Add render function to <gradio-app> (#5158)

* add function on_load to gradio-app web element

* typo

* fix test

* add ready event

* add custom events and use onMount

* add changeset

* add changeset

* move event logic

* add changeset

* clean up whitespace

* add onloadcomplete to guide

* add changeset

* add changeset

* add highlight

* change event name to render and ensure it runs after DOM mounting is complete

* update docs

* rename var

* tweak

* renaming

* tweak

* tweaks

* mount statustracker nodes

* typo

* tweaks

* copy tweak

---------

Co-authored-by: gradio-pr-bot <gradio-pr-bot@users.noreply.github.com>

.changeset/stale-houses-grin.md

@@ -0,0 +1,20 @@
+---
+"@gradio/app": minor
+"gradio": minor
+---
+
+highlight:
+
+#### Add `render` function to `<gradio-app>`
+
+We now have an event `render` on the <gradio-app> web component, which is triggered once the embedded space has finished rendering.
+
+```html
+<script>
+	function handleLoadComplete() {
+		console.log("Embedded space has finished rendering");
+	}
+	const gradioApp = document.querySelector("gradio-app");
+	gradioApp.addEventListener("render", handleLoadComplete);
+</script>
+```

guides/01_getting-started/03_sharing-your-app.md

@@ -108,6 +108,7 @@ You can also customize the appearance and behavior of your web component with at
 - `autoscroll`: whether to autoscroll to the output when prediction has finished (by default `"false"`)
 - `eager`: whether to load the Gradio app as soon as the page loads (by default `"false"`)
 - `theme_mode`: whether to use the `dark`, `light`, or default `system` theme mode (by default `"system"`)
+- `render`: an event that is triggered once the embedded space has finished rendering.
 
 Here's an example of how to use these attributes to create a Gradio app that does not lazy load and has an initial height of 0px.
 
@@ -119,6 +120,19 @@ Here's an example of how to use these attributes to create a Gradio app that doe
 ></gradio-app>
 ```
 
+Here's another example of how to use the `render` event. An event listener is used to capture the `render` event and will call the `handleLoadComplete()` function once rendering is complete. 
+
+```html
+<script>
+	function handleLoadComplete() {
+		console.log("Embedded space has finished rendering");
+	}
+
+	const gradioApp = document.querySelector("gradio-app");
+	gradioApp.addEventListener("render", handleLoadComplete);
+</script>
+```
+
 _Note: While Gradio's CSS will never impact the embedding page, the embedding page can affect the style of the embedded Gradio app. Make sure that any CSS in the parent page isn't so general that it could also apply to the embedded Gradio app and cause the styling to break. Element selectors such as `header { ... }` and `footer { ... }` will be the most likely to cause issues._
 
 ### Embedding with IFrames

js/app/src/Blocks.svelte

@@ -19,6 +19,7 @@
 	import { Toast } from "@gradio/statustracker";
 	import type { ToastMessage } from "@gradio/statustracker";
 	import type { ShareData } from "@gradio/utils";
+	import { dequal } from "dequal";
 
 	import logo from "./images/logo.svg";
 	import api_logo from "./api_docs/img/api-logo.svg";
@@ -44,6 +45,9 @@
 
 	let loading_status = create_loading_status_store();
 
+	const walked_node_ids = new Set();
+	const mounted_node_ids = new Set();
+
 	$: app_state.update((s) => ({ ...s, autoscroll }));
 
 	let rootNode: ComponentMeta = {
@@ -180,6 +184,8 @@
 
 	async function walk_layout(node: LayoutNode): Promise<void> {
 		let instance = instance_map[node.id];
+		walked_node_ids.add(node.id);
+
 		const _component = (await _component_map.get(
 			`${instance.type}_${_type_for_id.get(node.id) || "static"}`
 		))!.component;
@@ -209,6 +215,7 @@
 	});
 
 	export let ready = false;
+	export let render_complete = false;
 	Promise.all(Array.from(component_set)).then(() => {
 		walk_layout(layout)
 			.then(async () => {
@@ -490,7 +497,9 @@
 
 	let attached_error_listeners: number[] = [];
 	let shareable_components: number[] = [];
-	async function handle_mount(): Promise<void> {
+	async function handle_mount({ detail }: { detail: number }): Promise<void> {
+		mounted_node_ids.add(detail);
+
 		await tick();
 
 		var a = target.getElementsByTagName("a");
@@ -564,6 +573,8 @@
 				}
 			}
 		});
+
+		checkRenderCompletion();
 	}
 
 	function handle_destroy(id: number): void {
@@ -592,6 +603,12 @@
 			set_prop(instance_map[id], "pending", pending_status === "pending");
 		}
 	}
+
+	function checkRenderCompletion(): void {
+		if (dequal(walked_node_ids, mounted_node_ids)) {
+			render_complete = true;
+		}
+	}
 </script>
 
 <svelte:head>

js/app/src/Index.svelte

@@ -98,6 +98,7 @@
 	let app_id: string | null = null;
 	let wrapper: HTMLDivElement;
 	let ready = false;
+	let render_complete = false;
 	let config: Config;
 	let loading_text = $_("common.loading") + "...";
 	let active_theme_mode: ThemeMode;
@@ -285,6 +286,16 @@
 	onMount(async () => {
 		intersecting.register(_id, wrapper);
 	});
+
+	$: if (render_complete) {
+		wrapper.dispatchEvent(
+			new CustomEvent("render", {
+				bubbles: true,
+				cancelable: false,
+				composed: true,
+			})
+		);
+	}
 </script>
 
 <Embed
@@ -345,6 +356,7 @@
 			target={wrapper}
 			{autoscroll}
 			bind:ready
+			bind:render_complete
 			show_footer={!is_embed}
 			{app_mode}
 		/>

js/app/src/Render.svelte

@@ -17,16 +17,33 @@
 	export let theme_mode: ThemeMode;
 
 	const dispatch = createEventDispatcher<{ mount: number; destroy: number }>();
+	let filtered_children: ComponentMeta[] = [];
 
 	onMount(() => {
 		dispatch("mount", id);
 
-		return () => dispatch("destroy", id);
+		for (const child of filtered_children) {
+			dispatch("mount", child.id);
+		}
+
+		return () => {
+			dispatch("destroy", id);
+
+			for (const child of filtered_children) {
+				dispatch("mount", child.id);
+			}
+		};
 	});
 
 	$: children =
 		children &&
-		children.filter((v) => instance_map[v.id].type !== "statustracker");
+		children.filter((v) => {
+			const valid_node = instance_map[v.id].type !== "statustracker";
+			if (!valid_node) {
+				filtered_children.push(v);
+			}
+			return valid_node;
+		});
 
 	setContext("BLOCK_KEY", parent);
 

js/app/src/main.ts

@@ -73,8 +73,6 @@ function create_custom_element(): void {
 
 			observer.observe(this, { childList: true });
 
-			// if (this.)
-
 			this.app = new Index({
 				target: this,
 				props: {

package.json

@@ -56,6 +56,7 @@
 		"autoprefixer": "^10.4.4",
 		"babylonjs": "^5.17.1",
 		"babylonjs-loaders": "^5.17.1",
+		"dequal": "^2.0.2",
 		"eslint": "^8.46.0",
 		"eslint-plugin-svelte": "^2.32.4",
 		"globals": "^13.20.0",