This is declared in the header [http://mxr.mozilla.org/mozilla-central/source/layout/xul/base/src/nsBox.h#111 here] as taking an ncoord& parameter however it is defined [http://mxr.mozilla.org/mozilla-central/source/layout/xul/base/src/nsBox.cpp#412 here] as taking PRInt32&. This could be problematic Won't compile if [http://mxr.mozilla.org/mozilla-central/source/gfx/public/nsCoord.h#74 NS_COORD_IS_FLOAT] is defined.