[All-in-one patch] Implement own grapheme boundary breaker for editing.

third_party/WebKit/Source/core/editing/state_machines/ForwardGraphemeBoundaryStateMachine.h

Index: third_party/WebKit/Source/core/editing/state_machines/ForwardGraphemeBoundaryStateMachine.h
diff --git a/third_party/WebKit/Source/core/editing/state_machines/ForwardGraphemeBoundaryStateMachine.h b/third_party/WebKit/Source/core/editing/state_machines/ForwardGraphemeBoundaryStateMachine.h
new file mode 100644
index 0000000000000000000000000000000000000000..a0fd6a524ad9103b63447ea1fc8025f5804c2a23
--- /dev/null
+++ b/third_party/WebKit/Source/core/editing/state_machines/ForwardGraphemeBoundaryStateMachine.h
@@ -0,0 +1,80 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ForwardGraphemeBoundaryStateMachine_h
+#define ForwardGraphemeBoundaryStateMachine_h
+
+#include "core/CoreExport.h"
+#include "core/editing/state_machines/TextSegmentationMachineState.h"
+#include "wtf/Allocator.h"
+#include "wtf/Noncopyable.h"
+#include "wtf/text/Unicode.h"
+#include <iosfwd>
+
+namespace blink {
+
+class CORE_EXPORT ForwardGraphemeBoundaryStateMachine {
+    STACK_ALLOCATED();
+    WTF_MAKE_NONCOPYABLE(ForwardGraphemeBoundaryStateMachine);
+public:
+    ForwardGraphemeBoundaryStateMachine();
+
+    // Find boundary offset by feeding preceding text.
+    // This method must not be called after feedFollowingCodeUnit().
+    TextSegmentationMachineState feedPrecedingCodeUnit(UChar codeUnit);
+
+    // Tells the end of preceding text to the state machine.
+    TextSegmentationMachineState tellEndOfPrecedingText();
+
+    // This method must be called after feedPrecedingCodeUnit() returns
+    // NeedsFollowingCodeUnit.
+    TextSegmentationMachineState feedFollowingCodeUnit(UChar codeUnit);
+
+    // Returns the next boundary offset. This method finalizes the state machine
+    // if it is not finished.
+    int finalizeAndGetBoundaryOffset();
+
+    // Resets the internal state to the initial state.
+    void reset();
+
+private:
+    enum class InternalState;
+    friend std::ostream& operator<<(std::ostream&, InternalState);
+
+    // Changes internal state to start searching grapheme cluster boundary.
+    TextSegmentationMachineState startSearchingBoundary();
+
+    // Updates the internal state to InternalState::Finished then
+    // returnsTextSegmentationMachineState::Finished.
+    TextSegmentationMachineState finish();
+
+    // Handles broken surrogate pair. This method always finishes the state
+    // machine.
+    TextSegmentationMachineState finishWithBrokenSurrogatePair();
+
+    // Handles end of text. This method always finishes the state machine.
+    TextSegmentationMachineState finishWithEndOfText();
+
+    // Used for composing supplementary code point with surrogate pairs.
+    UChar m_pendingCodeUnit = 0;
+
+    // The code point at the m_BoundaryOffset.
+    UChar32 m_nextCodePoint = 0;
+
+    // The code point immediately before the m_BoundaryOffset.
+    UChar32 m_prevCodePoint = 0;
+
+    // The relative offset from the begging of this state machine.
+    int m_boundaryOffset = 0;
+
+    // The number of regional indicator symbols preceding to the begging offset.
+    int m_precedingRISCount = 0;
+
+    // The internal state.
+    InternalState m_internalState;
+};
+
+} // namespace blink
+
+#endif