DIBs with negative width/height

[Damjan Jovanovic]

Hi

Does anyone know (or know where to find) what it means for biWidth
and/or biHeight for a DIB section's BITMAPINFOHEADER to be negative?
It seems largely undocumented. The MSDN says a negative biHeight is a
top-down bitmap (the normal positive biHeight is bottom-up), so does a
negative biWidth mean scanlines run from right to left?

Thank you
Damjan