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#ifndef nsChangeHint_h___
#define nsChangeHint_h___

#include "prtypes.h"

// Defines for various style related constants

enum nsChangeHint {
  nsChangeHint_RepaintFrame = 0x01,  // change was visual only (e.g., COLOR=)
  nsChangeHint_ReflowFrame = 0x02,   // change requires reflow (e.g., WIDTH=)
  nsChangeHint_SyncFrameView = 0x04, // change requires view to be updated, if there is one (e.g., clip:)
  nsChangeHint_ReconstructFrame = 0x08   // change requires frame change (e.g., display:)
                                         // This subsumes all the above
  // TBD: add nsChangeHint_ForceFrameView to force frame reconstruction if the frame doesn't yet
  // have a view
};

#ifdef DEBUG_roc
// Redefine these operators to return nothing. This will catch any use
// of these operators on hints. We should not be using these operators
// on nsChangeHints
inline void operator<(nsChangeHint s1, nsChangeHint s2) {}
inline void operator>(nsChangeHint s1, nsChangeHint s2) {}
inline void operator!=(nsChangeHint s1, nsChangeHint s2) {}
inline void operator==(nsChangeHint s1, nsChangeHint s2) {}
inline void operator<=(nsChangeHint s1, nsChangeHint s2) {}
inline void operator>=(nsChangeHint s1, nsChangeHint s2) {}
#endif

// Operators on nsChangeHints

// Merge two hints, taking the union
inline nsChangeHint NS_CombineHint(nsChangeHint aH1, nsChangeHint aH2) {
  return (nsChangeHint)(aH1 | aH2);
}

// Merge two hints, taking the union
inline nsChangeHint NS_SubtractHint(nsChangeHint aH1, nsChangeHint aH2) {
  return (nsChangeHint)(aH1 & ~aH2);
}

// Merge the "src" hint into the "dst" hint
// Returns true iff the destination changed
inline PRBool NS_UpdateHint(nsChangeHint& aDest, nsChangeHint aSrc) {
  nsChangeHint r = (nsChangeHint)(aDest | aSrc);
  PRBool changed = (int)r != (int)aDest;
  aDest = r;
  return changed;
}

// Returns true iff the second hint contains all the hints of the first hint
inline PRBool NS_IsHintSubset(nsChangeHint aSubset, nsChangeHint aSuperSet) {
  return (aSubset & aSuperSet) == aSubset;
}

// Redefine the old NS_STYLE_HINT constants in terms of the new hint structure
#define NS_STYLE_HINT_NONE \
  nsChangeHint(0)
#define NS_STYLE_HINT_VISUAL \
  nsChangeHint(nsChangeHint_RepaintFrame | nsChangeHint_SyncFrameView)
#define NS_STYLE_HINT_REFLOW \
  nsChangeHint(NS_STYLE_HINT_VISUAL | nsChangeHint_ReflowFrame)
#define NS_STYLE_HINT_FRAMECHANGE \
  nsChangeHint(NS_STYLE_HINT_REFLOW | nsChangeHint_ReconstructFrame)


/**
 * |nsReStyleHint| is a bitfield for the result of |HasStateDependentStyle|
 * and |HasAttributeDependentStyle|.  All values have an implied "and
 * descendants."  When no restyling is necesary, use |nsReStyleHint(0)|.
 */
enum nsReStyleHint {
  eReStyle_Self = 0x1,
  eReStyle_LaterSiblings = 0x2
};


#endif /* nsChangeHint_h___ */
