🚀 go-pugleaf

Hello out there.  I realize that I'm about to be flamed for being such an
advocate of WC and end up asking a question about it, however ...

I have been trying to call my VESA driver from a WC 9.0 program.  The 
DOS4GW version is 1.8 (which is pretty ancient, but it mostly works well
for me).  The scenario is pretty simply.  I need to set AX=4F00, and
ES:DI to my _far address (i.e., below the first meg) then call int 10
and watch ES:DI fill up with lotsa goodly info.

In real mode this is not a problem (I wrote a little .com file which
functions perfectly).  To do this in WC, I first allocated some low
memory using DPMI function 0x0400.  I got back a segment and selector
that I verified were reasonable values.  Then to use it, I simply
calculated the flat address equivalent (i.e., segment*0x10) in a
variable I called "VIS".  Then, before calling int 10 I set ES to 
(VIS & 0xF0000) >> 4 and DI to (VIS & 0xFFFF), AX=0x4F00.  Upon return
from the int 10, I got the required 0x004F.  But the information in
VIS was untouched.  I verified this with 3 different VESA drivers, so
I am pretty sure that the VESA drivers are not at fault.

Does anyone know exactly what's going wrong?  I might be mixing up the
definition of selector and segment, but in most cases ES becomes 0,
which I assume was translated to 0 either as a selector or a segment.
Is version 1.8 of DOS4GW just too old or buggy?  Have I pulled a major
braino here?  Any help on this problem would be greatly appreciated.

Paul Hsieh