From 8b4e9191e5be4efa66edd62e68c575010853a032 Mon Sep 17 00:00:00 2001
From: Tilman Vatteroth <git@tilmanvatteroth.de>
Date: Mon, 14 Feb 2022 17:37:34 +0100
Subject: [PATCH] Fix smooth scroll and other bugs (#1861)

This PR fixes:

- The wrong clean up of window post message communicators
- The smooth scroll bug in chrome (Fixes Anchor navigation in render view not working #1770)
- Scroll by using touch devices in renderer
- Lazy loading of the editor (code mirror doesn't need to be lazy loaded any more)
---
 .../editor-page/editor-page-content.tsx       | 168 ++++++++++++++++++
 .../editor-page/editor-pane/editor-pane.tsx   |   7 +-
 .../hooks/use-cursor-activity-callback.ts     |  12 +-
 .../emoji-picker/emoji-picker-button.tsx      |   2 +
 .../editor-pane/tool-bar/tool-bar.tsx         |   9 +-
 ...renderer-communicator-context-provider.tsx |  10 +-
 ...o-editor-communicator-context-provider.tsx |  10 +-
 .../renderer-pane/render-iframe.tsx           |   8 +-
 .../link-replacer/jump-anchor.tsx             |   9 +-
 .../use-document-sync-scrolling.ts            |   6 +-
 .../hooks/sync-scroll/use-on-user-scroll.ts   |   6 +-
 .../render-page/markdown-document.tsx         |   4 +-
 .../hooks/use-send-to-renderer.ts             |   4 +-
 .../window-post-message-communicator.ts       |  57 +++---
 src/pages/n/[id].tsx                          | 161 +----------------
 15 files changed, 260 insertions(+), 213 deletions(-)
 create mode 100644 src/components/editor-page/editor-page-content.tsx

diff --git a/src/components/editor-page/editor-page-content.tsx b/src/components/editor-page/editor-page-content.tsx
new file mode 100644
index 000000000..c97f2fdff
--- /dev/null
+++ b/src/components/editor-page/editor-page-content.tsx
@@ -0,0 +1,168 @@
+/*
+ * SPDX-FileCopyrightText: 2022 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import React, { Fragment, useCallback, useEffect, useMemo, useRef, useState } from 'react'
+import { useTranslation } from 'react-i18next'
+import { useApplyDarkMode } from '../../hooks/common/use-apply-dark-mode'
+import { setCheckboxInMarkdownContent, updateNoteTitleByFirstHeading } from '../../redux/note-details/methods'
+import { MotdModal } from '../common/motd-modal/motd-modal'
+import { ShowIf } from '../common/show-if/show-if'
+import { ErrorWhileLoadingNoteAlert } from '../document-read-only-page/ErrorWhileLoadingNoteAlert'
+import { LoadingNoteAlert } from '../document-read-only-page/LoadingNoteAlert'
+import { AppBar, AppBarMode } from './app-bar/app-bar'
+import { EditorMode } from './app-bar/editor-view-mode'
+import { useLoadNoteFromServer } from './hooks/useLoadNoteFromServer'
+import { useViewModeShortcuts } from './hooks/useViewModeShortcuts'
+import { Sidebar } from './sidebar/sidebar'
+import { Splitter } from './splitter/splitter'
+import type { DualScrollState, ScrollState } from './synced-scroll/scroll-props'
+import { RendererType } from '../render-page/window-post-message-communicator/rendering-message'
+import { useEditorModeFromUrl } from './hooks/useEditorModeFromUrl'
+import { UiNotifications } from '../notifications/ui-notifications'
+import { useUpdateLocalHistoryEntry } from './hooks/useUpdateLocalHistoryEntry'
+import { useApplicationState } from '../../hooks/common/use-application-state'
+import { EditorDocumentRenderer } from './editor-document-renderer/editor-document-renderer'
+import { Logger } from '../../utils/logger'
+import { NoteType } from '../../redux/note-details/types/note-details'
+import { NoteAndAppTitleHead } from '../layout/note-and-app-title-head'
+import equal from 'fast-deep-equal'
+import { EditorPane } from './editor-pane/editor-pane'
+
+export interface EditorPagePathParams {
+  id: string
+}
+
+export enum ScrollSource {
+  EDITOR = 'editor',
+  RENDERER = 'renderer'
+}
+
+const log = new Logger('EditorPage')
+
+/**
+ * This is the content of the actual editor page.
+ */
+export const EditorPageContent: React.FC = () => {
+  useTranslation()
+  const scrollSource = useRef<ScrollSource>(ScrollSource.EDITOR)
+  const editorMode: EditorMode = useApplicationState((state) => state.editorConfig.editorMode)
+  const editorSyncScroll: boolean = useApplicationState((state) => state.editorConfig.syncScroll)
+
+  const [scrollState, setScrollState] = useState<DualScrollState>(() => ({
+    editorScrollState: { firstLineInView: 1, scrolledPercentage: 0 },
+    rendererScrollState: { firstLineInView: 1, scrolledPercentage: 0 }
+  }))
+
+  const onMarkdownRendererScroll = useCallback(
+    (newScrollState: ScrollState) => {
+      if (scrollSource.current === ScrollSource.RENDERER && editorSyncScroll) {
+        setScrollState((old) => {
+          const newState: DualScrollState = {
+            editorScrollState: newScrollState,
+            rendererScrollState: old.rendererScrollState
+          }
+          return equal(newState, old) ? old : newState
+        })
+      }
+    },
+    [editorSyncScroll]
+  )
+
+  useEffect(() => {
+    log.debug('New scroll state', scrollState, scrollSource.current)
+  }, [scrollState])
+
+  const onEditorScroll = useCallback(
+    (newScrollState: ScrollState) => {
+      if (scrollSource.current === ScrollSource.EDITOR && editorSyncScroll) {
+        setScrollState((old) => {
+          const newState: DualScrollState = {
+            rendererScrollState: newScrollState,
+            editorScrollState: old.editorScrollState
+          }
+          return equal(newState, old) ? old : newState
+        })
+      }
+    },
+    [editorSyncScroll]
+  )
+
+  useViewModeShortcuts()
+  useApplyDarkMode()
+  useEditorModeFromUrl()
+
+  const [error, loading] = useLoadNoteFromServer()
+
+  useUpdateLocalHistoryEntry(!error && !loading)
+
+  const setRendererToScrollSource = useCallback(() => {
+    if (scrollSource.current !== ScrollSource.RENDERER) {
+      scrollSource.current = ScrollSource.RENDERER
+      log.debug('Make renderer scroll source')
+    }
+  }, [])
+
+  const setEditorToScrollSource = useCallback(() => {
+    if (scrollSource.current !== ScrollSource.EDITOR) {
+      scrollSource.current = ScrollSource.EDITOR
+      log.debug('Make editor scroll source')
+    }
+  }, [])
+
+  const leftPane = useMemo(
+    () => (
+      <EditorPane
+        scrollState={scrollState.editorScrollState}
+        onScroll={onEditorScroll}
+        onMakeScrollSource={setEditorToScrollSource}
+      />
+    ),
+    [onEditorScroll, scrollState.editorScrollState, setEditorToScrollSource]
+  )
+  const noteType: NoteType = useApplicationState((state) => state.noteDetails.frontmatter.type)
+
+  const rightPane = useMemo(
+    () => (
+      <EditorDocumentRenderer
+        frameClasses={'h-100 w-100'}
+        onMakeScrollSource={setRendererToScrollSource}
+        onFirstHeadingChange={updateNoteTitleByFirstHeading}
+        onTaskCheckedChange={setCheckboxInMarkdownContent}
+        onScroll={onMarkdownRendererScroll}
+        scrollState={scrollState.rendererScrollState}
+        rendererType={noteType === NoteType.SLIDE ? RendererType.SLIDESHOW : RendererType.DOCUMENT}
+      />
+    ),
+    [noteType, onMarkdownRendererScroll, scrollState.rendererScrollState, setRendererToScrollSource]
+  )
+
+  return (
+    <Fragment>
+      <NoteAndAppTitleHead />
+      <UiNotifications />
+      <MotdModal />
+      <div className={'d-flex flex-column vh-100'}>
+        <AppBar mode={AppBarMode.EDITOR} />
+        <div className={'container'}>
+          <ErrorWhileLoadingNoteAlert show={error} />
+          <LoadingNoteAlert show={loading} />
+        </div>
+        <ShowIf condition={!error && !loading}>
+          <div className={'flex-fill d-flex h-100 w-100 overflow-hidden flex-row'}>
+            <Splitter
+              showLeft={editorMode === EditorMode.EDITOR || editorMode === EditorMode.BOTH}
+              left={leftPane}
+              showRight={editorMode === EditorMode.PREVIEW || editorMode === EditorMode.BOTH}
+              right={rightPane}
+              additionalContainerClassName={'overflow-hidden'}
+            />
+            <Sidebar />
+          </div>
+        </ShowIf>
+      </div>
+    </Fragment>
+  )
+}
diff --git a/src/components/editor-page/editor-pane/editor-pane.tsx b/src/components/editor-page/editor-pane/editor-pane.tsx
index eaa95a7a9..2a70d6ee3 100644
--- a/src/components/editor-page/editor-pane/editor-pane.tsx
+++ b/src/components/editor-page/editor-pane/editor-pane.tsx
@@ -91,7 +91,10 @@ export const EditorPane: React.FC<ScrollProps> = ({ scrollState, onScroll, onMak
   const { t } = useTranslation()
 
   return (
-    <div className={`d-flex flex-column h-100 position-relative`} onMouseEnter={onMakeScrollSource}>
+    <div
+      className={`d-flex flex-column h-100 position-relative`}
+      onTouchStart={onMakeScrollSource}
+      onMouseEnter={onMakeScrollSource}>
       <MaxLengthWarning />
       <ToolBar />
       <ReactCodeMirror
@@ -112,5 +115,3 @@ export const EditorPane: React.FC<ScrollProps> = ({ scrollState, onScroll, onMak
     </div>
   )
 }
-
-export default EditorPane
diff --git a/src/components/editor-page/editor-pane/hooks/use-cursor-activity-callback.ts b/src/components/editor-page/editor-pane/hooks/use-cursor-activity-callback.ts
index 60a84b436..a1ce7c06a 100644
--- a/src/components/editor-page/editor-pane/hooks/use-cursor-activity-callback.ts
+++ b/src/components/editor-page/editor-pane/hooks/use-cursor-activity-callback.ts
@@ -5,12 +5,12 @@
  */
 
 import type { RefObject } from 'react'
-import { useMemo } from 'react'
+import { useMemo, useRef } from 'react'
 import { updateCursorPositions } from '../../../../redux/note-details/methods'
 import type { ViewUpdate } from '@codemirror/view'
 import { EditorView } from '@codemirror/view'
 import { Logger } from '../../../../utils/logger'
-import type { Extension } from '@codemirror/state'
+import type { Extension, SelectionRange } from '@codemirror/state'
 
 const logger = new Logger('useCursorActivityCallback')
 
@@ -20,14 +20,20 @@ const logger = new Logger('useCursorActivityCallback')
  * @return the generated callback
  */
 export const useCursorActivityCallback = (editorFocused: RefObject<boolean>): Extension => {
+  const lastMainSelection = useRef<SelectionRange>()
+
   return useMemo(
     () =>
       EditorView.updateListener.of((viewUpdate: ViewUpdate): void => {
+        const firstSelection = viewUpdate.state.selection.main
+        if (lastMainSelection.current === firstSelection) {
+          return
+        }
+        lastMainSelection.current = firstSelection
         if (!editorFocused.current) {
           logger.debug("Don't post updated cursor because editor isn't focused")
           return
         }
-        const firstSelection = viewUpdate.state.selection.main
         const newCursorPos = {
           from: firstSelection.from,
           to: firstSelection.to === firstSelection.from ? undefined : firstSelection.to
diff --git a/src/components/editor-page/editor-pane/tool-bar/emoji-picker/emoji-picker-button.tsx b/src/components/editor-page/editor-pane/tool-bar/emoji-picker/emoji-picker-button.tsx
index 86f989478..4aed09abd 100644
--- a/src/components/editor-page/editor-pane/tool-bar/emoji-picker/emoji-picker-button.tsx
+++ b/src/components/editor-page/editor-pane/tool-bar/emoji-picker/emoji-picker-button.tsx
@@ -38,3 +38,5 @@ export const EmojiPickerButton: React.FC = () => {
     </Fragment>
   )
 }
+
+export default EmojiPickerButton
diff --git a/src/components/editor-page/editor-pane/tool-bar/tool-bar.tsx b/src/components/editor-page/editor-pane/tool-bar/tool-bar.tsx
index d46bdd451..f4e6c77ae 100644
--- a/src/components/editor-page/editor-pane/tool-bar/tool-bar.tsx
+++ b/src/components/editor-page/editor-pane/tool-bar/tool-bar.tsx
@@ -4,15 +4,16 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-import React from 'react'
+import React, { Fragment, Suspense } from 'react'
 import { ButtonGroup, ButtonToolbar } from 'react-bootstrap'
-import { EmojiPickerButton } from './emoji-picker/emoji-picker-button'
 import { TablePickerButton } from './table-picker/table-picker-button'
 import styles from './tool-bar.module.scss'
 import { UploadImageButton } from './upload-image-button'
 import { ToolbarButton } from './toolbar-button'
 import { FormatType } from '../../../../redux/note-details/types'
 
+const EmojiPickerButton = React.lazy(() => import('./emoji-picker/emoji-picker-button'))
+
 export const ToolBar: React.FC = () => {
   return (
     <ButtonToolbar className={`bg-light ${styles.toolbar}`}>
@@ -43,7 +44,9 @@ export const ToolBar: React.FC = () => {
         <ToolbarButton icon={'minus'} formatType={FormatType.HORIZONTAL_LINE} />
         <ToolbarButton icon={'caret-square-o-down'} formatType={FormatType.COLLAPSIBLE_BLOCK} />
         <ToolbarButton icon={'comment'} formatType={FormatType.COMMENT} />
-        <EmojiPickerButton />
+        <Suspense fallback={<Fragment />}>
+          <EmojiPickerButton />
+        </Suspense>
       </ButtonGroup>
     </ButtonToolbar>
   )
diff --git a/src/components/editor-page/render-context/editor-to-renderer-communicator-context-provider.tsx b/src/components/editor-page/render-context/editor-to-renderer-communicator-context-provider.tsx
index 034cf6b93..85f2c7495 100644
--- a/src/components/editor-page/render-context/editor-to-renderer-communicator-context-provider.tsx
+++ b/src/components/editor-page/render-context/editor-to-renderer-communicator-context-provider.tsx
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-import React, { createContext, useContext, useMemo } from 'react'
+import React, { createContext, useContext, useEffect, useMemo } from 'react'
 import { EditorToRendererCommunicator } from '../../render-page/window-post-message-communicator/editor-to-renderer-communicator'
 
 const EditorToRendererCommunicatorContext = createContext<EditorToRendererCommunicator | undefined>(undefined)
@@ -29,6 +29,14 @@ export const useEditorToRendererCommunicator: () => EditorToRendererCommunicator
 export const EditorToRendererCommunicatorContextProvider: React.FC = ({ children }) => {
   const communicator = useMemo<EditorToRendererCommunicator>(() => new EditorToRendererCommunicator(), [])
 
+  useEffect(() => {
+    const currentCommunicator = communicator
+    currentCommunicator.registerEventListener()
+    return () => {
+      currentCommunicator.unregisterEventListener()
+    }
+  }, [communicator])
+
   return (
     <EditorToRendererCommunicatorContext.Provider value={communicator}>
       {children}
diff --git a/src/components/editor-page/render-context/renderer-to-editor-communicator-context-provider.tsx b/src/components/editor-page/render-context/renderer-to-editor-communicator-context-provider.tsx
index ba82b37d8..636394ad9 100644
--- a/src/components/editor-page/render-context/renderer-to-editor-communicator-context-provider.tsx
+++ b/src/components/editor-page/render-context/renderer-to-editor-communicator-context-provider.tsx
@@ -27,20 +27,18 @@ export const useRendererToEditorCommunicator: () => RendererToEditorCommunicator
 
 export const RendererToEditorCommunicatorContextProvider: React.FC = ({ children }) => {
   const editorOrigin = useOriginFromConfig(ORIGIN_TYPE.EDITOR)
-  const communicator = useMemo<RendererToEditorCommunicator>(() => {
-    const newCommunicator = new RendererToEditorCommunicator()
-    newCommunicator.setMessageTarget(window.parent, editorOrigin)
-    return newCommunicator
-  }, [editorOrigin])
+  const communicator = useMemo<RendererToEditorCommunicator>(() => new RendererToEditorCommunicator(), [])
 
   useEffect(() => {
     const currentCommunicator = communicator
+    currentCommunicator.setMessageTarget(window.parent, editorOrigin)
+    currentCommunicator.registerEventListener()
     currentCommunicator.enableCommunication()
     currentCommunicator.sendMessageToOtherSide({
       type: CommunicationMessageType.RENDERER_READY
     })
     return () => currentCommunicator?.unregisterEventListener()
-  }, [communicator])
+  }, [communicator, editorOrigin])
 
   /**
    * Provides a {@link RendererToEditorCommunicator renderer to editor communicator} for the child components via Context.
diff --git a/src/components/editor-page/renderer-pane/render-iframe.tsx b/src/components/editor-page/renderer-pane/render-iframe.tsx
index db2657267..3de12e0f8 100644
--- a/src/components/editor-page/renderer-pane/render-iframe.tsx
+++ b/src/components/editor-page/renderer-pane/render-iframe.tsx
@@ -58,13 +58,7 @@ export const RenderIframe: React.FC<RenderIframeProps> = ({
   const onIframeLoad = useForceRenderPageUrlOnIframeLoadCallback(frameReference, rendererOrigin, resetRendererReady)
   const [frameHeight, setFrameHeight] = useState<number>(0)
 
-  useEffect(
-    () => () => {
-      iframeCommunicator.unregisterEventListener()
-      setRendererStatus(false)
-    },
-    [iframeCommunicator]
-  )
+  useEffect(() => () => setRendererStatus(false), [iframeCommunicator])
 
   useEffect(() => {
     if (!rendererReady) {
diff --git a/src/components/markdown-renderer/markdown-extension/link-replacer/jump-anchor.tsx b/src/components/markdown-renderer/markdown-extension/link-replacer/jump-anchor.tsx
index e90b29340..6c8c8a12c 100644
--- a/src/components/markdown-renderer/markdown-extension/link-replacer/jump-anchor.tsx
+++ b/src/components/markdown-renderer/markdown-extension/link-replacer/jump-anchor.tsx
@@ -14,7 +14,14 @@ export interface JumpAnchorProps extends AllHTMLAttributes<HTMLAnchorElement> {
 export const JumpAnchor: React.FC<JumpAnchorProps> = ({ jumpTargetId, children, ...props }) => {
   const jumpToTargetId = useCallback(
     (event: React.MouseEvent<HTMLElement, MouseEvent>): void => {
-      document.getElementById(jumpTargetId)?.scrollIntoView({ behavior: 'smooth' })
+      const intoViewElement = document.getElementById(jumpTargetId)
+      const scrollElement = document.querySelector('[data-scroll-element]')
+      if (!intoViewElement || !scrollElement) {
+        return
+      }
+      //It would be much easier to use scrollIntoView here but since the code mirror also uses smooth scroll and bugs like
+      // https://stackoverflow.com/a/63563437/13103995 exist, we must use scrollTo.
+      scrollElement.scrollTo({ behavior: 'smooth', top: intoViewElement.offsetTop })
       event.preventDefault()
     },
     [jumpTargetId]
diff --git a/src/components/render-page/hooks/sync-scroll/use-document-sync-scrolling.ts b/src/components/render-page/hooks/sync-scroll/use-document-sync-scrolling.ts
index d06584860..89f4948a3 100644
--- a/src/components/render-page/hooks/sync-scroll/use-document-sync-scrolling.ts
+++ b/src/components/render-page/hooks/sync-scroll/use-document-sync-scrolling.ts
@@ -5,7 +5,7 @@
  */
 
 import type React from 'react'
-import { useCallback, useState } from 'react'
+import { useCallback, useMemo, useState } from 'react'
 import type { LineMarkerPosition } from '../../../markdown-renderer/markdown-extension/linemarker/types'
 import type { ScrollState } from '../../../editor-page/synced-scroll/scroll-props'
 import { useOnUserScroll } from './use-on-user-scroll'
@@ -17,7 +17,7 @@ export const useDocumentSyncScrolling = (
   numberOfLines: number,
   scrollState?: ScrollState,
   onScroll?: (scrollState: ScrollState) => void
-): [(lineMarkers: LineMarkerPosition[]) => void, () => void] => {
+): [(lineMarkers: LineMarkerPosition[]) => void, React.UIEventHandler<HTMLElement>] => {
   const [lineMarks, setLineMarks] = useState<LineMarkerPosition[]>()
 
   const onLineMarkerPositionChanged = useCallback(
@@ -40,5 +40,5 @@ export const useDocumentSyncScrolling = (
   const onUserScroll = useOnUserScroll(lineMarks, outerContainerRef, onScroll)
   useScrollToLineMark(scrollState, lineMarks, numberOfLines, outerContainerRef)
 
-  return [onLineMarkerPositionChanged, onUserScroll]
+  return useMemo(() => [onLineMarkerPositionChanged, onUserScroll], [onLineMarkerPositionChanged, onUserScroll])
 }
diff --git a/src/components/render-page/hooks/sync-scroll/use-on-user-scroll.ts b/src/components/render-page/hooks/sync-scroll/use-on-user-scroll.ts
index c868aa6f6..32e460b45 100644
--- a/src/components/render-page/hooks/sync-scroll/use-on-user-scroll.ts
+++ b/src/components/render-page/hooks/sync-scroll/use-on-user-scroll.ts
@@ -4,16 +4,16 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-import type { RefObject } from 'react'
+import type React from 'react'
 import { useCallback } from 'react'
 import type { LineMarkerPosition } from '../../../markdown-renderer/markdown-extension/linemarker/types'
 import type { ScrollState } from '../../../editor-page/synced-scroll/scroll-props'
 
 export const useOnUserScroll = (
   lineMarks: LineMarkerPosition[] | undefined,
-  scrollContainer: RefObject<HTMLElement>,
+  scrollContainer: React.RefObject<HTMLElement>,
   onScroll: ((newScrollState: ScrollState) => void) | undefined
-): (() => void) => {
+): React.UIEventHandler<HTMLElement> => {
   return useCallback(() => {
     if (!scrollContainer.current || !lineMarks || lineMarks.length === 0 || !onScroll) {
       return
diff --git a/src/components/render-page/markdown-document.tsx b/src/components/render-page/markdown-document.tsx
index be69dd96a..52be031cd 100644
--- a/src/components/render-page/markdown-document.tsx
+++ b/src/components/render-page/markdown-document.tsx
@@ -84,7 +84,9 @@ export const MarkdownDocument: React.FC<MarkdownDocumentProps> = ({
       className={`${styles['markdown-document']} ${additionalOuterContainerClasses ?? ''}`}
       ref={internalDocumentRenderPaneRef}
       onScroll={onUserScroll}
-      onMouseEnter={onMakeScrollSource}>
+      data-scroll-element={true}
+      onMouseEnter={onMakeScrollSource}
+      onTouchStart={onMakeScrollSource}>
       <div className={styles['markdown-document-side']} />
       <div className={styles['markdown-document-content']}>
         <InvalidYamlAlert show={!!frontmatterInfo?.frontmatterInvalid} />
diff --git a/src/components/render-page/window-post-message-communicator/hooks/use-send-to-renderer.ts b/src/components/render-page/window-post-message-communicator/hooks/use-send-to-renderer.ts
index 2037ef98c..caf9d5529 100644
--- a/src/components/render-page/window-post-message-communicator/hooks/use-send-to-renderer.ts
+++ b/src/components/render-page/window-post-message-communicator/hooks/use-send-to-renderer.ts
@@ -7,11 +7,11 @@
 import { useCallback } from 'react'
 import type { CommunicationMessages, EditorToRendererMessageType } from '../rendering-message'
 import { useEditorToRendererCommunicator } from '../../../editor-page/render-context/editor-to-renderer-communicator-context-provider'
-import type { PostMessage } from '../window-post-message-communicator'
+import type { MessagePayload } from '../window-post-message-communicator'
 import { useEffectOnRendererReady } from './use-effect-on-renderer-ready'
 
 export const useSendToRenderer = (
-  message: undefined | Extract<CommunicationMessages, PostMessage<EditorToRendererMessageType>>
+  message: undefined | Extract<CommunicationMessages, MessagePayload<EditorToRendererMessageType>>
 ): void => {
   const iframeCommunicator = useEditorToRendererCommunicator()
 
diff --git a/src/components/render-page/window-post-message-communicator/window-post-message-communicator.ts b/src/components/render-page/window-post-message-communicator/window-post-message-communicator.ts
index b0cef7678..f2e2f5c66 100644
--- a/src/components/render-page/window-post-message-communicator/window-post-message-communicator.ts
+++ b/src/components/render-page/window-post-message-communicator/window-post-message-communicator.ts
@@ -5,6 +5,7 @@
  */
 
 import type { Logger } from '../../../utils/logger'
+import Optional from 'optional-js'
 
 /**
  * Error that will be thrown if a message couldn't be sent.
@@ -12,7 +13,7 @@ import type { Logger } from '../../../utils/logger'
 export class IframeCommunicatorSendingError extends Error {}
 
 export type Handler<MESSAGES, MESSAGE_TYPE extends string> = (
-  values: Extract<MESSAGES, PostMessage<MESSAGE_TYPE>>
+  values: Extract<MESSAGES, MessagePayload<MESSAGE_TYPE>>
 ) => void
 
 export type MaybeHandler<MESSAGES, MESSAGE_TYPE extends string> = Handler<MESSAGES, MESSAGE_TYPE> | undefined
@@ -21,7 +22,7 @@ export type HandlerMap<MESSAGES, MESSAGE_TYPE extends string> = Partial<{
   [key in MESSAGE_TYPE]: MaybeHandler<MESSAGES, MESSAGE_TYPE>
 }>
 
-export interface PostMessage<MESSAGE_TYPE extends string> {
+export interface MessagePayload<MESSAGE_TYPE extends string> {
   type: MESSAGE_TYPE
 }
 
@@ -31,16 +32,17 @@ export interface PostMessage<MESSAGE_TYPE extends string> {
 export abstract class WindowPostMessageCommunicator<
   RECEIVE_TYPE extends string,
   SEND_TYPE extends string,
-  MESSAGES extends PostMessage<RECEIVE_TYPE | SEND_TYPE>
+  MESSAGES extends MessagePayload<RECEIVE_TYPE | SEND_TYPE>
 > {
   private messageTarget?: Window
   private targetOrigin?: string
   private communicationEnabled: boolean
-  private handlers: HandlerMap<MESSAGES, RECEIVE_TYPE> = {}
-  private log
+  private readonly handlers: HandlerMap<MESSAGES, RECEIVE_TYPE> = {}
+  private readonly log: Logger
+  private readonly boundListener: (event: MessageEvent) => void
 
-  constructor() {
-    window.addEventListener('message', this.handleEvent.bind(this))
+  public constructor() {
+    this.boundListener = this.handleEvent.bind(this)
     this.communicationEnabled = false
     this.log = this.createLogger()
   }
@@ -48,10 +50,17 @@ export abstract class WindowPostMessageCommunicator<
   protected abstract createLogger(): Logger
 
   /**
-   * Removes the message event listener from the {@link window}
+   * Registers the event listener on the current global {@link window}.
+   */
+  public registerEventListener(): void {
+    window.addEventListener('message', this.boundListener, { passive: true })
+  }
+
+  /**
+   * Removes the message event listener from the {@link window}.
    */
   public unregisterEventListener(): void {
-    window.removeEventListener('message', this.handleEvent.bind(this))
+    window.removeEventListener('message', this.boundListener)
   }
 
   /**
@@ -90,7 +99,7 @@ export abstract class WindowPostMessageCommunicator<
    *
    * @param message The message to send.
    */
-  public sendMessageToOtherSide(message: Extract<MESSAGES, PostMessage<SEND_TYPE>>): void {
+  public sendMessageToOtherSide(message: Extract<MESSAGES, MessagePayload<SEND_TYPE>>): void {
     if (this.messageTarget === undefined || this.targetOrigin === undefined) {
       throw new IframeCommunicatorSendingError(`Other side is not set.\nMessage was: ${JSON.stringify(message)}`)
     }
@@ -121,18 +130,22 @@ export abstract class WindowPostMessageCommunicator<
    * @param event The received event
    * @return {@code true} if the event was processed.
    */
-  protected handleEvent(event: MessageEvent<PostMessage<RECEIVE_TYPE>>): boolean | undefined {
-    const data = event.data
+  protected handleEvent(event: MessageEvent<MessagePayload<RECEIVE_TYPE>>): void {
+    Optional.ofNullable(event.data).ifPresent((payload) => {
+      event.stopPropagation()
+      event.preventDefault()
+      this.processPayload(payload)
+    })
+  }
 
-    if (!(data.type in this.handlers)) {
-      return true
-    }
-    const handler = this.handlers[data.type]
-    if (!handler) {
-      return true
-    }
-    this.log.debug('Received event', data)
-    handler(data as Extract<MESSAGES, PostMessage<RECEIVE_TYPE>>)
-    return false
+  /**
+   * Processes a {@link MessagePayload message payload} using the correct {@link Handler handler}.
+   * @param payload The payload that should be processed
+   */
+  private processPayload(payload: MessagePayload<RECEIVE_TYPE>): void {
+    return Optional.ofNullable<Handler<MESSAGES, RECEIVE_TYPE>>(this.handlers[payload.type]).ifPresent((handler) => {
+      this.log.debug('Received event', payload)
+      handler(payload as Extract<MESSAGES, MessagePayload<RECEIVE_TYPE>>)
+    })
   }
 }
diff --git a/src/pages/n/[id].tsx b/src/pages/n/[id].tsx
index b47c205ff..0e3158137 100644
--- a/src/pages/n/[id].tsx
+++ b/src/pages/n/[id].tsx
@@ -4,173 +4,18 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-import React, { Suspense, useCallback, useEffect, useMemo, useRef, useState } from 'react'
-import { useTranslation } from 'react-i18next'
-import { useApplyDarkMode } from '../../hooks/common/use-apply-dark-mode'
-import { setCheckboxInMarkdownContent, updateNoteTitleByFirstHeading } from '../../redux/note-details/methods'
-import { MotdModal } from '../../components/common/motd-modal/motd-modal'
-import { ShowIf } from '../../components/common/show-if/show-if'
-import { ErrorWhileLoadingNoteAlert } from '../../components/document-read-only-page/ErrorWhileLoadingNoteAlert'
-import { LoadingNoteAlert } from '../../components/document-read-only-page/LoadingNoteAlert'
-import { AppBar, AppBarMode } from '../../components/editor-page/app-bar/app-bar'
-import { EditorMode } from '../../components/editor-page/app-bar/editor-view-mode'
-import { useLoadNoteFromServer } from '../../components/editor-page/hooks/useLoadNoteFromServer'
-import { useViewModeShortcuts } from '../../components/editor-page/hooks/useViewModeShortcuts'
-import { Sidebar } from '../../components/editor-page/sidebar/sidebar'
-import { Splitter } from '../../components/editor-page/splitter/splitter'
-import type { DualScrollState, ScrollState } from '../../components/editor-page/synced-scroll/scroll-props'
-import { RendererType } from '../../components/render-page/window-post-message-communicator/rendering-message'
-import { useEditorModeFromUrl } from '../../components/editor-page/hooks/useEditorModeFromUrl'
-import { UiNotifications } from '../../components/notifications/ui-notifications'
-import { useUpdateLocalHistoryEntry } from '../../components/editor-page/hooks/useUpdateLocalHistoryEntry'
-import { useApplicationState } from '../../hooks/common/use-application-state'
-import { EditorDocumentRenderer } from '../../components/editor-page/editor-document-renderer/editor-document-renderer'
+import React from 'react'
 import { EditorToRendererCommunicatorContextProvider } from '../../components/editor-page/render-context/editor-to-renderer-communicator-context-provider'
-import { Logger } from '../../utils/logger'
-import { NoteType } from '../../redux/note-details/types/note-details'
 import type { NextPage } from 'next'
-import { isClientSideRendering } from '../../utils/is-client-side-rendering'
-import { LoadingScreen } from '../../components/application-loader/loading-screen/loading-screen'
-import { NoteAndAppTitleHead } from '../../components/layout/note-and-app-title-head'
-import equal from 'fast-deep-equal'
-
-const EditorPane = React.lazy(() => import('../../components/editor-page/editor-pane/editor-pane'))
-
-export interface EditorPagePathParams {
-  id: string
-}
-
-export enum ScrollSource {
-  EDITOR,
-  RENDERER
-}
-
-const log = new Logger('EditorPage')
+import { EditorPageContent } from '../../components/editor-page/editor-page-content'
 
 /**
  * Renders a page that is used by the user to edit markdown notes. It contains the editor and a renderer.
  */
 export const EditorPage: NextPage = () => {
-  useTranslation()
-  const scrollSource = useRef<ScrollSource>(ScrollSource.EDITOR)
-  const editorMode: EditorMode = useApplicationState((state) => state.editorConfig.editorMode)
-  const editorSyncScroll: boolean = useApplicationState((state) => state.editorConfig.syncScroll)
-
-  const [scrollState, setScrollState] = useState<DualScrollState>(() => ({
-    editorScrollState: { firstLineInView: 1, scrolledPercentage: 0 },
-    rendererScrollState: { firstLineInView: 1, scrolledPercentage: 0 }
-  }))
-
-  const onMarkdownRendererScroll = useCallback(
-    (newScrollState: ScrollState) => {
-      if (scrollSource.current === ScrollSource.RENDERER && editorSyncScroll) {
-        setScrollState((old) => {
-          const newState: DualScrollState = {
-            editorScrollState: newScrollState,
-            rendererScrollState: old.rendererScrollState
-          }
-          return equal(newState, old) ? old : newState
-        })
-      }
-    },
-    [editorSyncScroll]
-  )
-
-  useEffect(() => {
-    log.debug('New scroll state', scrollState, scrollSource)
-  }, [scrollState])
-
-  const onEditorScroll = useCallback(
-    (newScrollState: ScrollState) => {
-      if (scrollSource.current === ScrollSource.EDITOR && editorSyncScroll) {
-        setScrollState((old) => {
-          const newState: DualScrollState = {
-            rendererScrollState: newScrollState,
-            editorScrollState: old.editorScrollState
-          }
-          return equal(newState, old) ? old : newState
-        })
-      }
-    },
-    [editorSyncScroll]
-  )
-
-  useViewModeShortcuts()
-  useApplyDarkMode()
-  useEditorModeFromUrl()
-
-  const [error, loading] = useLoadNoteFromServer()
-
-  useUpdateLocalHistoryEntry(!error && !loading)
-
-  const setRendererToScrollSource = useCallback(() => {
-    if (scrollSource.current !== ScrollSource.RENDERER) {
-      scrollSource.current = ScrollSource.RENDERER
-      log.debug('Make renderer scroll source')
-    }
-  }, [])
-
-  const setEditorToScrollSource = useCallback(() => {
-    if (scrollSource.current !== ScrollSource.EDITOR) {
-      scrollSource.current = ScrollSource.EDITOR
-      log.debug('Make editor scroll source')
-    }
-  }, [])
-
-  const leftPane = useMemo(
-    () =>
-      isClientSideRendering() ? (
-        <Suspense fallback={<LoadingScreen />}>
-          <EditorPane
-            scrollState={scrollState.editorScrollState}
-            onScroll={onEditorScroll}
-            onMakeScrollSource={setEditorToScrollSource}
-          />
-        </Suspense>
-      ) : undefined,
-    [onEditorScroll, scrollState.editorScrollState, setEditorToScrollSource]
-  )
-  const noteType: NoteType = useApplicationState((state) => state.noteDetails.frontmatter.type)
-
-  const rightPane = useMemo(
-    () => (
-      <EditorDocumentRenderer
-        frameClasses={'h-100 w-100'}
-        onMakeScrollSource={setRendererToScrollSource}
-        onFirstHeadingChange={updateNoteTitleByFirstHeading}
-        onTaskCheckedChange={setCheckboxInMarkdownContent}
-        onScroll={onMarkdownRendererScroll}
-        scrollState={scrollState.rendererScrollState}
-        rendererType={noteType === NoteType.SLIDE ? RendererType.SLIDESHOW : RendererType.DOCUMENT}
-      />
-    ),
-    [noteType, onMarkdownRendererScroll, scrollState.rendererScrollState, setRendererToScrollSource]
-  )
-
   return (
     <EditorToRendererCommunicatorContextProvider>
-      <NoteAndAppTitleHead />
-      <UiNotifications />
-      <MotdModal />
-      <div className={'d-flex flex-column vh-100'}>
-        <AppBar mode={AppBarMode.EDITOR} />
-        <div className={'container'}>
-          <ErrorWhileLoadingNoteAlert show={error} />
-          <LoadingNoteAlert show={loading} />
-        </div>
-        <ShowIf condition={!error && !loading}>
-          <div className={'flex-fill d-flex h-100 w-100 overflow-hidden flex-row'}>
-            <Splitter
-              showLeft={editorMode === EditorMode.EDITOR || editorMode === EditorMode.BOTH}
-              left={leftPane}
-              showRight={editorMode === EditorMode.PREVIEW || editorMode === EditorMode.BOTH}
-              right={rightPane}
-              additionalContainerClassName={'overflow-hidden'}
-            />
-            <Sidebar />
-          </div>
-        </ShowIf>
-      </div>
+      <EditorPageContent />
     </EditorToRendererCommunicatorContextProvider>
   )
 }