From d763b69999d390b4b95ad1855ea33787aa0383ec Mon Sep 17 00:00:00 2001
From: Jonas Lochmann <git@inkompetenz.org>
Date: Mon, 10 May 2021 02:00:00 +0200
Subject: [PATCH] Add remote zoom support

---
 presentations/demo/index.html |   4 +-
 remote/plugin.js              |  12 +++-
 remote/remotezoom.js          | 104 ++++++++++++++++++++++++++++++++++
 3 files changed, 117 insertions(+), 3 deletions(-)
 create mode 100644 remote/remotezoom.js

diff --git a/presentations/demo/index.html b/presentations/demo/index.html
index a8e707b..6459eff 100644
--- a/presentations/demo/index.html
+++ b/presentations/demo/index.html
@@ -451,7 +451,7 @@ <h1>THE END</h1>
 		</div>
 
 		<script src="dist/reveal.js"></script>
-		<script src="plugin/zoom/zoom.js"></script>
+		<script src="../_remote/remotezoom.js"></script>
 		<script src="plugin/notes/notes.js"></script>
 		<script src="plugin/search/search.js"></script>
 		<script src="plugin/markdown/markdown.js"></script>
@@ -499,7 +499,7 @@ <h1>THE END</h1>
 				},
 
 				// Learn about plugins: https://revealjs.com/plugins/
-				plugins: [ RevealZoom, RevealNotes, RevealSearch, RevealMarkdown, RevealHighlight, RevealRemote ]
+				plugins: [ RevealRemoteZoom, RevealNotes, RevealSearch, RevealMarkdown, RevealHighlight, RevealRemote ]
 			});
 
 		</script>
diff --git a/remote/plugin.js b/remote/plugin.js
index c15449d..17b224d 100644
--- a/remote/plugin.js
+++ b/remote/plugin.js
@@ -186,6 +186,8 @@
           reveal.addEventListener("overviewshown", sendMultiplexState);
           reveal.addEventListener("paused", sendMultiplexState);
           reveal.addEventListener("resumed", sendMultiplexState);
+          reveal.addEventListener("enable-zoom", sendMultiplexState);
+          reveal.addEventListener("disable-zoom", sendMultiplexState);
 
           sendMultiplexState();
         }
@@ -227,7 +229,11 @@
 
 
       function sendMultiplexState() {
-        socket.emit("multiplex", { state: reveal.getState() });
+        var state = reveal.getState();
+        var zoomPlugin = reveal.getPlugin("remote-zoom");
+        var zoom = zoomPlugin ? zoomPlugin.getCurrentZoom() : null;
+
+        socket.emit("multiplex", { state: state, zoom: zoom });
       }
 
       function msgClientConnected() {
@@ -235,7 +241,11 @@
       }
 
       function msgSync(data) {
+        var zoomPlugin = reveal.getPlugin("remote-zoom");
+
         reveal.setState(data.state);
+
+        if (zoomPlugin) { zoomPlugin.setCurrentZoom(data.zoom); }
       }
 
       function on(cmd, fn) {
diff --git a/remote/remotezoom.js b/remote/remotezoom.js
new file mode 100644
index 0000000..e2a7024
--- /dev/null
+++ b/remote/remotezoom.js
@@ -0,0 +1,104 @@
+const RevealRemoteZoom = () => {
+  let reveal = null
+  let currentZoom = null
+  let currentSlideElement = null
+
+  function allowControl() {
+    const config = reveal.getConfig()
+
+    return config.controls && config.touch
+  }
+
+  function dispatchEnableZoom(focus) {
+    if (!isValidFocus(focus)) {
+      console.warn('invalid focus parameter for dispatchEnableZoom()'); return
+    }
+
+    reveal.dispatchEvent({
+      type: 'enable-zoom',
+      data: { focus }
+    })
+  }
+
+  function dispatchDisableZoom() {
+    reveal.dispatchEvent({ type: 'disable-zoom' })
+  }
+
+  const doubleClickListener = (e) => {
+    if (!allowControl()) return
+
+    if (currentZoom !== null) {
+      dispatchDisableZoom()
+    } else {
+      const location = getRelativeLocation({ element: currentSlideElement, event: e })
+
+      dispatchEnableZoom(location)
+    }
+  }
+
+  function setupForSlideElement(element) {
+    if (currentSlideElement !== null) {
+      applyZoom(null)
+      currentSlideElement.removeEventListener('dblclick', doubleClickListener)
+    }
+
+    element.addEventListener('dblclick', doubleClickListener)
+
+    currentSlideElement = element
+  }
+
+  function getRelativeLocation({event, element}) {
+    const elementLocation = element.getBoundingClientRect()
+
+    const x = Math.round((event.clientX - elementLocation.left) * 100 / (elementLocation.right - elementLocation.left))
+    const y = Math.round((event.clientY - elementLocation.top) * 100 / (elementLocation.bottom - elementLocation.top))
+
+    return { x, y }
+  }
+
+  function applyZoom(focus) {
+    if (focus === null) {
+      currentSlideElement.style.transform = ''
+      currentZoom = null
+    } else {
+      if (!isValidFocus(focus)) {
+        console.warn('invalid focus parameter for applyZoom()'); return
+      }
+
+      const transform = 'scale(200%) translate(' + (50 - focus.x) + '%, ' + (50 - focus.y) + '%)'
+
+      currentSlideElement.style.transform = transform
+      currentZoom = focus
+    }
+  }
+
+  function isValidFocus(focus) {
+    return typeof focus === 'object' && Number.isInteger(focus.x) && Number.isInteger(focus.y) &&
+      focus.x >= 0 && focus.x <= 100 && focus.y >= 0 && focus.y <= 100 && Object.keys(focus).length === 2
+  }
+
+  return {
+    id: 'remote-zoom',
+    init: (initReveal) => {
+      reveal = initReveal
+
+      reveal.addEventListener('slidechanged', (e) => setupForSlideElement(e.currentSlide))
+      reveal.addEventListener('ready', (e) => setupForSlideElement(e.currentSlide))
+      reveal.on('enable-zoom', (e) => applyZoom(e.focus))
+      reveal.on('disable-zoom', (e) => applyZoom(null))
+      reveal.on('overviewshown', () => dispatchDisableZoom());
+    },
+    getCurrentZoom: () => currentZoom,
+    setCurrentZoom: (focus) => {
+      if (focus === null) {
+        dispatchDisableZoom()
+      } else {
+        if (!isValidFocus(focus)) {
+          console.warn('invalid focus parameter for setCurrentZoom()'); return
+        }
+
+        dispatchEnableZoom(focus)
+      }
+    }
+  }
+};