Fix InputConnection.deleteSurroundingText()

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

Index: third_party/WebKit/Source/core/editing/InputMethodController.cpp
diff --git a/third_party/WebKit/Source/core/editing/InputMethodController.cpp b/third_party/WebKit/Source/core/editing/InputMethodController.cpp
index ca051a0c662ea21fe8e1dd82ca3db819b1c1d4e9..13203203de17198c325300ac71f516652e3008d3 100644
--- a/third_party/WebKit/Source/core/editing/InputMethodController.cpp
+++ b/third_party/WebKit/Source/core/editing/InputMethodController.cpp
@@ -472,6 +472,44 @@ void InputMethodController::extendSelectionAndDelete(int before, int after)
     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);