From a2bc6481a081a1093fad8b638c30d5bb8d099584 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Fri, 2 Apr 2021 12:26:39 +0200
Subject: [PATCH] [api-minor] Add an option, in `PDFDocumentProxy.cleanup`, to
 allow fonts to remain attached to the DOM

As mentioned in the JSDoc comment, this should not be used unless you know what you're doing, since it will lead to increased memory usage. However, in some situations (e.g. SVG-rendering), we still want to be able to run general clean-up on both the main/worker-thread while keeping loaded fonts attached to the DOM.[1]

As part of these changes, `WorkerTransport.startCleanup` is converted to an async method and we'll also skip clean-up when destruction has started (since it's redundant).

---
[1] The SVG-rendering mode is obviously not officially supported, since it's both rather incomplete and inherently slower. However with recent changes, whereby we cache repeated images on the document rather than the page level, memory usage can be *a lot* worse than before if we never attempt to release e.g. cached image-data when the viewer is in SVG-rendering mode.
---
 src/display/api.js | 41 ++++++++++++++++++++++++-----------------
 web/app.js         | 13 ++++++++-----
 2 files changed, 32 insertions(+), 22 deletions(-)

diff --git a/src/display/api.js b/src/display/api.js
index fa501b074..617e10a64 100644
--- a/src/display/api.js
+++ b/src/display/api.js
@@ -921,10 +921,13 @@ class PDFDocumentProxy {
    * NOTE: Do not, under any circumstances, call this method when rendering is
    * currently ongoing since that may lead to rendering errors.
    *
+   * @param {boolean} [keepLoadedFonts] - Let fonts remain attached to the DOM.
+   *   NOTE: This will increase persistent memory usage, hence don't use this
+   *   option unless absolutely necessary. The default value is `false`.
    * @returns {Promise} A promise that is resolved when clean-up has finished.
    */
-  cleanup() {
-    return this._transport.startCleanup();
+  cleanup(keepLoadedFonts = false) {
+    return this._transport.startCleanup(keepLoadedFonts || this.isPureXfa);
   }
 
   /**
@@ -2799,24 +2802,28 @@ class WorkerTransport {
     return this.messageHandler.sendWithPromise("GetStats", null);
   }
 
-  startCleanup() {
-    return this.messageHandler.sendWithPromise("Cleanup", null).then(() => {
-      for (let i = 0, ii = this.pageCache.length; i < ii; i++) {
-        const page = this.pageCache[i];
-        if (page) {
-          const cleanupSuccessful = page.cleanup();
+  async startCleanup(keepLoadedFonts = false) {
+    await this.messageHandler.sendWithPromise("Cleanup", null);
 
-          if (!cleanupSuccessful) {
-            throw new Error(
-              `startCleanup: Page ${i + 1} is currently rendering.`
-            );
-          }
-        }
+    if (this.destroyed) {
+      return; // No need to manually clean-up when destruction has started.
+    }
+    for (let i = 0, ii = this.pageCache.length; i < ii; i++) {
+      const page = this.pageCache[i];
+      if (!page) {
+        continue;
       }
-      this.commonObjs.clear();
+      const cleanupSuccessful = page.cleanup();
+
+      if (!cleanupSuccessful) {
+        throw new Error(`startCleanup: Page ${i + 1} is currently rendering.`);
+      }
+    }
+    this.commonObjs.clear();
+    if (!keepLoadedFonts) {
       this.fontLoader.clear();
-      this._hasJSActionsPromise = null;
-    });
+    }
+    this._hasJSActionsPromise = null;
   }
 
   get loadingParams() {
diff --git a/web/app.js b/web/app.js
index 3a66de48a..e9d5ca9b1 100644
--- a/web/app.js
+++ b/web/app.js
@@ -465,7 +465,7 @@ const PDFViewerApplication = {
     this.overlayManager = new OverlayManager();
 
     const pdfRenderingQueue = new PDFRenderingQueue();
-    pdfRenderingQueue.onIdle = this.cleanup.bind(this);
+    pdfRenderingQueue.onIdle = this._cleanup.bind(this);
     this.pdfRenderingQueue = pdfRenderingQueue;
 
     const pdfLinkService = new PDFLinkService({
@@ -1767,7 +1767,10 @@ const PDFViewerApplication = {
     }
   },
 
-  cleanup() {
+  /**
+   * @private
+   */
+  _cleanup() {
     if (!this.pdfDocument) {
       return; // run cleanup when document is loaded
     }
@@ -1775,9 +1778,9 @@ const PDFViewerApplication = {
     this.pdfThumbnailViewer.cleanup();
 
     // We don't want to remove fonts used by active page SVGs.
-    if (this.pdfViewer.renderer !== RendererType.SVG) {
-      this.pdfDocument.cleanup();
-    }
+    this.pdfDocument.cleanup(
+      /* keepLoadedFonts = */ this.pdfViewer.renderer === RendererType.SVG
+    );
   },
 
   forceRendering() {