gdiplus: negative stride from dipCreateBitmapFromFile

[bill lam]

WHen I read a jpeg file of size about 600x400 pixels using gdiplus like this,

GdipCreateBitmapFromFile fn BMP
GdipGetImageWidth BMP w
GdipGetImageHeight BMP h
rt=. 0 0, w, h
GdipBitmapLockBits BMP rt ImageLockModeRead PixelFormat32bppARGB DATA
'w h s f p r'=. DATA

the member stride inside bitmapdata is negative, and its data buffer cannot be 
read successfully.

when using native gdiplus that stride is positive, and it work ok.

wine said itself cannot handle negitive stride yet so why itself create a bitmap 
wih negative stride in GdipCreateBitmapFromFile?