Rewrite nine piece image painting code

Source/core/paint/NinePieceImagePainter.cpp

Index: Source/core/paint/NinePieceImagePainter.cpp
diff --git a/Source/core/paint/NinePieceImagePainter.cpp b/Source/core/paint/NinePieceImagePainter.cpp
index 2db23196689a6e3f199316f5c08b997e662e3caf..26f394f9c00775d65cad44c39f58a7599c2706f8 100644
--- a/Source/core/paint/NinePieceImagePainter.cpp
+++ b/Source/core/paint/NinePieceImagePainter.cpp
@@ -8,9 +8,10 @@
 #include "core/layout/ImageQualityController.h"
 #include "core/layout/LayoutBoxModelObject.h"
 #include "core/paint/BoxPainter.h"
+#include "core/paint/NinePieceImageGrid.h"
 #include "core/style/ComputedStyle.h"
 #include "core/style/NinePieceImage.h"
-#include "platform/LengthFunctions.h"
+#include "platform/geometry/IntSize.h"
 #include "platform/geometry/LayoutRect.h"
 #include "platform/graphics/GraphicsContext.h"
 
@@ -21,16 +22,8 @@ NinePieceImagePainter::NinePieceImagePainter(LayoutBoxModelObject& layoutObject)
 {
 }
 
-LayoutUnit NinePieceImagePainter::computeBorderImageSide(const BorderImageLength& borderSlice, LayoutUnit borderSide, LayoutUnit imageSide, LayoutUnit boxExtent)
-{
-    if (borderSlice.isNumber())
-        return borderSlice.number() * borderSide;
-    if (borderSlice.length().isAuto())
-        return imageSide;
-    return valueForLength(borderSlice.length(), boxExtent);
-}
-
-bool NinePieceImagePainter::paint(GraphicsContext* graphicsContext, const LayoutRect& rect, const ComputedStyle& style, const NinePieceImage& ninePieceImage, SkXfermode::Mode op) const
+bool NinePieceImagePainter::paint(GraphicsContext* graphicsContext, const LayoutRect& rect, const ComputedStyle& style,
+    const NinePieceImage& ninePieceImage, SkXfermode::Mode op) const
 {
     StyleImage* styleImage = ninePieceImage.image();
     if (!styleImage)
@@ -48,161 +41,40 @@ bool NinePieceImagePainter::paint(GraphicsContext* graphicsContext, const Layout
     rectWithOutsets.expand(style.imageOutsets(ninePieceImage));
     IntRect borderImageRect = pixelSnappedIntRect(rectWithOutsets);
 
-    IntSize imageSize = m_layoutObject.calculateImageIntrinsicDimensions(styleImage, borderImageRect.size(), LayoutBoxModelObject::DoNotScaleByEffectiveZoom);
+    IntSize imageSize = m_layoutObject.calculateImageIntrinsicDimensions(styleImage, borderImageRect.size(),
+        LayoutBoxModelObject::DoNotScaleByEffectiveZoom);
 
     // If both values are 'auto' then the intrinsic width and/or height of the image should be used, if any.
     styleImage->setContainerSizeForLayoutObject(&m_layoutObject, imageSize, style.effectiveZoom());
 
-    int imageWidth = imageSize.width();
-    int imageHeight = imageSize.height();
-
-    float imageScaleFactor = styleImage->imageScaleFactor();
-    int topSlice = std::min<int>(imageHeight, valueForLength(ninePieceImage.imageSlices().top(), imageHeight)) * imageScaleFactor;
-    int rightSlice = std::min<int>(imageWidth, valueForLength(ninePieceImage.imageSlices().right(), imageWidth)) * imageScaleFactor;
-    int bottomSlice = std::min<int>(imageHeight, valueForLength(ninePieceImage.imageSlices().bottom(), imageHeight)) * imageScaleFactor;
-    int leftSlice = std::min<int>(imageWidth, valueForLength(ninePieceImage.imageSlices().left(), imageWidth)) * imageScaleFactor;
-
-    ENinePieceImageRule hRule = ninePieceImage.horizontalRule();
-    ENinePieceImageRule vRule = ninePieceImage.verticalRule();
-
-    int topWidth = computeBorderImageSide(ninePieceImage.borderSlices().top(), style.borderTopWidth(), topSlice, borderImageRect.height());
-    int rightWidth = computeBorderImageSide(ninePieceImage.borderSlices().right(), style.borderRightWidth(), rightSlice, borderImageRect.width());
-    int bottomWidth = computeBorderImageSide(ninePieceImage.borderSlices().bottom(), style.borderBottomWidth(), bottomSlice, borderImageRect.height());
-    int leftWidth = computeBorderImageSide(ninePieceImage.borderSlices().left(), style.borderLeftWidth(), leftSlice, borderImageRect.width());
-
-    // Reduce the widths if they're too large.
-    // The spec says: Given Lwidth as the width of the border image area, Lheight as its height, and Wside as the border image width
-    // offset for the side, let f = min(Lwidth/(Wleft+Wright), Lheight/(Wtop+Wbottom)). If f < 1, then all W are reduced by
-    // multiplying them by f.
-    int borderSideWidth = std::max(1, leftWidth + rightWidth);
-    int borderSideHeight = std::max(1, topWidth + bottomWidth);
-    float borderSideScaleFactor = std::min((float)borderImageRect.width() / borderSideWidth, (float)borderImageRect.height() / borderSideHeight);
-    if (borderSideScaleFactor < 1) {
-        topWidth *= borderSideScaleFactor;
-        rightWidth *= borderSideScaleFactor;
-        bottomWidth *= borderSideScaleFactor;
-        leftWidth *= borderSideScaleFactor;
-    }
-
-    bool drawLeft = leftSlice > 0 && leftWidth > 0;
-    bool drawTop = topSlice > 0 && topWidth > 0;
-    bool drawRight = rightSlice > 0 && rightWidth > 0;
-    bool drawBottom = bottomSlice > 0 && bottomWidth > 0;
-    bool drawMiddle = ninePieceImage.fill() && (imageWidth - leftSlice - rightSlice) > 0 && (borderImageRect.width() - leftWidth - rightWidth) > 0
-        && (imageHeight - topSlice - bottomSlice) > 0 && (borderImageRect.height() - topWidth - bottomWidth) > 0;
+    IntRectOutsets borderWidths(style.borderTopWidth(), style.borderRightWidth(),
+        style.borderBottomWidth(), style.borderLeftWidth());
+    NinePieceImageGrid grid(ninePieceImage, imageSize, borderImageRect, borderWidths);
 
     RefPtr<Image> image = styleImage->image(&m_layoutObject, imageSize);
 
-    float destinationWidth = borderImageRect.width() - leftWidth - rightWidth;
-    float destinationHeight = borderImageRect.height() - topWidth - bottomWidth;
-
-    float sourceWidth = imageWidth - leftSlice - rightSlice;
-    float sourceHeight = imageHeight - topSlice - bottomSlice;
-
-    float leftSideScale = drawLeft ? (float)leftWidth / leftSlice : 1;
-    float rightSideScale = drawRight ? (float)rightWidth / rightSlice : 1;
-    float topSideScale = drawTop ? (float)topWidth / topSlice : 1;
-    float bottomSideScale = drawBottom ? (float)bottomWidth / bottomSlice : 1;
-
-    InterpolationQuality interpolationQuality = BoxPainter::chooseInterpolationQuality(m_layoutObject, graphicsContext, image.get(), 0, rectWithOutsets.size());
+    InterpolationQuality interpolationQuality = BoxPainter::chooseInterpolationQuality(m_layoutObject,
+        graphicsContext, image.get(), 0, rectWithOutsets.size());
     InterpolationQuality previousInterpolationQuality = graphicsContext->imageInterpolationQuality();
     graphicsContext->setImageInterpolationQuality(interpolationQuality);
 
-    TRACE_EVENT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "PaintImage", "data", InspectorPaintImageEvent::data(m_layoutObject, *styleImage));
-    if (drawLeft) {
-        // Paint the top and bottom left corners.
-
-        // The top left corner rect is (tx, ty, leftWidth, topWidth)
-        // The rect to use from within the image is obtained from our slice, and is (0, 0, leftSlice, topSlice)
-        if (drawTop) {
-            graphicsContext->drawImage(image.get(), IntRect(borderImageRect.location(), IntSize(leftWidth, topWidth)),
-                LayoutRect(0, 0, leftSlice, topSlice), op);
-        }
+    TRACE_EVENT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "PaintImage", "data",
+        InspectorPaintImageEvent::data(m_layoutObject, *styleImage));
 
-        // The bottom left corner rect is (tx, ty + h - bottomWidth, leftWidth, bottomWidth)
-        // The rect to use from within the image is (0, imageHeight - bottomSlice, leftSlice, botomSlice)
-        if (drawBottom) {
-            graphicsContext->drawImage(image.get(), IntRect(borderImageRect.x(), borderImageRect.maxY() - bottomWidth, leftWidth, bottomWidth),
-                LayoutRect(0, imageHeight - bottomSlice, leftSlice, bottomSlice), op);
-        }
+    for (NinePiece piece = MinPiece; piece < MaxPiece; ++piece) {
+        NinePieceImageGrid::NinePieceDrawInfo drawInfo = grid.getNinePieceDrawInfo(piece);
 
-        // Paint the left edge.
-        // Have to scale and tile into the border rect.
-        if (sourceHeight > 0) {
-            graphicsContext->drawTiledImage(image.get(), IntRect(borderImageRect.x(), borderImageRect.y() + topWidth, leftWidth, destinationHeight),
-                IntRect(0, topSlice, leftSlice, sourceHeight), FloatSize(leftSideScale, leftSideScale), Image::StretchTile, (Image::TileRule)vRule, op);
+        if (drawInfo.isDrawable) {
+            if (drawInfo.isCornerPiece) {
+                graphicsContext->drawImage(image.get(), drawInfo.destination, drawInfo.source, op);
+            } else {
+                graphicsContext->drawTiledImage(image.get(), enclosingIntRect(drawInfo.destination),
+                    enclosingIntRect(drawInfo.source), drawInfo.tileScale, drawInfo.tileRule.horizontal,
+                    drawInfo.tileRule.vertical, op);
+            }
         }
     }
 
-    if (drawRight) {
-        // Paint the top and bottom right corners
-        // The top right corner rect is (tx + w - rightWidth, ty, rightWidth, topWidth)
-        // The rect to use from within the image is obtained from our slice, and is (imageWidth - rightSlice, 0, rightSlice, topSlice)
-        if (drawTop) {
-            graphicsContext->drawImage(image.get(), IntRect(borderImageRect.maxX() - rightWidth, borderImageRect.y(), rightWidth, topWidth),
-                LayoutRect(imageWidth - rightSlice, 0, rightSlice, topSlice), op);
-        }
-
-        // The bottom right corner rect is (tx + w - rightWidth, ty + h - bottomWidth, rightWidth, bottomWidth)
-        // The rect to use from within the image is (imageWidth - rightSlice, imageHeight - bottomSlice, rightSlice, bottomSlice)
-        if (drawBottom) {
-            graphicsContext->drawImage(image.get(), IntRect(borderImageRect.maxX() - rightWidth, borderImageRect.maxY() - bottomWidth, rightWidth, bottomWidth),
-                LayoutRect(imageWidth - rightSlice, imageHeight - bottomSlice, rightSlice, bottomSlice), op);
-        }
-
-        // Paint the right edge.
-        if (sourceHeight > 0) {
-            graphicsContext->drawTiledImage(image.get(), IntRect(borderImageRect.maxX() - rightWidth, borderImageRect.y() + topWidth, rightWidth,
-                destinationHeight),
-                IntRect(imageWidth - rightSlice, topSlice, rightSlice, sourceHeight),
-                FloatSize(rightSideScale, rightSideScale),
-                Image::StretchTile, (Image::TileRule)vRule, op);
-        }
-    }
-
-    // Paint the top edge.
-    if (drawTop && sourceWidth > 0) {
-        graphicsContext->drawTiledImage(image.get(), IntRect(borderImageRect.x() + leftWidth, borderImageRect.y(), destinationWidth, topWidth),
-            IntRect(leftSlice, 0, sourceWidth, topSlice),
-            FloatSize(topSideScale, topSideScale), (Image::TileRule)hRule, Image::StretchTile, op);
-    }
-
-    // Paint the bottom edge.
-    if (drawBottom && sourceWidth > 0) {
-        graphicsContext->drawTiledImage(image.get(), IntRect(borderImageRect.x() + leftWidth, borderImageRect.maxY() - bottomWidth,
-            destinationWidth, bottomWidth),
-            IntRect(leftSlice, imageHeight - bottomSlice, sourceWidth, bottomSlice),
-            FloatSize(bottomSideScale, bottomSideScale),
-            (Image::TileRule)hRule, Image::StretchTile, op);
-    }
-
-    // Paint the middle.
-    if (drawMiddle) {
-        FloatSize middleScaleFactor(1, 1);
-        if (drawTop)
-            middleScaleFactor.setWidth(topSideScale);
-        else if (drawBottom)
-            middleScaleFactor.setWidth(bottomSideScale);
-        if (drawLeft)
-            middleScaleFactor.setHeight(leftSideScale);
-        else if (drawRight)
-            middleScaleFactor.setHeight(rightSideScale);
-
-        // For "stretch" rules, just override the scale factor and replace. We only had to do this for the
-        // center tile, since sides don't even use the scale factor unless they have a rule other than "stretch".
-        // The middle however can have "stretch" specified in one axis but not the other, so we have to
-        // correct the scale here.
-        if (hRule == StretchImageRule)
-            middleScaleFactor.setWidth(destinationWidth / sourceWidth);
-
-        if (vRule == StretchImageRule)
-            middleScaleFactor.setHeight(destinationHeight / sourceHeight);
-
-        graphicsContext->drawTiledImage(image.get(),
-            IntRect(borderImageRect.x() + leftWidth, borderImageRect.y() + topWidth, destinationWidth, destinationHeight),
-            IntRect(leftSlice, topSlice, sourceWidth, sourceHeight),
-            middleScaleFactor, (Image::TileRule)hRule, (Image::TileRule)vRule, op);
-    }
     graphicsContext->setImageInterpolationQuality(previousInterpolationQuality);
     return true;
 }