Use Shadow DOM to display fallback content for images

Source/core/rendering/RenderImage.cpp

Index: Source/core/rendering/RenderImage.cpp
diff --git a/Source/core/rendering/RenderImage.cpp b/Source/core/rendering/RenderImage.cpp
index 7fed328e648c9ddda67dd5ab8124dc25c2aa5f40..f48e2dc284d6ddb9bdb9a2bce285ad354e26bfb9 100644
--- a/Source/core/rendering/RenderImage.cpp
+++ b/Source/core/rendering/RenderImage.cpp
@@ -63,7 +63,6 @@ RenderImage::RenderImage(Element* element)
     , m_isGeneratedContent(false)
     , m_imageDevicePixelRatio(1.0f)
 {
-    updateAltText();
     ResourceLoadPriorityOptimizer::resourceLoadPriorityOptimizer()->addRenderObject(this);
 }
 
@@ -92,62 +91,6 @@ void RenderImage::setImageResource(PassOwnPtr<RenderImageResource> imageResource
     m_imageResource->initialize(this);
 }
 
-// If we'll be displaying either alt text or an image, add some padding.
-static const unsigned short paddingWidth = 4;
-static const unsigned short paddingHeight = 4;
-
-// Alt text is restricted to this maximum size, in pixels.  These are
-// signed integers because they are compared with other signed values.
-static const float maxAltTextWidth = 1024;
-static const int maxAltTextHeight = 256;
-
-IntSize RenderImage::imageSizeForError(ImageResource* newImage) const
-{
-    ASSERT_ARG(newImage, newImage);
-    ASSERT_ARG(newImage, newImage->imageForRenderer(this));
-
-    IntSize imageSize;
-    if (newImage->willPaintBrokenImage()) {
-        float deviceScaleFactor = blink::deviceScaleFactor(frame());
-        pair<Image*, float> brokenImageAndImageScaleFactor = ImageResource::brokenImage(deviceScaleFactor);
-        imageSize = brokenImageAndImageScaleFactor.first->size();
-        imageSize.scale(1 / brokenImageAndImageScaleFactor.second);
-    } else
-        imageSize = newImage->imageForRenderer(this)->size();
-
-    // imageSize() returns 0 for the error image. We need the true size of the
-    // error image, so we have to get it by grabbing image() directly.
-    return IntSize(paddingWidth + imageSize.width() * style()->effectiveZoom(), paddingHeight + imageSize.height() * style()->effectiveZoom());
-}
-
-// Sets the image height and width to fit the alt text.  Returns true if the
-// image size changed.
-bool RenderImage::setImageSizeForAltText(ImageResource* newImage /* = 0 */)
-{
-    IntSize imageSize;
-    if (newImage && newImage->imageForRenderer(this))
-        imageSize = imageSizeForError(newImage);
-    else if (!m_altText.isEmpty() || newImage) {
-        // If we'll be displaying either text or an image, add a little padding.
-        imageSize = IntSize(paddingWidth, paddingHeight);
-    }
-
-    // we have an alt and the user meant it (its not a text we invented)
-    if (!m_altText.isEmpty()) {
-        FontCachePurgePreventer fontCachePurgePreventer;
-
-        const Font& font = style()->font();
-        IntSize paddedTextSize(paddingWidth + std::min(ceilf(font.width(constructTextRun(this, font, m_altText, style()))), maxAltTextWidth), paddingHeight + std::min(font.fontMetrics().height(), maxAltTextHeight));
-        imageSize = imageSize.expandedTo(paddedTextSize);
-    }
-
-    if (imageSize == intrinsicSize())
-        return false;
-
-    setIntrinsicSize(imageSize);
-    return true;
-}
-
 void RenderImage::imageChanged(WrappedImagePtr newImage, const IntRect* rect)
 {
     if (documentBeingDestroyed())
@@ -173,13 +116,7 @@ void RenderImage::imageChanged(WrappedImagePtr newImage, const IntRect* rect)
         m_didIncrementVisuallyNonEmptyPixelCount = true;
     }
 
-    bool imageSizeChanged = false;
-
-    // Set image dimensions, taking into account the size of the alt text.
-    if (m_imageResource->errorOccurred() || !newImage)
-        imageSizeChanged = setImageSizeForAltText(m_imageResource->cachedImage());
-
-    paintInvalidationOrMarkForLayout(imageSizeChanged, rect);
+    repaintOrMarkForLayout(rect);
 }
 
 void RenderImage::updateIntrinsicSizeIfNeeded(const LayoutSize& newSize)
@@ -198,7 +135,7 @@ void RenderImage::updateInnerContentRect()
         m_imageResource->setContainerSizeForRenderer(containerSize);
 }
 
-void RenderImage::paintInvalidationOrMarkForLayout(bool imageSizeChangedToAccomodateAltText, const IntRect* rect)
+void RenderImage::repaintOrMarkForLayout(const IntRect* rect)
 {
     LayoutSize oldIntrinsicSize = intrinsicSize();
     LayoutSize newIntrinsicSize = m_imageResource->intrinsicSize(style()->effectiveZoom());
@@ -211,7 +148,7 @@ void RenderImage::paintInvalidationOrMarkForLayout(bool imageSizeChangedToAccomo
     if (!containingBlock())
         return;
 
-    bool imageSourceHasChangedSize = oldIntrinsicSize != newIntrinsicSize || imageSizeChangedToAccomodateAltText;
+    bool imageSourceHasChangedSize = oldIntrinsicSize != newIntrinsicSize;
     if (imageSourceHasChangedSize)
         setPreferredLogicalWidthsDirty();
 
@@ -283,79 +220,16 @@ void RenderImage::paintReplaced(PaintInfo& paintInfo, const LayoutPoint& paintOf
     LayoutUnit cHeight = contentHeight();
 
     GraphicsContext* context = paintInfo.context;
-
-    if (!m_imageResource->hasImage() || m_imageResource->errorOccurred()) {
+    if (!m_imageResource->hasImage()) {
         if (paintInfo.phase == PaintPhaseSelection)
             return;
 
         if (cWidth > 2 && cHeight > 2) {
-            const int borderWidth = 1;
-
-            LayoutUnit leftBorder = borderLeft();
-            LayoutUnit topBorder = borderTop();
-            LayoutUnit leftPad = paddingLeft();
-            LayoutUnit topPad = paddingTop();
-
             // Draw an outline rect where the image should be.
             context->setStrokeStyle(SolidStroke);
             context->setStrokeColor(Color::lightGray);
             context->setFillColor(Color::transparent);
-            context->drawRect(pixelSnappedIntRect(LayoutRect(paintOffset.x() + leftBorder + leftPad, paintOffset.y() + topBorder + topPad, cWidth, cHeight)));
-
-            bool errorPictureDrawn = false;
-            LayoutSize imageOffset;
-            // When calculating the usable dimensions, exclude the pixels of
-            // the ouline rect so the error image/alt text doesn't draw on it.
-            LayoutUnit usableWidth = cWidth - 2 * borderWidth;
-            LayoutUnit usableHeight = cHeight - 2 * borderWidth;
-
-            RefPtr<Image> image = m_imageResource->image();
-
-            if (m_imageResource->errorOccurred() && !image->isNull() && usableWidth >= image->width() && usableHeight >= image->height()) {
-                float deviceScaleFactor = blink::deviceScaleFactor(frame());
-                // Call brokenImage() explicitly to ensure we get the broken image icon at the appropriate resolution.
-                pair<Image*, float> brokenImageAndImageScaleFactor = ImageResource::brokenImage(deviceScaleFactor);
-                image = brokenImageAndImageScaleFactor.first;
-                IntSize imageSize = image->size();
-                imageSize.scale(1 / brokenImageAndImageScaleFactor.second);
-                // Center the error image, accounting for border and padding.
-                LayoutUnit centerX = (usableWidth - imageSize.width()) / 2;
-                if (centerX < 0)
-                    centerX = 0;
-                LayoutUnit centerY = (usableHeight - imageSize.height()) / 2;
-                if (centerY < 0)
-                    centerY = 0;
-                imageOffset = LayoutSize(leftBorder + leftPad + centerX + borderWidth, topBorder + topPad + centerY + borderWidth);
-                context->drawImage(image.get(), pixelSnappedIntRect(LayoutRect(paintOffset + imageOffset, imageSize)), CompositeSourceOver, shouldRespectImageOrientation());
-                errorPictureDrawn = true;
-            }
-
-            if (!m_altText.isEmpty()) {
-                const Font& font = style()->font();
-                const FontMetrics& fontMetrics = font.fontMetrics();
-                LayoutUnit ascent = fontMetrics.ascent();
-                LayoutPoint textRectOrigin = paintOffset;
-                textRectOrigin.move(leftBorder + leftPad + (paddingWidth / 2) - borderWidth, topBorder + topPad + (paddingHeight / 2) - borderWidth);
-                LayoutPoint textOrigin(textRectOrigin.x(), textRectOrigin.y() + ascent);
-
-                // Only draw the alt text if it'll fit within the content box,
-                // and only if it fits above the error image.
-                TextRun textRun = constructTextRun(this, font, m_altText, style(), TextRun::AllowTrailingExpansion | TextRun::ForbidLeadingExpansion, DefaultTextRunFlags | RespectDirection);
-                float textWidth = font.width(textRun);
-                TextRunPaintInfo textRunPaintInfo(textRun);
-                textRunPaintInfo.bounds = FloatRect(textRectOrigin, FloatSize(textWidth, fontMetrics.height()));
-                context->setFillColor(resolveColor(CSSPropertyColor));
-                if (textRun.direction() == RTL) {
-                    int availableWidth = cWidth - static_cast<int>(paddingWidth);
-                    textOrigin.move(availableWidth - ceilf(textWidth), 0);
-                }
-                if (errorPictureDrawn) {
-                    if (usableWidth >= textWidth && fontMetrics.height() <= imageOffset.height())
-                        context->drawBidiText(font, textRunPaintInfo, textOrigin);
-                } else if (usableWidth >= textWidth && usableHeight >= fontMetrics.height()) {
-                    context->drawBidiText(font, textRunPaintInfo, textOrigin);
-                }
-            }
+            context->drawRect(pixelSnappedIntRect(LayoutRect(paintOffset.x() + borderLeft() + paddingLeft(), paintOffset.y() + borderTop() + paddingTop(), cWidth, cHeight)));
         }
     } else if (m_imageResource->hasImage() && cWidth > 0 && cHeight > 0) {
         LayoutRect contentRect = contentBoxRect();
@@ -434,7 +308,7 @@ void RenderImage::areaElementFocusChanged(HTMLAreaElement* areaElement)
     paintInvalidationRect.moveBy(-absoluteContentBox().location());
     paintInvalidationRect.inflate(outlineWidth);
 
-    paintInvalidationOrMarkForLayout(false, &paintInvalidationRect);
+    repaintOrMarkForLayout(&paintInvalidationRect);
 }
 
 void RenderImage::paintIntoRect(GraphicsContext* context, const LayoutRect& rect)
@@ -542,17 +416,6 @@ bool RenderImage::nodeAtPoint(const HitTestRequest& request, HitTestResult& resu
     return inside;
 }
 
-void RenderImage::updateAltText()
-{
-    if (!node())
-        return;
-
-    if (isHTMLInputElement(*node()))
-        m_altText = toHTMLInputElement(node())->altText();
-    else if (isHTMLImageElement(*node()))
-        m_altText = toHTMLImageElement(node())->altText();
-}
-
 void RenderImage::layout()
 {
     LayoutRect oldContentRect = replacedContentRect();