[InputEvent] Fire 'beforeinput' during typing, pressing hot keys and IME composition

third_party/WebKit/Source/core/editing/InputMethodController.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 151 matching lines @@
         return false;
 
     // If text is empty, then delete the old composition here. If text is
     // non-empty, InsertTextCommand::input will delete the old composition with
     // an optimized replace operation.
     if (text.isEmpty())
         TypingCommand::deleteSelection(*frame().document(), 0);
 
     clear();
 
+    // According to spec 'beforeinput' should not be sent along with  CompositionEnd, so
+    // dispatch after CompositionEnd if there is any update.
+    // https://w3c.github.io/uievents/#h-events-composition-event-input-events
+    if (dispatchBeforeInputInsertText(frame().document()->focusedElement(), text) != DispatchEventResult::NotCanceled)
+        return false;
+
     insertTextForConfirmedComposition(text);
 
     return true;
 }
 
 bool InputMethodController::confirmCompositionOrInsertText(const String& text, ConfirmCompositionBehavior confirmBehavior)
 {
     if (!hasComposition()) {
         if (!text.length())
             return false;
+
+        if (dispatchBeforeInputInsertText(frame().document()->focusedElement(), text) != DispatchEventResult::NotCanceled)
+            return false;
+
         editor().insertText(text, 0);
         return true;
     }
 
     if (text.length()) {
         confirmComposition(text);
         return true;
     }
 
     if (confirmBehavior != KeepSelection)
@@ skipping 76 matching lines @@
             if (!text.isEmpty()) {
                 target->dispatchEvent(CompositionEvent::create(EventTypeNames::compositionstart, frame().domWindow(), frame().selectedText()));
                 event = CompositionEvent::create(EventTypeNames::compositionupdate, frame().domWindow(), text);
             }
         } else {
             if (!text.isEmpty())
                 event = CompositionEvent::create(EventTypeNames::compositionupdate, frame().domWindow(), text);
             else
                 event = CompositionEvent::create(EventTypeNames::compositionend, frame().domWindow(), text);
         }
-        if (event.get())
+        if (event.get()) {
+            // TODO(chongz): Support canceling IME composition.
+            if (event->type() == EventTypeNames::compositionupdate)
+                dispatchBeforeInputCompositionUpdate(target, text);
             target->dispatchEvent(event);
+        }
     }
 
     // If text is empty, then delete the old composition here. If text is non-empty, InsertTextCommand::input

[yosin_UTC9, 2016/03/16 01:46:51]

We also dispatch "beforeInput" with "deleteComposedCharacter" in
|InputMethodController::extendSelectionAndDelete()|.
Note: Blink doesn't have information about "forward delete" or "backward
delete".

[chongz, 2016/03/16 21:51:44]

Acknowledged.

[chongz, 2016/04/13 00:34:28]

Done. But I tried several keyboard layouts and Chinese IME and cannot figure out
when will |InputMethodController::extendSelectionAndDelete()| get called? 

     // will delete the old composition with an optimized replace operation.
     if (text.isEmpty()) {
         ASSERT(frame().document());
         TypingCommand::deleteSelection(*frame().document(), TypingCommand::PreventSpellChecking);
     }
 
     clear();
 
     if (text.isEmpty())
         return;
@@ skipping 160 matching lines @@
     TypingCommand::deleteSelection(*frame().document());
 }
 
 DEFINE_TRACE(InputMethodController)
 {
     visitor->trace(m_frame);
     visitor->trace(m_compositionRange);
 }
 
 } // namespace blink