From 00720d059a86430078595bc84077a15ef0340fef Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Mon, 11 Oct 2021 15:55:16 +0200
Subject: [PATCH] [api-minor] Include the /Lang-property in the `documentInfo`,
 and use it in the viewer (issue 14110)

*Please note:* This is a tentative patch, since I don't have the necessary a11y-software to actually test it.

To avoid having to add a new API-method just for a single string, I figured that adding the new property to the existing `documentInfo`-data (accessed via `PDFDocumentProxy.getMetadata` in the API) will hopefully be deemed acceptable.
---
 src/core/catalog.js   | 9 +++++++++
 src/core/document.js  | 1 +
 test/unit/api_spec.js | 3 +++
 web/app.js            | 4 ++++
 4 files changed, 17 insertions(+)

diff --git a/src/core/catalog.js b/src/core/catalog.js
index 2ace6fa40..5bc73d8af 100644
--- a/src/core/catalog.js
+++ b/src/core/catalog.js
@@ -89,6 +89,15 @@ class Catalog {
     );
   }
 
+  get lang() {
+    const lang = this._catDict.get("Lang");
+    return shadow(
+      this,
+      "lang",
+      typeof lang === "string" ? stringToPDFString(lang) : null
+    );
+  }
+
   /**
    * @type {boolean} `true` for pure XFA documents,
    *   `false` for XFA Foreground documents.
diff --git a/src/core/document.js b/src/core/document.js
index 4c77f10ca..61f630b66 100644
--- a/src/core/document.js
+++ b/src/core/document.js
@@ -1160,6 +1160,7 @@ class PDFDocument {
 
     const docInfo = {
       PDFFormatVersion: version,
+      Language: this.catalog.lang,
       IsLinearized: !!this.linearization,
       IsAcroFormPresent: this.formInfo.hasAcroForm,
       IsXFAPresent: this.formInfo.hasXfa,
diff --git a/test/unit/api_spec.js b/test/unit/api_spec.js
index f5a81f243..234905b9a 100644
--- a/test/unit/api_spec.js
+++ b/test/unit/api_spec.js
@@ -1161,6 +1161,7 @@ describe("api", function () {
       expect(info.Custom).toEqual(undefined);
       // The following are PDF.js specific, non-standard, properties.
       expect(info.PDFFormatVersion).toEqual("1.7");
+      expect(info.Language).toEqual("en");
       expect(info.IsLinearized).toEqual(false);
       expect(info.IsAcroFormPresent).toEqual(false);
       expect(info.IsXFAPresent).toEqual(false);
@@ -1195,6 +1196,7 @@ describe("api", function () {
       );
       // The following are PDF.js specific, non-standard, properties.
       expect(info.PDFFormatVersion).toEqual("1.4");
+      expect(info.Language).toEqual(null);
       expect(info.IsLinearized).toEqual(false);
       expect(info.IsAcroFormPresent).toEqual(false);
       expect(info.IsXFAPresent).toEqual(false);
@@ -1216,6 +1218,7 @@ describe("api", function () {
 
       // The following are PDF.js specific, non-standard, properties.
       expect(info.PDFFormatVersion).toEqual(null);
+      expect(info.Language).toEqual(null);
       expect(info.IsLinearized).toEqual(false);
       expect(info.IsAcroFormPresent).toEqual(false);
       expect(info.IsXFAPresent).toEqual(false);
diff --git a/web/app.js b/web/app.js
index 3c81f5dbe..0f7fb7d6a 100644
--- a/web/app.js
+++ b/web/app.js
@@ -812,6 +812,7 @@ const PDFViewerApplication = {
       const { container } = this.appConfig.errorWrapper;
       container.hidden = true;
     }
+    this.appConfig.viewerContainer.removeAttribute("lang");
 
     if (!this.pdfLoadingTask) {
       return;
@@ -1536,6 +1537,9 @@ const PDFViewerApplication = {
         `(PDF.js: ${version || "-"})`
     );
 
+    if (info.Language) {
+      this.appConfig.viewerContainer.lang = info.Language;
+    }
     let pdfTitle = info?.Title;
 
     const metadataTitle = metadata?.get("dc:title");