This does not fix the real problem (ie why does this DC not have a font even if the application called a 'SelectObject' on it), but well, it cannot harm to be more verbose and to prevent crashes if possible :-)
OK, found the 'error' : the problem comes from the fact that I am using client-side fonts (aka XRender) : so the 'font' part of the physDev structure is always '0'. And that also means that we cannot use as is the glXUseXFont function.
So basically, I need to implement it myself using 'GetGlyphOutline' (should not be that hard to do :-) ).
Now my question : is 'GetGlyphOutline' always working even when not using client-side fonts ? If yes, I will completely remove the call to glXUseXFonts (I know, in that case, fonts displayed by OpenGL will be different by the one displayed by X, but well, ...) and always use the manual 'GetGlyphOutline' function.
And I will try at the same time to remove all GLX calls from wgl.c and put them in special X11DRV escapes to have a real X11 free wgl.c file (ie for example, creating an OpenGL context would be a special escape for the X11DRV as it's basically something that is in GLX).
Lionel