From af887877aa0f5364f2804b84f82a360af1460eec Mon Sep 17 00:00:00 2001
From: Tilman Vatteroth <tilman.vatteroth@tu-dortmund.de>
Date: Sat, 3 Apr 2021 12:59:14 +0200
Subject: [PATCH] Add context for iframe communicator in editor page (#1146)

Signed-off-by: Tilman Vatteroth <git@tilmanvatteroth.de>
---
 src/components/editor-page/editor-page.tsx    | 54 ++++++++++---------
 .../iframe-communicator-context-provider.tsx  | 25 +++++++++
 .../renderer-pane/render-iframe.tsx           |  6 +--
 3 files changed, 58 insertions(+), 27 deletions(-)
 create mode 100644 src/components/editor-page/render-context/iframe-communicator-context-provider.tsx

diff --git a/src/components/editor-page/editor-page.tsx b/src/components/editor-page/editor-page.tsx
index 35493b064..836999b1d 100644
--- a/src/components/editor-page/editor-page.tsx
+++ b/src/components/editor-page/editor-page.tsx
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 
-import React, { Fragment, useCallback, useRef, useState } from 'react'
+import React, { useCallback, useMemo, useRef, useState } from 'react'
 import { useTranslation } from 'react-i18next'
 import { useSelector } from 'react-redux'
 import { useApplyDarkMode } from '../../hooks/common/use-apply-dark-mode'
@@ -34,6 +34,7 @@ import { RendererType } from '../render-page/rendering-message'
 import { useEditorModeFromUrl } from './hooks/useEditorModeFromUrl'
 import { UiNotifications } from '../notifications/ui-notifications'
 import { useNotificationTest } from './use-notification-test'
+import { IframeCommunicatorContextProvider } from './render-context/iframe-communicator-context-provider'
 
 export interface EditorPagePathParams {
   id: string
@@ -86,13 +87,35 @@ export const EditorPage: React.FC = () => {
 
   useNotificationTest()
 
+  const leftPane = useMemo(() =>
+      <EditorPane
+        onContentChange={ setNoteMarkdownContent }
+        content={ markdownContent }
+        scrollState={ scrollState.editorScrollState }
+        onScroll={ onEditorScroll }
+        onMakeScrollSource={ setEditorToScrollSource }/>
+    , [markdownContent, onEditorScroll, scrollState.editorScrollState, setEditorToScrollSource])
+
+  const rightPane = useMemo(() =>
+      <RenderIframe
+        frameClasses={ 'h-100 w-100' }
+        markdownContent={ markdownContent }
+        onMakeScrollSource={ setRendererToScrollSource }
+        onFirstHeadingChange={ updateNoteTitleByFirstHeading }
+        onTaskCheckedChange={ SetCheckboxInMarkdownContent }
+        onFrontmatterChange={ setNoteFrontmatter }
+        onScroll={ onMarkdownRendererScroll }
+        scrollState={ scrollState.rendererScrollState }
+        rendererType={ RendererType.DOCUMENT }/>
+    , [markdownContent, onMarkdownRendererScroll, scrollState.rendererScrollState,
+      setRendererToScrollSource])
+
   return (
-    <Fragment>
+    <IframeCommunicatorContextProvider>
       <UiNotifications/>
       <MotdBanner/>
       <div className={ 'd-flex flex-column vh-100' }>
         <AppBar mode={ AppBarMode.EDITOR }/>
-
         <div className={ 'container' }>
           <ErrorWhileLoadingNoteAlert show={ error }/>
           <LoadingNoteAlert show={ loading }/>
@@ -101,33 +124,16 @@ export const EditorPage: React.FC = () => {
           <div className={ 'flex-fill d-flex h-100 w-100 overflow-hidden flex-row' }>
             <Splitter
               showLeft={ editorMode === EditorMode.EDITOR || editorMode === EditorMode.BOTH }
-              left={
-                <EditorPane
-                  onContentChange={ setNoteMarkdownContent }
-                  content={ markdownContent }
-                  scrollState={ scrollState.editorScrollState }
-                  onScroll={ onEditorScroll }
-                  onMakeScrollSource={ setEditorToScrollSource }/>
-              }
+              left={ leftPane }
               showRight={ editorMode === EditorMode.PREVIEW || editorMode === EditorMode.BOTH }
-              right={
-                <RenderIframe
-                  frameClasses={ 'h-100 w-100' }
-                  markdownContent={ markdownContent }
-                  onMakeScrollSource={ setRendererToScrollSource }
-                  onFirstHeadingChange={ updateNoteTitleByFirstHeading }
-                  onTaskCheckedChange={ SetCheckboxInMarkdownContent }
-                  onFrontmatterChange={ setNoteFrontmatter }
-                  onScroll={ onMarkdownRendererScroll }
-                  scrollState={ scrollState.rendererScrollState }
-                  rendererType={ RendererType.DOCUMENT }/>
-              }
+              right={ rightPane }
               containerClassName={ 'overflow-hidden' }/>
             <Sidebar/>
           </div>
         </ShowIf>
       </div>
-    </Fragment>
+    </IframeCommunicatorContextProvider>
   )
 }
+
 export default EditorPage
diff --git a/src/components/editor-page/render-context/iframe-communicator-context-provider.tsx b/src/components/editor-page/render-context/iframe-communicator-context-provider.tsx
new file mode 100644
index 000000000..bab6c7f91
--- /dev/null
+++ b/src/components/editor-page/render-context/iframe-communicator-context-provider.tsx
@@ -0,0 +1,25 @@
+/*
+ * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import React, { useContext, useMemo } from 'react'
+import { IframeEditorToRendererCommunicator } from '../../render-page/iframe-editor-to-renderer-communicator'
+
+const IFrameEditorToRendererCommunicatorContext = React.createContext<IframeEditorToRendererCommunicator | undefined>(undefined)
+
+export const useIFrameCommunicator: () => IframeEditorToRendererCommunicator | undefined = () => useContext(IFrameEditorToRendererCommunicatorContext)
+
+export const useContextOrStandaloneIframeCommunicator: () => IframeEditorToRendererCommunicator = () => {
+  const contextCommunicator = useIFrameCommunicator()
+  return useMemo(() => contextCommunicator ? contextCommunicator : new IframeEditorToRendererCommunicator(), [contextCommunicator])
+}
+
+export const IframeCommunicatorContextProvider: React.FC = ({ children }) => {
+  const currentIFrameCommunicator = useMemo<IframeEditorToRendererCommunicator>(() => new IframeEditorToRendererCommunicator(), [])
+
+  return <IFrameEditorToRendererCommunicatorContext.Provider value={ currentIFrameCommunicator }>
+    { children }
+  </IFrameEditorToRendererCommunicatorContext.Provider>
+}
diff --git a/src/components/editor-page/renderer-pane/render-iframe.tsx b/src/components/editor-page/renderer-pane/render-iframe.tsx
index 1b2ea5a82..68c493c57 100644
--- a/src/components/editor-page/renderer-pane/render-iframe.tsx
+++ b/src/components/editor-page/renderer-pane/render-iframe.tsx
@@ -4,14 +4,14 @@
  * SPDX-License-Identifier: AGPL-3.0-only
  */
 import equal from 'fast-deep-equal'
-import React, { Fragment, useCallback, useEffect, useMemo, useRef, useState } from 'react'
+import React, { Fragment, useCallback, useEffect, useRef, useState } from 'react'
 import { useSelector } from 'react-redux'
 import { useIsDarkModeActivated } from '../../../hooks/common/use-is-dark-mode-activated'
 import { ApplicationState } from '../../../redux'
 import { isTestMode } from '../../../utils/is-test-mode'
-import { IframeEditorToRendererCommunicator } from '../../render-page/iframe-editor-to-renderer-communicator'
 import { RendererProps } from '../../render-page/markdown-document'
 import { ImageDetails, RendererType } from '../../render-page/rendering-message'
+import { useContextOrStandaloneIframeCommunicator } from '../render-context/iframe-communicator-context-provider'
 import { ScrollState } from '../synced-scroll/scroll-props'
 import { useOnIframeLoad } from './hooks/use-on-iframe-load'
 import { ShowOnPropChangeImageLightbox } from './show-on-prop-change-image-lightbox'
@@ -46,7 +46,7 @@ export const RenderIframe: React.FC<RenderIframeProps> = (
   const rendererOrigin = useSelector((state: ApplicationState) => state.config.iframeCommunication.rendererOrigin)
   const renderPageUrl = `${ rendererOrigin }/render`
   const resetRendererReady = useCallback(() => setRendererReady(false), [])
-  const iframeCommunicator = useMemo(() => new IframeEditorToRendererCommunicator(), [])
+  const iframeCommunicator = useContextOrStandaloneIframeCommunicator()
   const onIframeLoad = useOnIframeLoad(frameReference, iframeCommunicator, rendererOrigin, renderPageUrl, resetRendererReady)
   const [frameHeight, setFrameHeight] = useState<number>(0)