Move painting code from RenderBoxModelObject into BoxPainter.

Source/core/paint/BoxPainter.cpp

Index: Source/core/paint/BoxPainter.cpp
diff --git a/Source/core/paint/BoxPainter.cpp b/Source/core/paint/BoxPainter.cpp
index 684e70fba3c259d815c22e3b588e37f092ba9a78..1621ed78fa7a5474efbda32f676893a8b1e3e6ab 100644
--- a/Source/core/paint/BoxPainter.cpp
+++ b/Source/core/paint/BoxPainter.cpp
@@ -5,13 +5,22 @@
 #include "config.h"
 #include "core/paint/BoxPainter.h"
 
+#include "core/HTMLNames.h"
+#include "core/frame/Settings.h"
+#include "core/html/HTMLFrameOwnerElement.h"
+#include "core/paint/BackgroundImageGeometry.h"
 #include "core/paint/BoxDecorationData.h"
+#include "core/rendering/ImageQualityController.h"
 #include "core/rendering/PaintInfo.h"
 #include "core/rendering/RenderBox.h"
+#include "core/rendering/RenderBoxModelObject.h"
 #include "core/rendering/RenderLayer.h"
 #include "core/rendering/RenderTable.h"
 #include "core/rendering/RenderTheme.h"
 #include "core/rendering/RenderView.h"
+#include "core/rendering/compositing/CompositedLayerMapping.h"
+#include "core/rendering/style/ShadowList.h"
+#include "platform/LengthFunctions.h"
 #include "platform/geometry/LayoutPoint.h"
 #include "platform/graphics/GraphicsContextStateSaver.h"
 
@@ -157,8 +166,8 @@ void BoxPainter::paintFillLayers(const PaintInfo& paintInfo, const Color& c, con
 
         // Paint the document's base background color outside the transparency layer,
         // so that the background images don't blend with this color: http://crbug.com/389039.
-        if (isBaseColorVisible && m_renderBox.isDocumentElementWithOpaqueBackground()) {
-            m_renderBox.paintRootBackgroundColor(paintInfo, rect, Color());
+        if (isBaseColorVisible && isDocumentElementWithOpaqueBackground(m_renderBox)) {
+            paintRootBackgroundColor(m_renderBox, paintInfo, rect, Color());
             skipBaseColor = true;
         }
         context->beginTransparencyLayer(1);
@@ -175,7 +184,308 @@ void BoxPainter::paintFillLayers(const PaintInfo& paintInfo, const Color& c, con
 void BoxPainter::paintFillLayer(const PaintInfo& paintInfo, const Color& c, const FillLayer& fillLayer, const LayoutRect& rect,
     BackgroundBleedAvoidance bleedAvoidance, CompositeOperator op, RenderObject* backgroundObject, bool skipBaseColor)
 {
-    m_renderBox.paintFillLayerExtended(paintInfo, c, fillLayer, rect, bleedAvoidance, 0, LayoutSize(), op, backgroundObject, skipBaseColor);
+    BoxPainter::paintFillLayerExtended(m_renderBox, paintInfo, c, fillLayer, rect, bleedAvoidance, 0, LayoutSize(), op, backgroundObject, skipBaseColor);
+}
+
+void BoxPainter::applyBoxShadowForBackground(GraphicsContext* context, RenderObject& obj)
+{
+    const ShadowList* shadowList = obj.style()->boxShadow();
+    ASSERT(shadowList);
+    for (size_t i = shadowList->shadows().size(); i--; ) {
+        const ShadowData& boxShadow = shadowList->shadows()[i];
+        if (boxShadow.style() != Normal)
+            continue;
+        FloatSize shadowOffset(boxShadow.x(), boxShadow.y());
+        context->setShadow(shadowOffset, boxShadow.blur(), boxShadow.color(),
+            DrawLooperBuilder::ShadowRespectsTransforms, DrawLooperBuilder::ShadowIgnoresAlpha);
+        return;
+    }
+}
+
+// FIXME: See crbug.com/382491. The use of getCTM in this context is incorrect because the matrix returned does not
+// include scales applied at raster time, such as the device zoom.
+static LayoutRect shrinkRectByOnePixel(GraphicsContext* context, const LayoutRect& rect)
+{
+    LayoutRect shrunkRect = rect;
+    AffineTransform transform = context->getCTM();
+    shrunkRect.inflateX(-static_cast<LayoutUnit>(ceil(1 / transform.xScale())));
+    shrunkRect.inflateY(-static_cast<LayoutUnit>(ceil(1 / transform.yScale())));
+    return shrunkRect;
+}
+
+RoundedRect BoxPainter::getBackgroundRoundedRect(RenderObject& obj, const LayoutRect& borderRect, InlineFlowBox* box, LayoutUnit inlineBoxWidth, LayoutUnit inlineBoxHeight,
+    bool includeLogicalLeftEdge, bool includeLogicalRightEdge)
+{
+    RoundedRect border = obj.style()->getRoundedBorderFor(borderRect, includeLogicalLeftEdge, includeLogicalRightEdge);
+    if (box && (box->nextLineBox() || box->prevLineBox())) {
+        RoundedRect segmentBorder = obj.style()->getRoundedBorderFor(LayoutRect(0, 0, inlineBoxWidth, inlineBoxHeight), includeLogicalLeftEdge, includeLogicalRightEdge);
+        border.setRadii(segmentBorder.radii());
+    }
+
+    return border;
+}
+
+RoundedRect BoxPainter::backgroundRoundedRectAdjustedForBleedAvoidance(RenderObject& obj, GraphicsContext* context, const LayoutRect& borderRect, BackgroundBleedAvoidance bleedAvoidance, InlineFlowBox* box, const LayoutSize& boxSize, bool includeLogicalLeftEdge, bool includeLogicalRightEdge)
+{
+    if (bleedAvoidance == BackgroundBleedShrinkBackground) {
+        // We shrink the rectangle by one pixel on each side because the bleed is one pixel maximum.
+        return BoxPainter::getBackgroundRoundedRect(obj, shrinkRectByOnePixel(context, borderRect), box, boxSize.width(), boxSize.height(), includeLogicalLeftEdge, includeLogicalRightEdge);
+    }
+    if (bleedAvoidance == BackgroundBleedBackgroundOverBorder)
+        return obj.style()->getRoundedInnerBorderFor(borderRect, includeLogicalLeftEdge, includeLogicalRightEdge);
+
+    return BoxPainter::getBackgroundRoundedRect(obj, borderRect, box, boxSize.width(), boxSize.height(), includeLogicalLeftEdge, includeLogicalRightEdge);
+}
+
+void BoxPainter::clipRoundedInnerRect(GraphicsContext * context, const LayoutRect& rect, const RoundedRect& clipRect)
+{
+    if (clipRect.isRenderable()) {
+        context->clipRoundedRect(clipRect);
+    } else {
+        // We create a rounded rect for each of the corners and clip it, while making sure we clip opposing corners together.
+        if (!clipRect.radii().topLeft().isEmpty() || !clipRect.radii().bottomRight().isEmpty()) {
+            IntRect topCorner(clipRect.rect().x(), clipRect.rect().y(), rect.maxX() - clipRect.rect().x(), rect.maxY() - clipRect.rect().y());
+            RoundedRect::Radii topCornerRadii;
+            topCornerRadii.setTopLeft(clipRect.radii().topLeft());
+            context->clipRoundedRect(RoundedRect(topCorner, topCornerRadii));
+
+            IntRect bottomCorner(rect.x(), rect.y(), clipRect.rect().maxX() - rect.x(), clipRect.rect().maxY() - rect.y());
+            RoundedRect::Radii bottomCornerRadii;
+            bottomCornerRadii.setBottomRight(clipRect.radii().bottomRight());
+            context->clipRoundedRect(RoundedRect(bottomCorner, bottomCornerRadii));
+        }
+
+        if (!clipRect.radii().topRight().isEmpty() || !clipRect.radii().bottomLeft().isEmpty()) {
+            IntRect topCorner(rect.x(), clipRect.rect().y(), clipRect.rect().maxX() - rect.x(), rect.maxY() - clipRect.rect().y());
+            RoundedRect::Radii topCornerRadii;
+            topCornerRadii.setTopRight(clipRect.radii().topRight());
+            context->clipRoundedRect(RoundedRect(topCorner, topCornerRadii));
+
+            IntRect bottomCorner(clipRect.rect().x(), rect.y(), rect.maxX() - clipRect.rect().x(), clipRect.rect().maxY() - rect.y());
+            RoundedRect::Radii bottomCornerRadii;
+            bottomCornerRadii.setBottomLeft(clipRect.radii().bottomLeft());
+            context->clipRoundedRect(RoundedRect(bottomCorner, bottomCornerRadii));
+        }
+    }
+}
+
+void BoxPainter::paintFillLayerExtended(RenderBoxModelObject& obj, const PaintInfo& paintInfo, const Color& color, const FillLayer& bgLayer, const LayoutRect& rect,
+    BackgroundBleedAvoidance bleedAvoidance, InlineFlowBox* box, const LayoutSize& boxSize, CompositeOperator op, RenderObject* backgroundObject, bool skipBaseColor)
+{
+    GraphicsContext* context = paintInfo.context;
+    if (rect.isEmpty())
+        return;
+
+    bool includeLeftEdge = box ? box->includeLogicalLeftEdge() : true;
+    bool includeRightEdge = box ? box->includeLogicalRightEdge() : true;
+
+    bool hasRoundedBorder = obj.style()->hasBorderRadius() && (includeLeftEdge || includeRightEdge);
+    bool clippedWithLocalScrolling = obj.hasOverflowClip() && bgLayer.attachment() == LocalBackgroundAttachment;
+    bool isBorderFill = bgLayer.clip() == BorderFillBox;
+    bool isDocumentElementRenderer = obj.isDocumentElement();
+    bool isBottomLayer = !bgLayer.next();
+
+    Color bgColor = color;
+    StyleImage* bgImage = bgLayer.image();
+    bool shouldPaintBackgroundImage = bgImage && bgImage->canRender(obj, obj.style()->effectiveZoom());
+
+    bool forceBackgroundToWhite = false;
+    if (obj.document().printing()) {
+        if (obj.style()->printColorAdjust() == PrintColorAdjustEconomy)
+            forceBackgroundToWhite = true;
+        if (obj.document().settings() && obj.document().settings()->shouldPrintBackgrounds())
+            forceBackgroundToWhite = false;
+    }
+
+    // When printing backgrounds is disabled or using economy mode,
+    // change existing background colors and images to a solid white background.
+    // If there's no bg color or image, leave it untouched to avoid affecting transparency.
+    // We don't try to avoid loading the background images, because this style flag is only set
+    // when printing, and at that point we've already loaded the background images anyway. (To avoid
+    // loading the background images we'd have to do this check when applying styles rather than
+    // while rendering.)
+    if (forceBackgroundToWhite) {
+        // Note that we can't reuse this variable below because the bgColor might be changed
+        bool shouldPaintBackgroundColor = isBottomLayer && bgColor.alpha();
+        if (shouldPaintBackgroundImage || shouldPaintBackgroundColor) {
+            bgColor = Color::white;
+            shouldPaintBackgroundImage = false;
+        }
+    }
+
+    bool colorVisible = bgColor.alpha();
+
+    // Fast path for drawing simple color backgrounds.
+    if (!isDocumentElementRenderer && !clippedWithLocalScrolling && !shouldPaintBackgroundImage && isBorderFill && isBottomLayer) {
+        if (!colorVisible)
+            return;
+
+        bool boxShadowShouldBeAppliedToBackground = obj.boxShadowShouldBeAppliedToBackground(bleedAvoidance, box);
+        GraphicsContextStateSaver shadowStateSaver(*context, boxShadowShouldBeAppliedToBackground);
+        if (boxShadowShouldBeAppliedToBackground)
+            BoxPainter::applyBoxShadowForBackground(context, obj);
+
+        if (hasRoundedBorder && bleedAvoidance != BackgroundBleedClipBackground) {
+            RoundedRect border = backgroundRoundedRectAdjustedForBleedAvoidance(obj, context, rect, bleedAvoidance, box, boxSize, includeLeftEdge, includeRightEdge);
+            if (border.isRenderable()) {
+                context->fillRoundedRect(border, bgColor);
+            } else {
+                context->save();
+                clipRoundedInnerRect(context, rect, border);
+                context->fillRect(border.rect(), bgColor);
+                context->restore();
+            }
+        } else {
+            context->fillRect(pixelSnappedIntRect(rect), bgColor);
+        }
+
+        return;
+    }
+
+    // BorderFillBox radius clipping is taken care of by BackgroundBleedClipBackground
+    bool clipToBorderRadius = hasRoundedBorder && !(isBorderFill && bleedAvoidance == BackgroundBleedClipBackground);
+    GraphicsContextStateSaver clipToBorderStateSaver(*context, clipToBorderRadius);
+    if (clipToBorderRadius) {
+        RoundedRect border = isBorderFill ? backgroundRoundedRectAdjustedForBleedAvoidance(obj, context, rect, bleedAvoidance, box, boxSize, includeLeftEdge, includeRightEdge) : getBackgroundRoundedRect(obj, rect, box, boxSize.width(), boxSize.height(), includeLeftEdge, includeRightEdge);
+
+        // Clip to the padding or content boxes as necessary.
+        if (bgLayer.clip() == ContentFillBox) {
+            border = obj.style()->getRoundedInnerBorderFor(border.rect(),
+                obj.paddingTop() + obj.borderTop(), obj.paddingBottom() + obj.borderBottom(),
+                obj.paddingLeft() + obj.borderLeft(), obj.paddingRight() + obj.borderRight(), includeLeftEdge, includeRightEdge);
+        } else if (bgLayer.clip() == PaddingFillBox) {
+            border = obj.style()->getRoundedInnerBorderFor(border.rect(), includeLeftEdge, includeRightEdge);
+        }
+
+        clipRoundedInnerRect(context, rect, border);
+    }
+
+    int bLeft = includeLeftEdge ? obj.borderLeft() : 0;
+    int bRight = includeRightEdge ? obj.borderRight() : 0;
+    LayoutUnit pLeft = includeLeftEdge ? obj.paddingLeft() : LayoutUnit();
+    LayoutUnit pRight = includeRightEdge ? obj.paddingRight() : LayoutUnit();
+
+    GraphicsContextStateSaver clipWithScrollingStateSaver(*context, clippedWithLocalScrolling);
+    LayoutRect scrolledPaintRect = rect;
+    if (clippedWithLocalScrolling) {
+        // Clip to the overflow area.
+        RenderBox* thisBox = toRenderBox(&obj);
+        context->clip(thisBox->overflowClipRect(rect.location()));
+
+        // Adjust the paint rect to reflect a scrolled content box with borders at the ends.
+        IntSize offset = thisBox->scrolledContentOffset();
+        scrolledPaintRect.move(-offset);
+        scrolledPaintRect.setWidth(bLeft + thisBox->scrollWidth() + bRight);
+        scrolledPaintRect.setHeight(thisBox->borderTop() + thisBox->scrollHeight() + thisBox->borderBottom());
+    }
+
+    GraphicsContextStateSaver backgroundClipStateSaver(*context, false);
+    IntRect maskRect;
+
+    switch (bgLayer.clip()) {
+    case PaddingFillBox:
+    case ContentFillBox: {
+        if (clipToBorderRadius)
+            break;
+
+        // Clip to the padding or content boxes as necessary.
+        bool includePadding = bgLayer.clip() == ContentFillBox;
+        LayoutRect clipRect = LayoutRect(scrolledPaintRect.x() + bLeft + (includePadding ? pLeft : LayoutUnit()),
+            scrolledPaintRect.y() + obj.borderTop() + (includePadding ? obj.paddingTop() : LayoutUnit()),
+            scrolledPaintRect.width() - bLeft - bRight - (includePadding ? pLeft + pRight : LayoutUnit()),
+            scrolledPaintRect.height() - obj.borderTop() - obj.borderBottom() - (includePadding ? obj.paddingTop() + obj.paddingBottom() : LayoutUnit()));
+        backgroundClipStateSaver.save();
+        context->clip(clipRect);
+
+        break;
+    }
+    case TextFillBox: {
+        // First figure out how big the mask has to be. It should be no bigger than what we need
+        // to actually render, so we should intersect the dirty rect with the border box of the background.
+        maskRect = pixelSnappedIntRect(rect);
+        maskRect.intersect(paintInfo.rect);
+
+        // We draw the background into a separate layer, to be later masked with yet another layer
+        // holding the text content.
+        backgroundClipStateSaver.save();
+        context->clip(maskRect);
+        context->beginTransparencyLayer(1);
+
+        break;
+    }
+    case BorderFillBox:
+        break;
+    default:
+        ASSERT_NOT_REACHED();
+        break;
+    }
+
+    // Paint the color first underneath all images, culled if background image occludes it.
+    // FIXME: In the bgLayer->hasFiniteBounds() case, we could improve the culling test
+    // by verifying whether the background image covers the entire layout rect.
+    if (isBottomLayer) {
+        IntRect backgroundRect(pixelSnappedIntRect(scrolledPaintRect));
+        bool boxShadowShouldBeAppliedToBackground = obj.boxShadowShouldBeAppliedToBackground(bleedAvoidance, box);
+        bool isOpaqueRoot = (isDocumentElementRenderer && !bgColor.hasAlpha()) || isDocumentElementWithOpaqueBackground(obj);
+        if (boxShadowShouldBeAppliedToBackground || !shouldPaintBackgroundImage || !bgLayer.hasOpaqueImage(&obj) || !bgLayer.hasRepeatXY() || (isOpaqueRoot && !toRenderBox(&obj)->height()))  {
+            if (!boxShadowShouldBeAppliedToBackground)
+                backgroundRect.intersect(paintInfo.rect);
+
+            GraphicsContextStateSaver shadowStateSaver(*context, boxShadowShouldBeAppliedToBackground);
+            if (boxShadowShouldBeAppliedToBackground)
+                BoxPainter::applyBoxShadowForBackground(context, obj);
+
+            if (isOpaqueRoot && !skipBaseColor) {
+                paintRootBackgroundColor(obj, paintInfo, rect, bgColor);
+            } else if (bgColor.alpha()) {
+                context->fillRect(backgroundRect, bgColor, context->compositeOperation());
+            }
+        }
+    }
+
+    // no progressive loading of the background image
+    if (shouldPaintBackgroundImage) {
+        BackgroundImageGeometry geometry;
+        calculateBackgroundImageGeometry(obj, paintInfo.paintContainer(), bgLayer, scrolledPaintRect, geometry, backgroundObject);
+        geometry.clip(paintInfo.rect);
+        if (!geometry.destRect().isEmpty()) {
+            CompositeOperator compositeOp = op == CompositeSourceOver ? bgLayer.composite() : op;
+            RenderObject* clientForBackgroundImage = backgroundObject ? backgroundObject : &obj;
+            RefPtr<Image> image = bgImage->image(clientForBackgroundImage, geometry.tileSize());
+            InterpolationQuality interpolationQuality = chooseInterpolationQuality(obj, context, image.get(), &bgLayer, geometry.tileSize());
+            if (bgLayer.maskSourceType() == MaskLuminance)
+                context->setColorFilter(ColorFilterLuminanceToAlpha);
+            InterpolationQuality previousInterpolationQuality = context->imageInterpolationQuality();
+            context->setImageInterpolationQuality(interpolationQuality);
+            context->drawTiledImage(image.get(), geometry.destRect(), geometry.relativePhase(), geometry.tileSize(),
+                compositeOp, bgLayer.blendMode(), geometry.spaceSize());
+            context->setImageInterpolationQuality(previousInterpolationQuality);
+        }
+    }
+
+    if (bgLayer.clip() == TextFillBox) {
+        // Create the text mask layer.
+        context->setCompositeOperation(CompositeDestinationIn);
+        context->beginTransparencyLayer(1);
+
+        // FIXME: Workaround for https://code.google.com/p/skia/issues/detail?id=1291.
+        context->clearRect(maskRect);
+
+        // Now draw the text into the mask. We do this by painting using a special paint phase that signals to
+        // InlineTextBoxes that they should just add their contents to the clip.
+        PaintInfo info(context, maskRect, PaintPhaseTextClip, PaintBehaviorForceBlackText, 0);
+        context->setCompositeOperation(CompositeSourceOver);
+        if (box) {
+            RootInlineBox& root = box->root();
+            box->paint(info, LayoutPoint(scrolledPaintRect.x() - box->x(), scrolledPaintRect.y() - box->y()), root.lineTop(), root.lineBottom());
+        } else {
+            LayoutSize localOffset = obj.isBox() ? toRenderBox(&obj)->locationOffset() : LayoutSize();
+            obj.paint(info, scrolledPaintRect.location() - localOffset);
+        }
+
+        context->endLayer();
+        context->endLayer();
+    }
 }
 
 void BoxPainter::paintMask(PaintInfo& paintInfo, const LayoutPoint& paintOffset)
@@ -238,4 +548,320 @@ void BoxPainter::paintClippingMask(PaintInfo& paintInfo, const LayoutPoint& pain
     paintInfo.context->fillRect(pixelSnappedIntRect(paintRect), Color::black);
 }
 
+void BoxPainter::paintRootBackgroundColor(RenderObject& obj, const PaintInfo& paintInfo, const LayoutRect& rect, const Color& bgColor)
+{
+    GraphicsContext* context = paintInfo.context;
+    if (rect.isEmpty())
+        return;
+
+    ASSERT(obj.isDocumentElement());
+
+    IntRect backgroundRect(pixelSnappedIntRect(rect));
+    backgroundRect.intersect(paintInfo.rect);
+
+    Color baseColor = obj.view()->frameView()->baseBackgroundColor();
+    bool shouldClearDocumentBackground = obj.document().settings() && obj.document().settings()->shouldClearDocumentBackground();
+    CompositeOperator operation = shouldClearDocumentBackground ? CompositeCopy : context->compositeOperation();
+
+    // If we have an alpha go ahead and blend with the base background color.
+    if (baseColor.alpha()) {
+        if (bgColor.alpha())
+            baseColor = baseColor.blend(bgColor);
+        context->fillRect(backgroundRect, baseColor, operation);
+    } else if (bgColor.alpha()) {
+        context->fillRect(backgroundRect, bgColor, operation);
+    } else if (shouldClearDocumentBackground) {
+        context->clearRect(backgroundRect);
+    }
+}
+
+bool BoxPainter::isDocumentElementWithOpaqueBackground(RenderObject& obj)
+{
+    if (!obj.isDocumentElement())
+        return false;
+
+    // The background is opaque only if we're the root document, since iframes with
+    // no background in the child document should show the parent's background.
+    bool isOpaque = true;
+    Element* ownerElement = obj.document().ownerElement();
+    if (ownerElement) {
+        if (!isHTMLFrameElement(*ownerElement)) {
+            // Locate the <body> element using the DOM. This is easier than trying
+            // to crawl around a render tree with potential :before/:after content and
+            // anonymous blocks created by inline <body> tags etc. We can locate the <body>
+            // render object very easily via the DOM.
+            HTMLElement* body = obj.document().body();
+            if (body) {
+                // Can't scroll a frameset document anyway.
+                isOpaque = body->hasTagName(HTMLNames::framesetTag);
+            } else {
+                // FIXME: SVG specific behavior should be in the SVG code.
+                // SVG documents and XML documents with SVG root nodes are transparent.
+                isOpaque = !obj.document().hasSVGRootNode();
+            }
+        }
+    } else if (obj.view()->frameView()) {
+        isOpaque = !obj.view()->frameView()->isTransparent();
+    }
+
+    return isOpaque;
+}
+
+static inline int getSpace(int areaSize, int tileSize)
+{
+    int numberOfTiles = areaSize / tileSize;
+    int space = -1;
+
+    if (numberOfTiles > 1)
+        space = lroundf((float)(areaSize - numberOfTiles * tileSize) / (numberOfTiles - 1));
+
+    return space;
+}
+
+void BoxPainter::calculateBackgroundImageGeometry(RenderBoxModelObject& obj, const RenderLayerModelObject* paintContainer, const FillLayer& fillLayer, const LayoutRect& paintRect,
+    BackgroundImageGeometry& geometry, RenderObject* backgroundObject)
+{
+    LayoutUnit left = 0;
+    LayoutUnit top = 0;
+    IntSize positioningAreaSize;
+    IntRect snappedPaintRect = pixelSnappedIntRect(paintRect);
+
+    // Determine the background positioning area and set destRect to the background painting area.
+    // destRect will be adjusted later if the background is non-repeating.
+    // FIXME: transforms spec says that fixed backgrounds behave like scroll inside transforms.
+    bool fixedAttachment = fillLayer.attachment() == FixedBackgroundAttachment;
+
+    if (RuntimeEnabledFeatures::fastMobileScrollingEnabled()) {
+        // As a side effect of an optimization to blit on scroll, we do not honor the CSS
+        // property "background-attachment: fixed" because it may result in rendering
+        // artifacts. Note, these artifacts only appear if we are blitting on scroll of
+        // a page that has fixed background images.
+        fixedAttachment = false;
+    }
+
+    if (!fixedAttachment) {
+        geometry.setDestRect(snappedPaintRect);
+
+        LayoutUnit right = 0;
+        LayoutUnit bottom = 0;
+        // Scroll and Local.
+        if (fillLayer.origin() != BorderFillBox) {
+            left = obj.borderLeft();
+            right = obj.borderRight();
+            top = obj.borderTop();
+            bottom = obj.borderBottom();
+            if (fillLayer.origin() == ContentFillBox) {
+                left += obj.paddingLeft();
+                right += obj.paddingRight();
+                top += obj.paddingTop();
+                bottom += obj.paddingBottom();
+            }
+        }
+
+        // The background of the box generated by the root element covers the entire canvas including
+        // its margins. Since those were added in already, we have to factor them out when computing
+        // the background positioning area.
+        if (obj.isDocumentElement()) {
+            positioningAreaSize = pixelSnappedIntSize(toRenderBox(&obj)->size() - LayoutSize(left + right, top + bottom), toRenderBox(&obj)->location());
+            left += obj.marginLeft();
+            top += obj.marginTop();
+        } else {
+            positioningAreaSize = pixelSnappedIntSize(paintRect.size() - LayoutSize(left + right, top + bottom), paintRect.location());
+        }
+    } else {
+        geometry.setHasNonLocalGeometry();
+
+        IntRect viewportRect = pixelSnappedIntRect(obj.viewRect());
+        if (fixedBackgroundPaintsInLocalCoordinates(obj))
+            viewportRect.setLocation(IntPoint());
+        else if (FrameView* frameView = obj.view()->frameView())
+            viewportRect.setLocation(IntPoint(frameView->scrollOffsetForFixedPosition()));
+
+        if (paintContainer) {
+            IntPoint absoluteContainerOffset = roundedIntPoint(paintContainer->localToAbsolute(FloatPoint()));
+            viewportRect.moveBy(-absoluteContainerOffset);
+        }
+
+        geometry.setDestRect(pixelSnappedIntRect(viewportRect));
+        positioningAreaSize = geometry.destRect().size();
+    }
+
+    const RenderObject* clientForBackgroundImage = backgroundObject ? backgroundObject : &obj;
+    IntSize fillTileSize = calculateFillTileSize(obj, fillLayer, positioningAreaSize);
+    fillLayer.image()->setContainerSizeForRenderer(clientForBackgroundImage, fillTileSize, obj.style()->effectiveZoom());
+    geometry.setTileSize(fillTileSize);
+
+    EFillRepeat backgroundRepeatX = fillLayer.repeatX();
+    EFillRepeat backgroundRepeatY = fillLayer.repeatY();
+    int availableWidth = positioningAreaSize.width() - geometry.tileSize().width();
+    int availableHeight = positioningAreaSize.height() - geometry.tileSize().height();
+
+    LayoutUnit computedXPosition = roundedMinimumValueForLength(fillLayer.xPosition(), availableWidth);
+    if (backgroundRepeatX == RoundFill && positioningAreaSize.width() > 0 && fillTileSize.width() > 0) {
+        long nrTiles = std::max(1l, lroundf((float)positioningAreaSize.width() / fillTileSize.width()));
+
+        if (fillLayer.size().size.height().isAuto() && backgroundRepeatY != RoundFill) {
+            fillTileSize.setHeight(fillTileSize.height() * positioningAreaSize.width() / (nrTiles * fillTileSize.width()));
+        }
+
+        fillTileSize.setWidth(positioningAreaSize.width() / nrTiles);
+        geometry.setTileSize(fillTileSize);
+        geometry.setPhaseX(geometry.tileSize().width() ? geometry.tileSize().width() - roundToInt(computedXPosition + left) % geometry.tileSize().width() : 0);
+        geometry.setSpaceSize(IntSize());
+    }
+
+    LayoutUnit computedYPosition = roundedMinimumValueForLength(fillLayer.yPosition(), availableHeight);
+    if (backgroundRepeatY == RoundFill && positioningAreaSize.height() > 0 && fillTileSize.height() > 0) {
+        long nrTiles = std::max(1l, lroundf((float)positioningAreaSize.height() / fillTileSize.height()));
+
+        if (fillLayer.size().size.width().isAuto() && backgroundRepeatX != RoundFill) {
+            fillTileSize.setWidth(fillTileSize.width() * positioningAreaSize.height() / (nrTiles * fillTileSize.height()));
+        }
+
+        fillTileSize.setHeight(positioningAreaSize.height() / nrTiles);
+        geometry.setTileSize(fillTileSize);
+        geometry.setPhaseY(geometry.tileSize().height() ? geometry.tileSize().height() - roundToInt(computedYPosition + top) % geometry.tileSize().height() : 0);
+        geometry.setSpaceSize(IntSize());
+    }
+
+    if (backgroundRepeatX == RepeatFill) {
+        geometry.setPhaseX(geometry.tileSize().width() ? geometry.tileSize().width() - roundToInt(computedXPosition + left) % geometry.tileSize().width() : 0);
+        geometry.setSpaceSize(IntSize());
+    } else if (backgroundRepeatX == SpaceFill && fillTileSize.width() > 0) {
+        int space = getSpace(positioningAreaSize.width(), geometry.tileSize().width());
+        int actualWidth = geometry.tileSize().width() + space;
+
+        if (space >= 0) {
+            computedXPosition = roundedMinimumValueForLength(Length(), availableWidth);
+            geometry.setSpaceSize(IntSize(space, 0));
+            geometry.setPhaseX(actualWidth ? actualWidth - roundToInt(computedXPosition + left) % actualWidth : 0);
+        } else {
+            backgroundRepeatX = NoRepeatFill;
+        }
+    }
+    if (backgroundRepeatX == NoRepeatFill) {
+        int xOffset = fillLayer.backgroundXOrigin() == RightEdge ? availableWidth - computedXPosition : computedXPosition;
+        geometry.setNoRepeatX(left + xOffset);
+        geometry.setSpaceSize(IntSize(0, geometry.spaceSize().height()));
+    }
+
+    if (backgroundRepeatY == RepeatFill) {
+        geometry.setPhaseY(geometry.tileSize().height() ? geometry.tileSize().height() - roundToInt(computedYPosition + top) % geometry.tileSize().height() : 0);
+        geometry.setSpaceSize(IntSize(geometry.spaceSize().width(), 0));
+    } else if (backgroundRepeatY == SpaceFill && fillTileSize.height() > 0) {
+        int space = getSpace(positioningAreaSize.height(), geometry.tileSize().height());
+        int actualHeight = geometry.tileSize().height() + space;
+
+        if (space >= 0) {
+            computedYPosition = roundedMinimumValueForLength(Length(), availableHeight);
+            geometry.setSpaceSize(IntSize(geometry.spaceSize().width(), space));
+            geometry.setPhaseY(actualHeight ? actualHeight - roundToInt(computedYPosition + top) % actualHeight : 0);
+        } else {
+            backgroundRepeatY = NoRepeatFill;
+        }
+    }
+    if (backgroundRepeatY == NoRepeatFill) {
+        int yOffset = fillLayer.backgroundYOrigin() == BottomEdge ? availableHeight - computedYPosition : computedYPosition;
+        geometry.setNoRepeatY(top + yOffset);
+        geometry.setSpaceSize(IntSize(geometry.spaceSize().width(), 0));
+    }
+
+    if (fixedAttachment)
+        geometry.useFixedAttachment(snappedPaintRect.location());
+
+    geometry.clip(snappedPaintRect);
+    geometry.setDestOrigin(geometry.destRect().location());
+}
+
+InterpolationQuality BoxPainter::chooseInterpolationQuality(RenderBoxModelObject& obj, GraphicsContext* context, Image* image, const void* layer, const LayoutSize& size)
+{
+    return ImageQualityController::imageQualityController()->chooseInterpolationQuality(context, &obj, image, layer, size);
+}
+
+bool BoxPainter::fixedBackgroundPaintsInLocalCoordinates(const RenderObject& obj)
+{
+    if (!obj.isDocumentElement())
+        return false;
+
+    if (obj.view()->frameView() && obj.view()->frameView()->paintBehavior() & PaintBehaviorFlattenCompositingLayers)
+        return false;
+
+    RenderLayer* rootLayer = obj.view()->layer();
+    if (!rootLayer || rootLayer->compositingState() == NotComposited)
+        return false;
+
+    return rootLayer->compositedLayerMapping()->backgroundLayerPaintsFixedRootBackground();
+}
+
+static inline void applySubPixelHeuristicForTileSize(LayoutSize& tileSize, const IntSize& positioningAreaSize)
+{
+    tileSize.setWidth(positioningAreaSize.width() - tileSize.width() <= 1 ? tileSize.width().ceil() : tileSize.width().floor());
+    tileSize.setHeight(positioningAreaSize.height() - tileSize.height() <= 1 ? tileSize.height().ceil() : tileSize.height().floor());
+}
+
+IntSize BoxPainter::calculateFillTileSize(const RenderBoxModelObject& obj, const FillLayer& fillLayer, const IntSize& positioningAreaSize)
+{
+    StyleImage* image = fillLayer.image();
+    EFillSizeType type = fillLayer.size().type;
+
+    IntSize imageIntrinsicSize = obj.calculateImageIntrinsicDimensions(image, positioningAreaSize, RenderBoxModelObject::ScaleByEffectiveZoom);
+    imageIntrinsicSize.scale(1 / image->imageScaleFactor(), 1 / image->imageScaleFactor());
+    switch (type) {
+    case SizeLength: {
+        LayoutSize tileSize = positioningAreaSize;
+
+        Length layerWidth = fillLayer.size().size.width();
+        Length layerHeight = fillLayer.size().size.height();
+
+        if (layerWidth.isFixed())
+            tileSize.setWidth(layerWidth.value());
+        else if (layerWidth.isPercent())
+            tileSize.setWidth(valueForLength(layerWidth, positioningAreaSize.width()));
+
+        if (layerHeight.isFixed())
+            tileSize.setHeight(layerHeight.value());
+        else if (layerHeight.isPercent())
+            tileSize.setHeight(valueForLength(layerHeight, positioningAreaSize.height()));
+
+        applySubPixelHeuristicForTileSize(tileSize, positioningAreaSize);
+
+        // If one of the values is auto we have to use the appropriate
+        // scale to maintain our aspect ratio.
+        if (layerWidth.isAuto() && !layerHeight.isAuto()) {
+            if (imageIntrinsicSize.height())
+                tileSize.setWidth(imageIntrinsicSize.width() * tileSize.height() / imageIntrinsicSize.height());
+        } else if (!layerWidth.isAuto() && layerHeight.isAuto()) {
+            if (imageIntrinsicSize.width())
+                tileSize.setHeight(imageIntrinsicSize.height() * tileSize.width() / imageIntrinsicSize.width());
+        } else if (layerWidth.isAuto() && layerHeight.isAuto()) {
+            // If both width and height are auto, use the image's intrinsic size.
+            tileSize = imageIntrinsicSize;
+        }
+
+        tileSize.clampNegativeToZero();
+        return flooredIntSize(tileSize);
+    }
+    case SizeNone: {
+        // If both values are ‘auto’ then the intrinsic width and/or height of the image should be used, if any.
+        if (!imageIntrinsicSize.isEmpty())
+            return imageIntrinsicSize;
+
+        // If the image has neither an intrinsic width nor an intrinsic height, its size is determined as for ‘contain’.
+        type = Contain;
+    }
+    case Contain:
+    case Cover: {
+        float horizontalScaleFactor = imageIntrinsicSize.width()
+            ? static_cast<float>(positioningAreaSize.width()) / imageIntrinsicSize.width() : 1;
+        float verticalScaleFactor = imageIntrinsicSize.height()
+            ? static_cast<float>(positioningAreaSize.height()) / imageIntrinsicSize.height() : 1;
+        float scaleFactor = type == Contain ? std::min(horizontalScaleFactor, verticalScaleFactor) : std::max(horizontalScaleFactor, verticalScaleFactor);
+        return IntSize(std::max(1l, lround(imageIntrinsicSize.width() * scaleFactor)), std::max(1l, lround(imageIntrinsicSize.height() * scaleFactor)));
+    }
+    }
+
+    ASSERT_NOT_REACHED();
+    return IntSize();
+}
+
 } // namespace blink