gecko/xpcom/ds/nsUnitConversion.h

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#ifndef nsUnitConversion_h__
#define nsUnitConversion_h__

#include "nscore.h"
#include "nsCoord.h"
#include "nsMathUtils.h"
#include <math.h>
#include <float.h>

/// handy constants
#define TWIPS_PER_POINT_INT           20
#define TWIPS_PER_POINT_FLOAT         20.0f

/*
 * Coord Rounding Functions
 */
inline nscoord NSToCoordFloor(float aValue)
{
  return nscoord(NS_floorf(aValue));
}

inline nscoord NSToCoordCeil(float aValue)
{
  return nscoord(NS_ceilf(aValue));
}

inline nscoord NSToCoordRound(float aValue)
{
  return nscoord(NS_floorf(aValue + 0.5f));
}

/*
 * Int Rounding Functions
 */
inline PRInt32 NSToIntFloor(float aValue)
{
  return PRInt32(NS_floorf(aValue));
}

inline PRInt32 NSToIntCeil(float aValue)
{
  return PRInt32(NS_ceilf(aValue));
}

inline PRInt32 NSToIntRound(float aValue)
{
  return NS_lroundf(aValue);
}

/* 
 * App Unit/Pixel conversions
 */
inline nscoord NSFloatPixelsToAppUnits(float aPixels, PRInt32 aAppUnitsPerPixel)
{
  float product = aPixels * aAppUnitsPerPixel;
  nscoord result;

#ifdef NS_COORD_IS_FLOAT
  // No need to bounds-check if converting float to float
  result = NSToCoordRound(product);
#else
  // Bounds-check before converting out of float, to avoid overflow
  if (product >= nscoord_MAX) {
    NS_WARNING("Overflowed nscoord_MAX in conversion to nscoord");
    result = nscoord_MAX;
  } else if (product <= nscoord_MIN) {
    NS_WARNING("Overflowed nscoord_MIN in conversion to nscoord");
    result = nscoord_MIN;
  } else {
    result = NSToCoordRound(product);
  }
#endif

  VERIFY_COORD(result);
  return result;
}

inline nscoord NSIntPixelsToAppUnits(PRInt32 aPixels, PRInt32 aAppUnitsPerPixel)
{
  // The cast to nscoord makes sure we don't overflow if we ever change
  // nscoord to float
  nscoord r = aPixels * (nscoord)aAppUnitsPerPixel;
  VERIFY_COORD(r);
  return r;
}

inline float NSAppUnitsToFloatPixels(nscoord aAppUnits, PRInt32 aAppUnitsPerPixel)
{
  return (float(aAppUnits) / aAppUnitsPerPixel);
}

inline PRInt32 NSAppUnitsToIntPixels(nscoord aAppUnits, PRInt32 aAppUnitsPerPixel)
{
  return NSToIntRound(float(aAppUnits) / aAppUnitsPerPixel);
}

/* 
 * Twips/unit conversions
 */
inline nscoord NSUnitsToTwips(float aValue, float aPointsPerUnit)
{
  return NSToCoordRound(aValue * aPointsPerUnit * TWIPS_PER_POINT_FLOAT);
}

inline float NSTwipsToUnits(nscoord aTwips, float aUnitsPerPoint)
{
  return (aTwips * (aUnitsPerPoint / TWIPS_PER_POINT_FLOAT));
}


/// Unit conversion macros
//@{
#define NS_POINTS_TO_TWIPS(x)         NSUnitsToTwips((x), 1.0f)
#define NS_INCHES_TO_TWIPS(x)         NSUnitsToTwips((x), 72.0f)                      // 72 points per inch
#define NS_FEET_TO_TWIPS(x)           NSUnitsToTwips((x), (72.0f * 12.0f))            // 12 inches per foot
#define NS_MILES_TO_TWIPS(x)          NSUnitsToTwips((x), (72.0f * 12.0f * 5280.0f))  // 5280 feet per mile

#define NS_MILLIMETERS_TO_TWIPS(x)    NSUnitsToTwips((x), (72.0f * 0.03937f))
#define NS_CENTIMETERS_TO_TWIPS(x)    NSUnitsToTwips((x), (72.0f * 0.3937f))
#define NS_METERS_TO_TWIPS(x)         NSUnitsToTwips((x), (72.0f * 39.37f))
#define NS_KILOMETERS_TO_TWIPS(x)     NSUnitsToTwips((x), (72.0f * 39370.0f))

#define NS_PICAS_TO_TWIPS(x)          NSUnitsToTwips((x), 12.0f)                      // 12 points per pica
#define NS_DIDOTS_TO_TWIPS(x)         NSUnitsToTwips((x), (16.0f / 15.0f))            // 15 didots per 16 points
#define NS_CICEROS_TO_TWIPS(x)        NSUnitsToTwips((x), (12.0f * (16.0f / 15.0f)))  // 12 didots per cicero

#define NS_TWIPS_TO_POINTS(x)         NSTwipsToUnits((x), 1.0f)
#define NS_TWIPS_TO_INCHES(x)         NSTwipsToUnits((x), 1.0f / 72.0f)
#define NS_TWIPS_TO_FEET(x)           NSTwipsToUnits((x), 1.0f / (72.0f * 12.0f))
#define NS_TWIPS_TO_MILES(x)          NSTwipsToUnits((x), 1.0f / (72.0f * 12.0f * 5280.0f))

#define NS_TWIPS_TO_MILLIMETERS(x)    NSTwipsToUnits((x), 1.0f / (72.0f * 0.03937f))
#define NS_TWIPS_TO_CENTIMETERS(x)    NSTwipsToUnits((x), 1.0f / (72.0f * 0.3937f))
#define NS_TWIPS_TO_METERS(x)         NSTwipsToUnits((x), 1.0f / (72.0f * 39.37f))
#define NS_TWIPS_TO_KILOMETERS(x)     NSTwipsToUnits((x), 1.0f / (72.0f * 39370.0f))

#define NS_TWIPS_TO_PICAS(x)          NSTwipsToUnits((x), 1.0f / 12.0f)
#define NS_TWIPS_TO_DIDOTS(x)         NSTwipsToUnits((x), 1.0f / (16.0f / 15.0f))
#define NS_TWIPS_TO_CICEROS(x)        NSTwipsToUnits((x), 1.0f / (12.0f * (16.0f / 15.0f)))
//@}

#endif