Add experimental Presentation API presenter plugin

details-notes/plugin.js

@@ -19,7 +19,7 @@ for (let details of document.querySelectorAll("details.notes")) {
 		create.start(details, `<summary>Notes</summary>`);
 	}
 
-	if (Inspire.projector) {
+	if (Inspire.projector || document.body.classList.contains("presenter")) {
 		// Speaker view, let's have the notes open by default
 		details.open = true;
 	}

plugin-autoload.js

@@ -4,7 +4,8 @@
  */
 export default {
 	timer: "[data-duration]",
-	presenter: "details.notes",
+	presenter: "body:not(.experimental-presentation-api) details.notes",
+	presenter2: "body.experimental-presentation-api details.notes",
 	"lazy-load": "[data-src]:not(.slide)",
 	"slide-style": "style[data-slide]",
 	overview: "*",

presenter/plugin.js

@@ -1,5 +1,5 @@
 import Inspire from "@inspirejs/core";
-import { $$ } from "@inspirejs/core/util";
+import { enterPresenterView, onPresenterSlidechange } from "./presenter-ui.js";
 
 export const hasCSS = true;
 
@@ -22,10 +22,7 @@ Inspire.hooks.add({
 			window.focus();
 
 			// Switch this one to presenter view
-			document.body.classList.add("presenter", "show-next");
-
-			// Are there <details class="notes"> elements in the current slide? Open them
-			$$("details.notes", Inspire.currentSlide).forEach(d => (d.open = true));
+			enterPresenterView();
 		}
 	},
 	slidechange: env => {
@@ -36,48 +33,7 @@ Inspire.hooks.add({
 			otherWindow.Inspire.goto(env.which);
 		}
 
-		if (Inspire.projector) {
-			// We are in the presenter window
-			$$("details.notes", Inspire.currentSlide).forEach(d => (d.open = true));
-
-			if (Inspire.currentSlide.matches("[data-start-time] [data-time]")) {
-				// This slide has a time hint, show if we're running behind
-
-				// Scheduled start time
-				let startTime = Inspire.currentSlide
-					.closest("[data-start-time]")
-					?.getAttribute("data-start-time");
-				let startTimeParsed = startTime.split(":").map(n => +n);
-
-				// Ideal offset from start time
-				let time = Inspire.currentSlide.dataset.time;
-				let timeParsed = time.split(":").map(n => +n);
-
-				// Current local time
-				let currentTime = new Date().toLocaleString("en", {
-					timeStyle: "short",
-					hour12: false,
-				});
-				let currentTimeParsed = currentTime.split(":").map(n => +n);
-
-				// Actual offset from start time, in minutes
-				let actualTime =
-					(currentTimeParsed[0] - startTimeParsed[0]) * 60 +
-					(currentTimeParsed[1] - startTimeParsed[1]);
-
-				let offset = actualTime - (timeParsed[0] * 60 + timeParsed[1]);
-				let offsetHours = Math.floor(Math.abs(offset / 60))
-					.toString()
-					.padStart(2, "0");
-				let offsetMinutes = (Math.abs(offset) % 60).toString().padStart(2, "0");
-
-				Inspire.currentSlide.dataset.offset = `${offsetHours}:${offsetMinutes}`;
-
-				if (offset !== 0) {
-					Inspire.currentSlide.dataset.running = offset > 0 ? "behind" : "ahead";
-				}
-			}
-		}
+		onPresenterSlidechange();
 	},
 	"gotoitem-end": env => {
 		let otherWindow = Inspire.projector || Inspire.presenter;

presenter/presenter-ui.js

@@ -0,0 +1,71 @@
+import Inspire from "@inspirejs/core";
+import { $$ } from "@inspirejs/core/util";
+
+/**
+ * Transport-independent presenter UI, shared between the classic `presenter`
+ * plugin (window.open transport) and the experimental `presenter2` plugin
+ * (Presentation API transport). Anything here only touches the *local*
+ * presenter view, never the audience view, so it works regardless of how the
+ * two views are linked.
+ */
+
+/**
+ * Turn the current window into the presenter view: show the next-slide preview,
+ * and open any speaker notes in the current slide.
+ */
+export function enterPresenterView () {
+	document.body.classList.add("presenter", "show-next");
+	$$("details.notes", Inspire.currentSlide).forEach(d => (d.open = true));
+}
+
+/**
+ * Run on every slide change, on the presenter view only. Opens the new slide's
+ * speaker notes and, if the slide carries timing hints, computes how far ahead
+ * or behind schedule we are (surfaced via `data-offset` / `data-running`).
+ */
+export function onPresenterSlidechange () {
+	if (!document.body.classList.contains("presenter")) {
+		// Not the presenter view, nothing to do
+		return;
+	}
+
+	$$("details.notes", Inspire.currentSlide).forEach(d => (d.open = true));
+
+	if (Inspire.currentSlide.matches("[data-start-time] [data-time]")) {
+		// This slide has a time hint, show if we're running behind
+
+		// Scheduled start time
+		let startTime = Inspire.currentSlide
+			.closest("[data-start-time]")
+			?.getAttribute("data-start-time");
+		let startTimeParsed = startTime.split(":").map(n => +n);
+
+		// Ideal offset from start time
+		let time = Inspire.currentSlide.dataset.time;
+		let timeParsed = time.split(":").map(n => +n);
+
+		// Current local time
+		let currentTime = new Date().toLocaleString("en", {
+			timeStyle: "short",
+			hour12: false,
+		});
+		let currentTimeParsed = currentTime.split(":").map(n => +n);
+
+		// Actual offset from start time, in minutes
+		let actualTime =
+			(currentTimeParsed[0] - startTimeParsed[0]) * 60 +
+			(currentTimeParsed[1] - startTimeParsed[1]);
+
+		let offset = actualTime - (timeParsed[0] * 60 + timeParsed[1]);
+		let offsetHours = Math.floor(Math.abs(offset / 60))
+			.toString()
+			.padStart(2, "0");
+		let offsetMinutes = (Math.abs(offset) % 60).toString().padStart(2, "0");
+
+		Inspire.currentSlide.dataset.offset = `${offsetHours}:${offsetMinutes}`;
+
+		if (offset !== 0) {
+			Inspire.currentSlide.dataset.running = offset > 0 ? "behind" : "ahead";
+		}
+	}
+}

presenter2/README.md

@@ -0,0 +1,56 @@
+# Presenter View (experimental, Presentation API)
+
+An experimental, opt-in alternative to the classic [`presenter`](../presenter)
+plugin, built on the [W3C Presentation API](https://developer.mozilla.org/en-US/docs/Web/API/Presentation_API)
+instead of `window.open()`. The presenter (controller) asks the browser to
+render the deck on a **secondary attached display or Cast device**, and the two
+views stay in sync by exchanging messages over a `PresentationConnection`.
+
+It shares all of its presenter UI (speaker notes, next-slide preview, future
+delayed items, timing help) with the classic plugin, and is intended to
+eventually replace it.
+
+## Why use it
+
+- Picks the secondary display through the browser's own picker — no dragging a
+  popup across screens, no popup blockers.
+- Can target Cast / AirPlay-style remote displays, not just attached monitors.
+- **Auto-reconnects when the presenter view is reloaded**, with no picker and no
+  extra keypress, by reattaching to the still-open audience view.
+
+## Enabling
+
+Add the `experimental-presentation-api` class to `<body>`:
+
+```html
+<body class="experimental-presentation-api">
+```
+
+This **disables the classic `presenter` plugin** for that deck, so the two never
+run together. Without the class, the classic window.open presenter loads as
+before — that's the fallback wherever the Presentation API isn't available.
+
+## Autoload
+
+Like the classic plugin, this autoloads when speaker notes
+(`<details class="notes">`) are found in any slide **and** the
+`experimental-presentation-api` class is present on `<body>`.
+
+## Usage
+
+Enter presenter mode by pressing <kbd>Ctrl</kbd> + <kbd>P</kbd>, then pick the
+display to present on. This window becomes the Presenter view; the audience view
+is rendered on the chosen display. Slide and item navigation (including
+`.delayed` items) is synced across the two views.
+
+If you reload the presenter view, it reconnects to the audience view
+automatically. To exit, close/stop the presentation from the browser.
+
+## Requirements & limitations
+
+- Needs a browser that supports the Presentation API (Chromium-based) and a
+  **secure context** (HTTPS or `localhost`). On unsupported browsers, remove the
+  `experimental-presentation-api` class to fall back to the classic presenter.
+- Only slide/item navigation is synced, not keyboard or mouse events — interact
+  with the presenter view to drive navigation; play videos / open links / run
+  live demos on the audience display directly.

presenter2/plugin.css

@@ -0,0 +1,4 @@
+/* Experimental Presentation API presenter view.
+   Reuses the classic presenter styling (next-slide preview, dimmed delayed
+   items, timing badges); add experimental-only tweaks below it as needed. */
+@import url("../presenter/plugin.css");

presenter2/plugin.js

@@ -0,0 +1,147 @@
+import Inspire from "@inspirejs/core";
+import { enterPresenterView, onPresenterSlidechange } from "../presenter/presenter-ui.js";
+
+export const hasCSS = true;
+
+/**
+ * Experimental presenter plugin built on the W3C Presentation API instead of
+ * `window.open()`. The presenter (controller) asks the browser to render the
+ * deck on a secondary display or Cast device, and the two views stay in sync
+ * by exchanging serialized messages over a PresentationConnection.
+ *
+ * Opt in by adding `class="experimental-presentation-api"` to <body>; doing so
+ * also disables the classic `presenter` plugin (see plugin-autoload.js), so the
+ * classic window.open presenter is the fallback wherever this isn't supported.
+ *
+ * The transport-independent presenter UI (notes, next-slide preview, timing) is
+ * shared with the classic plugin via ../presenter/presenter-ui.js.
+ */
+
+// sessionStorage key holding the live presentation id, used to silently
+// reconnect the presenter view after a reload.
+const STORAGE_KEY = "inspire-presentation-id";
+
+let transport = null; // { send(message) } while connected, else null
+let applyingRemote = false; // guards against echoing a remote update back
+
+const supported = () => "presentation" in navigator && "PresentationRequest" in window;
+
+/** Send a navigation message to the other view, unless we're applying one. */
+function sync (message) {
+	if (!applyingRemote) {
+		transport?.send(message);
+	}
+}
+
+/** Apply a navigation message received from the other view. */
+function applyRemote (message) {
+	applyingRemote = true;
+
+	try {
+		if (message.type === "goto") {
+			Inspire.goto(message.which);
+		}
+		else if (message.type === "gotoItem") {
+			Inspire.gotoItem(message.which);
+		}
+	}
+	finally {
+		applyingRemote = false;
+	}
+}
+
+/**
+ * Wire up a PresentationConnection as our transport. `isController` is true on
+ * the presenter side (which persists the id so it can reconnect after reload).
+ */
+function wireConnection (connection, isController) {
+	transport = {
+		send: message => {
+			if (connection.state === "connected") {
+				connection.send(JSON.stringify(message));
+			}
+		},
+	};
+
+	connection.addEventListener("message", e => applyRemote(JSON.parse(e.data)));
+
+	let drop = () => {
+		transport = null;
+
+		if (isController) {
+			sessionStorage.removeItem(STORAGE_KEY);
+		}
+	};
+
+	connection.addEventListener("close", drop);
+	connection.addEventListener("terminate", drop);
+
+	if (isController) {
+		sessionStorage.setItem(STORAGE_KEY, connection.id);
+	}
+}
+
+Inspire.hooks.add({
+	"init-end": () => {
+		if (navigator.presentation?.receiver) {
+			// We are the audience view, rendered on the secondary display
+			document.body.classList.add("projector");
+
+			navigator.presentation.receiver.connectionList.then(list => {
+				list.connections.forEach(c => wireConnection(c, false));
+				list.addEventListener("connectionavailable", e =>
+					wireConnection(e.connection, false));
+			});
+		}
+		else if (supported() && sessionStorage.getItem(STORAGE_KEY)) {
+			// Presenter view was reloaded: silently reconnect to the still-open
+			// audience display (no picker and no user gesture required).
+			let id = sessionStorage.getItem(STORAGE_KEY);
+
+			new PresentationRequest([location.href]).reconnect(id)
+				.then(connection => {
+					enterPresenterView();
+					wireConnection(connection, true);
+				})
+				.catch(() => sessionStorage.removeItem(STORAGE_KEY)); // audience gone
+		}
+	},
+	keyup: env => {
+		// Ctrl+P : Open Presenter view
+		if (env.letter !== "P" || transport) {
+			// Not our shortcut, or we're already presenting
+			return;
+		}
+
+		if (!supported()) {
+			console.warn(
+				"[presenter2] The Presentation API is not supported in this browser. " +
+				"Remove the `experimental-presentation-api` class to use the classic presenter.",
+			);
+			return;
+		}
+
+		// Switch this window to presenter view
+		enterPresenterView();
+
+		// Ask the browser to render the deck on a secondary display. start()
+		// must run inside this user gesture (the keypress).
+		new PresentationRequest([location.href]).start()
+			.then(connection => {
+				wireConnection(connection, true);
+				window.focus();
+			})
+			.catch(() => {}); // picker cancelled or no display available
+	},
+	slidechange: env => {
+		// Sync slide navigation. Send the slide id (stable & serializable);
+		// env.which may be an Element, which wouldn't survive JSON.
+		sync({ type: "goto", which: Inspire.currentSlide.id });
+
+		onPresenterSlidechange();
+	},
+	"gotoitem-end": env => {
+		// Sync slide item navigation
+		sync({ type: "gotoItem", which: env.which });
+	},
+});