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 438 matching lines @@
     do {
         if (!setSelectionOffsets(PlainTextRange(std::max(static_cast<int>(selectionOffsets.start()) - before, 0), selectionOffsets.end() + after)))
             return;
         if (before == 0)
             break;
         ++before;
     } while (frame().selection().start() == frame().selection().end() && before <= static_cast<int>(selectionOffsets.start()));
     TypingCommand::deleteSelection(*frame().document());
 }
 
+void InputMethodController::deleteSurroundingText(int before, int after)
+{
+    if (!editor().canEdit())
+        return;
+    PlainTextRange selectionOffsets(getSelectionOffsets());
+    if (selectionOffsets.isNull())
+        return;
+
+    int selectionStart = static_cast<int>(selectionOffsets.start());
+    int selectionEnd = static_cast<int>(selectionOffsets.end());
+
+    // A common call of before=1 and after=0 will fail if the last character
+    // is multi-code-word UTF-16, including both multi-16bit code-points and
+    // Unicode combining character sequences of multiple single-16bit code-
+    // points (officially called "compositions"). Try more until success.
+    // It's similar to InputMethodController#extendSelectionAndDelete.
+    // http://crbug.com/355995
+    if (before > 0) {
+        int deleteLength, leftStart, leftEnd;
+        do {
+            deleteLength = std::min(selectionStart, before);
+            leftStart = selectionStart - deleteLength;
+            leftEnd = selectionStart;
+            if (!setSelectionOffsets(PlainTextRange(leftStart, leftEnd)))
+                return;
+            ++before;
+        } while (frame().selection().start() == frame().selection().end() && before <= static_cast<int>(selectionOffsets.start()));
+        TypingCommand::deleteSelection(*frame().document());
+
+        selectionStart = leftStart;
+        selectionEnd = selectionEnd - deleteLength;
+    }
+
+    if (after > 0) {

[Changwan Ryu, 2016/04/21 01:07:06]

shouldn't we apply the same logic to afterText? do we need more tests?

[Changwan Ryu, 2016/04/21 01:19:26]

talked to yabinh@ offline. It's already covered by the test.

[yabinh, 2016/04/21 01:24:16]

We don't need that.

Some multi-code-texts take 2 positions, like "\xF0\x9F\x8F\x86"(U+1F3C6 ==
"trophy"). We can select the whole multi-code-text successfully if we only
select the left half of it, but sometimes we can't select it successfully if we
only select the right half of it, so we need to select more. That's why we need
to apply a while-loop to the beforeText and don't need to apply it to the
afterText.

[aelias_OOO_until_Jul13, 2016/04/21 04:01:29]

OK, but can we call a generic method to snap to the beginning instead of walking
through the codepoints ourselves?  It's extremely likely that such a method
already exists somewhere in the codebase.  I'd look for such a method in the ICU
headers, for example.

[aelias_OOO_until_Jul13, 2016/04/22 08:18:29]

I suggest looking in http://icu-project.org/apiref/icu4c/utf16_8h.html, would
U16_BACK_1 be equivalent?

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