fix: RTL `WindowButtonsProxy` buttons (#36852)

* fix: RTL WindowButtonsProxy buttons

Co-authored-by: Shelley Vohr <[email protected]>

* chore: address review feedback

Co-authored-by: Shelley Vohr <[email protected]>

Co-authored-by: trop[bot] <37223003+trop[bot]@users.noreply.github.com>
Co-authored-by: Shelley Vohr <[email protected]>

shell/browser/browser.h

@@ -202,6 +202,8 @@ class Browser : public WindowListObserver {
   bool UpdateUserActivityState(const std::string& type,
                                base::Value::Dict user_info);
 
+  void ApplyForcedRTL();
+
   // Bounce the dock icon.
   enum class BounceType{
       kCritical = 0,        // NSCriticalRequest

shell/browser/browser_mac.mm

@@ -8,12 +8,14 @@
 #include <string>
 #include <utility>
 
+#include "base/i18n/rtl.h"
 #include "base/mac/bundle_locations.h"
 #include "base/mac/foundation_util.h"
 #include "base/mac/mac_util.h"
 #include "base/mac/scoped_cftyperef.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/sys_string_conversions.h"
+#include "chrome/browser/browser_process.h"
 #include "net/base/mac/url_conversions.h"
 #include "shell/browser/badging/badge_manager.h"
 #include "shell/browser/mac/dict_util.h"
@@ -36,6 +38,13 @@ namespace electron {
 
 namespace {
 
+bool IsAppRTL() {
+  const std::string& locale = g_browser_process->GetApplicationLocale();
+  base::i18n::TextDirection text_direction =
+      base::i18n::GetTextDirectionForLocaleInStartUp(locale.c_str());
+  return text_direction == base::i18n::RIGHT_TO_LEFT;
+}
+
 NSString* GetAppPathForProtocol(const GURL& url) {
   NSURL* ns_url = [NSURL
       URLWithString:base::SysUTF8ToNSString(url.possibly_invalid_spec())];
@@ -306,6 +315,32 @@ bool Browser::UpdateUserActivityState(const std::string& type,
   return prevent_default;
 }
 
+// Modified from chrome/browser/ui/cocoa/l10n_util.mm.
+void Browser::ApplyForcedRTL() {
+  NSUserDefaults* defaults = NSUserDefaults.standardUserDefaults;
+
+  auto dir = base::i18n::GetForcedTextDirection();
+
+  // An Electron app should respect RTL behavior of application locale over
+  // system locale.
+  auto should_be_rtl = dir == base::i18n::RIGHT_TO_LEFT || IsAppRTL();
+  auto should_be_ltr = dir == base::i18n::LEFT_TO_RIGHT || !IsAppRTL();
+
+  // -registerDefaults: won't do the trick here because these defaults exist
+  // (in the global domain) to reflect the system locale. They need to be set
+  // in Chrome's domain to supersede the system value.
+  if (should_be_rtl) {
+    [defaults setBool:YES forKey:@"AppleTextDirection"];
+    [defaults setBool:YES forKey:@"NSForceRightToLeftWritingDirection"];
+  } else if (should_be_ltr) {
+    [defaults setBool:YES forKey:@"AppleTextDirection"];
+    [defaults setBool:NO forKey:@"NSForceRightToLeftWritingDirection"];
+  } else {
+    [defaults removeObjectForKey:@"AppleTextDirection"];
+    [defaults removeObjectForKey:@"NSForceRightToLeftWritingDirection"];
+  }
+}
+
 Browser::LoginItemSettings Browser::GetLoginItemSettings(
     const LoginItemSettings& options) {
   LoginItemSettings settings;

shell/browser/electron_browser_main_parts.cc

@@ -353,6 +353,7 @@ int ElectronBrowserMainParts::PreCreateThreads() {
 
 #if BUILDFLAG(IS_MAC)
   ui::InitIdleMonitor();
+  Browser::Get()->ApplyForcedRTL();
 #endif
 
   fake_browser_process_->PreCreateThreads();