public AssembledStyles WithFontItalic(FwTextToggleVal ttv)
{
int val = (int) ttv;
if (ttv == FwTextToggleVal.kttvInvert)
val = FontItalic ? (int) FwTextToggleVal.kttvOff : (int) FwTextToggleVal.kttvForceOn;
return m_styleCache.GetDerivedStyle(this, (int)FwTextPropType.ktptItalic, val,
(newStyles, w) => newStyles.m_chrp.ttvItalic = val);
}