Pixel snap SVG's root border box to local transform [spv2]

third_party/WebKit/Source/core/paint/SVGRootPainter.cpp

 // Copyright 2014 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.
 
 #include "core/paint/SVGRootPainter.h"
 
 #include "core/layout/svg/LayoutSVGRoot.h"
 #include "core/layout/svg/SVGLayoutSupport.h"
 #include "core/paint/BoxPainter.h"
 #include "core/paint/ObjectPaintProperties.h"
 #include "core/paint/PaintInfo.h"
 #include "core/paint/PaintTiming.h"
 #include "core/paint/SVGPaintContext.h"
 #include "core/paint/TransformRecorder.h"
 #include "core/svg/SVGSVGElement.h"
 #include "platform/graphics/paint/ClipRecorder.h"
 #include "wtf/Optional.h"
 
 namespace blink {
 
+IntRect SVGRootPainter::pixelSnappedSize(const LayoutPoint& paintOffset) const
+{
+    return pixelSnappedIntRect(paintOffset, m_layoutSVGRoot.size());
+}
+
+AffineTransform SVGRootPainter::snappedPaintOffsetToBorderBox(const LayoutPoint& paintOffset) const
+{
+    const IntRect snappedSize = pixelSnappedSize(paintOffset);
+    AffineTransform paintOffsetToBorderBox =
+        AffineTransform::translation(snappedSize.x(), snappedSize.y());
+    paintOffsetToBorderBox.scale(
+        snappedSize.width() / m_layoutSVGRoot.size().width().toFloat(),
+        snappedSize.height() / m_layoutSVGRoot.size().height().toFloat());
+    paintOffsetToBorderBox.multiply(m_layoutSVGRoot.localToBorderBoxTransform());
+    return paintOffsetToBorderBox;
+}
+
 void SVGRootPainter::paint(const PaintInfo& paintInfo, const LayoutPoint& paintOffset)
 {
-    // Pixel-snap to match BoxPainter's alignment.
-    const IntRect adjustedRect = pixelSnappedIntRect(paintOffset, m_layoutSVGRoot.size());
-
     // An empty viewport disables rendering.
-    if (adjustedRect.isEmpty())
+    if (pixelSnappedSize(paintOffset).isEmpty())
         return;
 
     // SVG outlines are painted during PaintPhaseForeground.
     if (shouldPaintSelfOutline(paintInfo.phase))
         return;
 
     // An empty viewBox also disables rendering.
     // (http://www.w3.org/TR/SVG/coords.html#ViewBoxAttribute)
     SVGSVGElement* svg = toSVGSVGElement(m_layoutSVGRoot.node());
     ASSERT(svg);
     if (svg->hasEmptyViewBox())
         return;
 
     PaintInfo paintInfoBeforeFiltering(paintInfo);
 
     // Apply initial viewport clip.
     Optional<ClipRecorder> clipRecorder;
     if (m_layoutSVGRoot.shouldApplyViewportClip()) {
         // TODO(pdr): Clip the paint info cull rect here.
         clipRecorder.emplace(paintInfoBeforeFiltering.context, m_layoutSVGRoot, paintInfoBeforeFiltering.displayItemTypeForClipping(), pixelSnappedIntRect(m_layoutSVGRoot.overflowClipRect(paintOffset)));
     }
 
-    // Convert from container offsets (html layoutObjects) to a relative transform (svg layoutObjects).
-    // Transform from our paint container's coordinate system to our local coords.
-    AffineTransform paintOffsetToBorderBox =
-        AffineTransform::translation(adjustedRect.x(), adjustedRect.y());
-    // Compensate for size snapping.
-    paintOffsetToBorderBox.scale(
-        adjustedRect.width() / m_layoutSVGRoot.size().width().toFloat(),
-        adjustedRect.height() / m_layoutSVGRoot.size().height().toFloat());
-    paintOffsetToBorderBox.multiply(m_layoutSVGRoot.localToBorderBoxTransform());
-
+    AffineTransform paintOffsetToBorderBox = snappedPaintOffsetToBorderBox(paintOffset);
     paintInfoBeforeFiltering.updateCullRect(paintOffsetToBorderBox);
     SVGTransformContext transformContext(paintInfoBeforeFiltering.context, m_layoutSVGRoot, paintOffsetToBorderBox);
 
     SVGPaintContext paintContext(m_layoutSVGRoot, paintInfoBeforeFiltering);
     if (paintContext.paintInfo().phase == PaintPhaseForeground && !paintContext.applyClipMaskAndFilterIfNecessary())
         return;
 
     BoxPainter(m_layoutSVGRoot).paint(paintContext.paintInfo(), LayoutPoint());
 
     PaintTiming& timing = PaintTiming::from(m_layoutSVGRoot.node()->document().topDocument());
     timing.markFirstContentfulPaint();
 }
 
 } // namespace blink