Mypal/layout/base/RestyleManagerBase.h

/* -*- Mode: C++; tab-width: 8; 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/. */

#ifndef mozilla_RestyleManagerBase_h
#define mozilla_RestyleManagerBase_h

#include "mozilla/OverflowChangedTracker.h"
#include "nsChangeHint.h"
#include "nsPresContext.h"

class nsCString;
class nsCSSFrameConstructor;
class nsStyleChangeList;

namespace mozilla {

class EventStates;
class RestyleManager;
class ServoRestyleManager;

namespace dom {
class Element;
}

/**
 * Class for sharing data and logic common to both RestyleManager and
 * ServoRestyleManager.
 */
class RestyleManagerBase
{
protected:
  explicit RestyleManagerBase(nsPresContext* aPresContext);

public:
  typedef mozilla::dom::Element Element;

  // Get an integer that increments every time we process pending restyles.
  // The value is never 0.
  uint32_t GetRestyleGeneration() const { return mRestyleGeneration; }

  // Get an integer that increments every time there is a style change
  // as a result of a change to the :hover content state.
  uint32_t GetHoverGeneration() const { return mHoverGeneration; }

  bool ObservingRefreshDriver() const { return mObservingRefreshDriver; }

  void SetObservingRefreshDriver(bool aObserving) {
      mObservingRefreshDriver = aObserving;
  }

  void Disconnect() { mPresContext = nullptr; }

  static nsCString RestyleHintToString(nsRestyleHint aHint);

#ifdef DEBUG
  static nsCString ChangeHintToString(nsChangeHint aHint);

  /**
   * DEBUG ONLY method to verify integrity of style tree versus frame tree
   */
  static void DebugVerifyStyleTree(nsIFrame* aFrame);
#endif

  void FlushOverflowChangedTracker() {
    mOverflowChangedTracker.Flush();
  }

  // Should be called when a frame is going to be destroyed and
  // WillDestroyFrameTree hasn't been called yet.
  void NotifyDestroyingFrame(nsIFrame* aFrame) {
    mOverflowChangedTracker.RemoveFrame(aFrame);
    // If ProcessRestyledFrames is tracking frames which have been
    // destroyed (to avoid re-visiting them), add this one to its set.
    if (mDestroyedFrames) {
      mDestroyedFrames->PutEntry(aFrame);
    }
  }

  // Note: It's the caller's responsibility to make sure to wrap a
  // ProcessRestyledFrames call in a view update batch and a script blocker.
  // This function does not call ProcessAttachedQueue() on the binding manager.
  // If the caller wants that to happen synchronously, it needs to handle that
  // itself.
  nsresult ProcessRestyledFrames(nsStyleChangeList& aChangeList);

protected:
  void ContentStateChangedInternal(Element* aElement,
                                   EventStates aStateMask,
                                   nsChangeHint* aOutChangeHint,
                                   nsRestyleHint* aOutRestyleHint);

  bool IsDisconnected() { return mPresContext == nullptr; }

  void IncrementHoverGeneration() {
    ++mHoverGeneration;
  }

  void IncrementRestyleGeneration() {
    if (++mRestyleGeneration == 0) {
      // Keep mRestyleGeneration from being 0, since that's what
      // nsPresContext::GetRestyleGeneration returns when it no
      // longer has a RestyleManager.
      ++mRestyleGeneration;
    }
  }

  nsPresContext* PresContext() const {
    MOZ_ASSERT(mPresContext);
    return mPresContext;
  }

  nsCSSFrameConstructor* FrameConstructor() const {
    return PresContext()->FrameConstructor();
  }

  inline bool IsGecko() const {
    return !IsServo();
  }

  inline bool IsServo() const {
#ifdef MOZ_STYLO
    return PresContext()->StyleSet()->IsServo();
#else
    return false;
#endif
  }

private:
  nsPresContext* mPresContext; // weak, can be null after Disconnect().
  uint32_t mRestyleGeneration;
  uint32_t mHoverGeneration;
  
  // Used to keep track of frames that have been destroyed during
  // ProcessRestyledFrames, so we don't try to touch them again even if
  // they're referenced again later in the changelist.
  mozilla::UniquePtr<nsTHashtable<nsPtrHashKey<const nsIFrame>>> mDestroyedFrames;

  // True if we're already waiting for a refresh notification.
  bool mObservingRefreshDriver;

protected:
  // True if we're in the middle of a nsRefreshDriver refresh
  bool mInStyleRefresh;

  OverflowChangedTracker mOverflowChangedTracker;

  void PostRestyleEventInternal(bool aForLazyConstruction);

  /**
   * These are protected static methods that help with the change hint
   * processing bits of the restyle managers.
   */
  static nsIFrame*
  GetNearestAncestorFrame(nsIContent* aContent);

  static nsIFrame*
  GetNextBlockInInlineSibling(nsIFrame* aFrame);

  /**
   * Get the next continuation or similar ib-split sibling (assuming
   * block/inline alternation), conditionally on it having the same style.
   *
   * Since this is used when deciding to copy the new style context, it
   * takes as an argument the old style context to check if the style is
   * the same.  When it is used in other contexts (i.e., where the next
   * continuation would already have the new style context), the current
   * style context should be passed.
   */
  static nsIFrame*
  GetNextContinuationWithSameStyle(nsIFrame* aFrame,
                                   nsStyleContext* aOldStyleContext,
                                   bool* aHaveMoreContinuations = nullptr);
};

} // namespace mozilla

#endif