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#ifndef nsIPercentHeightObserver_h___
#define nsIPercentHeightObserver_h___

struct nsHTMLReflowState;
class  nsPresContext;

// IID for the nsIPercentHeightObserver interface 
#define NS_IPERCENTHEIGHTOBSERVER_IID \
 { 0x9cdc174b, 0x4f39, 0x41ad, {0xbc, 0x16, 0x5a, 0xc5, 0xa8, 0x64, 0x14, 0xa1}}

/**
 * This interface is supported by frames that need to provide computed height
 * values to children during reflow which would otherwise not happen. Currently only
 * table cells support this.
 */
class nsIPercentHeightObserver : public nsISupports
{
public:
  NS_DECLARE_STATIC_IID_ACCESSOR(NS_IPERCENTHEIGHTOBSERVER_IID)

  // Notify the observer that aReflowState has no computed height, but it has a percent height
  virtual void NotifyPercentHeight(const nsHTMLReflowState& aReflowState) = 0;

  // Ask the observer if it should observe aReflowState.frame
  virtual PRBool NeedsToObserve(const nsHTMLReflowState& aReflowState) = 0;
};

NS_DEFINE_STATIC_IID_ACCESSOR(nsIPercentHeightObserver,
                              NS_IPERCENTHEIGHTOBSERVER_IID)

#endif // nsIPercentHeightObserver_h___ 
