VWFD: A VxD that Tells MS-DOS(R) Applications Whether They are Running Full Screen or in a Window
VWFD is the virtual windowed/full-screen device. When installed on a system running Microsoft(R) Windows(TM) in enhanced mode, VWFD allows MS-DOS(R) applications to determine whether they are running full screen or in a window. VWFD supplies the following callback to accomplish this:
call: VWFD_API_Callback
entry: BX=VMID of the VM to test
exit: AX=0 if VM is full screen
VWFD uses the following virtual machine manager (VMM) services:
Allocate_Device_CB_Area
Hook_Device_Service
Get_Next_VM_Handle
Test_Cur_VM_Handle
TSTWF.ASM is a sample MS-DOS program that uses the VWFD callback to find out if it is being run in a windowed or full-screen Virtual Machine (VM). TSTWF uses the following APIs:
Interrupt 2Fh, AX=1600h--determine if enhanced mode Windows is running
Interrupt 2Fh, AX=1684h--get VxD API callback address
To install this VxD, copy it to your Windows SYSTEM directory and add the line DEVICE=VWFD.386 to the [386Enh] section of your SYSTEM.INI file. Restart Windows, run an MS-DOS VM (for example, COMMAND.COM), and run TSTWF.EXE. TSTWF will report whether the VM is windowed or full-screen. Press ALT+ENTER to switch the VM between windowed and full-screen mode, then run TSTWF.EXE again; it will report the opposite state.
This sample code requires special VxD tools and include files; see the "VxD Tools" and "VxD Include Files" abstracts to copy these files to your development system. For more information on using the Microsoft Windows version 3.1 Device Driver Kit (DDK) files included on this CD, read the technical article "The VxD-Lite Mini-DDK." For more information on virtual device programming, see the DDK "Virtual Device Adaptation Guide."
VWFD was built and tested under Microsoft Windows version 3.1.
{ewc navigate.dll, ewbutton, /Bcodeview /T"Click to open or copy files in the vwfd project." /C"samples}
THIS TOOL IS NOT SUPPORTED BY MICROSOFT CORPORATION. IT IS PROVIDED "AS IS" BECAUSE WE BELIEVE IT MAY BE USEFUL TO YOU. PLEASE DO NOT CONTACT MICROSOFT PRODUCT SUPPORT SERVICES FOR SUPPORT OR ASSISTANCE SHOULD YOU HAVE PROBLEMS USING THIS TOOL.
READ THE ASSOCIATED DOCUMENTATION, IF ANY, REGARDING THIS TOOL PRIOR TO USING. ANY USE BY YOU OF THE TOOL IS AT YOUR OWN RISK. THE TOOL IS PROVIDED FOR USE "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT AND ITS SUPPLIERS DISCLAIM ALL WARRANTIES OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING, WITHOUT LIMITATION, IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.