Allow transitions and animations to work within iframes

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 * Allow `<svelte:self>` to be used in a slot ([#2798](https://github.com/sveltejs/svelte/issues/2798))
 * Expose object of unknown props in `$$restProps` ([#2930](https://github.com/sveltejs/svelte/issues/2930))
+* Allow transitions and animations to work within iframes ([#3624](https://github.com/sveltejs/svelte/issues/3624))
 * Disallow binding directly to `const` variables ([#4479](https://github.com/sveltejs/svelte/issues/4479))
 * Fix updating keyed `{#each}` blocks with `{:else}` ([#4536](https://github.com/sveltejs/svelte/issues/4536), [#4549](https://github.com/sveltejs/svelte/issues/4549))
 * Fix hydration of top-level content ([#4542](https://github.com/sveltejs/svelte/issues/4542))

src/runtime/internal/style_manager.ts

@@ -1,9 +1,13 @@
 import { element } from './dom';
 import { raf } from './environment';
 
-let stylesheet;
+interface ExtendedDoc extends Document {
+	__svelte_stylesheet: CSSStyleSheet;
+	__svelte_rules: Record<string, true>;
+}
+
+const active_docs = new Set<ExtendedDoc>();
 let active = 0;
-let current_rules = {};
 
 // https://github.com/darkskyapp/string-hash/blob/master/index.js
 function hash(str: string) {
@@ -25,14 +29,12 @@ export function create_rule(node: Element & ElementCSSInlineStyle, a: number, b:
 
 	const rule = keyframes + `100% {${fn(b, 1 - b)}}\n}`;
 	const name = `__svelte_${hash(rule)}_${uid}`;
+	const doc = node.ownerDocument as ExtendedDoc;
+	active_docs.add(doc);
+	const stylesheet = doc.__svelte_stylesheet || (doc.__svelte_stylesheet = doc.head.appendChild(element('style') as HTMLStyleElement).sheet as CSSStyleSheet);
+	const current_rules = doc.__svelte_rules || (doc.__svelte_rules = {});
 
 	if (!current_rules[name]) {
-		if (!stylesheet) {
-			const style = element('style');
-			document.head.appendChild(style);
-			stylesheet = style.sheet;
-		}
-
 		current_rules[name] = true;
 		stylesheet.insertRule(`@keyframes ${name} ${rule}`, stylesheet.cssRules.length);
 	}
@@ -45,22 +47,28 @@ export function create_rule(node: Element & ElementCSSInlineStyle, a: number, b:
 }
 
 export function delete_rule(node: Element & ElementCSSInlineStyle, name?: string) {
-	node.style.animation = (node.style.animation || '')
-		.split(', ')
-		.filter(name
-			? anim => anim.indexOf(name) < 0 // remove specific animation
-			: anim => anim.indexOf('__svelte') === -1 // remove all Svelte animations
-		)
-		.join(', ');
-
-	if (name && !--active) clear_rules();
+	const previous = (node.style.animation || '').split(', ');
+	const next = previous.filter(name
+		? anim => anim.indexOf(name) < 0 // remove specific animation
+		: anim => anim.indexOf('__svelte') === -1 // remove all Svelte animations
+	);
+	const deleted = previous.length - next.length;
+	if (deleted) {
+		node.style.animation = next.join(', ');
+		active -= deleted;
+		if (!active) clear_rules();
+	}
 }
 
 export function clear_rules() {
 	raf(() => {
 		if (active) return;
-		let i = stylesheet.cssRules.length;
-		while (i--) stylesheet.deleteRule(i);
-		current_rules = {};
+		active_docs.forEach(doc => {
+			const stylesheet = doc.__svelte_stylesheet;
+			let i = stylesheet.cssRules.length;
+			while (i--) stylesheet.deleteRule(i);
+			doc.__svelte_rules = {};
+		});
+		active_docs.clear();
 	});
 }

test/runtime/samples/transition-css-iframe/Foo.svelte

@@ -0,0 +1,16 @@
+<script>
+	export let visible;
+
+	function foo() {
+		return {
+			duration: 100,
+			css: t => {
+				return `opacity: ${t}`;
+			}
+		};
+	}
+</script>
+
+{#if visible}
+	<div transition:foo></div>
+{/if}

test/runtime/samples/transition-css-iframe/Frame.svelte

@@ -0,0 +1,58 @@
+<script>
+import { onMount, onDestroy, tick } from 'svelte';
+
+export let component;
+
+let frame;
+let doc;
+let content;
+
+$: mountComponent(doc, component);
+$: updateProps($$props);
+
+function mountComponent(doc) {
+  if (content) content.$destroy();
+  if (doc && component) {
+    const { component, ...props } = $$props;
+    content = new component({ target: doc.body, props });
+  }
+}
+
+function updateProps(props) {
+  if (content) {
+    const { component, ...rest } = props;
+    content.$set(rest);
+  }
+}
+
+function loadHandler() {
+  doc = frame.contentDocument;
+  // import styles
+  Array.from(document.querySelectorAll('style, link[rel="stylesheet"]'))
+    .forEach(node => doc.head.appendChild(node.cloneNode(true)));
+}
+
+onMount(async () => {
+  await tick();
+  if (frame.contentDocument.readyState === 'complete' && frame.contentDocument.defaultView) {
+    loadHandler();
+  } else {
+    frame.addEventListener('load', loadHandler);
+  }
+});
+
+onDestroy(() => {
+  if (frame) frame.removeEventListener('load', loadHandler);
+  if (content) content.$destroy();
+});
+</script>
+
+<iframe bind:this={frame} title="frame"></iframe>
+
+<style>
+iframe {
+  border: none;
+  width: 100%;
+  height: 100%;
+}
+</style>

test/runtime/samples/transition-css-iframe/_config.js

@@ -0,0 +1,18 @@
+export default {
+	skip_if_ssr: true,
+
+	async test({ assert, component, target, window, raf }) {
+		const frame = target.querySelector('iframe');
+		await Promise.resolve();
+
+		component.visible = true;
+		const div = frame.contentDocument.querySelector('div');
+
+		raf.tick(25);
+
+		component.visible = false;
+
+		raf.tick(26);
+		assert.ok(~div.style.animation.indexOf('25ms'));
+	},
+};

test/runtime/samples/transition-css-iframe/main.svelte

@@ -0,0 +1,8 @@
+<script>
+	import Frame from './Frame.svelte';
+	import Foo from './Foo.svelte';
+
+	export let visible;
+</script>
+
+<Frame component={Foo} {visible}/>