chromium/src/third_party/blink/renderer/core/page/scrolling/fragment_anchor.h

// Copyright 2019 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.

#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_PAGE_SCROLLING_FRAGMENT_ANCHOR_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_PAGE_SCROLLING_FRAGMENT_ANCHOR_H_

#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/scroll/scroll_types.h"
#include "third_party/blink/renderer/platform/heap/handle.h"

namespace blink {

class LocalFrame;
class KURL;

// This class is an interface for the concept of a "fragment anchor". A
// fragment anchor allows a page to link to a specific part of a page by using
// the URL fragment. The fragment is the part after the '#' character. E.g.
// navigating to www.example.com/index.html#section3 will find the element with
// id "section3" and focus and scroll it into view.
//
// This class provides an interface that different types of fragment anchors
// can implement, allowing fragments to specify different kinds of anchors.
// Callers should use the TryCreate static method to create and return the
// appropriate type of base class.
class CORE_EXPORT FragmentAnchor : public GarbageCollected<FragmentAnchor> {
 public:
  // Parses the fragment string and tries to create a FragmentAnchor object of
  // the appropriate derived type. If no anchor could be created from the given
  // url, this returns nullptr. In either case, side-effects on the document
  // will be performed, for example, setting/clearing :target and svgView().
  static FragmentAnchor* TryCreate(const KURL& url,
                                   LocalFrame& frame,
                                   bool should_scroll);

  FragmentAnchor() = default;
  virtual ~FragmentAnchor() = default;

  // Invoking the fragment anchor scrolls it into view and performs any other
  // desired actions. This is called repeatedly during loading as the lifecycle
  // is updated to keep the element in view. If true, the anchor should be kept
  // alive and invoked again. Otherwise it may be disposed.
  virtual bool Invoke() = 0;

  // This should be called when the anchor is "installed". In other words, when
  // the caller receives the FragmentAnchor and stores it. This allows the
  // anchor to perform some initialization.
  virtual void Installed() = 0;

  virtual void DidScroll(mojom::blink::ScrollType type) = 0;
  virtual void PerformPreRafActions() = 0;

  // Dismissing the fragment anchor removes indicators of the anchor, such as
  // text highlighting on a text fragment anchor. If true, the anchor has been
  // dismissed and can be disposed.
  virtual bool Dismiss() = 0;

  virtual void Trace(Visitor*) const {}
};

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_PAGE_SCROLLING_FRAGMENT_ANCHOR_H_