gecko/layout/style/Declaration.h

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
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 *
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 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is mozilla.org code.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1998
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Daniel Glazman <glazman@netscape.com>
 *
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 * either of the GNU General Public License Version 2 or later (the "GPL"),
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 * ***** END LICENSE BLOCK ***** */

/*
 * representation of a declaration block (or style attribute) in a CSS
 * stylesheet
 */

#ifndef mozilla_css_Declaration_h
#define mozilla_css_Declaration_h

// This header is in EXPORTS because it's used in several places in content/,
// but it's not really a public interface.
#ifndef _IMPL_NS_LAYOUT
#error "This file should only be included within the layout library"
#endif

#include "nsCSSDataBlock.h"
#include "nsCSSProperty.h"
#include "nsCSSProps.h"
#include "nsStringFwd.h"
#include "nsTArray.h"
#include <stdio.h>

namespace mozilla {
namespace css {

// Declaration objects have unusual lifetime rules.  Every declaration
// begins life in an invalid state which ends when InitializeEmpty or
// CompressFrom is called upon it.  After that, it can be attached to
// exactly one style rule, and will be destroyed when that style rule
// is destroyed.  A declaration becomes immutable when its style rule's
// |RuleMatched| method is called; after that, it must be copied before
// it can be modified, which is taken care of by |EnsureMutable|.

class Declaration {
public:
  /**
   * Construct an |Declaration| that is in an invalid state (null
   * |mData|) and cannot be used until its |CompressFrom| method or
   * |InitializeEmpty| method is called.
   */
  Declaration();

  Declaration(const Declaration& aCopy);

  ~Declaration();

  /**
   * |ValueAppended| must be called to maintain this declaration's
   * |mOrder| whenever a property is parsed into an expanded data block
   * for this declaration.  aProperty must not be a shorthand.
   */
  void ValueAppended(nsCSSProperty aProperty);

  void RemoveProperty(nsCSSProperty aProperty);

  void GetValue(nsCSSProperty aProperty, nsAString& aValue) const;

  PRBool HasImportantData() const { return mImportantData != nsnull; }
  PRBool GetValueIsImportant(nsCSSProperty aProperty) const;
  PRBool GetValueIsImportant(const nsAString& aProperty) const;

  PRUint32 Count() const {
    return mOrder.Length();
  }
  void GetNthProperty(PRUint32 aIndex, nsAString& aReturn) const;

  void ToString(nsAString& aString) const;

  nsCSSCompressedDataBlock* GetNormalBlock() const { return mData; }
  nsCSSCompressedDataBlock* GetImportantBlock() const { return mImportantData; }

  /**
   * Initialize this declaration as holding no data.  Cannot fail.
   */
  void InitializeEmpty();

  /**
   * Transfer all of the state from |aExpandedData| into this declaration.
   * After calling, |aExpandedData| should be in its initial state.
   */
  void CompressFrom(nsCSSExpandedDataBlock *aExpandedData) {
    NS_ABORT_IF_FALSE(!mData, "oops");
    NS_ABORT_IF_FALSE(!mImportantData, "oops");
    aExpandedData->Compress(getter_Transfers(mData),
                            getter_Transfers(mImportantData));
    aExpandedData->AssertInitialState();
  }

  /**
   * Transfer all of the state from this declaration into
   * |aExpandedData| and put this declaration temporarily into an
   * invalid state (ended by |CompressFrom| or |InitializeEmpty|) that
   * should last only during parsing.  During this time only
   * |ValueAppended| should be called.
   */
  void ExpandTo(nsCSSExpandedDataBlock *aExpandedData) {
    AssertMutable();
    aExpandedData->AssertInitialState();

    NS_ABORT_IF_FALSE(mData, "oops");
    aExpandedData->Expand(mData.forget(), mImportantData.forget());
  }

  /**
   * Do what |nsIStyleRule::MapRuleInfoInto| needs to do for a style
   * rule using this declaration for storage.
   */
  void MapNormalRuleInfoInto(nsRuleData *aRuleData) const {
    NS_ABORT_IF_FALSE(mData, "called while expanded");
    mData->MapRuleInfoInto(aRuleData);
  }
  void MapImportantRuleInfoInto(nsRuleData *aRuleData) const {
    NS_ABORT_IF_FALSE(mData, "called while expanded");
    NS_ABORT_IF_FALSE(mImportantData, "must have important data");
    mImportantData->MapRuleInfoInto(aRuleData);
  }

  /**
   * Attempt to replace the value for |aProperty| stored in this
   * declaration with the matching value from |aFromBlock|.
   * This method may only be called on a mutable declaration.
   * It will fail (returning PR_FALSE) if |aProperty| is shorthand,
   * is not already in this declaration, or does not have the indicated
   * importance level.  If it returns PR_TRUE, it erases the value in
   * |aFromBlock|.  |aChanged| is set to PR_TRUE if the declaration
   * changed as a result of the call, and to PR_FALSE otherwise.
   */
  PRBool TryReplaceValue(nsCSSProperty aProperty, PRBool aIsImportant,
                         nsCSSExpandedDataBlock& aFromBlock,
                         PRBool* aChanged)
  {
    AssertMutable();
    NS_ABORT_IF_FALSE(mData, "called while expanded");

    if (nsCSSProps::IsShorthand(aProperty)) {
      *aChanged = PR_FALSE;
      return PR_FALSE;
    }
    nsCSSCompressedDataBlock *block = aIsImportant ? mImportantData : mData;
    // mImportantData might be null
    if (!block) {
      *aChanged = PR_FALSE;
      return PR_FALSE;
    }

#ifdef DEBUG
    {
      nsCSSCompressedDataBlock *other = aIsImportant ? mData : mImportantData;
      NS_ABORT_IF_FALSE(!other || !other->ValueFor(aProperty) ||
                        !block->ValueFor(aProperty),
                        "Property both important and not?");
    }
#endif
    return block->TryReplaceValue(aProperty, aFromBlock, aChanged);
  }

  PRBool HasNonImportantValueFor(nsCSSProperty aProperty) const {
    NS_ABORT_IF_FALSE(!nsCSSProps::IsShorthand(aProperty), "must be longhand");
    return !!mData->ValueFor(aProperty);
  }

  /**
   * Return whether |this| may be modified.
   */
  bool IsMutable() const {
    return !mImmutable;
  }

  /**
   * Copy |this|, if necessary to ensure that it can be modified.
   */
  Declaration* EnsureMutable();

  /**
   * Crash if |this| cannot be modified.
   */
  void AssertMutable() const {
    NS_ABORT_IF_FALSE(IsMutable(), "someone forgot to call EnsureMutable");
  }

  /**
   * Mark this declaration as unmodifiable.  It's 'const' so it can
   * be called from ToString.
   */
  void SetImmutable() const { mImmutable = PR_TRUE; }

  /**
   * Clear the data, in preparation for its replacement with entirely
   * new data by a call to |CompressFrom|.
   */
  void ClearData() {
    AssertMutable();
    mData = nsnull;
    mImportantData = nsnull;
    mOrder.Clear();
  }

#ifdef DEBUG
  void List(FILE* out = stdout, PRInt32 aIndent = 0) const;
#endif

private:
  // Not implemented, and not supported.
  Declaration& operator=(const Declaration& aCopy);
  PRBool operator==(const Declaration& aCopy) const;

  static void AppendImportanceToString(PRBool aIsImportant, nsAString& aString);
  // return whether there was a value in |aValue| (i.e., it had a non-null unit)
  PRBool AppendValueToString(nsCSSProperty aProperty, nsAString& aResult) const;
  // Helper for ToString with strange semantics regarding aValue.
  void AppendPropertyAndValueToString(nsCSSProperty aProperty,
                                      nsAutoString& aValue,
                                      nsAString& aResult) const;

  nsCSSProperty OrderValueAt(PRUint32 aValue) const {
    return nsCSSProperty(mOrder.ElementAt(aValue));
  }

  nsAutoTArray<PRUint8, 8> mOrder;

  // never null, except while expanded, or before the first call to
  // InitializeEmpty or CompressFrom.
  nsAutoPtr<nsCSSCompressedDataBlock> mData;

  // may be null
  nsAutoPtr<nsCSSCompressedDataBlock> mImportantData;

  // set by style rules when |RuleMatched| is called;
  // also by ToString (hence the 'mutable').
  mutable PRPackedBool mImmutable;
};

} // namespace css
} // namespace mozilla

#endif /* mozilla_css_Declaration_h */