From 3ce94a9f6d2fa5ca78ca15e09e3775b6f517e9c9 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Fri, 19 Mar 2021 12:09:41 +0100
Subject: [PATCH 1/3] Change how landscape pages are rotated, for printing,
 with `enablePrintAutoRotate = true` set

Currently landscape pages are rotated *clockwise*, which for most documents feel wrong since holding the printed pages at their *left* edge causes the landscape pages to be viewed "upside down".
In general, since most documents are LTR ones, it feels more appropriate to instead rotate landscape pages *counterclockwise* for printing.
---
 web/base_viewer.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/web/base_viewer.js b/web/base_viewer.js
index a57bd50c5..34f2e796a 100644
--- a/web/base_viewer.js
+++ b/web/base_viewer.js
@@ -1365,7 +1365,7 @@ class BaseViewer {
       return {
         width: size.height,
         height: size.width,
-        rotation: (size.rotation + 90) % 360,
+        rotation: (size.rotation - 90) % 360,
       };
     });
   }

From 1de466896d123486bdffd06bfbbd5735f5792d5b Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Fri, 19 Mar 2021 12:19:29 +0100
Subject: [PATCH 2/3] Remove one loop from `BaseViewer.getPagesOverview`

Currently, with `enablePrintAutoRotate = true` set, we're forced to loop through all the pages *twice* when checking for any landscape pages.
This seems completely unnecessary now, and using only *one* loop should be marginally more efficient in general.
---
 web/base_viewer.js | 28 ++++++++++++----------------
 1 file changed, 12 insertions(+), 16 deletions(-)

diff --git a/web/base_viewer.js b/web/base_viewer.js
index 34f2e796a..9d77e8bbb 100644
--- a/web/base_viewer.js
+++ b/web/base_viewer.js
@@ -1347,25 +1347,21 @@ class BaseViewer {
    * @returns {Array} Array of objects with width/height/rotation fields.
    */
   getPagesOverview() {
-    const pagesOverview = this._pages.map(function (pageView) {
+    return this._pages.map(pageView => {
       const viewport = pageView.pdfPage.getViewport({ scale: 1 });
-      return {
-        width: viewport.width,
-        height: viewport.height,
-        rotation: viewport.rotation,
-      };
-    });
-    if (!this.enablePrintAutoRotate) {
-      return pagesOverview;
-    }
-    return pagesOverview.map(function (size) {
-      if (isPortraitOrientation(size)) {
-        return size;
+
+      if (!this.enablePrintAutoRotate || isPortraitOrientation(viewport)) {
+        return {
+          width: viewport.width,
+          height: viewport.height,
+          rotation: viewport.rotation,
+        };
       }
+      // Landscape orientation.
       return {
-        width: size.height,
-        height: size.width,
-        rotation: (size.rotation - 90) % 360,
+        width: viewport.height,
+        height: viewport.width,
+        rotation: (viewport.rotation - 90) % 360,
       };
     });
   }

From 30c06849d81358c0372abcdb5b741e931a60cd00 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Fri, 19 Mar 2021 12:27:23 +0100
Subject: [PATCH 3/3] Rotate landscape pages, during printing, by default in
 the viewer (`enablePrintAutoRotate = true`)

While this will perhaps not be perfect for *every* PDF document with mixed page orientation, based on the large number of bugs/issues seen over the years I'm however pretty convinced that it'll be an overall improvement in a majority of cases.

In order to improve things further, we'd probably need Firefox to support e.g. `@page` such that the viewer can provide better information to the print engine.
---
 extensions/chromium/preferences_schema.json | 2 +-
 web/app_options.js                          | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/extensions/chromium/preferences_schema.json b/extensions/chromium/preferences_schema.json
index de2ae62df..b88a5dc4b 100644
--- a/extensions/chromium/preferences_schema.json
+++ b/extensions/chromium/preferences_schema.json
@@ -173,7 +173,7 @@
       "title": "Automatically rotate printed pages",
       "description": "When enabled, landscape pages are rotated when printed.",
       "type": "boolean",
-      "default": false
+      "default": true
     },
     "scrollModeOnLoad": {
       "title": "Scroll mode on load",
diff --git a/web/app_options.js b/web/app_options.js
index 72ad6d091..9a91ab697 100644
--- a/web/app_options.js
+++ b/web/app_options.js
@@ -62,7 +62,7 @@ const defaultOptions = {
   },
   enablePrintAutoRotate: {
     /** @type {boolean} */
-    value: false,
+    value: true,
     kind: OptionKind.VIEWER + OptionKind.PREFERENCE,
   },
   enableScripting: {