feat: add MenuItem.userAccelerator property (electron#26682)

* feat: add MenuItem.userAccelerator property

This allows folks to read the user-assigned accelerator that macOS users can provide in system preferences. Useful for showing in-app shortcut help dialogs, you need to know if the accelerator you provided is not being used in favor of a user assigned one.

* chore: update syntax

* chore: add safety check for command index being -1

docs/api/menu-item.md

@@ -159,7 +159,13 @@ A `String` (optional) indicating the item's role, if set. Can be `undo`, `redo`,
 
 #### `menuItem.accelerator`
 
-A `Accelerator` (optional) indicating the item's accelerator, if set.
+An `Accelerator` (optional) indicating the item's accelerator, if set.
+
+#### `menuItem.userAccelerator` _Readonly_ _macOS_
+
+An `Accelerator | null` indicating the item's [user-assigned accelerator](https://developer.apple.com/documentation/appkit/nsmenuitem/1514850-userkeyequivalent?language=objc) for the menu item.
+
+**Note:** This property is only initialized after the `MenuItem` has been added to a `Menu`. Either via `Menu.buildFromTemplate` or via `Menu.append()/insert()`.  Accessing before initialization will just return `null`.
 
 #### `menuItem.icon`
 

lib/browser/api/menu-item.ts

@@ -43,6 +43,15 @@ const MenuItem = function (this: any, options: any) {
 
   this.overrideReadOnlyProperty('commandId', ++nextCommandId);
 
+  Object.defineProperty(this, 'userAccelerator', {
+    get: () => {
+      if (process.platform !== 'darwin') return null;
+      if (!this.menu) return null;
+      return this.menu._getUserAcceleratorAt(this.commandId);
+    },
+    enumerable: true
+  });
+
   const click = options.click;
   this.click = (event: Event, focusedWindow: BrowserWindow, focusedWebContents: WebContents) => {
     // Manually flip the checked flags when clicked.

shell/browser/api/electron_api_menu.cc

@@ -212,7 +212,7 @@ void Menu::Clear() {
   model_->Clear();
 }
 
-int Menu::GetIndexOfCommandId(int command_id) {
+int Menu::GetIndexOfCommandId(int command_id) const {
   return model_->GetIndexOfCommandId(command_id);
 }
 
@@ -299,6 +299,9 @@ v8::Local<v8::ObjectTemplate> Menu::FillObjectTemplate(
       .SetMethod("closePopupAt", &Menu::ClosePopupAt)
 #if DCHECK_IS_ON()
       .SetMethod("getAcceleratorTextAt", &Menu::GetAcceleratorTextAtForTesting)
+#endif
+#if defined(OS_MAC)
+      .SetMethod("_getUserAcceleratorAt", &Menu::GetUserAcceleratorAt)
 #endif
       .Build();
 }

shell/browser/api/electron_api_menu.h

@@ -68,6 +68,7 @@ class Menu : public gin::Wrappable<Menu>,
   bool GetSharingItemForCommandId(
       int command_id,
       ElectronMenuModel::SharingItem* item) const override;
+  v8::Local<v8::Value> GetUserAcceleratorAt(int command_id) const;
 #endif
   void ExecuteCommand(int command_id, int event_flags) override;
   void OnMenuWillShow(ui::SimpleMenuModel* source) override;
@@ -108,7 +109,7 @@ class Menu : public gin::Wrappable<Menu>,
   void SetToolTip(int index, const std::u16string& toolTip);
   void SetRole(int index, const std::u16string& role);
   void Clear();
-  int GetIndexOfCommandId(int command_id);
+  int GetIndexOfCommandId(int command_id) const;
   int GetItemCount() const;
   int GetCommandIdAt(int index) const;
   std::u16string GetLabelAt(int index) const;

shell/browser/api/electron_api_menu_mac.mm

@@ -16,12 +16,31 @@
 #include "content/public/browser/web_contents.h"
 #include "shell/browser/native_window.h"
 #include "shell/browser/unresponsive_suppressor.h"
+#include "shell/common/keyboard_util.h"
 #include "shell/common/node_includes.h"
 
 namespace {
 
 static scoped_nsobject<NSMenu> applicationMenu_;
 
+ui::Accelerator GetAcceleratorFromKeyEquivalentAndModifierMask(
+    NSString* key_equivalent,
+    NSUInteger modifier_mask) {
+  absl::optional<char16_t> shifted_char;
+  ui::KeyboardCode code = electron::KeyboardCodeFromStr(
+      base::SysNSStringToUTF8(key_equivalent), &shifted_char);
+  int modifiers = 0;
+  if (modifier_mask & NSEventModifierFlagShift)
+    modifiers |= ui::EF_SHIFT_DOWN;
+  if (modifier_mask & NSEventModifierFlagControl)
+    modifiers |= ui::EF_CONTROL_DOWN;
+  if (modifier_mask & NSEventModifierFlagOption)
+    modifiers |= ui::EF_ALT_DOWN;
+  if (modifier_mask & NSEventModifierFlagCommand)
+    modifiers |= ui::EF_COMMAND_DOWN;
+  return ui::Accelerator(code, modifiers);
+}
+
 }  // namespace
 
 namespace electron {
@@ -52,6 +71,32 @@
   base::SequencedTaskRunnerHandle::Get()->PostTask(FROM_HERE, std::move(popup));
 }
 
+v8::Local<v8::Value> Menu::GetUserAcceleratorAt(int command_id) const {
+  v8::Isolate* isolate = JavascriptEnvironment::GetIsolate();
+  if (![NSMenuItem usesUserKeyEquivalents])
+    return v8::Null(isolate);
+
+  auto controller = base::scoped_nsobject<ElectronMenuController>(
+      [[ElectronMenuController alloc] initWithModel:model()
+                              useDefaultAccelerator:NO]);
+
+  int command_index = GetIndexOfCommandId(command_id);
+  if (command_index == -1)
+    return v8::Null(isolate);
+
+  base::scoped_nsobject<NSMenuItem> item =
+      [controller makeMenuItemForIndex:command_index fromModel:model()];
+  if ([[item userKeyEquivalent] length] == 0)
+    return v8::Null(isolate);
+
+  NSString* user_key_equivalent = [item keyEquivalent];
+  NSUInteger user_modifier_mask = [item keyEquivalentModifierMask];
+  ui::Accelerator accelerator = GetAcceleratorFromKeyEquivalentAndModifierMask(
+      user_key_equivalent, user_modifier_mask);
+
+  return gin::ConvertToV8(isolate, accelerator.GetShortcutText());
+}
+
 void MenuMac::PopupOnUI(const base::WeakPtr<NativeWindow>& native_window,
                         int32_t window_id,
                         int x,

shell/browser/ui/cocoa/electron_menu_controller.h

@@ -52,6 +52,10 @@ class ElectronMenuModel;
 // default initializer was used, then this will create the menu on first call.
 - (NSMenu*)menu;
 
+- (base::scoped_nsobject<NSMenuItem>)
+    makeMenuItemForIndex:(NSInteger)index
+               fromModel:(electron::ElectronMenuModel*)model;
+
 // Whether the menu is currently open.
 - (BOOL)isMenuOpen;
 

shell/browser/ui/cocoa/electron_menu_controller.mm

@@ -315,11 +315,9 @@ - (NSMenuItem*)menuItemForService:(NSSharingService*)service
   return item.autorelease();
 }
 
-// Adds an item or a hierarchical menu to the item at the |index|,
-// associated with the entry in the model identified by |modelIndex|.
-- (void)addItemToMenu:(NSMenu*)menu
-              atIndex:(NSInteger)index
-            fromModel:(electron::ElectronMenuModel*)model {
+- (base::scoped_nsobject<NSMenuItem>)
+    makeMenuItemForIndex:(NSInteger)index
+               fromModel:(electron::ElectronMenuModel*)model {
   std::u16string label16 = model->GetLabelAt(index);
   NSString* label = l10n_util::FixUpWindowsStyleLabel(label16);
 
@@ -437,7 +435,17 @@ - (void)addItemToMenu:(NSMenu*)menu
       }
     }
   }
-  [menu insertItem:item atIndex:index];
+
+  return item;
+}
+
+// Adds an item or a hierarchical menu to the item at the |index|,
+// associated with the entry in the model identified by |modelIndex|.
+- (void)addItemToMenu:(NSMenu*)menu
+              atIndex:(NSInteger)index
+            fromModel:(electron::ElectronMenuModel*)model {
+  [menu insertItem:[self makeMenuItemForIndex:index fromModel:model]
+           atIndex:index];
 }
 
 // Called before the menu is to be displayed to update the state (enabled,