From 4919dae2943e8021a3b543c659368442feb63022 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Mon, 15 Aug 2022 16:21:58 +0200
Subject: [PATCH] Refresh the viewer if the window resolution changes (bug
 1784850)

*Please note:* This probably fixes bug 1784850, however I don't have the necessary hardware to reproduce the situation described in https://bugzilla.mozilla.org/show_bug.cgi?id=1784850#c0

Unfortunately it doesn't, as far as I can tell, appear possible to detect *all* resolution changes with a single media query. Instead we have to update it, and its listener, on every resolution change as outlined in [this MDN example](https://developer.mozilla.org/en-US/docs/Web/API/Window/devicePixelRatio#monitoring_screen_resolution_or_zoom_level_changes).
---
 web/app.js         | 26 ++++++++++++++++++++++++++
 web/base_viewer.js | 11 +++++++++++
 2 files changed, 37 insertions(+)

diff --git a/web/app.js b/web/app.js
index 749b829fb..c53ebc71e 100644
--- a/web/app.js
+++ b/web/app.js
@@ -2004,6 +2004,27 @@ const PDFViewerApplication = {
   bindWindowEvents() {
     const { eventBus, _boundEvents } = this;
 
+    function addWindowResolutionChange(evt = null) {
+      if (evt) {
+        webViewerResolutionChange(evt);
+      }
+      const mediaQueryList = window.matchMedia(
+        `(resolution: ${window.devicePixelRatio || 1}dppx)`
+      );
+      mediaQueryList.addEventListener("change", addWindowResolutionChange, {
+        once: true,
+      });
+
+      if (typeof PDFJSDev !== "undefined" && PDFJSDev.test("MOZCENTRAL")) {
+        return;
+      }
+      _boundEvents.removeWindowResolutionChange ||= function () {
+        mediaQueryList.removeEventListener("change", addWindowResolutionChange);
+        _boundEvents.removeWindowResolutionChange = null;
+      };
+    }
+    addWindowResolutionChange();
+
     _boundEvents.windowResize = () => {
       eventBus.dispatch("resize", { source: window });
     };
@@ -2123,6 +2144,7 @@ const PDFViewerApplication = {
       _boundEvents.windowUpdateFromSandbox
     );
 
+    _boundEvents.removeWindowResolutionChange?.();
     _boundEvents.windowResize = null;
     _boundEvents.windowHashChange = null;
     _boundEvents.windowBeforePrint = null;
@@ -2689,6 +2711,10 @@ function webViewerPageChanging({ pageNumber, pageLabel }) {
   }
 }
 
+function webViewerResolutionChange(evt) {
+  PDFViewerApplication.pdfViewer.refresh();
+}
+
 function webViewerVisibilityChange(evt) {
   if (document.visibilityState === "visible") {
     // Ignore mouse wheel zooming during tab switches (bug 1503412).
diff --git a/web/base_viewer.js b/web/base_viewer.js
index e1541235f..5ff689585 100644
--- a/web/base_viewer.js
+++ b/web/base_viewer.js
@@ -2247,6 +2247,17 @@ class BaseViewer {
     }
     this.#annotationEditorUIManager.updateParams(type, value);
   }
+
+  refresh() {
+    if (!this.pdfDocument) {
+      return;
+    }
+    const updateArgs = {};
+    for (const pageView of this._pages) {
+      pageView.update(updateArgs);
+    }
+    this.update();
+  }
 }
 
 export { BaseViewer, PagesCountLimit, PDFPageViewBuffer };