas element.</p>
</div>
<div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> addInitialCanvasElement = <span class="hljs-keyword">function</span> (<span class="hljs-params">el</span>) {
<span class="hljs-keyword">let</span> mygroup = el.<span class="hljs-title function_">getAttribute</span>(<span class="hljs-string">'data-scrawl-group'</span>),
myname = el.<span class="hljs-property">id</span> || el.<span class="hljs-title function_">getAttribute</span>(<span class="hljs-string">'name'</span>),
position = <span class="hljs-string">'absolute'</span>;
<span class="hljs-keyword">if</span> (!mygroup) {
el.<span class="hljs-title function_">setAttribute</span>(<span class="hljs-string">'data-scrawl-group'</span>, <span class="hljs-string">'root'</span>);
mygroup = <span class="hljs-string">'root'</span>;
position = el.<span class="hljs-property">style</span>.<span class="hljs-property">position</span>;
}
<span class="hljs-keyword">if</span> (!myname) {
myname = <span class="hljs-title function_">generateUniqueString</span>();
el.<span class="hljs-property">id</span> = myname;
}
<span class="hljs-keyword">return</span> <span class="hljs-title function_">makeCanvas</span>({
<span class="hljs-attr">name</span>: myname,
<span class="hljs-attr">domElement</span>: el,
<span class="hljs-attr">group</span>: mygroup,
<span class="hljs-attr">host</span>: mygroup,
<span class="hljs-attr">position</span>: position,
<span class="hljs-attr">setInitialDimensions</span>: <span class="hljs-literal">true</span>
});
};</pre></div></div>
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<li id="section-28">
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<p><code>Exported function</code> (to modules and scrawl object). Parse the DOM, looking for a specific <canvas> element; then create a <strong>Canvas</strong> artefact and <strong>Cell</strong> asset wrapper for it.</p>
</div>
<div class="content"><div class='highlight'><pre><span class="hljs-keyword">const</span> getCanvas = <span class="hljs-keyword">function</span> (<span class="hljs-params">search</span>) {
<span class="hljs-keyword">let</span> el = <span class="hljs-variable language_">document</span>.<span class="hljs-title function_">querySelector</span>(search),
canvas = <span class="hljs-literal">false</span>;
<span class="hljs-keyword">if</span> (el) canvas = <span class="hljs-title function_">addInitialCa