Fix InputConnection.deleteSurroundingText()

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 454 matching lines @@
             return;
         if (before == 0)
             break;
         ++before;
     } while (frame().selection().start() == frame().selection().end() && before <= static_cast<int>(selectionOffsets.start()));
     // TODO(chongz): According to spec |data| should be "forward" or "backward".
     dispatchBeforeInputEditorCommand(frame().document()->focusedElement(), InputEvent::InputType::DeleteContent);
     TypingCommand::deleteSelection(*frame().document());
 }
 
+void InputMethodController::deleteSurroundingText(size_t before, size_t after)
+{
+    if (!editor().canEdit())
+        return;
+    PlainTextRange selectionOffsets(getSelectionOffsets());
+    if (selectionOffsets.isNull())
+        return;
+
+    size_t selectionStart = selectionOffsets.start();
+    size_t selectionEnd = selectionOffsets.end();
+
+    if (before != 0) {
+        before = std::min(selectionStart, before);
+
+        // Select the text to be deleted before selectionStart,
+        // and adjust the start of selection in case of multi-code text.
+        size_t adjustedStart = selectionStart + 1 - before;
+        const LChar* text = frame().document()->activeElement()->innerText().characters8();
+        U8_SET_CP_START(text, 0, adjustedStart);

[Changwan Ryu, 2016/04/25 10:21:08]

This is incorrect if the given text is UTF16 string. It's quite confusing that
WTFString allows both UTF8 and UTF16. (Hence the name...?)

Could you try using EditingUtilities::previousPositionOfAlgorithm with
PositionMoveType::BackwardDeletion?

Then it will check the surrogate for you in
BackspaceStateMachine::feedPrecedingCodeUnit().

+        --adjustedStart;
+
+        if (!setSelectionOffsets(PlainTextRange(static_cast<int>(adjustedStart), static_cast<int>(selectionStart))))
+            return;
+        TypingCommand::deleteSelection(*frame().document());
+
+        selectionEnd = selectionEnd - (selectionStart - adjustedStart);
+        selectionStart = adjustedStart;
+    }
+
+    if (after != 0) {
+        if (!setSelectionOffsets(PlainTextRange(static_cast<int>(selectionEnd), static_cast<int>(selectionEnd + after))))
+            return;
+        TypingCommand::deleteSelection(*frame().document());
+    }
+
+    setSelectionOffsets(PlainTextRange(selectionStart, selectionEnd));
+}
+
 DEFINE_TRACE(InputMethodController)
 {
     visitor->trace(m_frame);
     visitor->trace(m_compositionRange);
 }
 
 } // namespace blink