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());

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

Why static_cast, is there a warning/error if you just used  size_t here?  If so,
can you fix the warning/error by changing more things to size_t?  Most things
here cannot be negative, right?

[yabinh, 2016/04/22 01:26:48]

Since we use "std::min(selectionStart, before)", and
PlainTextRange#PlainTextRange(int, int) takes int as its papameter, it might be
better if "selectionStart" is int in the first place.

+    int selectionEnd = static_cast<int>(selectionOffsets.end());
+
+    // 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.
+    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) {
+        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