Fade out user cursor labels after five seconds of inactivity

If we don't receive an update from a user within five seconds, hide the
label of their cursor.

Implementation details:
* Add CSS to fade out the cursor label after five seconds per default.
* Listen for Yjs updates. In case it's an awareness message, update the
  cursor of the author, remove the fade out CSS class and add it again
  after five seconds.

Fixes: #4126

Signed-off-by: Jonas <jonas@freesources.org>

Author: mejo-

src/components/Editor.vue

@@ -82,8 +82,8 @@ import { getCurrentUser } from '@nextcloud/auth'
 import { loadState } from '@nextcloud/initial-state'
 import { emit, subscribe, unsubscribe } from '@nextcloud/event-bus'
 import { Collaboration } from '@tiptap/extension-collaboration'
-import { CollaborationCursor } from '@tiptap/extension-collaboration-cursor'
 import { Doc } from 'yjs'
+import debounce from 'debounce'
 
 import {
 	EDITOR,
@@ -98,7 +98,7 @@ import {
 import ReadonlyBar from './Menu/ReadonlyBar.vue'
 
 import { logger } from '../helpers/logger.js'
-import { getDocumentState, applyDocumentState } from '../helpers/yjs.js'
+import { yjsMessageTypes, getDocumentState, applyDocumentState, getMessageType, getAwarenessMessageClientIds } from '../helpers/yjs.js'
 import { SyncService, ERROR_TYPE, IDLE_TIMEOUT } from './../services/SyncService.js'
 import createSyncServiceProvider from './../services/SyncServiceProvider.js'
 import AttachmentResolver from './../services/AttachmentResolver.js'
@@ -107,7 +107,7 @@ import { createEditor, serializePlainText, loadSyntaxHighlight } from './../Edit
 import { createMarkdownSerializer } from './../extensions/Markdown.js'
 import markdownit from './../markdownit/index.js'
 
-import { Keymap } from './../extensions/index.js'
+import { CollaborationCursor, Keymap } from '../extensions/index.js'
 import DocumentStatus from './Editor/DocumentStatus.vue'
 import isMobile from './../mixins/isMobile.js'
 import setContent from './../mixins/setContent.js'
@@ -321,10 +321,12 @@ export default {
 	},
 	created() {
 		this.$ydoc = new Doc()
+		this.$ydoc.on('update', this.onYjsUpdate)
 		this.$providers = []
 		this.$editor = null
 		this.$syncService = null
 		this.$attachmentResolver = null
+		this.$cursorLabelTimeouts = {}
 	},
 	beforeDestroy() {
 		if (!this.richWorkspace) {
@@ -642,6 +644,35 @@ export default {
 			this.emit('delete-image-node', imageUrl)
 		},
 
+		onYjsUpdate(update, _origin, _doc, _tr) {
+			// Update cursor labels for clients from awareness message
+			if (getMessageType(update) === yjsMessageTypes.awareness) {
+				if (!this.$editor) {
+					return
+				}
+
+				const clientIds = getAwarenessMessageClientIds(update)
+				const updateUsers = this.$editor.storage.collaborationCursor.users
+					.filter(u => clientIds.includes(u.clientId))
+				for (const user of updateUsers) {
+					this.updateCursorLabel(user)
+				}
+			}
+		},
+
+		updateCursorLabel: debounce(function(user) {
+			// Remove CSS class that fades out and hides the cursor label and bring it back after five seconds.
+			// Limit this to once every second to prevent it from happening with each awareness update.
+			const cursorLabelEls = document.getElementsByClassName(`collaboration-cursor__label__${user.name}`)
+			for (const el of cursorLabelEls) {
+				el.classList.remove('collaboration-cursor__label_fadeout')
+				clearTimeout(this.$cursorLabelTimeouts[user.clientId])
+				this.$cursorLabelTimeouts[user.clientId] = setTimeout(() => {
+					el.classList.add('collaboration-cursor__label_fadeout')
+				}, 5000)
+			}
+		}, 1000, true),
+
 		async close() {
 			if (this.currentSession && this.$syncService) {
 				try {
@@ -782,7 +813,6 @@ export default {
 	width: 100%;
 	background-color: var(--color-main-background);
 }
-
 </style>
 
 <style lang="scss">
@@ -914,4 +944,13 @@ export default {
 		white-space: nowrap;
 	}
 
+	.collaboration-cursor__label_fadeout {
+		// transition: visibility 0s 1s, opacity 1s linear;
+		animation: fade-out-label var(--animation-slow) forwards;
+	}
+
+	@keyframes fade-out-label {
+		0% { opacity: 1; }
+		100% { opacity: 0; }
+	}
 </style>