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 e0bec0d04b7f7e5410c475b8e79a6102a73e6c87..994c178c9dd8a18c5337c65684363d2e8bd84292 100644
--- a/third_party/WebKit/Source/core/editing/InputMethodController.cpp
+++ b/third_party/WebKit/Source/core/editing/InputMethodController.cpp
@@ -456,6 +456,50 @@ void InputMethodController::extendSelectionAndDelete(int before, int after)
     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);