gecko-dev/dom/base/mozAutoDocUpdate.h

/* 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 mozAutoDocUpdate_h_
#define mozAutoDocUpdate_h_

#include "nsContentUtils.h" // For AddScriptBlocker() and RemoveScriptBlocker().
#include "nsIDocument.h"
#include "nsIDocumentObserver.h"

/**
 * Helper class to automatically handle batching of document updates.  This
 * class will call BeginUpdate on construction and EndUpdate on destruction on
 * the given document with the given update type.  The document could be null,
 * in which case no updates will be called.  The constructor also takes a
 * boolean that can be set to false to prevent notifications.
 */
class MOZ_STACK_CLASS mozAutoDocUpdate
{
public:
  mozAutoDocUpdate(nsIDocument* aDocument, nsUpdateType aUpdateType,
                   bool aNotify) :
    mDocument(aNotify ? aDocument : nullptr),
    mUpdateType(aUpdateType)
  {
    if (mDocument) {
      mDocument->BeginUpdate(mUpdateType);
    }
    else {
      nsContentUtils::AddScriptBlocker();
    }
  }

  ~mozAutoDocUpdate()
  {
    if (mDocument) {
      mDocument->EndUpdate(mUpdateType);
    }
    else {
      nsContentUtils::RemoveScriptBlocker();
    }
  }

private:
  nsCOMPtr<nsIDocument> mDocument;
  nsUpdateType mUpdateType;
};

#define MOZ_AUTO_DOC_UPDATE_PASTE2(tok,line) tok##line
#define MOZ_AUTO_DOC_UPDATE_PASTE(tok,line) \
  MOZ_AUTO_DOC_UPDATE_PASTE2(tok,line)
#define MOZ_AUTO_DOC_UPDATE(doc,type,notify) \
  mozAutoDocUpdate MOZ_AUTO_DOC_UPDATE_PASTE(_autoDocUpdater_, __LINE__) \
  (doc,type,notify)


/**
 * Creates an update batch only under certain conditions.
 * Use this rather than mozAutoDocUpdate when you expect inner updates
 * to notify but you don't always want to spec cycles creating a batch.
 * This is needed to avoid having this batch always create a blocker,
 * but then have inner mozAutoDocUpdate call the last EndUpdate before.
 * we remove that blocker. See bug 423269.
 */
class MOZ_STACK_CLASS mozAutoDocConditionalContentUpdateBatch
{
public:
  mozAutoDocConditionalContentUpdateBatch(nsIDocument* aDocument,
                                          bool aNotify) :
    mDocument(aNotify ? aDocument : nullptr)
  {
    if (mDocument) {
      mDocument->BeginUpdate(UPDATE_CONTENT_MODEL);
    }
  }

  ~mozAutoDocConditionalContentUpdateBatch()
  {
    if (mDocument) {
      mDocument->EndUpdate(UPDATE_CONTENT_MODEL);
    }
  }

private:
  nsCOMPtr<nsIDocument> mDocument;
};

#endif