86 lines
3.1 KiB
JavaScript
86 lines
3.1 KiB
JavaScript
// Spells are a simplistic, composition-based replacement for the is="" attribute, which is not
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// supported on Webkit due to Apple's engineering being a bunch of obstinate idiots who explicitly
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// choose not to follow web standards.
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// Limitations:
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// - The data-cast attribute cannot be added dynamically.
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// - There is no disconnectedCallback. Only a constructor which initializes a spell.
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let spells = new Map();
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let elementsWithUnknownSpells = new Map();
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const sSpells = Symbol("spells");
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function castSpellOnElement(spellName, element) {
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element[sSpells] ??= new Map();
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if (!elementsWithUnknownSpells.has(spellName)) {
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elementsWithUnknownSpells.set(spellName, new Set());
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}
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let Spell = spells.get(spellName);
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if (Spell != null && !element[sSpells].has(Spell)) {
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element[sSpells].set(Spell, new Spell(element));
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elementsWithUnknownSpells.get(spellName).delete(element);
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} else {
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elementsWithUnknownSpells.get(spellName).add(element);
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}
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}
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function applySpells(elements) {
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for (let element of elements) {
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if (element instanceof Element) {
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let spellListString = element.getAttribute("data-cast");
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if (spellListString != null) {
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let spellList = spellListString.split(' ');
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for (let spellName of spellList) {
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castSpellOnElement(spellName, element);
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}
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}
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}
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}
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}
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export function addSpell(name, spell) {
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spells.set(name, spell);
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let elementsWithThisSpell = elementsWithUnknownSpells.get(name);
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if (elementsWithThisSpell != null) {
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for (let element of elementsWithThisSpell) {
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castSpellOnElement(name, element);
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}
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}
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}
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// Returns a spell's data. Gotchas: the spell needs to already be on the element.
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// Therefore, if this is used from within a spell, the requested spell must have already been
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// applied by this point.
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// Someday I may change this to an async function that resumes whenever the spell is available to
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// iron over this limitation. But today is not that day.
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export function spell(element, spell) {
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return element[sSpells].get(spell);
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}
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// Apply spells to elements which have them and have been loaded so far.
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let loadedSoFar = document.querySelectorAll("[data-cast]");
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applySpells(loadedSoFar);
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// For all other elements, add a mutation observer that will handle them.
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let mutationObserver = new MutationObserver(records => {
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for (let record of records) {
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let mutatedNodes = new Set();
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// NOTE: Added nodes may contain children which also need to be processed.
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// Collect those that have [data-cast] on them and apply spells to them.
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for (let addedNode of record.addedNodes) {
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addedNode.querySelectorAll("[data-cast]").forEach(element => mutatedNodes.add(element));
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}
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applySpells(mutatedNodes);
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}
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});
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mutationObserver.observe(document, { subtree: true, childList: true });
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// ------------ Common spells ------------
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// js makes things visible only when JavaScript is enabled.
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addSpell("js", function (element) {
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element.style.display = "block";
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});
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