Add a function that can check if a menu item would be fired by a keypress.

chrome/browser/cocoa/nsmenuitem_additions.mm

+#import "chrome/browser/cocoa/nsmenuitem_additions.h"
+
+#include <Carbon/Carbon.h>
+
+#include "base/logging.h"
+
+@implementation NSMenuItem(ChromeAdditions)
+
+- (BOOL)cr_firesForKeyEvent:(NSEvent*)event {
+  DCHECK([event type] == NSKeyDown);
+  if (![self isEnabled])
+    return NO;
+
+  // In System Preferences->Keyboard->Keyboard Shortcuts, it is possible to add
+  // arbitrary keyboard shortcuts to applications. It is not documented how this
+  // works in detail, but |NSMenuItem| has a method |userKeyEquivalent| that
+  // sounds related.
+  // However, it looks like |userKeyEquivalent| is equal to |keyEquivalent| when
+  // a user shortcut is set in system preferences, i.e. Cocoa automatically
+  // sets/overwrites |keyEquivalent| as well. Hence, this method can ignore
+  // |userKeyEquivalent| and check |keyEquivalent| only.
+
+  // Menu item key equivalents are nearly all stored without modifiers. The
+  // exception is shift, which is included in the key and not in the modifiers
+  // for printable characters (but not for stuff like arrow keys etc).
+  NSString* eventString = [event charactersIgnoringModifiers];
+  NSUInteger eventModifiers =
+      [event modifierFlags] & NSDeviceIndependentModifierFlagsMask;
+
+  if ([eventString length] == 0 || [[self keyEquivalent] length] == 0)
+    return NO;
+
+  // Turns out esc never fires unless cmd or ctrl is down.
+  if ([event keyCode] == kVK_Escape &&
+      (eventModifiers & (NSControlKeyMask | NSCommandKeyMask)) == 0)
+    return NO;
+
+  // From the |NSMenuItem setKeyEquivalent:| documentation:
+  //
+  // If you want to specify the Backspace key as the key equivalent for a menu
+  // item, use a single character string with NSBackspaceCharacter (defined in
+  // NSText.h as 0x08) and for the Forward Delete key, use NSDeleteCharacter
+  // (defined in NSText.h as 0x7F). Note that these are not the same characters
+  // you get from an NSEvent key-down event when pressing those keys.
+  if ([[self keyEquivalent] characterAtIndex:0] == NSBackspaceCharacter
+      && [eventString characterAtIndex:0] == NSDeleteCharacter) {
+    unichar chr = NSBackspaceCharacter;
+    eventString = [NSString stringWithCharacters:&chr length:1];
+
+    // Make sure "shift" is not removed from modifiers below.
+    eventModifiers |= NSFunctionKeyMask;
+  }
+  if ([[self keyEquivalent] characterAtIndex:0] == NSDeleteCharacter &&
+      [eventString characterAtIndex:0] == NSDeleteFunctionKey) {
+    unichar chr = NSDeleteCharacter;
+    eventString = [NSString stringWithCharacters:&chr length:1];
+
+    // Make sure "shift" is not removed from modifiers below.
+    eventModifiers |= NSFunctionKeyMask;
+  }
+
+  // cmd-opt-a gives some weird char as characters and "a" as
+  // charactersWithoutModifiers with an US layout, but an "a" as characters and
+  // a weird char as "charactersWithoutModifiers" with a cyrillic layout. Oh,
+  // Cocoa! Instead of getting the current layout from Text Input Services,
+  // and then requesting the kTISPropertyUnicodeKeyLayoutData and looking in
+  // there, let's try a pragmatic hack.
+  if ([eventString characterAtIndex:0] > 0x7f &&
+      [[event characters] length] > 0 &&
+      [[event characters] characterAtIndex:0] <= 0x7f)
+    eventString = [event characters];
+
+  // When both |characters| and |charactersIgnoringModifiers| are ascii, we
+  // want to use |characters| if it's a character and
+  // |charactersIgnoringModifiers| else (on dvorak, cmd-shift-z should fire
+  // "cmd-:" instead of "cmd-;", but on dvorak-qwerty, cmd-shift-z should fire
+  // cmd-shift-z instead of cmd-:).
+  if ([eventString characterAtIndex:0] <= 0x7f &&
+      [[event characters] length] > 0 &&
+      [[event characters] characterAtIndex:0] <= 0x7f &&
+      isalpha([[event characters] characterAtIndex:0]))
+    eventString = [event characters];

[James Su, 2009/10/26 03:10:13]

Is it possible to make above two if statements easier to understand? For
example, is it ok to just compare [self keyEquivalent] to both [event
characters] and [event charactersIgnoringModifiers] and returns YES if any of
them matches?

[Nico, 2009/10/26 03:22:14]

No, on the dvorak-qwertycmd layout, cmd-z will send "z" in "characters" and ";"
in "charactersIgnoringModifiers". For a menu item with accelerator "cmd-;", this
event should not fire.

+
+  // Clear shift key for printable characters.
+  if ((eventModifiers & (NSNumericPadKeyMask | NSFunctionKeyMask)) == 0 &&
+      [[self keyEquivalent] characterAtIndex:0] != '\r')
+    eventModifiers &= ~NSShiftKeyMask;
+
+  // Clear all non-interesting modifiers
+  eventModifiers &= NSCommandKeyMask |
+                    NSControlKeyMask |
+                    NSAlternateKeyMask |
+                    NSShiftKeyMask;
+
+  return [eventString isEqualToString:[self keyEquivalent]]
+      && eventModifiers == [self keyEquivalentModifierMask];
+}
+
+@end
+