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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "CssAltContent.h"
#include "DocAccessible-inl.h"
#include "mozilla/a11y/DocManager.h"
#include "mozilla/dom/Document.h"
#include "mozilla/dom/Element.h"
#include "nsCoreUtils.h"
#include "nsIContent.h"
#include "nsIFrame.h"
#include "nsLayoutUtils.h"
#include "nsNameSpaceManager.h"
namespace mozilla::a11y {
CssAltContent::CssAltContent(nsIContent* aContent) {
if (!aContent) {
return;
}
nsIFrame* frame = aContent->GetPrimaryFrame();
if (!frame) {
return;
}
// Check if this is for a pseudo-element.
if (nsCoreUtils::IsPseudoElement(aContent)) {
// If there are children, we want to expose the alt text on those instead,
// so ignore it for the pseudo-element itself.
if (aContent->HasChildren()) {
return;
}
// No children only happens when there is alt text with an empty content
// string; e.g. content: "" / "alt"
// In this case, we need to expose the alt text on the pseudo-element
// itself.
mPseudoElement = aContent->AsElement();
} else if (aContent->IsInNativeAnonymousSubtree()) {
if (!frame->IsReplaced()) {
return;
}
dom::Element* parent = aContent->GetParentElement();
if (parent && nsCoreUtils::IsPseudoElement(parent)) {
// aContent is a child of a pseudo-element.
mPseudoElement = parent;
// We need the frame from the pseudo-element to get the content style.
frame = parent->GetPrimaryFrame();
if (!frame) {
return;
}
}
}
if (mPseudoElement) {
// We need the real element to get any attributes.
mRealElement = mPseudoElement->GetParentElement();
if (!mRealElement) {
return;
}
}
if (!mRealElement) {
// This isn't for a pseudo-element. It might be an element which has its
// content replaced using CSS content.
if (aContent->IsElement()) {
if (!frame->IsReplaced()) {
return;
}
mRealElement = aContent->AsElement();
} else {
return;
}
}
mItems = frame->StyleContent()->AltContentItems();
}
void CssAltContent::AppendToString(nsAString& aOut) {
// There can be multiple alt text items.
for (const auto& item : mItems) {
if (item.IsString()) {
aOut.Append(NS_ConvertUTF8toUTF16(item.AsString().AsString()));
} else if (item.IsAttr()) {
// This item gets its value from an attribute on the element or from
// fallback text.
MOZ_ASSERT(mRealElement);
const auto& attr = item.AsAttr();
RefPtr<nsAtom> name = attr.attribute.AsAtom();
int32_t nsId = kNameSpaceID_None;
RefPtr<nsAtom> ns = attr.namespace_url.AsAtom();
if (!ns->IsEmpty()) {
nsresult rv = nsNameSpaceManager::GetInstance()->RegisterNameSpace(
ns.forget(), nsId);
if (NS_FAILED(rv)) {
continue;
}
}
if (mRealElement->IsHTMLElement() &&
mRealElement->OwnerDoc()->IsHTMLDocument()) {
ToLowerCaseASCII(name);
}
nsAutoString val;
if (!mRealElement->GetAttr(nsId, name, val)) {
if (RefPtr<nsAtom> fallback = attr.fallback.AsAtom()) {
fallback->ToString(val);
}
}
aOut.Append(val);
}
}
}
/* static */
bool CssAltContent::HandleAttributeChange(nsIContent* aContent,
int32_t aNameSpaceID,
nsAtom* aAttribute) {
// Handle CSS content which replaces the content of aContent itself.
if (CssAltContent(aContent).HandleAttributeChange(aNameSpaceID, aAttribute)) {
return true;
}
// Handle any pseudo-elements with CSS alt content.
for (dom::Element* pseudo : {nsLayoutUtils::GetBeforePseudo(aContent),
nsLayoutUtils::GetAfterPseudo(aContent),
nsLayoutUtils::GetMarkerPseudo(aContent)}) {
// CssAltContent wants a child of a pseudo-element if there is one.
nsIContent* content = pseudo ? pseudo->GetFirstChild() : nullptr;
if (!content) {
content = pseudo;
}
if (content && CssAltContent(content).HandleAttributeChange(aNameSpaceID,
aAttribute)) {
return true;
}
}
return false;
}
bool CssAltContent::HandleAttributeChange(int32_t aNameSpaceID,
nsAtom* aAttribute) {
for (const auto& item : mItems) {
if (!item.IsAttr()) {
continue;
}
MOZ_ASSERT(mRealElement);
const auto& attr = item.AsAttr();
RefPtr<nsAtom> name = attr.attribute.AsAtom();
if (mRealElement->IsHTMLElement() &&
mRealElement->OwnerDoc()->IsHTMLDocument()) {
ToLowerCaseASCII(name);
}
if (name != aAttribute) {
continue;
}
int32_t nsId = kNameSpaceID_None;
RefPtr<nsAtom> ns = attr.namespace_url.AsAtom();
if (!ns->IsEmpty()) {
nsresult rv = nsNameSpaceManager::GetInstance()->RegisterNameSpace(
ns.forget(), nsId);
if (NS_FAILED(rv)) {
continue;
}
}
if (nsId != aNameSpaceID) {
continue;
}
// The CSS alt content references this attribute which has just changed.
DocAccessible* docAcc = GetExistingDocAccessible(mRealElement->OwnerDoc());
MOZ_ASSERT(docAcc);
if (mPseudoElement) {
// For simplicity, we just recreate the pseudo-element subtree. If this
// becomes a performance problem, we can probably do better. For images,
// we can just fire a name change event. Text is a bit more complicated,
// as we need to update the text leaf with the new alt text and fire the
// appropriate text change events. Mixed content gets even messier.
docAcc->RecreateAccessible(mPseudoElement);
} else {
// This is CSS content replacing an element's content.
MOZ_ASSERT(mRealElement->GetPrimaryFrame());
MOZ_ASSERT(mRealElement->GetPrimaryFrame()->IsReplaced());
LocalAccessible* acc = docAcc->GetAccessible(mRealElement);
MOZ_ASSERT(acc);
docAcc->FireDelayedEvent(nsIAccessibleEvent::EVENT_NAME_CHANGE, acc);
}
return true;
}
return false;
}
} // namespace mozilla::a11y
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