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Unified Diff: Source/core/html/HTMLImageFallbackHelper.cpp

Issue 481753002: Use Shadow DOM to display fallback content for images (Closed) Base URL: svn://svn.chromium.org/blink/trunk
Patch Set: Updated Created 6 years ago
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Index: Source/core/html/HTMLImageFallbackHelper.cpp
diff --git a/Source/core/html/HTMLImageFallbackHelper.cpp b/Source/core/html/HTMLImageFallbackHelper.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..b487c2854ef1cc5f9b936f831e371bc51d2a4008
--- /dev/null
+++ b/Source/core/html/HTMLImageFallbackHelper.cpp
@@ -0,0 +1,112 @@
+// 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 "config.h"
+#include "core/html/HTMLImageFallbackHelper.h"
+
+#include "core/HTMLNames.h"
+#include "core/InputTypeNames.h"
+#include "core/dom/ElementRareData.h"
+#include "core/dom/Text.h"
+#include "core/dom/shadow/ShadowRoot.h"
+#include "core/fetch/ImageResource.h"
+#include "core/html/FormDataList.h"
+#include "core/html/HTMLDivElement.h"
+#include "core/html/HTMLElement.h"
+#include "core/html/HTMLImageElement.h"
+#include "core/html/HTMLImageLoader.h"
+#include "core/html/HTMLInputElement.h"
+#include "core/html/HTMLStyleElement.h"
+#include "wtf/PassOwnPtr.h"
+#include "wtf/text/StringBuilder.h"
+
+namespace blink {
+
+using namespace HTMLNames;
+
+static bool noImageSourceSpecified(const Element& element)
+{
+ bool noSrcSpecified = !element.hasAttribute(srcAttr) || element.getAttribute(srcAttr).isNull() || element.getAttribute(srcAttr).isEmpty();
+ bool noSrcsetSpecified = !element.hasAttribute(srcsetAttr) || element.getAttribute(srcsetAttr).isNull() || element.getAttribute(srcsetAttr).isEmpty();
+ return noSrcSpecified && noSrcsetSpecified;
+}
+
+void HTMLImageFallbackHelper::createAltTextShadowTree(Element& element)
+{
+ ShadowRoot& root = element.ensureUserAgentShadowRoot();
+
+ RefPtrWillBeRawPtr<HTMLDivElement> container = HTMLDivElement::create(element.document());
+ root.appendChild(container);
+ container->setAttribute(idAttr, AtomicString("alttext-container", AtomicString::ConstructFromLiteral));
+ container->setInlineStyleProperty(CSSPropertyOverflow, CSSValueHidden);
+ container->setInlineStyleProperty(CSSPropertyBorderWidth, 1, CSSPrimitiveValue::CSS_PX);
+ container->setInlineStyleProperty(CSSPropertyBorderStyle, CSSValueSolid);
+ container->setInlineStyleProperty(CSSPropertyBorderColor, CSSValueSilver);
+ container->setInlineStyleProperty(CSSPropertyDisplay, CSSValueInlineBlock);
+ container->setInlineStyleProperty(CSSPropertyBoxSizing, CSSValueBorderBox);
+ container->setInlineStyleProperty(CSSPropertyPadding, 1, CSSPrimitiveValue::CSS_PX);
+
+ RefPtrWillBeRawPtr<HTMLImageElement> brokenImage = HTMLImageElement::create(element.document());
+ container->appendChild(brokenImage);
+ brokenImage->setIsFallbackImage();
+ brokenImage->setAttribute(idAttr, AtomicString("alttext-image", AtomicString::ConstructFromLiteral));
+ brokenImage->setAttribute(widthAttr, AtomicString("16", AtomicString::ConstructFromLiteral));
+ brokenImage->setAttribute(heightAttr, AtomicString("16", AtomicString::ConstructFromLiteral));
+ brokenImage->setAttribute(alignAttr, AtomicString("left", AtomicString::ConstructFromLiteral));
+ brokenImage->setInlineStyleProperty(CSSPropertyMargin, 0, CSSPrimitiveValue::CSS_PX);
+
+ RefPtrWillBeRawPtr<HTMLDivElement> altText = HTMLDivElement::create(element.document());
+ container->appendChild(altText);
+ altText->setInlineStyleProperty(CSSPropertyOverflow, CSSValueHidden);
+ altText->setInlineStyleProperty(CSSPropertyDisplay, CSSValueBlock);
+
+ RefPtrWillBeRawPtr<Text> text = Text::create(element.document(), toHTMLElement(element).altText());
+ altText->appendChild(text);
+}
+
+PassRefPtr<RenderStyle> HTMLImageFallbackHelper::customStyleForAltText(Element& element, PassRefPtr<RenderStyle> newStyle)
+{
+ // If we have an author shadow root or have not created the UA shadow root yet, bail early. We can't
+ // use ensureUserAgentShadowRoot() here because that would alter the DOM tree during style recalc.
+ if (element.shadowRoot() || !element.userAgentShadowRoot())
+ return newStyle;
+
+ Element* placeHolder = element.userAgentShadowRoot()->getElementById("alttext-container");
+ Element* brokenImage = element.userAgentShadowRoot()->getElementById("alttext-image");
+
+ if (element.document().inQuirksMode()) {
+ // Mimic the behaviour of the image host by setting symmetric dimensions if only one dimension is specified.
+ if (newStyle->width().isSpecifiedOrIntrinsic() && newStyle->height().isAuto())
+ newStyle->setHeight(newStyle->width());
+ else if (newStyle->height().isSpecifiedOrIntrinsic() && newStyle->width().isAuto())
+ newStyle->setWidth(newStyle->height());
+ if (newStyle->width().isSpecifiedOrIntrinsic() && newStyle->height().isSpecifiedOrIntrinsic()) {
+ placeHolder->setInlineStyleProperty(CSSPropertyVerticalAlign, CSSValueBaseline);
+ }
+ }
+
+ // If the image has specified dimensions allow the alt-text container expand to fill them.
+ if (newStyle->width().isSpecifiedOrIntrinsic() && newStyle->height().isSpecifiedOrIntrinsic()) {
+ placeHolder->setInlineStyleProperty(CSSPropertyWidth, 100, CSSPrimitiveValue::CSS_PERCENTAGE);
+ placeHolder->setInlineStyleProperty(CSSPropertyHeight, 100, CSSPrimitiveValue::CSS_PERCENTAGE);
+ }
+
+ // Make sure the broken image icon appears on the appropriate side of the image for the element's writing direction.
+ brokenImage->setInlineStyleProperty(CSSPropertyFloat, AtomicString(newStyle->direction() == LTR ? "left" : "right"));
+
+ // This is an <img> with no attributes, so don't display anything.
+ if (noImageSourceSpecified(element) && !newStyle->width().isSpecifiedOrIntrinsic() && !newStyle->height().isSpecifiedOrIntrinsic() && toHTMLElement(element).altText().isEmpty())
+ newStyle->setDisplay(NONE);
+
+ // This preserves legacy behaviour originally defined when alt-text was managed by RenderImage.
+ if (noImageSourceSpecified(element))
+ brokenImage->setInlineStyleProperty(CSSPropertyDisplay, CSSValueNone);
+ else
+ brokenImage->setInlineStyleProperty(CSSPropertyDisplay, CSSValueInline);
+
+ return newStyle;
+}
+
+} // namespace blink
+

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