fix: prevent navigator.fonts.query() from crashing

filenames.gni

@@ -382,6 +382,8 @@ filenames = {
     "shell/browser/file_select_helper.cc",
     "shell/browser/file_select_helper.h",
     "shell/browser/file_select_helper_mac.mm",
+    "shell/browser/font/electron_font_access_delegate.cc",
+    "shell/browser/font/electron_font_access_delegate.h",
     "shell/browser/font_defaults.cc",
     "shell/browser/font_defaults.h",
     "shell/browser/javascript_environment.cc",

patches/chromium/.patches

@@ -108,3 +108,4 @@ chore_do_not_use_chrome_windows_in_cryptotoken_webrequestsender.patch
 fix_chrome_root_store_codegen_for_cross-compile_builds.patch
 process_singleton.patch
 fix_expose_decrementcapturercount_in_web_contents_impl.patch
+fix_font_access_chooser_dcheck.patch

patches/chromium/fix_font_access_chooser_dcheck.patch

@@ -0,0 +1,33 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Shelley Vohr <shelley.vohr@gmail.com>
+Date: Mon, 13 Sep 2021 16:06:52 +0200
+Subject: Fix: font access chooser DCHECK
+
+This patch is necessary to prevent a crash when navigator.fonts.query()
+in the intermediary period prior to Electron actually implementing the
+feature. Chromium relies on a user choice via a UI they pop up to run
+the callback, and in contrast we don't really have a way to run the
+closure post-construction of the FontAccessChooser and therefore must
+run it in the constructor, which makes it such that
+FontAccessManagerImpl::DidChooseLocalFonts runs before the FontAccessChooser
+is assigned in the choosers_ map and DCHECKS.
+
+As we don't yet have a standardized permissions model
+for this and similar APIs, this just mediates the crash and adds
+appropriate simple scaffolding for a proper implementation.
+
+diff --git a/content/browser/font_access/font_access_manager_impl.cc b/content/browser/font_access/font_access_manager_impl.cc
+index 518854d5370cdb5dc5131ad47442ac2bc748eae5..8b2b6ab23d1d12a0bb202dd1227ba5a28236a934 100644
+--- a/content/browser/font_access/font_access_manager_impl.cc
++++ b/content/browser/font_access/font_access_manager_impl.cc
+@@ -262,8 +262,8 @@ void FontAccessManagerImpl::DidChooseLocalFonts(
+   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+
+   // The chooser has fulfilled its purpose. It's safe to dispose of it.
+-  size_t erased = choosers_.erase(frame_id);
+-  DCHECK_EQ(erased, 1u);
++  // size_t erased = choosers_.erase(frame_id);
++  // DCHECK_EQ(erased, 1u);
+
+   std::move(callback).Run(std::move(status), std::move(fonts));
+ }

shell/browser/electron_browser_client.cc

@@ -1670,6 +1670,12 @@ content::BluetoothDelegate* ElectronBrowserClient::GetBluetoothDelegate() {
   return bluetooth_delegate_.get();
 }
 
+content::FontAccessDelegate* ElectronBrowserClient::GetFontAccessDelegate() {
+  if (!font_access_delegate_)
+    font_access_delegate_ = std::make_unique<ElectronFontAccessDelegate>();
+  return font_access_delegate_.get();
+}
+
 void BindBadgeServiceForServiceWorker(
     const content::ServiceWorkerVersionBaseInfo& info,
     mojo::PendingReceiver<blink::mojom::BadgeService> receiver) {

shell/browser/electron_browser_client.h

@@ -20,6 +20,7 @@
 #include "net/ssl/client_cert_identity.h"
 #include "services/metrics/public/cpp/ukm_source_id.h"
 #include "shell/browser/bluetooth/electron_bluetooth_delegate.h"
+#include "shell/browser/font/electron_font_access_delegate.h"
 #include "shell/browser/serial/electron_serial_delegate.h"
 #include "third_party/blink/public/mojom/badging/badging.mojom-forward.h"
 
@@ -91,6 +92,8 @@ class ElectronBrowserClient : public content::ContentBrowserClient,
 
   content::SerialDelegate* GetSerialDelegate() override;
 
+  content::FontAccessDelegate* GetFontAccessDelegate() override;
+
   content::BluetoothDelegate* GetBluetoothDelegate() override;
 
   device::GeolocationManager* GetGeolocationManager() override;
@@ -305,6 +308,7 @@ class ElectronBrowserClient : public content::ContentBrowserClient,
 
   std::unique_ptr<ElectronSerialDelegate> serial_delegate_;
   std::unique_ptr<ElectronBluetoothDelegate> bluetooth_delegate_;
+  std::unique_ptr<ElectronFontAccessDelegate> font_access_delegate_;
 
 #if defined(OS_MAC)
   ElectronBrowserMainParts* browser_main_parts_ = nullptr;

shell/browser/font/electron_font_access_delegate.cc

@@ -0,0 +1,38 @@
+// Copyright (c) 2021 Microsoft, Inc.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#include <utility>
+
+#include "shell/browser/font/electron_font_access_delegate.h"
+
+#include "content/public/browser/font_access_chooser.h"
+#include "content/public/browser/render_frame_host.h"
+
+// #include <memory>
+// #include <string>
+
+class ElectronFontAccessChooser : public content::FontAccessChooser {
+ public:
+  explicit ElectronFontAccessChooser(base::OnceClosure close_callback) {
+    std::move(close_callback).Run();
+  }
+  ~ElectronFontAccessChooser() override = default;
+};
+
+ElectronFontAccessDelegate::ElectronFontAccessDelegate() = default;
+ElectronFontAccessDelegate::~ElectronFontAccessDelegate() = default;
+
+std::unique_ptr<content::FontAccessChooser>
+ElectronFontAccessDelegate::RunChooser(
+    content::RenderFrameHost* frame,
+    const std::vector<std::string>& selection,
+    content::FontAccessChooser::Callback callback) {
+  // TODO(codebytere) : implement with proper permissions model.
+  return std::make_unique<ElectronFontAccessChooser>(base::BindOnce(
+      [](content::FontAccessChooser::Callback callback) {
+        std::move(callback).Run(
+            blink::mojom::FontEnumerationStatus::kUnimplemented, {});
+      },
+      std::move(callback)));
+}

shell/browser/font/electron_font_access_delegate.h

@@ -0,0 +1,28 @@
+// Copyright (c) 2021 Microsoft, Inc.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#ifndef SHELL_BROWSER_FONT_ELECTRON_FONT_ACCESS_DELEGATE_H_
+#define SHELL_BROWSER_FONT_ELECTRON_FONT_ACCESS_DELEGATE_H_
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "content/public/browser/font_access_chooser.h"
+#include "content/public/browser/font_access_delegate.h"
+
+class ElectronFontAccessDelegate : public content::FontAccessDelegate {
+ public:
+  ElectronFontAccessDelegate();
+  ~ElectronFontAccessDelegate() override;
+
+  std::unique_ptr<content::FontAccessChooser> RunChooser(
+      content::RenderFrameHost* frame,
+      const std::vector<std::string>& selection,
+      content::FontAccessChooser::Callback callback) override;
+
+  DISALLOW_COPY_AND_ASSIGN(ElectronFontAccessDelegate);
+};
+
+#endif  // SHELL_BROWSER_FONT_ELECTRON_FONT_ACCESS_DELEGATE_H_