Implement MathML a tag in blink/chromium.

Wed, 30 Oct 2024 14:23:11 +0000

First create MathMLAnchorElement mathml_anchor_element.h and mathml_anchor_element.cc in third_party/blink/renderer/core/mathml/

// mathml_anchor_element.idl
// Copyright 2026 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// https://mathml-refresh.github.io/mathml-core/#dom-and-global-attributes
[Exposed=Window]
interface MathMLAnchorElement : MathMLElement {
 [CEReactions, Reflect] attribute USVString href;
 [CEReactions, Reflect] attribute DOMString target;
 [CEReactions, Reflect] attribute DOMString download;
 [CEReactions, Reflect] attribute DOMString rel;
 [CEReactions, Reflect, ReflectOnly="noreferrer", ReflectOnly="no-referrer", ReflectOnly="origin", ReflectOnly="no-referrer-when-downgrade", ReflectOnly="origin-when-cross-origin", ReflectOnly="unsafe-url"] attribute DOMString referrerpolicy;
 [PutForwards=value] readonly attribute DOMTokenList relList;

 // 添加 Ping 属性以对齐 HTML/SVG 的功能
 [CEReactions, Reflect] attribute DOMString ping;
};

// mathml_anchor_element.h

// Copyright 2026 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_MATHML_MATHML_ANCHOR_ELEMENT_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_MATHML_MATHML_ANCHOR_ELEMENT_H_

#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/dom/rel_list.h"
#include "third_party/blink/renderer/core/mathml/mathml_element.h"

namespace blink {

class MouseEvent;

class CORE_EXPORT MathMLAnchorElement final : public MathMLElement {
 DEFINE_WRAPPERTYPEINFO();

 public:
 explicit MathMLAnchorElement(Document&);

 void Trace(Visitor*) const override;

 // 链接核心状态
 bool HasActivationBehavior() const override;
 void DefaultEventHandler(Event&) override;
 bool IsInteractiveContent() const override { return true; }

 // 属性解析
 void ParseAttribute(const AttributeModificationParams&) override;
 bool IsURLAttribute(const Attribute&) const override;

 // 布局与焦点
 LayoutObject* CreateLayoutObject(const ComputedStyle&) override;
 FocusableState SupportsFocus(UpdateBehavior) const override;
 int DefaultTabIndex() const override;

 RelList* relList() const { return rel_list_.Get(); }

 private:
 void HandleClick(MouseEvent&);

 Member<RelList> rel_list_;
 unsigned link_relations_ : 16;
};

} // namespace blink

#endif // THIRD_PARTY_BLINK_RENDERER_CORE_MATHML_MATHML_ANCHOR_ELEMENT_H_

// mathml_anchor_element.cc
// Copyright 2026 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "third_party/blink/renderer/core/mathml/mathml_anchor_element.h"

#include "third_party/blink/renderer/core/dom/document.h"
#include "third_party/blink/renderer/core/events/mouse_event.h"
#include "third_party/blink/renderer/core/html/anchor_element_utils.h"
#include "third_party/blink/renderer/core/html/html_anchor_element.h"
#include "third_party/blink/renderer/core/layout/mathml/layout_mathml_block.h"
#include "third_party/blink/renderer/core/mathml_names.h"
#include "third_party/blink/renderer/core/loader/frame_load_request.h"
#include "third_party/blink/renderer/platform/weborigin/security_origin.h"

namespace blink {

MathMLAnchorElement::MathMLAnchorElement(Document& document)
 : MathMLElement(mathml_names::kATag, document),
 rel_list_(MakeGarbageCollected<RelList>(this, mathml_names::kRelAttr)),
 link_relations_(0) {}

void MathMLAnchorElement::Trace(Visitor* visitor) const {
 visitor->Trace(rel_list_);
 MathMLElement::Trace(visitor);
}

LayoutObject* MathMLAnchorElement::CreateLayoutObject(const ComputedStyle& style) {
 // 借鉴 SVG：MathML <a> 作为一个“透明”的容器块
 // LayoutMathMLBlock 会根据 MathML 规则排列其子元素
 return MakeGarbageCollected<LayoutMathMLBlock>(this);
}

void MathMLAnchorElement::ParseAttribute(const AttributeModificationParams& params) {
 if (params.name == mathml_names::kHrefAttr) {
 bool was_link = IsLink();
 SetIsLink(!params.new_value.IsNull());
 if (was_link != IsLink()) {
 PseudoStateChanged(CSSSelector::kPseudoLink);
 PseudoStateChanged(CSSSelector::kPseudoVisited);
 PseudoStateChanged(CSSSelector::kPseudoAnyLink);
 }
 } else if (params.name == mathml_names::kRelAttr) {
 link_relations_ = AnchorElementUtils::ParseRelAttribute(params.new_value, GetDocument());
 rel_list_->DidUpdateAttributeValue(params.old_value, params.new_value);
 } else {
 MathMLElement::ParseAttribute(params);
 }
}

bool MathMLAnchorElement::IsURLAttribute(const Attribute& attribute) const {
 return attribute.GetName() == mathml_names::kHrefAttr ||
 MathMLElement::IsURLAttribute(attribute);
}

bool MathMLAnchorElement::HasActivationBehavior() const {
 return IsLink();
}

void MathMLAnchorElement::DefaultEventHandler(Event& event) {
 if (IsLink()) {
 // 1. 处理键盘激活 (Enter)
 if (IsFocused() && IsEnterKeyKeydownEvent(event)) {
 event.SetDefaultHandled();
 DispatchSimulatedClick(&event);
 return;
 }

 // 2. 处理鼠标点击
 if (IsLinkClick(event)) {
 HandleClick(To<MouseEvent>(event));
 return;
 }
 }
 MathMLElement::DefaultEventHandler(event);
}

void MathMLAnchorElement::HandleClick(MouseEvent& event) {
 event.SetDefaultHandled();

 LocalDOMWindow* window = GetDocument().domWindow();
 if (!window || !window->GetFrame()) return;

 const KURL& completed_url = GetDocument().CompleteURL(
 StripLeadingAndTrailingHtmlSpaces(FastGetAttribute(mathml_names::kHrefAttr)));

 AnchorElementUtils::SendPings(completed_url, GetDocument(), FastGetAttribute(mathml_names::kPingAttr));

 ResourceRequest request(completed_url);
 AnchorElementUtils::HandleReferrerPolicyAttribute(
request, FastGetAttribute(mathml_names::kReferrerpolicyAttr), link_relations_, GetDocument());

 if (AnchorElementUtils::HasRel(link_relations_, kRelationNoReferrer)) {
 request.SetReferrerPolicy(network::mojom::ReferrerPolicy::kNever);
 }

 request.SetHasUserGesture(LocalFrame::HasTransientUserActivation(window->GetFrame()));
 NavigationPolicy navigation_policy = NavigationPolicyFromEvent(&event);

 if (FastHasAttribute(mathml_names::kDownloadAttr) &&
 navigation_policy != kNavigationPolicyDownload &&
 window->GetSecurityOrigin()->CanReadContent(completed_url)) {
 const String download_attr = FastGetAttribute(mathml_names::kDownloadAttr);
 AnchorElementUtils::HandleDownloadAttribute(this, download_attr, completed_url, window, event.isTrusted(), std::move(request));
 return;
 }

 FrameLoadRequest frame_request(window, request);
 frame_request.SetNavigationPolicy(navigation_policy);
 frame_request.SetClientNavigationReason(ClientNavigationReason::kAnchorClick);
 frame_request.SetSourceElement(this);

 // 建议在 NavigateToHyperlink 或 HandleClick 中加入针对隐私的逻辑
 if (AnchorElementUtils::HasRel(link_relations_, kRelationNoOpener)) {
 frame_request.SetNoOpener();
 }

 AtomicString target(FastGetAttribute(mathml_names::kTargetAttr));
 frame_request.SetTriggeringEventInfo(event.isTrusted() ? mojom::blink::TriggeringEventInfo::kFromTrustedEvent : mojom::blink::TriggeringEventInfo::kFromUntrustedEvent);

 if (Frame* target_frame = window->GetFrame()->Tree().FindOrCreateFrameForNavigation(frame_request, target).frame) {
 target_frame->Navigate(frame_request, WebFrameLoadType::kStandard);
 }
}

FocusableState MathMLAnchorElement::SupportsFocus(UpdateBehavior update_behavior) const {
 if (IsLink()) return FocusableState::kFocusable;
 return MathMLElement::SupportsFocus(update_behavior);
}

int MathMLAnchorElement::DefaultTabIndex() const {
 return 0;
}

} // namespace blink

/* renderer/core/css/mathml.css */
math a:-webkit-any-link {
 cursor: pointer;
 text-decoration: none; 数学公式通常不加下划线
}

// third_party/blink/renderer/core/mathml_tag_names.json5
{
 name: "a",
 interfaceName: "MathMLAnchorElement",
},

// third_party/blink/renderer/core/core_idl_files.gni
mathml_anchor_element.idl

// third_party/blink/renderer/core/mathml/build.gni
mathml_anchor_element.cc
mathml_anchor_element.h

Blink on tannal

Implement MathML a tag in blink/chromium.