pjs/layout/style/nsStyleSet.cpp

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 *
 * The contents of this file are subject to the Netscape Public License
 * Version 1.0 (the "NPL"); you may not use this file except in
 * compliance with the NPL.  You may obtain a copy of the NPL at
 * http://www.mozilla.org/NPL/
 *
 * Software distributed under the NPL is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the NPL
 * for the specific language governing rights and limitations under the
 * NPL.
 *
 * The Initial Developer of this code under the NPL is Netscape
 * Communications Corporation.  Portions created by Netscape are
 * Copyright (C) 1998 Netscape Communications Corporation.  All Rights
 * Reserved.
 */
#include "nsCOMPtr.h"
#include "nsIStyleSet.h"
#include "nsIStyleSheet.h"
#include "nsIStyleRule.h"
#include "nsIStyleContext.h"
#include "nsISupportsArray.h"
#include "nsIFrame.h"
//#include "nsHashtable.h"
#include "nsIPresContext.h"
#include "nsIPresShell.h"
#include "nsIContent.h"
#include "nsIDocument.h"
#include "nsIStyleFrameConstruction.h"
#include "nsLayoutAtoms.h"

static NS_DEFINE_IID(kIStyleSetIID, NS_ISTYLE_SET_IID);
static NS_DEFINE_IID(kIStyleFrameConstructionIID, NS_ISTYLE_FRAME_CONSTRUCTION_IID);


class StyleSetImpl : public nsIStyleSet {
public:
  StyleSetImpl();

  NS_DECL_ISUPPORTS

  virtual void AppendOverrideStyleSheet(nsIStyleSheet* aSheet);
  virtual void InsertOverrideStyleSheetAfter(nsIStyleSheet* aSheet,
                                             nsIStyleSheet* aAfterSheet);
  virtual void InsertOverrideStyleSheetBefore(nsIStyleSheet* aSheet,
                                              nsIStyleSheet* aBeforeSheet);
  virtual void RemoveOverrideStyleSheet(nsIStyleSheet* aSheet);
  virtual PRInt32 GetNumberOfOverrideStyleSheets();
  virtual nsIStyleSheet* GetOverrideStyleSheetAt(PRInt32 aIndex);

  virtual void AddDocStyleSheet(nsIStyleSheet* aSheet, nsIDocument* aDocument);
  virtual void RemoveDocStyleSheet(nsIStyleSheet* aSheet);
  virtual PRInt32 GetNumberOfDocStyleSheets();
  virtual nsIStyleSheet* GetDocStyleSheetAt(PRInt32 aIndex);

  virtual void AppendBackstopStyleSheet(nsIStyleSheet* aSheet);
  virtual void InsertBackstopStyleSheetAfter(nsIStyleSheet* aSheet,
                                             nsIStyleSheet* aAfterSheet);
  virtual void InsertBackstopStyleSheetBefore(nsIStyleSheet* aSheet,
                                              nsIStyleSheet* aBeforeSheet);
  virtual void RemoveBackstopStyleSheet(nsIStyleSheet* aSheet);
  virtual PRInt32 GetNumberOfBackstopStyleSheets();
  virtual nsIStyleSheet* GetBackstopStyleSheetAt(PRInt32 aIndex);

  virtual nsIStyleContext* ResolveStyleFor(nsIPresContext* aPresContext,
                                           nsIContent* aContent,
                                           nsIStyleContext* aParentContext,
                                           PRBool aForceUnique = PR_FALSE);

  virtual nsIStyleContext* ResolvePseudoStyleFor(nsIPresContext* aPresContext,
                                                 nsIContent* aParentContent,
                                                 nsIAtom* aPseudoTag,
                                                 nsIStyleContext* aParentContext,
                                                 PRBool aForceUnique = PR_FALSE);

  virtual nsIStyleContext* ProbePseudoStyleFor(nsIPresContext* aPresContext,
                                               nsIContent* aParentContent,
                                               nsIAtom* aPseudoTag,
                                               nsIStyleContext* aParentContext,
                                               PRBool aForceUnique = PR_FALSE);

  NS_IMETHOD ReParentStyleContext(nsIPresContext* aPresContext,
                                  nsIStyleContext* aStyleContext, 
                                  nsIStyleContext* aNewParentContext,
                                  nsIStyleContext** aNewStyleContext);

  NS_IMETHOD  HasStateDependentStyle(nsIPresContext* aPresContext,
                                     nsIContent*     aContent);

  NS_IMETHOD ConstructRootFrame(nsIPresContext* aPresContext,
                                nsIContent*     aContent,
                                nsIFrame*&      aFrameSubTree);
  NS_IMETHOD ReconstructDocElementHierarchy(nsIPresContext* aPresContext);
  NS_IMETHOD ContentAppended(nsIPresContext* aPresContext,
                             nsIContent*     aContainer,
                             PRInt32         aNewIndexInContainer);
  NS_IMETHOD ContentInserted(nsIPresContext* aPresContext,
                             nsIContent*     aContainer,
                             nsIContent*     aChild,
                             PRInt32         aIndexInContainer);
  NS_IMETHOD ContentReplaced(nsIPresContext* aPresContext,
                             nsIContent*     aContainer,
                             nsIContent*     aOldChild,
                             nsIContent*     aNewChild,
                             PRInt32         aIndexInContainer);
  NS_IMETHOD ContentRemoved(nsIPresContext* aPresContext,
                            nsIContent*     aContainer,
                            nsIContent*     aChild,
                            PRInt32         aIndexInContainer);

  NS_IMETHOD ContentChanged(nsIPresContext*  aPresContext,
                            nsIContent* aContent,
                            nsISupports* aSubContent);
  NS_IMETHOD ContentStatesChanged(nsIPresContext* aPresContext, 
                                  nsIContent* aContent1,
                                  nsIContent* aContent2);
  NS_IMETHOD AttributeChanged(nsIPresContext*  aPresContext,
                              nsIContent* aChild,
                              nsIAtom* aAttribute,
                              PRInt32 aHint); // See nsStyleConsts fot hint values

  // xxx style rules enumeration

  // Style change notifications
  NS_IMETHOD StyleRuleChanged(nsIPresContext* aPresContext,
                              nsIStyleSheet* aStyleSheet,
                              nsIStyleRule* aStyleRule,
                              PRInt32 aHint); // See nsStyleConsts fot hint values
  NS_IMETHOD StyleRuleAdded(nsIPresContext* aPresContext,
                            nsIStyleSheet* aStyleSheet,
                            nsIStyleRule* aStyleRule);
  NS_IMETHOD StyleRuleRemoved(nsIPresContext* aPresContext,
                              nsIStyleSheet* aStyleSheet,
                              nsIStyleRule* aStyleRule);

  // Notification that we were unable to render a replaced element.
  NS_IMETHOD CantRenderReplacedElement(nsIPresContext* aPresContext,
                                       nsIFrame*       aFrame);
  
  // Request to create a continuing frame
  NS_IMETHOD CreateContinuingFrame(nsIPresContext* aPresContext,
                                   nsIFrame*       aFrame,
                                   nsIFrame*       aParentFrame,
                                   nsIFrame**      aContinuingFrame);
  
  // Request to find the primary frame associated with a given content object.
  // This is typically called by the pres shell when there is no mapping in
  // the pres shell hash table
  NS_IMETHOD FindPrimaryFrameFor(nsIPresContext*  aPresContext,
                                 nsIFrameManager* aFrameManager,
                                 nsIContent*      aContent,
                                 nsIFrame**       aFrame);

  virtual void List(FILE* out = stdout, PRInt32 aIndent = 0);

private:
  // These are not supported and are not implemented!
  StyleSetImpl(const StyleSetImpl& aCopy);
  StyleSetImpl& operator=(const StyleSetImpl& aCopy);

protected:
  virtual ~StyleSetImpl();
  PRBool EnsureArray(nsISupportsArray** aArray);
  nsIStyleContext* GetContext(nsIPresContext* aPresContext, nsIStyleContext* aParentContext, 
                              nsIAtom* aPseudoTag, nsISupportsArray* aRules, PRBool aForceUnique, 
                              PRBool& aUsedRules);
  void  List(FILE* out, PRInt32 aIndent, nsISupportsArray* aSheets);
  void  ListContexts(nsIStyleContext* aRootContext, FILE* out, PRInt32 aIndent);

  nsISupportsArray* mOverrideSheets;
  nsISupportsArray* mDocSheets;
  nsISupportsArray* mBackstopSheets;
  nsISupportsArray* mRecycler;

  nsIStyleFrameConstruction* mFrameConstructor;
};


StyleSetImpl::StyleSetImpl()
  : mOverrideSheets(nsnull),
    mDocSheets(nsnull),
    mBackstopSheets(nsnull),
    mRecycler(nsnull),
    mFrameConstructor(nsnull)
{
  NS_INIT_REFCNT();
}

StyleSetImpl::~StyleSetImpl()
{
  NS_IF_RELEASE(mOverrideSheets);
  NS_IF_RELEASE(mDocSheets);
  NS_IF_RELEASE(mBackstopSheets);
  NS_IF_RELEASE(mFrameConstructor);
  NS_IF_RELEASE(mRecycler);
}

NS_IMPL_ISUPPORTS(StyleSetImpl, kIStyleSetIID)

PRBool StyleSetImpl::EnsureArray(nsISupportsArray** aArray)
{
  if (nsnull == *aArray) {
    if (NS_OK != NS_NewISupportsArray(aArray)) {
      return PR_FALSE;
    }
  }
  return PR_TRUE;
}

// ----- Override sheets

void StyleSetImpl::AppendOverrideStyleSheet(nsIStyleSheet* aSheet)
{
  NS_PRECONDITION(nsnull != aSheet, "null arg");
  if (EnsureArray(&mOverrideSheets)) {
    mOverrideSheets->RemoveElement(aSheet);
    mOverrideSheets->AppendElement(aSheet);
  }
}

void StyleSetImpl::InsertOverrideStyleSheetAfter(nsIStyleSheet* aSheet,
                                                 nsIStyleSheet* aAfterSheet)
{
  NS_PRECONDITION(nsnull != aSheet, "null arg");
  if (EnsureArray(&mOverrideSheets)) {
    mOverrideSheets->RemoveElement(aSheet);
    PRInt32 index = mOverrideSheets->IndexOf(aAfterSheet);
    mOverrideSheets->InsertElementAt(aSheet, ++index);
  }
}

void StyleSetImpl::InsertOverrideStyleSheetBefore(nsIStyleSheet* aSheet,
                                                  nsIStyleSheet* aBeforeSheet)
{
  NS_PRECONDITION(nsnull != aSheet, "null arg");
  if (EnsureArray(&mOverrideSheets)) {
    mOverrideSheets->RemoveElement(aSheet);
    PRInt32 index = mOverrideSheets->IndexOf(aBeforeSheet);
    mOverrideSheets->InsertElementAt(aSheet, ((-1 < index) ? index : 0));
  }
}

void StyleSetImpl::RemoveOverrideStyleSheet(nsIStyleSheet* aSheet)
{
  NS_PRECONDITION(nsnull != aSheet, "null arg");

  if (nsnull != mOverrideSheets) {
    mOverrideSheets->RemoveElement(aSheet);
  }
}

PRInt32 StyleSetImpl::GetNumberOfOverrideStyleSheets()
{
  if (nsnull != mOverrideSheets) {
    PRUint32 cnt;
    nsresult rv = mOverrideSheets->Count(&cnt);
    if (NS_FAILED(rv)) return 0;        // XXX error?
    return cnt;
  }
  return 0;
}

nsIStyleSheet* StyleSetImpl::GetOverrideStyleSheetAt(PRInt32 aIndex)
{
  nsIStyleSheet* sheet = nsnull;
  if (nsnull != mOverrideSheets) {
    sheet = (nsIStyleSheet*)mOverrideSheets->ElementAt(aIndex);
  }
  return sheet;
}

// -------- Doc Sheets

void StyleSetImpl::AddDocStyleSheet(nsIStyleSheet* aSheet, nsIDocument* aDocument)
{
  NS_PRECONDITION((nsnull != aSheet) && (nsnull != aDocument), "null arg");
  if (EnsureArray(&mDocSheets)) {
    mDocSheets->RemoveElement(aSheet);
    // lowest index last
    PRInt32 newDocIndex = aDocument->GetIndexOfStyleSheet(aSheet);
    PRUint32 count;
    nsresult rv = mDocSheets->Count(&count);
    if (NS_FAILED(rv)) return;  // XXX error?
    PRUint32 index;
    for (index = 0; index < count; index++) {
      nsIStyleSheet* sheet = (nsIStyleSheet*)mDocSheets->ElementAt(index);
      PRInt32 sheetDocIndex = aDocument->GetIndexOfStyleSheet(sheet);
      if (sheetDocIndex < newDocIndex) {
        mDocSheets->InsertElementAt(aSheet, index);
        index = count; // break loop
      }
      NS_RELEASE(sheet);
    }
    PRUint32 cnt;
    rv = mDocSheets->Count(&cnt);
    if (NS_FAILED(rv)) return;  // XXX error?
    if (cnt == count) {  // didn't insert it
      mDocSheets->AppendElement(aSheet);
    }

    if (nsnull == mFrameConstructor) {
      aSheet->QueryInterface(kIStyleFrameConstructionIID, (void **)&mFrameConstructor);
    }
  }
}

void StyleSetImpl::RemoveDocStyleSheet(nsIStyleSheet* aSheet)
{
  NS_PRECONDITION(nsnull != aSheet, "null arg");

  if (nsnull != mDocSheets) {
    mDocSheets->RemoveElement(aSheet);
  }
}

PRInt32 StyleSetImpl::GetNumberOfDocStyleSheets()
{
  if (nsnull != mDocSheets) {
    PRUint32 cnt;
    nsresult rv = mDocSheets->Count(&cnt);
    if (NS_FAILED(rv)) return 0;        // XXX error?
    return cnt;
  }
  return 0;
}

nsIStyleSheet* StyleSetImpl::GetDocStyleSheetAt(PRInt32 aIndex)
{
  nsIStyleSheet* sheet = nsnull;
  if (nsnull != mDocSheets) {
    sheet = (nsIStyleSheet*)mDocSheets->ElementAt(aIndex);
  }
  return sheet;
}

// ------ backstop sheets

void StyleSetImpl::AppendBackstopStyleSheet(nsIStyleSheet* aSheet)
{
  NS_PRECONDITION(nsnull != aSheet, "null arg");
  if (EnsureArray(&mBackstopSheets)) {
    mBackstopSheets->RemoveElement(aSheet);
    mBackstopSheets->AppendElement(aSheet);
  }
}

void StyleSetImpl::InsertBackstopStyleSheetAfter(nsIStyleSheet* aSheet,
                                                 nsIStyleSheet* aAfterSheet)
{
  NS_PRECONDITION(nsnull != aSheet, "null arg");
  if (EnsureArray(&mBackstopSheets)) {
    mBackstopSheets->RemoveElement(aSheet);
    PRInt32 index = mBackstopSheets->IndexOf(aAfterSheet);
    mBackstopSheets->InsertElementAt(aSheet, ++index);
  }
}

void StyleSetImpl::InsertBackstopStyleSheetBefore(nsIStyleSheet* aSheet,
                                                  nsIStyleSheet* aBeforeSheet)
{
  NS_PRECONDITION(nsnull != aSheet, "null arg");
  if (EnsureArray(&mBackstopSheets)) {
    mBackstopSheets->RemoveElement(aSheet);
    PRInt32 index = mBackstopSheets->IndexOf(aBeforeSheet);
    mBackstopSheets->InsertElementAt(aSheet, ((-1 < index) ? index : 0));
  }
}

void StyleSetImpl::RemoveBackstopStyleSheet(nsIStyleSheet* aSheet)
{
  NS_PRECONDITION(nsnull != aSheet, "null arg");

  if (nsnull != mBackstopSheets) {
    mBackstopSheets->RemoveElement(aSheet);
  }
}

PRInt32 StyleSetImpl::GetNumberOfBackstopStyleSheets()
{
  if (nsnull != mBackstopSheets) {
    PRUint32 cnt;
    nsresult rv = mBackstopSheets->Count(&cnt);
    if (NS_FAILED(rv)) return 0;        // XXX error?
    return cnt;
  }
  return 0;
}

nsIStyleSheet* StyleSetImpl::GetBackstopStyleSheetAt(PRInt32 aIndex)
{
  nsIStyleSheet* sheet = nsnull;
  if (nsnull != mBackstopSheets) {
    sheet = (nsIStyleSheet*)mBackstopSheets->ElementAt(aIndex);
  }
  return sheet;
}

struct RulesMatchingData {
  RulesMatchingData(nsIPresContext* aPresContext,
                    nsIAtom* aMedium,
                    nsIContent* aContent,
                    nsIStyleContext* aParentContext,
                    nsISupportsArray* aResults)
    : mPresContext(aPresContext),
      mMedium(aMedium),
      mContent(aContent),
      mParentContext(aParentContext),
      mResults(aResults),
      mCount(0)
  {
  }
  nsIPresContext*   mPresContext;
  nsIAtom*          mMedium;
  nsIContent*       mContent;
  nsIStyleContext*  mParentContext;
  nsISupportsArray* mResults;
  PRInt32           mCount;

};

static PRBool
EnumRulesMatching(nsISupports* aSheet, void* aData)
{
  nsIStyleSheet*  sheet = (nsIStyleSheet*)aSheet;
  RulesMatchingData* data = (RulesMatchingData*)aData;

  if (NS_OK == sheet->UseForMedium(data->mMedium)) {
    data->mCount += sheet->RulesMatching(data->mPresContext, data->mContent, 
                                         data->mParentContext, data->mResults);
  }
  return PR_TRUE;
}


nsIStyleContext* StyleSetImpl::GetContext(nsIPresContext* aPresContext, 
                                          nsIStyleContext* aParentContext, nsIAtom* aPseudoTag, 
                                          nsISupportsArray* aRules,
                                          PRBool aForceUnique, PRBool& aUsedRules)
{
  nsIStyleContext* result = nsnull;

  aUsedRules = PR_FALSE;
  if ((PR_FALSE == aForceUnique) && 
      (nsnull != aParentContext) && (nsnull == aRules) && 
      (0 == aParentContext->GetStyleRuleCount())) {
    nsIAtom*  parentTag = nsnull;
    aParentContext->GetPseudoType(parentTag);
    if (parentTag == aPseudoTag) {
      // this and parent are empty, and compatible
      result = aParentContext;
      NS_ADDREF(result);  // add ref for the caller
    }
    NS_IF_RELEASE(parentTag);
//fprintf(stdout, ".");
  }
  if (nsnull == result) {
    if ((PR_FALSE == aForceUnique) && (nsnull != aParentContext)) {
      aParentContext->FindChildWithRules(aPseudoTag, aRules, result);
    }
    if (nsnull == result) {
      if (NS_OK == NS_NewStyleContext(&result, aParentContext, aPseudoTag, aRules, aPresContext)) {
        if (PR_TRUE == aForceUnique) {
          result->ForceUnique();
        }
        aUsedRules = PRBool(nsnull != aRules);
      }
//fprintf(stdout, "+");
    }
    else {
//fprintf(stdout, "-");
    }
  }
  return result;
}

// XXX for now only works for strength 0 & 1
static void SortRulesByStrength(nsISupportsArray* aRules, PRInt32& aBackstopRuleCount)
{
  PRUint32 cnt;
  nsresult rv = aRules->Count(&cnt);
  if (NS_FAILED(rv)) return;    // XXX error?
  PRInt32 count = (PRInt32)cnt;

  if (1 < count) {
    PRInt32 index;
    PRInt32 strength;
    for (index = 0; index < count; ) {
      nsIStyleRule* rule = (nsIStyleRule*)aRules->ElementAt(index);
      rule->GetStrength(strength);
      if (0 < strength) {
        aRules->RemoveElementAt(index);
        aRules->AppendElement(rule);
        count--;
        if (index < aBackstopRuleCount) {
          aBackstopRuleCount--;
        }
      }
      else {
        index++;
      }
      NS_RELEASE(rule);
    }
  }
}

#ifdef NS_DEBUG
#define NS_ASSERT_REFCOUNT(ptr,cnt,msg) { \
  nsrefcnt  count = ptr->AddRef();        \
  ptr->Release();                         \
  NS_ASSERTION(--count == cnt, msg);      \
}
#else
#define NS_ASSERT_REFCOUNT(ptr,cnt,msg) {}
#endif

nsIStyleContext* StyleSetImpl::ResolveStyleFor(nsIPresContext* aPresContext,
                                               nsIContent* aContent,
                                               nsIStyleContext* aParentContext,
                                               PRBool aForceUnique)
{
  nsIStyleContext*  result = nsnull;

  NS_ASSERTION(aContent, "must have content");
  NS_ASSERTION(aPresContext, "must have pres context");

  if (aContent && aPresContext) {
    nsISupportsArray*  rules = mRecycler;
    mRecycler = nsnull;
    if (nsnull == rules) {
      NS_NewISupportsArray(&rules);
    }

    if (nsnull != rules) {
      nsIAtom* medium = nsnull;
      aPresContext->GetMedium(&medium);
      RulesMatchingData data(aPresContext, medium, aContent, aParentContext, rules);
      if (mBackstopSheets) {
        mBackstopSheets->EnumerateBackwards(EnumRulesMatching, &data);
      }
      PRInt32 backstopRules = data.mCount;
      if (mDocSheets) {
        mDocSheets->EnumerateBackwards(EnumRulesMatching, &data);
      }
      if (mOverrideSheets) {
        mOverrideSheets->EnumerateBackwards(EnumRulesMatching, &data);
      }

      PRBool usedRules = PR_FALSE;
      if (0 < data.mCount) {
        SortRulesByStrength(rules, backstopRules);
        result = GetContext(aPresContext, aParentContext, nsnull, rules, aForceUnique, usedRules);
        if (usedRules) {
          NS_ASSERT_REFCOUNT(rules, 2, "rules array was used elsewhere");
          NS_RELEASE(rules);
        }
        else {
          NS_ASSERT_REFCOUNT(rules, 1, "rules array was used elsewhere");
          rules->Clear();
          mRecycler = rules;
        }
      }
      else {
        NS_ASSERT_REFCOUNT(rules, 1, "rules array was used elsewhere");
        mRecycler = rules;
        result = GetContext(aPresContext, aParentContext, nsnull, nsnull, aForceUnique, usedRules);
      }
      NS_RELEASE(medium);
    }
  }

  return result;
}

struct PseudoRulesMatchingData {
  PseudoRulesMatchingData(nsIPresContext* aPresContext,
                          nsIAtom* aMedium,
                          nsIContent* aParentContent,
                          nsIAtom* aPseudoTag,
                          nsIStyleContext* aParentContext,
                          nsISupportsArray* aResults)
    : mPresContext(aPresContext),
      mMedium(aMedium),
      mParentContent(aParentContent),
      mPseudoTag(aPseudoTag),
      mParentContext(aParentContext),
      mResults(aResults),
      mCount(0)
  {
  }
  nsIPresContext*   mPresContext;
  nsIAtom*          mMedium;
  nsIContent*       mParentContent;
  nsIAtom*          mPseudoTag;
  nsIStyleContext*  mParentContext;
  nsISupportsArray* mResults;
  PRInt32           mCount;

};

static PRBool
EnumPseudoRulesMatching(nsISupports* aSheet, void* aData)
{
  nsIStyleSheet*  sheet = (nsIStyleSheet*)aSheet;
  PseudoRulesMatchingData* data = (PseudoRulesMatchingData*)aData;

  if (NS_OK == sheet->UseForMedium(data->mMedium)) {
    data->mCount += sheet->RulesMatching(data->mPresContext, data->mParentContent, 
                                         data->mPseudoTag, 
                                         data->mParentContext, data->mResults);
  }
  return PR_TRUE;
}

nsIStyleContext* StyleSetImpl::ResolvePseudoStyleFor(nsIPresContext* aPresContext,
                                                     nsIContent* aParentContent,
                                                     nsIAtom* aPseudoTag,
                                                     nsIStyleContext* aParentContext,
                                                     PRBool aForceUnique)
{
  nsIStyleContext*  result = nsnull;

  NS_ASSERTION(aPseudoTag, "must have pseudo tag");
  NS_ASSERTION(aPresContext, "must have pres context");

  if (aPseudoTag && aPresContext) {
    nsISupportsArray*  rules = mRecycler;
    mRecycler = nsnull;
    if (nsnull == rules) {
      NS_NewISupportsArray(&rules);
    }

    if (nsnull != rules) {
      nsIAtom* medium = nsnull;
      aPresContext->GetMedium(&medium);
      PseudoRulesMatchingData data(aPresContext, medium, aParentContent, 
                                   aPseudoTag, aParentContext, rules);
      if (mBackstopSheets) {
        mBackstopSheets->EnumerateBackwards(EnumPseudoRulesMatching, &data);
      }
      PRInt32 backstopRules = data.mCount;
      if (mDocSheets) {
        mDocSheets->EnumerateBackwards(EnumPseudoRulesMatching, &data);
      }
      if (mOverrideSheets) {
        mOverrideSheets->EnumerateBackwards(EnumPseudoRulesMatching, &data);
      }

      PRBool usedRules = PR_FALSE;
      if (0 < data.mCount) {
        SortRulesByStrength(rules, backstopRules);
        result = GetContext(aPresContext, aParentContext, aPseudoTag, rules, aForceUnique, usedRules);
        if (usedRules) {
          NS_ASSERT_REFCOUNT(rules, 2, "rules array was used elsewhere");
          NS_RELEASE(rules);
        }
        else {
          NS_ASSERT_REFCOUNT(rules, 1, "rules array was used elsewhere");
          rules->Clear();
          mRecycler = rules;
        }
      }
      else {
        NS_ASSERT_REFCOUNT(rules, 1, "rules array was used elsewhere");
        mRecycler = rules;
        result = GetContext(aPresContext, aParentContext, aPseudoTag, nsnull, aForceUnique, usedRules);
      }
      NS_IF_RELEASE(medium);
    }
  }

  return result;
}

nsIStyleContext* StyleSetImpl::ProbePseudoStyleFor(nsIPresContext* aPresContext,
                                                   nsIContent* aParentContent,
                                                   nsIAtom* aPseudoTag,
                                                   nsIStyleContext* aParentContext,
                                                   PRBool aForceUnique)
{
  nsIStyleContext*  result = nsnull;

  NS_ASSERTION(aPseudoTag, "must have pseudo tag");
  NS_ASSERTION(aPresContext, "must have pres context");

  if (aPseudoTag && aPresContext) {
    nsISupportsArray*  rules = mRecycler;
    mRecycler = nsnull;
    if (nsnull == rules) {
      NS_NewISupportsArray(&rules);
    }

    if (nsnull != rules) {
      nsIAtom* medium = nsnull;
      aPresContext->GetMedium(&medium);
      PseudoRulesMatchingData data(aPresContext, medium, aParentContent, 
                                   aPseudoTag, aParentContext, rules);
      if (mBackstopSheets) {
        mBackstopSheets->EnumerateBackwards(EnumPseudoRulesMatching, &data);
      }
      PRInt32 backstopRules = data.mCount;
      if (mDocSheets) {
        mDocSheets->EnumerateBackwards(EnumPseudoRulesMatching, &data);
      }
      if (mOverrideSheets) {
        mOverrideSheets->EnumerateBackwards(EnumPseudoRulesMatching, &data);
      }

      PRBool usedRules = PR_FALSE;
      if (0 < data.mCount) {
        SortRulesByStrength(rules, backstopRules);
        result = GetContext(aPresContext, aParentContext, aPseudoTag, rules, aForceUnique, usedRules);
        if (usedRules) {
          NS_ASSERT_REFCOUNT(rules, 2, "rules array was used elsewhere");
          NS_RELEASE(rules);
        }
        else {
          NS_ASSERT_REFCOUNT(rules, 1, "rules array was used elsewhere");
          rules->Clear();
          mRecycler = rules;
        }
      }
      else {
        NS_ASSERT_REFCOUNT(rules, 1, "rules array was used elsewhere");
        mRecycler = rules;
      }
      NS_IF_RELEASE(medium);
    }
  }

  return result;
}


NS_IMETHODIMP
StyleSetImpl::ReParentStyleContext(nsIPresContext* aPresContext,
                                   nsIStyleContext* aStyleContext, 
                                   nsIStyleContext* aNewParentContext,
                                   nsIStyleContext** aNewStyleContext)
{
  NS_ASSERTION(aPresContext, "must have pres context");
  NS_ASSERTION(aPresContext, "must have pres context");
  NS_ASSERTION(aPresContext, "must have pres context");

  nsresult result = NS_ERROR_NULL_POINTER;

  if (aPresContext && aStyleContext && aNewStyleContext) {
    nsIStyleContext* oldParent = aStyleContext->GetParent();

    if (oldParent == aNewParentContext) {
      result = NS_OK;
      NS_ADDREF(aStyleContext);   // for return
      *aNewStyleContext = aStyleContext;
    }
    else {  // really a new parent
      nsIStyleContext*  newChild = nsnull;
      nsIAtom*  pseudoTag = nsnull;
      aStyleContext->GetPseudoType(pseudoTag);
      nsISupportsArray* rules = aStyleContext->GetStyleRules();
      if (aNewParentContext) {
        result = aNewParentContext->FindChildWithRules(pseudoTag, rules, newChild);
      }
      if (newChild) { // new parent already has one
        *aNewStyleContext = newChild;
      }
      else {  // need to make one in the new parent
        nsISupportsArray*  newRules = nsnull;
        if (rules) {
          newRules = mRecycler;
          mRecycler = nsnull;
          if (! newRules) {
            result = NS_NewISupportsArray(&newRules);
          }
          if (newRules) {
            newRules->AppendElements(rules);
          }
        }
        result = NS_NewStyleContext(aNewStyleContext, aNewParentContext, pseudoTag,
                                    newRules, aPresContext);
        NS_IF_RELEASE(newRules);
      }

      NS_IF_RELEASE(rules);
      NS_IF_RELEASE(pseudoTag);
    }

    NS_IF_RELEASE(oldParent);
  }
  return result;
}

struct StatefulData {
  StatefulData(nsIPresContext* aPresContext, nsIContent* aContent)
    : mPresContext(aPresContext),
      mContent(aContent),
      mStateful(PR_FALSE)
  {}
  nsIPresContext* mPresContext;
  nsIContent*     mContent;
  PRBool          mStateful;
}; 

static PRBool SheetHasStatefulStyle(nsISupports* aElement, void *aData)
{
  nsIStyleSheet* sheet = (nsIStyleSheet*)aElement;
  StatefulData* data = (StatefulData*)aData;
  if (NS_OK == sheet->HasStateDependentStyle(data->mPresContext, data->mContent)) {
    data->mStateful = PR_TRUE;
    return PR_FALSE;  // stop iteration
  }
  return PR_TRUE; // continue
}

// Test if style is dependent on content state
NS_IMETHODIMP
StyleSetImpl::HasStateDependentStyle(nsIPresContext* aPresContext,
                                     nsIContent*     aContent)
{
  StatefulData data(aPresContext, aContent);
  if (mBackstopSheets) {
    mBackstopSheets->EnumerateForwards(SheetHasStatefulStyle, &data);
  }
  if (mDocSheets && (! data.mStateful)) {
    mDocSheets->EnumerateForwards(SheetHasStatefulStyle, &data);
  }
  if (mOverrideSheets && (! data.mStateful)) {
    mOverrideSheets->EnumerateForwards(SheetHasStatefulStyle, &data);
  }
  return ((data.mStateful) ? NS_OK : NS_COMFALSE);
}


NS_IMETHODIMP StyleSetImpl::ConstructRootFrame(nsIPresContext* aPresContext,
                                               nsIContent*     aDocElement,
                                               nsIFrame*&      aFrameSubTree)
{
  return mFrameConstructor->ConstructRootFrame(aPresContext, aDocElement,
                                               aFrameSubTree);
}

NS_IMETHODIMP   
StyleSetImpl::ReconstructDocElementHierarchy(nsIPresContext* aPresContext)
{
  return mFrameConstructor->ReconstructDocElementHierarchy(aPresContext);
}

NS_IMETHODIMP StyleSetImpl::ContentAppended(nsIPresContext* aPresContext,
                                            nsIContent*     aContainer,
                                            PRInt32         aNewIndexInContainer)
{
  return mFrameConstructor->ContentAppended(aPresContext, 
                                            aContainer, aNewIndexInContainer);
}

NS_IMETHODIMP StyleSetImpl::ContentInserted(nsIPresContext* aPresContext,
                                            nsIContent*     aContainer,
                                            nsIContent*     aChild,
                                            PRInt32         aIndexInContainer)
{
  return mFrameConstructor->ContentInserted(aPresContext, aContainer,
                                            aChild, aIndexInContainer);
}

NS_IMETHODIMP StyleSetImpl::ContentReplaced(nsIPresContext* aPresContext,
                                            nsIContent*     aContainer,
                                            nsIContent*     aOldChild,
                                            nsIContent*     aNewChild,
                                            PRInt32         aIndexInContainer)
{
  return mFrameConstructor->ContentReplaced(aPresContext, aContainer,
                                            aOldChild, aNewChild, aIndexInContainer);
}

NS_IMETHODIMP StyleSetImpl::ContentRemoved(nsIPresContext* aPresContext,
                                           nsIContent*     aContainer,
                                           nsIContent*     aChild,
                                           PRInt32         aIndexInContainer)
{
  return mFrameConstructor->ContentRemoved(aPresContext, aContainer,
                                           aChild, aIndexInContainer);
}

NS_IMETHODIMP
StyleSetImpl::ContentChanged(nsIPresContext* aPresContext,
                             nsIContent* aContent,
                             nsISupports* aSubContent)
{
  return mFrameConstructor->ContentChanged(aPresContext, 
                                           aContent, aSubContent);
}

NS_IMETHODIMP
StyleSetImpl::ContentStatesChanged(nsIPresContext* aPresContext, 
                                   nsIContent* aContent1,
                                   nsIContent* aContent2)
{
  return mFrameConstructor->ContentStatesChanged(aPresContext, aContent1, aContent2);
}


NS_IMETHODIMP
StyleSetImpl::AttributeChanged(nsIPresContext* aPresContext,
                               nsIContent* aContent,
                               nsIAtom* aAttribute,
                               PRInt32 aHint)
{
  return mFrameConstructor->AttributeChanged(aPresContext, aContent, 
                                             aAttribute, aHint);
}


// Style change notifications
NS_IMETHODIMP
StyleSetImpl::StyleRuleChanged(nsIPresContext* aPresContext,
                               nsIStyleSheet* aStyleSheet,
                               nsIStyleRule* aStyleRule,
                               PRInt32 aHint)
{
  return mFrameConstructor->StyleRuleChanged(aPresContext, aStyleSheet, aStyleRule, aHint);
}

NS_IMETHODIMP
StyleSetImpl::StyleRuleAdded(nsIPresContext* aPresContext,
                             nsIStyleSheet* aStyleSheet,
                             nsIStyleRule* aStyleRule)
{
  return mFrameConstructor->StyleRuleAdded(aPresContext, aStyleSheet, aStyleRule);
}

NS_IMETHODIMP
StyleSetImpl::StyleRuleRemoved(nsIPresContext* aPresContext,
                               nsIStyleSheet* aStyleSheet,
                               nsIStyleRule* aStyleRule)
{
  return mFrameConstructor->StyleRuleRemoved(aPresContext, aStyleSheet, aStyleRule);
}

NS_IMETHODIMP
StyleSetImpl::CantRenderReplacedElement(nsIPresContext* aPresContext,
                                        nsIFrame*       aFrame)
{
  return mFrameConstructor->CantRenderReplacedElement(aPresContext, aFrame);
}

NS_IMETHODIMP
StyleSetImpl::CreateContinuingFrame(nsIPresContext* aPresContext,
                                    nsIFrame*       aFrame,
                                    nsIFrame*       aParentFrame,
                                    nsIFrame**      aContinuingFrame)
{
  return mFrameConstructor->CreateContinuingFrame(aPresContext, aFrame, aParentFrame,
                                                  aContinuingFrame);
}

// Request to find the primary frame associated with a given content object.
// This is typically called by the pres shell when there is no mapping in
// the pres shell hash table
NS_IMETHODIMP
StyleSetImpl::FindPrimaryFrameFor(nsIPresContext*  aPresContext,
                                  nsIFrameManager* aFrameManager,
                                  nsIContent*      aContent,
                                  nsIFrame**       aFrame)
{
  return mFrameConstructor->FindPrimaryFrameFor(aPresContext, aFrameManager,
                                                aContent, aFrame);
}

void StyleSetImpl::List(FILE* out, PRInt32 aIndent, nsISupportsArray* aSheets)
{
  PRUint32 cnt = 0;
  if (aSheets) {
    nsresult rv = aSheets->Count(&cnt);
    if (NS_FAILED(rv)) return;    // XXX error?
  }

  for (PRInt32 index = 0; index < (PRInt32)cnt; index++) {
    nsIStyleSheet* sheet = (nsIStyleSheet*)aSheets->ElementAt(index);
    sheet->List(out, aIndent);
    fputs("\n", out);
    NS_RELEASE(sheet);
  }
}

void StyleSetImpl::List(FILE* out, PRInt32 aIndent)
{
//  List(out, aIndent, mOverrideSheets);
  List(out, aIndent, mDocSheets);
//  List(out, aIndent, mBackstopSheets);
}

void StyleSetImpl::ListContexts(nsIStyleContext* aRootContext, FILE* out, PRInt32 aIndent)
{
  aRootContext->List(out, aIndent);
}


NS_LAYOUT nsresult
NS_NewStyleSet(nsIStyleSet** aInstancePtrResult)
{
  if (aInstancePtrResult == nsnull) {
    return NS_ERROR_NULL_POINTER;
  }

  StyleSetImpl  *it = new StyleSetImpl();

  if (nsnull == it) {
    return NS_ERROR_OUT_OF_MEMORY;
  }

  return it->QueryInterface(kIStyleSetIID, (void **) aInstancePtrResult);
}