[Mac] Produce correct DomKey when Ctrl/Shift/Command is down

ui/events/keycodes/keyboard_code_conversion_mac.mm

Index: ui/events/keycodes/keyboard_code_conversion_mac.mm
diff --git a/ui/events/keycodes/keyboard_code_conversion_mac.mm b/ui/events/keycodes/keyboard_code_conversion_mac.mm
index f435f4ed2b966d19a8524ccc2fe63ef61c93c91f..96f75a5a86ee918090aa4c8684ffe640764f24b7 100644
--- a/ui/events/keycodes/keyboard_code_conversion_mac.mm
+++ b/ui/events/keycodes/keyboard_code_conversion_mac.mm
@@ -9,6 +9,7 @@
 #import <Carbon/Carbon.h>
 
 #include "base/logging.h"
+#include "base/mac/scoped_cftyperef.h"
 #include "base/macros.h"
 #include "ui/events/keycodes/dom/keycode_converter.h"
 
@@ -635,6 +636,57 @@ DomKey DomKeyFromCharCode(unichar char_code) {
   }
 }
 
+UniChar KeycodeAndModifiersToCharacter(unsigned short native_key_code,
+                                       int modifiers,
+                                       bool& is_deadkey) {
+  // Convert EventRecord modifiers to format UCKeyTranslate accepts. See docs
+  // on UCKeyTranslate for more info.
+  int native_modifiersers = 0;
+  if (modifiers & NSShiftKeyMask)
+    native_modifiersers |= shiftKey;
+  if (modifiers & NSAlphaShiftKeyMask)
+    native_modifiersers |= alphaLock;
+  if (modifiers & NSControlKeyMask)
+    native_modifiersers |= controlKey;
+  if (modifiers & NSAlternateKeyMask)
+    native_modifiersers |= optionKey;
+  if (modifiers & NSCommandKeyMask)
+    native_modifiersers |= cmdKey;
+  UInt32 modifier_key_state = (native_modifiersers >> 8) & 0xFF;
+
+  base::ScopedCFTypeRef<TISInputSourceRef> input_source_copy(
+      TISCopyCurrentKeyboardLayoutInputSource());
+  CFDataRef layout_data = static_cast<CFDataRef>(TISGetInputSourceProperty(
+      input_source_copy, kTISPropertyUnicodeKeyLayoutData));
+
+  UInt32 dead_key_state = 0;
+  UniCharCount char_count = 0;
+  UniChar character = 0;
+  OSStatus status = UCKeyTranslate(
+      reinterpret_cast<const UCKeyboardLayout*>(CFDataGetBytePtr(layout_data)),
+      static_cast<UInt16>(native_key_code), kUCKeyActionDown,
+      modifier_key_state, LMGetKbdLast(), kUCKeyTranslateNoDeadKeysBit,
+      &dead_key_state, 1, &char_count, &character);
+
+  // According to Apple's doc an empty string means dead keys.
+  // https://developer.apple.com/library/mac/documentation/Cocoa/Reference/ApplicationKit/Classes/NSEvent_Class/#//apple_ref/occ/instp/NSEvent/characters
+  if (status == noErr && char_count == 0)
+    is_deadkey = true;
+  else
+    is_deadkey = false;
+
+  if (is_deadkey) {
+    // Inject space to get character value of dead key.
+    UCKeyTranslate(reinterpret_cast<const UCKeyboardLayout*>(
+                       CFDataGetBytePtr(layout_data)),
+                   static_cast<UInt16>(kVK_Space), kUCKeyActionDown, 0,
+                   LMGetKbdLast(), kUCKeyTranslateNoDeadKeysBit,
+                   &dead_key_state, 1, &char_count, &character);
+  }
+
+  return character;
+}
+
 }  // namespace
 
 int MacKeyCodeForWindowsKeyCode(KeyboardCode keycode,
@@ -745,9 +797,29 @@ DomKey DomKeyFromNSEvent(NSEvent* event) {
   // Keyboard layout and modifers already applied; whereas the keyCode
   // doesn't.
   if ([event type] == NSKeyDown || [event type] == NSKeyUp) {
+    // Need [event characters] to handle dead key state.
     NSString* characters = [event characters];
-    if ([characters length] > 0)
-      return DomKeyFromCharCode([characters characterAtIndex:0]);
+    if ([characters length] > 0) {
+      // An invalid dead key combination will produce two characters, according
+      // to spec DomKey should be the last character.
+      // e.g. On French keyboard [+a will produce "^q", DomKey should be 'q'.
+      unichar dom_key_char =

[chongz, 2016/02/18 06:04:08]

French [Digit2] and [Shift + Digit2] will both produce a printable character, so
DomKey will be the correct character.

+          [characters characterAtIndex:[characters length] - 1];
+      if ([event modifierFlags] != 0 && std::iscntrl(dom_key_char)) {
+        // According to spec if the key combination produces a non-printable
+        // character, the key value should be the character without modifiers
+        // except Shift and AltGr.
+        // See https://w3c.github.io/uievents/#keys-guidelines
+        bool is_deadkey;
+        const int fallback_modifiers =
+            NSShiftKeyMask | NSAlphaShiftKeyMask | NSAlternateKeyMask;

[chongz, 2016/02/18 06:04:07]

Use custom fallback modifiers here since NSEvent::charactersIgnoringModifiers
only cares about Shift.

Should I add NSAlphaShiftKeyMask (CapsLock) here to match Firefox?

+        // KeycodeAndModifiersToCharacter() is efficient (around 1.2E-3 ms).
+        dom_key_char = KeycodeAndModifiersToCharacter(

[chongz, 2016/02/18 06:04:08]

In this stage we don't care about dead keys any more.

+            [event keyCode], [event modifierFlags] & fallback_modifiers,
+            is_deadkey);
+      }
+      return DomKeyFromCharCode(dom_key_char);
+    }
   }
   return DomKeyFromKeyCode([event keyCode]);
 }