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#ifndef nsIStyleContext_h___
#define nsIStyleContext_h___

#include "nsISupports.h"
#include "nsColor.h"
#include "nsCoord.h"
#include "nsMargin.h"
#include "nsRect.h"
#include "nsFont.h"
#include "nsVoidArray.h"
#include "nsStyleCoord.h"
#include "nsStyleStruct.h"
#include "nsStyleConsts.h"
#include "nsCOMPtr.h"
#include "nsILanguageAtom.h"

class nsISizeOfHandler;

class nsIFrame;
class nsIStyleSet;
class nsIPresContext;
class nsISupportsArray;
class nsIStyleContext;
class nsRuleNode;

//----------------------------------------------------------------------

#define NS_ISTYLECONTEXT_IID   \
 { 0x26a4d970, 0xa342, 0x11d1, \
   {0x89, 0x74, 0x00, 0x60, 0x08, 0x91, 0x1b, 0x81} }

class nsIStyleContext : public nsISupports {
public:
  static const nsIID& GetIID() { static nsIID iid = NS_ISTYLECONTEXT_IID; return iid; }

  virtual PRBool    Equals(const nsIStyleContext* aOther) const = 0;
  
  virtual nsIStyleContext*  GetParent(void) const = 0;
  NS_IMETHOD GetFirstChild(nsIStyleContext** aContext)=0;

  NS_IMETHOD GetPseudoType(nsIAtom*& aPseudoTag) const = 0;

  NS_IMETHOD FindChildWithRules(const nsIAtom* aPseudoTag, 
                                nsRuleNode* aRules,
                                nsIStyleContext*& aResult) = 0;

  virtual PRBool HasTextDecorations()=0;

   
  NS_IMETHOD GetBorderPaddingFor(nsStyleBorderPadding& aBorderPadding)=0;

  // This method computes the effective difference between two contexts that are both at the
  // same position in the style context tree.  The |this| parameter must always
  // be the old context.  This method will only peek at style data on the old
  // context, and will not instantiate new data in order to compute a difference.
  // That is why the old context must always be used (since the new context will
  // have no data on it yet) for determining the actual difference.
  NS_IMETHOD CalcStyleDifference(nsIStyleContext* aOther, PRInt32& aHint) = 0;

  NS_IMETHOD GetRuleNode(nsRuleNode** aResult)=0;
  NS_IMETHOD AddStyleBit(const PRUint32& aBit)=0;
  NS_IMETHOD GetStyleBits(PRUint32* aBits)=0;

#ifdef DEBUG
  // debugging
  virtual void List(FILE* out, PRInt32 aIndent) = 0;
  virtual void SizeOf(nsISizeOfHandler *aSizeOfHandler, PRUint32 &aSize) = 0;
  virtual void DumpRegressionData(nsIPresContext* aPresContext, FILE* out, PRInt32 aIndent)=0;
#endif

  // XXXdwh Make this function private.  It should not be possible to call this
  // function from layout.
  // Fill a style struct with data.  
  NS_IMETHOD SetStyle(nsStyleStructID aSID, const nsStyleStruct& aStruct) = 0;
  
  // Get the data for a style struct.
  NS_IMETHOD GetStyle(nsStyleStructID aSID, const nsStyleStruct** aStruct) = 0;

  virtual const nsStyleStruct* GetStyleData(nsStyleStructID aSID) = 0;

  // Avoid using this method at all costs.  It defeats sharing of style data, forcing the context
  // to have its own unique copy.  At the moment the only supported structs are text, background, and
  // display.  Don't add support for new structs or use this method without careful consideration! -dwh
  virtual nsStyleStruct* GetUniqueStyleData(nsIPresContext* aPresContext, const nsStyleStructID& aSID) = 0;

  // Used only for inline style.
  virtual nsresult ClearCachedDataForRule(nsIStyleRule* aRule) = 0;

  // Used to clear away the style data for a given style context if it matches the specified |aRule|.
  // If |aRule| is null, then the style data is always blown away.
  virtual nsresult ClearStyleData(nsIPresContext* aPresContext, nsIStyleRule* aRule) = 0;
 
  // call this to prevent context from getting shared
  virtual void  ForceUnique(void) = 0;
};


// this is private to nsStyleSet, don't call it
extern NS_EXPORT nsresult
  NS_NewStyleContext(nsIStyleContext** aInstancePtrResult,
                     nsIStyleContext* aParentContext,
                     nsIAtom* aPseudoType,
                     nsRuleNode* aRuleNode,
                     nsIPresContext* aPresContext);

// typesafe way to access style data.  See nsStyleStruct.h and also
// overloaded function in nsIFrame.h.
template <class T>
inline void
GetStyleData(nsIStyleContext* aStyleContext, const T** aStyleStruct)
{
    *aStyleStruct = NS_STATIC_CAST(const T*,
                         aStyleContext->GetStyleData(NS_GET_STYLESTRUCTID(T)));
}

#endif /* nsIStyleContext_h___ */