Implementing directional selection strategy in Blink.

Source/core/editing/GranularityStrategy.h

Index: Source/core/editing/GranularityStrategy.h
diff --git a/Source/core/editing/GranularityStrategy.h b/Source/core/editing/GranularityStrategy.h
new file mode 100644
index 0000000000000000000000000000000000000000..0ad8b0b8c6ec7457093ffd0e5365763bfe83f3cf
--- /dev/null
+++ b/Source/core/editing/GranularityStrategy.h
@@ -0,0 +1,94 @@
+/*

[yosin_UTC9, 2015/04/21 01:59:52]

nit: Let's use the short version of licence comment.
http://dev.chromium.org/blink/coding-style#TOC-License

[mfomitchev, 2015/04/21 18:44:25]

Done - for all 3 new files.

+ * Copyright 2015, Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef GranularityStrategy_h
+#define GranularityStrategy_h
+
+#include "core/editing/SelectionStrategy.h"
+#include "core/editing/VisibleSelection.h"
+
+namespace blink {
+
+class GranularityStrategy {
+public:
+    virtual ~GranularityStrategy() { };

[yosin_UTC9, 2015/04/21 01:59:52]

Let's move inline virtual functions into .cpp files:
http://dev.chromium.org/developers/coding-style/cpp-dos-and-donts#TOC-Stop-in...

[mfomitchev, 2015/04/21 18:44:25]

Done.

+    virtual SelectionStrategy GetType() const = 0;
+    virtual void Clear() = 0;
+
+    // Calculates and returns the new selection based on the updated user selection extent |extentPosition| and the granularity strategy.
+    virtual VisibleSelection updateExtent(const VisiblePosition& extentPosition, const VisibleSelection&) = 0;
+protected:
+    GranularityStrategy() { };
+};
+
+// Always uses character granularity.
+class CharacterGranularityStrategy final : public GranularityStrategy {
+public:
+    CharacterGranularityStrategy() { };
+    ~CharacterGranularityStrategy() override { };

[yosin_UTC9, 2015/04/21 01:59:52]

nit: |final|.
This comment is applied rest of |override| in |final| class.

[mfomitchev, 2015/04/21 18:44:25]

Done.

+
+    // GranularityStrategy:
+    SelectionStrategy GetType() const override { return StrategyCharacter; }
+    void Clear() override { };
+    VisibleSelection updateExtent(const VisiblePosition& extentPosition, const VisibleSelection&) override;
+};
+
+// "Expand by word, shrink by character" selection strategy.
+// Uses character granularity when selection is shrinking. If the selection is expanding,
+// granularity doesn't change until a word boundary is passed, after which the granularity
+// switches to "word".
+class DirectionGranularityStrategy final : public GranularityStrategy {
+public:
+    DirectionGranularityStrategy();
+    ~DirectionGranularityStrategy() override { };
+
+    // GranularityStrategy:
+    SelectionStrategy GetType() const override { return StrategyDirection; }
+    void Clear() override;
+    VisibleSelection updateExtent(const VisiblePosition&, const VisibleSelection&) override;
+private:
+    enum class EBoundAdjust {CurrentPosIfOnBound, NextBoundIfOnBound};

[yosin_UTC9, 2015/04/21 01:59:52]

I think we don't need to have prefix "E". Since, this enum class is a private
member and won't conflict with future classes.

[mfomitchev, 2015/04/21 18:44:25]

Done.

+    enum class ESearchDirection {SearchBackwards, SearchForward};
+
+    // Returns the next word boundary starting from |pos|. |direction| specifies the direction
+    // in which to search for the next bound. nextIfOnBound controls whether |pos| or the next boundary
+    // is returned when |pos| is located exactly on word boundary.
+    VisiblePosition nextWordBound(const VisiblePosition& /*pos*/, ESearchDirection /*direction*/, EBoundAdjust /*nextIfOnBound*/);
+
+    // Current selection granularity being used
+    TextGranularity m_granularity;
+    // Set to true if the selection was shrunk (without changing relative base/extent order)
+    // as a result of the most recent updateExtent call.
+    bool m_lastMoveShrunkSelection;
+};
+
+} // namespace blink
+
+#endif // GranularityStrategy_h