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The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

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Microsoft has made every effort to preserve compatibility of Windows 3.0
display drivers with Windows 3.1. However, there are some basic guidelines
that must be followed to ensure full compatibility.
 
Font Caching for TrueType Fonts
 
Display drivers that do their own font caching may encounter conflicts with
the new TrueType font technology provided with Windows 3.1. Display drivers
that use glyph caching rather than caching the entire character set should
work without problems. The 8514/a driver source code provides a sample of a
driver that uses glyph caching.
 
Virtual Display Devices and Screen Grabbers
 
Many third party display drivers utilize VDDs and grabbers included in
Windows 3.0. Combinations of Windows 3.0 VDDs and grabbers with their
counterpart components included in Windows 3.1 may not be compatible. For
example, a grabber designed to work with the standard VGA VDD included in
Windows 3.0 (*VDDVGA) may not be compatible with the standard VGA VDD
included in Windows 3.1.
 
In general, grabbers and VDDs should always be used as a set. Do not run
Windows 3.0 grabbers with Windows 3.1 VDDs, and vice versa.
 
Properly built third-party display driver OEM setup disks will already
include appropriate VDD and grabber files, and no changes should be
required. Unfortunately, some vendors do not ship VDD and grabber files that
are already available on the Windows 3.0 setup disks.
 
If your driver installation disk provides a propietary VDD, but relies on
standard Windows 3.0 disks for a grabber, you should rebuild your
installation disks in order to ensure compatibility with Windows 3.1.
 
Likewise, if your driver installation disk provides a propietary grabber,
but relies on standard Windows 3.0 disks for a VDD, you should rebuild your
installation disks in order to ensure compatibility with Windows 3.1.
 
The driver installation disks must include all necessary files. You can
determine the necessary file from the table below. In general, if your
driver uses the specified Windows 3.0 file, your setup disks should include
the corresponding Windows 3.1 file.
 
Windows 3.0       Windows 3.1       Description
File              File
───────────────────────────────────────────────────────────────────────────
 
*VDDVGA           VDDVGA30.386      Windows 3.0 VGA Virtual Display Device
 
                                    3.0 WIN386.EXE file. It should be used
                                    only with enhanced mode grabbers known
                                    to be compatible, such as VGA30.3GR.
 
VGA.GR3           VGA30.3GR         Windows 3.0 VGA Enhanced Mode Grabber.
 
                                    grabber. It should be used only with
                                    VDDs known to be compatible, such as
                                    VDDVGA30.386.
 
VDD8514.386       VDD8514A.386      Windows 3.0 8514 Virtual Display
                                    Device.
 
                                    minor updates since the original Windows
                                    3.0 8514 VDD. It should be used only
                                    with enhanced mode grabbers known to be
                                    compatible, such as 8514A.3GR.
 
8514.GR3          8514A.3GR         Windows 3.0 8514 Enhanced Mode Grabber.
 
                                    grabber. It should be used only with
                                    VDDs known to be compatible, such as
                                    VDD8514A.386.
 
The Windows 3.1 DDK disks include the Windows 3.0 versions of VDDs and
grabbers described above in the \display\win30 subdirectory.
 
VGACOLOR.2GR, the Windows 3.1 standard mode VGA color grabber, should be
fully compatible with drivers that use the Windows 3.0 version,
VGACOLOR.GR2.
 
V7VGA.3GR, the Windows 3.1 version of the Video Seven enhanced mode grabber,
should be fully compatible with drivers that use the Windows 3.0 version,
V7VGA.GR3.
 
                                      ♦