float
SVGLength::GetValueInSpecifiedUnit(PRUint8 aUnit,
const nsSVGElement *aElement,
PRUint8 aAxis) const
{
if (aUnit == mUnit) {
return mValue;
}
if ((aUnit == nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER &&
mUnit == nsIDOMSVGLength::SVG_LENGTHTYPE_PX) ||
(aUnit == nsIDOMSVGLength::SVG_LENGTHTYPE_PX &&
mUnit == nsIDOMSVGLength::SVG_LENGTHTYPE_NUMBER)) {
return mValue;
}
if (IsAbsoluteUnit(aUnit) && IsAbsoluteUnit(mUnit)) {
return mValue * GetAbsUnitsPerAbsUnit(aUnit, mUnit);
}
// Otherwise we do a two step convertion via user units. This can only
// succeed if aElement is non-null (although that's not sufficent to
// guarantee success).
float userUnitsPerCurrentUnit = GetUserUnitsPerUnit(aElement, aAxis);
float userUnitsPerNewUnit =
SVGLength(0.0f, aUnit).GetUserUnitsPerUnit(aElement, aAxis);
NS_ASSERTION(userUnitsPerCurrentUnit >= 0 ||
!NS_finite(userUnitsPerCurrentUnit),
"bad userUnitsPerCurrentUnit");
NS_ASSERTION(userUnitsPerNewUnit >= 0 ||
!NS_finite(userUnitsPerNewUnit),
"bad userUnitsPerNewUnit");
float value = mValue * userUnitsPerCurrentUnit / userUnitsPerNewUnit;
// userUnitsPerCurrentUnit could be infinity, or userUnitsPerNewUnit could
// be zero.
if (NS_finite(value)) {
return value;
}
return std::numeric_limits<float>::quiet_NaN();
}
/**
* Helper to convert between different CSS absolute units without the need for
* an element, which provides more flexibility at the DOM level (and without
* the need for an intermediary conversion to user units, which avoids
* unnecessary overhead and rounding error).
*
* Example usage: to find out how many centimeters there are per inch:
*
* GetAbsUnitsPerAbsUnit(nsIDOMSVGLength::SVG_LENGTHTYPE_CM,
* nsIDOMSVGLength::SVG_LENGTHTYPE_IN)
*/
inline static float GetAbsUnitsPerAbsUnit(PRUint8 aUnits, PRUint8 aPerUnit)
{
NS_ABORT_IF_FALSE(IsAbsoluteUnit(aUnits), "Not a CSS absolute unit");
NS_ABORT_IF_FALSE(IsAbsoluteUnit(aPerUnit), "Not a CSS absolute unit");
float CSSAbsoluteUnitConversionFactors[5][5] = { // columns: cm, mm, in, pt, pc
// cm per...:
{ 1.0, 0.1, 2.54, 0.035277777777777778, 0.42333333333333333 },
// mm per...:
{ 10.0, 1.0, 25.4, 0.35277777777777778, 4.2333333333333333 },
// in per...:
{ 0.39370078740157481, 0.039370078740157481, 1.0, 0.013888888888888889, 0.16666666666666667 },
// pt per...:
{ 28.346456692913386, 2.8346456692913386, 72.0, 1.0, 12.0 },
// pc per...:
{ 2.3622047244094489, 0.23622047244094489, 6.0, 0.083333333333333333, 1.0 }
};
// First absolute unit is SVG_LENGTHTYPE_CM = 6
return CSSAbsoluteUnitConversionFactors[aUnits - 6][aPerUnit - 6];
}
/**
* Helper to convert between different CSS absolute units without the need for
* an element, which provides more flexibility at the DOM level (and without
* the need for an intermediary conversion to user units, which avoids
* unnecessary overhead and rounding error).
*
* Example usage: to find out how many centimeters there are per inch:
*
* GetAbsUnitsPerAbsUnit(nsIDOMSVGLength::SVG_LENGTHTYPE_CM,
* nsIDOMSVGLength::SVG_LENGTHTYPE_IN)
*/
inline static float GetAbsUnitsPerAbsUnit(uint8_t aUnits, uint8_t aPerUnit)
{
MOZ_ASSERT(IsAbsoluteUnit(aUnits), "Not a CSS absolute unit");
MOZ_ASSERT(IsAbsoluteUnit(aPerUnit), "Not a CSS absolute unit");
float CSSAbsoluteUnitConversionFactors[5][5] = { // columns: cm, mm, in, pt, pc
// cm per...:
{ 1.0f, 0.1f, 2.54f, 0.035277777777777778f, 0.42333333333333333f },
// mm per...:
{ 10.0f, 1.0f, 25.4f, 0.35277777777777778f, 4.2333333333333333f },
// in per...:
{ 0.39370078740157481f, 0.039370078740157481f, 1.0f, 0.013888888888888889f, 0.16666666666666667f },
// pt per...:
{ 28.346456692913386f, 2.8346456692913386f, 72.0f, 1.0f, 12.0f },
// pc per...:
{ 2.3622047244094489f, 0.23622047244094489f, 6.0f, 0.083333333333333333f, 1.0f }
};
// First absolute unit is SVG_LENGTHTYPE_CM = 6
return CSSAbsoluteUnitConversionFactors[aUnits - 6][aPerUnit - 6];
}
