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diff --git a/WebCore/platform/graphics/qt/ContextShadow.cpp b/WebCore/platform/graphics/qt/ContextShadow.cpp
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+++ b/WebCore/platform/graphics/qt/ContextShadow.cpp
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+/*
+ * Copyright (C) 2010 Sencha, 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:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``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 APPLE COMPUTER, INC. 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.
+ */
+
+#include "config.h"
+#include "ContextShadow.h"
+
+namespace WebCore {
+
+ContextShadow::ContextShadow()
+    : type(NoShadow)
+    , blurRadius(0)
+{
+}
+
+ContextShadow::ContextShadow(const QColor& c, float r, qreal dx, qreal dy)
+    : color(c)
+    , blurRadius(qRound(r))
+    , offset(dx, dy)
+{
+    // The type of shadow is decided by the blur radius, shadow offset, and shadow color.
+    if (!color.isValid() || !color.alpha()) {
+        // Can't paint the shadow with invalid or invisible color.
+        type = NoShadow;
+    } else if (r > 0) {
+        // Shadow is always blurred, even the offset is zero.
+        type = BlurShadow;
+    } else if (offset.isNull()) {
+        // Without blur and zero offset means the shadow is fully hidden.
+        type = NoShadow;
+    } else {
+        if (color.alpha() > 0)
+            type = AlphaSolidShadow;
+        else
+            type = OpaqueSolidShadow;
+    }
+}
+
+void ContextShadow::clear()
+{
+    type = NoShadow;
+    color = QColor();
+    blurRadius = 0;
+    offset = QPointF(0, 0);
+}
+
+// Instead of integer division, we use 18.14 for fixed-point division.
+static const int BlurSumShift = 14;
+
+// Note: image must be RGB32 format
+static void blurHorizontal(QImage& image, int radius, bool swap = false)
+{
+    Q_ASSERT(image.format() == QImage::Format_ARGB32_Premultiplied);
+
+    // See comments in http://webkit.org/b/40793, it seems sensible
+    // to follow Skia's limit of 128 pixels of blur radius
+    radius = qMin(128, radius);
+
+    int imgWidth = image.width();
+    int imgHeight = image.height();
+
+    // Check http://www.w3.org/TR/SVG/filters.html#feGaussianBlur
+    // for the approaches when the box-blur radius is even vs odd.
+    int dmax = radius >> 1;
+    int dmin = qMax(0, dmax - 1 + (radius & 1));
+
+    for (int y = 0; y < imgHeight; ++y) {
+
+        unsigned char* pixels = image.scanLine(y);
+
+        int left;
+        int right;
+        int pixelCount;
+        int prev;
+        int next;
+        int firstAlpha;
+        int lastAlpha;
+        int totalAlpha;
+        unsigned char* target;
+        unsigned char* prevPtr;
+        unsigned char* nextPtr;
+
+        int invCount;
+
+        static const int alphaChannel = 3;
+        static const int blueChannel = 0;
+        static const int greenChannel = 1;
+
+        // For each step, we use sliding window algorithm. This is much more
+        // efficient than computing the sum of each pixels covered by the box
+        // kernel size for each x.
+
+        // As noted in the SVG filter specification, running box blur 3x
+        // approximates a real gaussian blur nicely.
+
+        // Step 1: blur alpha channel and store the result in the blue channel.
+        left = swap ? dmax : dmin;
+        right = swap ? dmin : dmax;
+        pixelCount = left + 1 + right;
+        invCount = (1 << BlurSumShift) / pixelCount;
+        prev = -left;
+        next = 1 + right;
+        firstAlpha = pixels[alphaChannel];
+        lastAlpha = pixels[(imgWidth - 1) * 4 + alphaChannel];
+        totalAlpha = 0;
+        for (int i = 0; i < pixelCount; ++i)
+            totalAlpha += pixels[qBound(0, i - left, imgWidth - 1) * 4 + alphaChannel];
+        target = pixels + blueChannel;
+        prevPtr = pixels + prev * 4 + alphaChannel;
+        nextPtr = pixels + next * 4 + alphaChannel;
+        for (int x = 0; x < imgWidth; ++x, ++prev, ++next, target += 4, prevPtr += 4, nextPtr += 4) {
+            *target = (totalAlpha * invCount) >> BlurSumShift;
+            int delta = ((next < imgWidth) ? *nextPtr : lastAlpha) -
+                        ((prev > 0) ? *prevPtr : firstAlpha);
+            totalAlpha += delta;
+        }
+
+        // Step 2: blur blue channel and store the result in the green channel.
+        left = swap ? dmin : dmax;
+        right = swap ? dmax : dmin;
+        pixelCount = left + 1 + right;
+        invCount = (1 << BlurSumShift) / pixelCount;
+        prev = -left;
+        next = 1 + right;
+        firstAlpha = pixels[blueChannel];
+        lastAlpha = pixels[(imgWidth - 1) * 4 + blueChannel];
+        totalAlpha = 0;
+        for (int i = 0; i < pixelCount; ++i)
+            totalAlpha += pixels[qBound(0, i - left, imgWidth - 1) * 4 + blueChannel];
+        target = pixels + greenChannel;
+        prevPtr = pixels + prev * 4 + blueChannel;
+        nextPtr = pixels + next * 4 + blueChannel;
+        for (int x = 0; x < imgWidth; ++x, ++prev, ++next, target += 4, prevPtr += 4, nextPtr += 4) {
+            *target = (totalAlpha * invCount) >> BlurSumShift;
+            int delta = ((next < imgWidth) ? *nextPtr : lastAlpha) -
+                        ((prev > 0) ? *prevPtr : firstAlpha);
+            totalAlpha += delta;
+        }
+
+        // Step 3: blur green channel and store the result in the alpha channel.
+        left = dmax;
+        right = dmax;
+        pixelCount = left + 1 + right;
+        invCount = (1 << BlurSumShift) / pixelCount;
+        prev = -left;
+        next = 1 + right;
+        firstAlpha = pixels[greenChannel];
+        lastAlpha = pixels[(imgWidth - 1) * 4 + greenChannel];
+        totalAlpha = 0;
+        for (int i = 0; i < pixelCount; ++i)
+            totalAlpha += pixels[qBound(0, i - left, imgWidth - 1) * 4 + greenChannel];
+        target = pixels + alphaChannel;
+        prevPtr = pixels + prev * 4 + greenChannel;
+        nextPtr = pixels + next * 4 + greenChannel;
+        for (int x = 0; x < imgWidth; ++x, ++prev, ++next, target += 4, prevPtr += 4, nextPtr += 4) {
+            *target = (totalAlpha * invCount) >> BlurSumShift;
+            int delta = ((next < imgWidth) ? *nextPtr : lastAlpha) -
+                        ((prev > 0) ? *prevPtr : firstAlpha);
+            totalAlpha += delta;
+        }
+    }
+}
+
+static void shadowBlur(QImage& image, int radius, const QColor& shadowColor)
+{
+    blurHorizontal(image, radius);
+
+    QTransform transform;
+    transform.rotate(90);
+    image = image.transformed(transform);
+    blurHorizontal(image, radius, true);
+    transform.reset();
+    transform.rotate(270);
+    image = image.transformed(transform);
+
+    // "Colorize" with the right shadow color.
+    QPainter p(&image);
+    p.setCompositionMode(QPainter::CompositionMode_SourceIn);
+    p.fillRect(image.rect(), shadowColor.rgb());
+    p.end();
+}
+
+void ContextShadow::drawShadowRect(QPainter* p, const QRectF& rect)
+{
+    if (type == NoShadow)
+        return;
+
+    if (type == BlurShadow) {
+        QRectF shadowRect = rect.translated(offset);
+
+        // We expand the area by the blur radius * 2 to give extra space
+        // for the blur transition.
+        int extra = blurRadius * 2;
+        QRectF bufferRect = shadowRect.adjusted(-extra, -extra, extra, extra);
+        QRect alignedBufferRect = bufferRect.toAlignedRect();
+
+        QRect clipRect;
+        if (p->hasClipping())
+            clipRect = p->clipRegion().boundingRect();
+        else
+            clipRect = p->transform().inverted().mapRect(p->window());
+
+        if (!clipRect.contains(alignedBufferRect)) {
+
+            // No need to have the buffer larger that the clip.
+            alignedBufferRect = alignedBufferRect.intersected(clipRect);
+            if (alignedBufferRect.isEmpty())
+                return;
+
+            // We adjust again because the pixels at the borders are still
+            // potentially affected by the pixels outside the buffer.
+            alignedBufferRect.adjust(-extra, -extra, extra, extra);
+        }
+
+        QImage shadowImage(alignedBufferRect.size(), QImage::Format_ARGB32_Premultiplied);
+        shadowImage.fill(Qt::transparent);
+        QPainter shadowPainter(&shadowImage);
+
+        shadowPainter.fillRect(shadowRect.translated(-alignedBufferRect.topLeft()), color);
+        shadowPainter.end();
+
+        shadowBlur(shadowImage, blurRadius, color);
+
+        p->drawImage(alignedBufferRect.topLeft(), shadowImage);
+
+        return;
+    }
+
+    p->fillRect(rect.translated(offset), color);
+}
+
+
+}