Store glyph bounds in WordMeasurement to avoid slow path width calc

Source/core/layout/line/GlyphOverflow.h

+/*
+ * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
+ *           (C) 2000 Antti Koivisto (koivisto@kde.org)
+ *           (C) 2000 Dirk Mueller (mueller@kde.org)
+ * Copyright (C) 2003, 2006, 2007, 2010, 2011 Apple Inc. All rights reserved.
+ * Copyright (C) 2008 Holger Hans Peter Freyther
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public License
+ * along with this library; see the file COPYING.LIB.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ *
+ */
+
+#ifndef GlyphOverflow_h
+#define GlyphOverflow_h
+
+#include "platform/geometry/FloatRect.h"
+#include <math.h>
+
+namespace blink {
+
+struct GlyphOverflow {
+    GlyphOverflow()
+        : left(0)
+        , right(0)
+        , top(0)
+        , bottom(0)
+        , computeBounds(false)
+    {
+    }
+
+    bool isZero() const
+    {
+        return !left && !right && !top && !bottom;
+    }
+
+    void setFromBounds(const FloatRect& bounds, float ascent, float descent, float textWidth)
+    {
+        top = ceilf(computeBounds ? -bounds.y() : std::max(0.0f, -bounds.y() - ascent));
+        bottom = ceilf(computeBounds ? bounds.maxY() : std::max(0.0f, bounds.maxY() - descent));
+        left = ceilf(std::max(0.0f, -bounds.x()));
+        right = ceilf(std::max(0.0f, bounds.maxX() - textWidth));
+    }
+
+    // If computeBounds, top and bottom are the maximum heights of the glyphs above and below the baseline, respectively.
+    // Otherwise they are the amounts of glyph overflows exceeding the font metrics' ascent and descent, respectively.
+    // Left and right are the amounts of glyph overflows exceeding the left and right edge of normal layout boundary, respectively.
+    // All fields are in absolute number of pixels rounded up to the nearest integer.
+    int left;
+    int right;
+    int top;
+    int bottom;
+    bool computeBounds;
+};
+
+} // namespace blink
+
+#endif // GlyphOverflow_h