Handle newCursorPosition correctly for Android's commitText()

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 215 matching lines @@
     // Event handler might destroy document.
     if (!frame().document())
         return false;
 
     // No DOM update after 'compositionend'.
     dispatchCompositionEndEvent(frame(), text);
 
     return true;
 }
 
-bool InputMethodController::confirmCompositionOrInsertText(const String& text, ConfirmCompositionBehavior confirmBehavior)
+bool InputMethodController::confirmCompositionOrInsertText(const String& text, ConfirmCompositionBehavior confirmBehavior, int newCursorPosition)
 {
+    if (confirmBehavior == DoNotKeepSelection) {
+        // If newCursorPosition > 0, it's relative to the end of the text - 1;
+        // if newCursorPosition <= 0, it is relative to the start of the text.
+        if (newCursorPosition > 0)
+            newCursorPosition = newCursorPosition + text.length() - 1;

[Changwan Ryu, 2016/08/03 07:37:30]

newCursorPosition += text.length() - 1;

[yabinh, 2016/08/08 07:33:43]

Done.

+
+        // According to Android documentation, the new cursor position is
+        // relative to the composing text if any, or relative to the selection
+        // if no composing text.
+        if (hasComposition()) {
+            Element* rootEditableElement = frame().selection().rootEditableElement();
+            if (!rootEditableElement)
+                return false;

[yabinh, 2016/08/03 05:12:09]

Note that |m_compositionRange->startOffset()| is relative to its  anchor node,
not root node. So we need to convert it for multiple nodes.

+            PlainTextRange compositionRange = PlainTextRange::create(*rootEditableElement, *m_compositionRange);
+
+            if (text.length() == 0)
+                newCursorPosition += compositionRange.end();

[Changwan Ryu, 2016/08/03 07:37:30]

Why should this differ from the else line?

[yabinh, 2016/08/08 07:33:44]

There are 2 cases when hasCompositio() == true:


Case 1. text.length() != 0
This happens when we call ImeTest#setComposingText("hello", newCursorPosition),
then call ImeTest#commitText("world", newCursorPosition).

In this case, we should drop the composing "hello", and insert the committing
"world".


Case 2.text.length() == 0
This happens in the test RenderViewImplTest#ImeComposition. 
(https://cs.chromium.org/chromium/src/content/renderer/render_view_browsertest...)

(in Scenario 2 and Scenario 3)

Firstly, we call RenderWidget#OnImeSetComposition to set the composing text. 
Then we call RenderWidget#OnImeConfirmComposition with empty text(I.E.,
IME_CONFIRMCOMPOSITION, false, -1, -1, L"", L"\x6F22\x5B57"). 
Here, we mean to confirm the composing text, not to replace it with empty text.

By the way, it may seem confusing here. Consider such a case: if we call
ImeTest#commitText("", newCursorPosition) after
ImeTest#setComposingText("hello", newCursorPosition), will it cancel the
composing "hello", or confirm it? Actually, there is no problem in this case,
because it won't go to WebWidget#confirmComposition(). Instead, it will go to
WebWidget#setComposition.

[aelias_OOO_until_Jul13, 2016/08/24 08:13:07]

Acknowledged, but checking "text.length() == 0" is a nonobvious way to make this
distinction.  On Android, there is no such thing as "confirm with no text", so
it sounds like what is going on here is different platform-specific semantics. 
We should check for this more explicitly instead of relying on implicit signals
like "text == 0".  For example, does the enum value "ConfirmCompositionBehavior"
help?  If not, can we add another enum value, or possibly make the other
platforms not run this code at all?

[aelias_OOO_until_Jul13, 2016/08/24 08:16:01]

Sorry, please disregard this particular comment, it's a draft comment I meant to
delete (I realized later it's not platform-specific at all really).  I proposed
a clearer common way of handling text == 0 below.

+            else
+                newCursorPosition += compositionRange.start();
+        } else {
+            PlainTextRange selectionRange = getSelectionOffsets();
+            if (selectionRange.isNull())
+                return false;
+            newCursorPosition += getSelectionOffsets().start();
+        }
+    }
+
     if (!hasComposition()) {
         if (!text.length())
             return false;
 
         if (dispatchBeforeInputInsertText(frame().document()->focusedElement(), text) != DispatchEventResult::NotCanceled)
             return false;
 
         editor().insertText(text, 0);
-        return true;
+    } else if (text.length()) {
+        confirmComposition(text);
+    } else if (confirmBehavior == DoNotKeepSelection) {
+        if (!confirmComposition(composingText(), DoNotKeepSelection))
+            return false;
+    } else {
+        SelectionOffsetsScope selectionOffsetsScope(this);
+        return confirmComposition();
     }
 
-    if (text.length()) {
-        confirmComposition(text);
+    if (confirmBehavior == KeepSelection)
         return true;
-    }
 
-    if (confirmBehavior == DoNotKeepSelection)
-        return confirmComposition(composingText(), DoNotKeepSelection);
-
-    SelectionOffsetsScope selectionOffsetsScope(this);
-    return confirmComposition();
+    PlainTextRange selectedRange = createRangeForSelection(newCursorPosition, newCursorPosition, 0);
+    if (selectedRange.isNull())
+        return false;
+    return setEditableSelectionOffsets(selectedRange);
 }
 
 void InputMethodController::cancelComposition()
 {
     if (!hasComposition())
         return;
 
     Editor::RevealSelectionScope revealSelectionScope(&editor());
 
     if (frame().selection().isNone())
@@ skipping 247 matching lines @@
     start = std::max(start, 0);
     end = std::max(end, start);
 
     // In case of exceeding the right boundary.
     Element* rootEditableElement = frame().selection().rootEditableElement();
     if (!rootEditableElement)
         return PlainTextRange();
     const EphemeralRange& range = EphemeralRange::rangeOfContents(*rootEditableElement);
     if (range.isNull())
         return PlainTextRange();
 

[yabinh, 2016/08/03 05:12:09]

There is a DCHECK in the constructor of TextIterator:
DCHECK(!start.document()->needsLayoutTreeUpdate());

So it's better to make sure the condition is met here.

+    if (frame().document()->needsLayoutTreeUpdate())

[Changwan Ryu, 2016/08/03 07:37:30]

You probably need to call updateStyleAndLayoutTree() somewhere else.

[yabinh, 2016/08/08 07:33:44]

I tried to call it in InputMethodController#confirmCompositionOrInsertText, but
it doesn't work. However, updateStyleAndLayoutIgnorePendingStylesheets() works.
It's also called in InputMethodController#setComposition after inserting text.

+        return PlainTextRange();
+
     const TextIteratorBehaviorFlags behaviorFlags = TextIteratorEmitsObjectReplacementCharacter | TextIteratorEmitsCharactersBetweenAllVisiblePositions;
     TextIterator it(range.startPosition(), range.endPosition(), behaviorFlags);
 
     int rightBoundary = 0;
     for (; !it.atEnd(); it.advance())
         rightBoundary += it.length();
 
     if (hasComposition())
         rightBoundary -= compositionRange()->text().length();
 
@@ skipping 37 matching lines @@
     TypingCommand::deleteSelection(*frame().document());
 }
 
 DEFINE_TRACE(InputMethodController)
 {
     visitor->trace(m_frame);
     visitor->trace(m_compositionRange);
 }
 
 } // namespace blink