Get rid of background-clip:text and PaintBehaviorForceBlackText.

http://blog.ericzhang.com/punch-through-text-masks-with-css-and-html5/
shows that you can achieve the similar effects using canvas. This
doesn't need to be built into the core engine. It's OK for this
to require more than a line of CSS to achieve.

Unfortunately, the test included this this patch doesn't actually
show that I didn't break anything because background-image
is broken. I got the test from
47e0d126e8%5E%21/#F4

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/756183004

engine/core/css/CSSPrimitiveValueMappings.h

@@ -348,9 +348,6 @@ template<> inline CSSPrimitiveValue::CSSPrimitiveValue(EFillBox e)
     case ContentFillBox:
         m_value.valueID = CSSValueContentBox;
         break;
-    case TextFillBox:
-        m_value.valueID = CSSValueText;
-        break;
     }
 }
 
@@ -367,8 +364,6 @@ template<> inline CSSPrimitiveValue::operator EFillBox() const
     case CSSValueContent:
     case CSSValueContentBox:
         return ContentFillBox;
-    case CSSValueText:
-        return TextFillBox;
     default:
         break;
     }

engine/core/rendering/EllipsisBox.cpp

@@ -53,7 +53,7 @@ void EllipsisBox::paint(PaintInfo& paintInfo, const LayoutPoint& paintOffset, La
         paintSelection(context, boxOrigin, style, font);
 
         // Select the correct color for painting the text.
-        Color foreground = paintInfo.forceBlackText() ? Color::black : renderer().selectionForegroundColor();
+        Color foreground = renderer().selectionForegroundColor();
         if (foreground != styleTextColor)
             context->setFillColor(foreground);
     }

engine/core/rendering/InlineTextBox.cpp

@@ -309,13 +309,6 @@ float InlineTextBox::placeEllipsisBox(bool flowIsLTR, float visibleLeftEdge, flo
     return -1;
 }
 
-static Color textColorForWhiteBackground(Color textColor)
-{
-    int distanceFromWhite = differenceSquared(textColor, Color::white);
-    // semi-arbitrarily chose 65025 (255^2) value here after a few tests;
-    return distanceFromWhite > 65025 ? textColor : textColor.dark();
-}
-
 bool InlineTextBox::isLineBreak() const
 {
     return renderer().style()->preserveNewline() && len() == 1 && (*renderer().text().impl())[start()] == '\n';
@@ -366,44 +359,24 @@ struct TextPaintingStyle {
     bool operator!=(const TextPaintingStyle& other) { return !(*this == other); }
 };
 
-TextPaintingStyle textPaintingStyle(RenderText& renderer, RenderStyle* style, bool forceBlackText)
+TextPaintingStyle textPaintingStyle(RenderText& renderer, RenderStyle* style)
 {
     TextPaintingStyle textStyle;
-
-    if (forceBlackText) {
-        textStyle.fillColor = Color::black;
-        textStyle.strokeColor = Color::black;
-        textStyle.emphasisMarkColor = Color::black;
-        textStyle.strokeWidth = style->textStrokeWidth();
-        textStyle.shadow = 0;
-    } else {
-        textStyle.fillColor = renderer.resolveColor(style, CSSPropertyWebkitTextFillColor);
-        textStyle.strokeColor = renderer.resolveColor(style, CSSPropertyWebkitTextStrokeColor);
-        textStyle.emphasisMarkColor = renderer.resolveColor(style, CSSPropertyWebkitTextEmphasisColor);
-        textStyle.strokeWidth = style->textStrokeWidth();
-        textStyle.shadow = style->textShadow();
-
-        // Adjust text color when printing with a white background.
-        bool forceBackgroundToWhite = false;
-        if (forceBackgroundToWhite) {
-            textStyle.fillColor = textColorForWhiteBackground(textStyle.fillColor);
-            textStyle.strokeColor = textColorForWhiteBackground(textStyle.strokeColor);
-            textStyle.emphasisMarkColor = textColorForWhiteBackground(textStyle.emphasisMarkColor);
-        }
-    }
-
+    textStyle.fillColor = renderer.resolveColor(style, CSSPropertyWebkitTextFillColor);
+    textStyle.strokeColor = renderer.resolveColor(style, CSSPropertyWebkitTextStrokeColor);
+    textStyle.emphasisMarkColor = renderer.resolveColor(style, CSSPropertyWebkitTextEmphasisColor);
+    textStyle.strokeWidth = style->textStrokeWidth();
+    textStyle.shadow = style->textShadow();
     return textStyle;
 }
 
-TextPaintingStyle selectionPaintingStyle(RenderText& renderer, bool haveSelection, bool forceBlackText, const TextPaintingStyle& textStyle)
+TextPaintingStyle selectionPaintingStyle(RenderText& renderer, bool haveSelection, const TextPaintingStyle& textStyle)
 {
     TextPaintingStyle selectionStyle = textStyle;
 
     if (haveSelection) {
-        if (!forceBlackText) {
-            selectionStyle.fillColor = renderer.selectionForegroundColor();
-            selectionStyle.emphasisMarkColor = renderer.selectionEmphasisMarkColor();
-        }
+        selectionStyle.fillColor = renderer.selectionForegroundColor();
+        selectionStyle.emphasisMarkColor = renderer.selectionEmphasisMarkColor();
     }
 
     return selectionStyle;
@@ -564,8 +537,8 @@ void InlineTextBox::paint(PaintInfo& paintInfo, const LayoutPoint& paintOffset,
     bool useCustomUnderlines = containsComposition && renderer().frame()->inputMethodController().compositionUsesCustomUnderlines();
 
     // Determine text colors.
-    TextPaintingStyle textStyle = textPaintingStyle(renderer(), styleToUse, paintInfo.forceBlackText());
-    TextPaintingStyle selectionStyle = selectionPaintingStyle(renderer(), haveSelection, paintInfo.forceBlackText(), textStyle);
+    TextPaintingStyle textStyle = textPaintingStyle(renderer(), styleToUse);
+    TextPaintingStyle selectionStyle = selectionPaintingStyle(renderer(), haveSelection, textStyle);
     bool paintSelectedTextOnly = (paintInfo.phase == PaintPhaseSelection);
     bool paintSelectedTextSeparately = !paintSelectedTextOnly && textStyle != selectionStyle;
 

engine/core/rendering/PaintInfo.h

@@ -76,8 +76,6 @@ struct PaintInfo {
         return !paintingRoot || paintingRoot == renderer;
     }
 
-    bool forceBlackText() const { return paintBehavior & PaintBehaviorForceBlackText; }
-
     void applyTransform(const AffineTransform& localToAncestorTransform, bool identityStatusUnknown = true)
     {
         if (identityStatusUnknown && localToAncestorTransform.isIdentity())

engine/core/rendering/PaintPhase.h

@@ -51,9 +51,9 @@ enum PaintPhase {
     PaintPhaseClippingMask,
 };
 
+// FIXME(sky): Remove this enum now that it's unused.
 enum PaintBehaviorFlags {
     PaintBehaviorNormal = 0,
-    PaintBehaviorForceBlackText = 1 << 0,
 };
 
 typedef unsigned PaintBehavior;

engine/core/rendering/RenderBoxModelObject.cpp

@@ -480,20 +480,6 @@ void RenderBoxModelObject::paintFillLayerExtended(const PaintInfo& paintInfo, co
 
         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:
@@ -544,30 +530,6 @@ void RenderBoxModelObject::paintFillLayerExtended(const PaintInfo& paintInfo, co
             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 = isBox() ? toRenderBox(this)->locationOffset() : LayoutSize();
-            paint(info, scrolledPaintRect.location() - localOffset);
-        }
-
-        context->endLayer();
-        context->endLayer();
-    }
 }
 
 static inline int resolveWidthForRatio(int height, const FloatSize& intrinsicRatio)

engine/core/rendering/RenderLayer.cpp

@@ -1109,8 +1109,6 @@ void RenderLayer::paintLayerContents(GraphicsContext* context, const LayerPainti
     if (localPaintingInfo.paintingRoot && !renderer()->isDescendantOf(localPaintingInfo.paintingRoot))
         paintingRootForRenderer = localPaintingInfo.paintingRoot;
 
-    ASSERT(!(localPaintingInfo.paintBehavior & PaintBehaviorForceBlackText));
-
     // FIXME(sky): Get rid of PaintBehavior argument now that it's always Normal.
     PaintBehavior paintBehavior = PaintBehaviorNormal;
 

engine/core/rendering/RenderView.cpp

@@ -241,9 +241,6 @@ static inline bool rendererObscuresBackground(RenderBox* rootBox)
         || style->hasTransform())
         return false;
 
-    if (rootBox->style()->backgroundClip() == TextFillBox)
-        return false;
-
     return true;
 }
 

engine/core/rendering/style/FillLayer.cpp

@@ -312,9 +312,7 @@ static EFillBox clipMax(EFillBox clipA, EFillBox clipB)
         return BorderFillBox;
     if (clipA == PaddingFillBox || clipB == PaddingFillBox)
         return PaddingFillBox;
-    if (clipA == ContentFillBox || clipB == ContentFillBox)
-        return ContentFillBox;
-    return TextFillBox;
+    return ContentFillBox;
 }
 
 void FillLayer::computeClipMax() const

engine/core/rendering/style/RenderStyleConstants.h

@@ -95,7 +95,7 @@ enum EFillAttachment {
 };
 
 enum EFillBox {
-    BorderFillBox, PaddingFillBox, ContentFillBox, TextFillBox
+    BorderFillBox, PaddingFillBox, ContentFillBox
 };
 
 enum EFillRepeat {

engine/platform/graphics/Color.cpp

@@ -167,14 +167,6 @@ bool Color::parseHexColor(const String& name, RGBA32& rgb)
     return parseHexColor(name.characters16(), name.length(), rgb);
 }
 
-int differenceSquared(const Color& c1, const Color& c2)
-{
-    int dR = c1.red() - c2.red();
-    int dG = c1.green() - c2.green();
-    int dB = c1.blue() - c2.blue();
-    return dR * dR + dG * dG + dB * dB;
-}
-
 bool Color::setFromString(const String& name)
 {
     if (name[0] != '#')

engine/platform/graphics/Color.h

@@ -45,8 +45,6 @@ PLATFORM_EXPORT RGBA32 makeRGBA32FromFloats(float r, float g, float b, float a);
 PLATFORM_EXPORT RGBA32 makeRGBAFromHSLA(double h, double s, double l, double a);
 PLATFORM_EXPORT RGBA32 makeRGBAFromCMYKA(float c, float m, float y, float k, float a);
 
-PLATFORM_EXPORT int differenceSquared(const Color&, const Color&);
-
 inline int redChannel(RGBA32 color) { return (color >> 16) & 0xFF; }
 inline int greenChannel(RGBA32 color) { return (color >> 8) & 0xFF; }
 inline int blueChannel(RGBA32 color) { return color & 0xFF; }

tests/clipping/background-opaque-clipped-gradients-expected.txt

@@ -0,0 +1,10 @@
+layer at (0,0) size 800x600
+  RenderView {#document} at (0,0) size 800x600
+layer at (0,0) size 800x238
+  RenderBlock {sky} at (0,0) size 800x238
+    RenderBlock (anonymous) at (0,0) size 800x38
+      RenderText {#text} at (0,0) size 778x38
+        text run at (0,0) width 778: "Test passes if the image below shows nested green, blue and yellow squares with a dotted black"
+        text run at (0,19) width 59: "border."
+    RenderBlock {div} at (0,38) size 200x200 [border: (25px dotted #000000)]
+

tests/clipping/background-opaque-clipped-gradients.sky

@@ -0,0 +1,17 @@
+<sky>
+<import src="../resources/dump-as-render-tree.sky" />
+<style>
+div {
+    width: 100px;
+    height: 100px;
+    padding: 25px;
+    border: 25px dotted;
+    /* TODO(ojan): background-image appears to be broken. */
+    background-image: linear-gradient(top, yellow, yellow), linear-gradient(top, blue, blue), -linear-gradient(top, green, green);
+    background-clip: content-box, padding-box, border-box;
+}
+</style>
+<!-- TODO(ojan): Make this a reftest once we support them. -->
+Test passes if the image below shows nested green, blue and yellow squares with a dotted black border.
+<div></div>
+</sky>