Driver: DOS
Author: Salvador E. Tropea, Robert Hoehne
Status: Not complete
Revision: $Revision: 1.2 $

  This is the driver used for the djgpp compiled binaries. The driver works
on DOS systems and any compatible variants. It can be used for any Windows
system including 3.1 and Win32 systems (95, 98, Me, NT, 2000, XP, etc.) and
systems like OS/2 that provides DOS emulation.

1. INTRODUCTION
2. FEATURES
3. CONFIGURATION VARIABLES SPECIFIC FOR THIS DRIVER
4. NOTES ABOUT WINDOWS


1. INTRODUCTION

  This driver is really complex and the only way to make it work properly is
to have a good ammount of testers and maintainers. As the driver is currently
maintained only by me (SET) this driver is in very bad shape.
  The main complexity of this driver is the need to support the restore of
the graphic video modes. This is a complex task because BIOSes have a lot of
bugs in their save/restore state routines. I saw this bugs are becoming more
and more frequent.
  We verified such a bug in Matrox boards, it was fixed, but some people
still have VGA BIOSes with this bug. Then we also saw a similar bug in nVidia
GeForce VGA BIOS, I think it wasn't fixed by nVidia. These are just two
examples of popular boards. As I can't have a collection of video boards and
test the code in each one to see if it works things become quite complex.
  My policy for TV 2.0.0 is to release the driver with the current problems,
but disabling some advanced features. These features won't impact on regular
programs but will most probably be a bad thing for RHIDE. RHIDE is an IDE for
djgpp that uses TV as TUI.
  I think the code should be splitted in at least two drivers. One really
simple driver that doesn't support restoring graphic modes and another more
complex driver. Then RHIDE could request the second driver when a user knows
that graphics are needed and the code works ok for the target system. I don't
plan to do it any time soon unless I get volunteers to help.


2. FEATURES

  The driver supports:

* Video mode configuration. Various modes are known and you can provide your
own mode or use an external program.
* Palette. The speed for it is high.
* Window title set/restore when running on Win32 systems.
* Most keyboard combinations. Some are lost if you use the BIOS strategy. [1]
* Restore command.com screen.
* Fonts. Primary and secondary.
* Mouse. Full support for drivers compatible with MSMouse v6.0.

  Notes about the screen:
  Any text mode fully supported by BIOS and that is compatible with
mode 3 (VGA color) is supported, VESA modes are supported too, if you have
problems please report it. If you use a program that sets the video mode by
tweaking the VGA registers it will also set the BIOS data area to reflect the
new screen size or it won't work.
  Additionally the library supports some build in modes: 82x25, 80x28, 80x30,
90x30, 94x30, 80x34, 90x34, 94x34, 80x35, 80x40, 80x43 and 80x50.
  Note: if you wonder why 82x25 that's a mode where the characters have 8
pixels of width and is very good for fonts with strange layouts like
ISO-Latin-1 (from Linux).
  The hercules monochrome mode should be supported but I didn't test it for
a long time so perhaps something is broken, please report your experience
if you try it.



3. CONFIGURATION VARIABLES SPECIFIC FOR THIS DRIVER

  Please read the documentation about the configuration file first.

BIOSKey       Integer  By default the driver reads the keystrokes from the
                       BIOS buffer directly. This is faster and gives more
                       information. On some systems it fails and you'll need
                       to enable it. If you have access to such a system
                       please contact us so we can look for a better
                       solution. Use a value different than 0 to enable it.
PollMouse     Integer  The mouse information can be obtained using a periodic
                       poll or asking the DOS mouse driver to call us when
                       the mouse is moved or a button is pressed. The second
                       option is faster and you can't lose information. The
                       first option is safer. Currently the driver uses a
                       poll strategy by default. You can try disabling this
                       option to get better mouse support. Note that it is
                       always disabled for Windows NT and similar systems
                       (2000, XP, etc.). Use 0 to disable it.
SaveVGAState  Integer  In order to save and restore graphic modes you must
                       save a lot of information. This is achieved using a
                       standard VGA BIOS call. Some buggy BIOSes doesn't
                       implement it or implements it wrongly and returns
                       success. When it happends the result is a mess with
                       the screen, it usually goes black. Currently the
                       default value for it is 0, it means the VGA state
                       isn't saved. If you need to save it try enabling it
                       using a value different than 0.
VGABIOSState  Integer  This is related to the SaveVGAState variable. When
                       enabled we use VGA BIOS for the job. If you disable it
                       the driver will do it manually. It works for the
                       boards with buggy BIOSes, but the board must be 100%
                       VGA compatible at registers level (also the Windows
                       driver if you are using Windows). This uses very low
                       level stuff.
FixKbdBuffer  Integer  When enabled we assume the start of the keyboard
                       buffer is at offset 0x1E and the end at offset 0x3D.
                       When disabled (default) the size is monitored all
                       the time.


4. NOTES ABOUT WINDOWS

  I strongly recommend using the Win32 drivers for Win32 platforms specially
if the application will run using Windows NT (note that Windows 2000 and XP
are Windows NT 5.x). Windows NT 4.x have a bad DOS emulation and it looks
like 5.x made it even worst.
  Here are some notes I had in the main readme file about this topic:

Windows 3.x:
  I didn't test it for years so I don't know the current status.

Windows 9x:
  Keyboard:
    Almost the same support as in plain DOS. The TSR works at least in
   Windows '95. Some keys are used by the GUI so not all are available I
   include a .pif example showing how to avoid W9x take control of Alt+Space
   and other keys. The example is in extra/pifexamp.
  Screen:
    The support is similar to the one found in DOS, but I know some video
   drivers have bugs in the VESA handling so perhaps it could make problems.
   If you face such a problem please contact me, in the past I fixed VESA
   problems with S3 boards thanks to the help of a user.
    Usually isn't a good idea to run applications that change the video mode
   inside a window, so if your program does it recommend not running in a
   window to your users. One way to avoid it is using a .pif file, it will
   prevent 98% of the people from "windowizing" the program. See the
   extra/pifexamp example for it, it instructs W95 to run the program in full
   screen and disable Alt+Enter, the example also gives up to 64Mb to the
   application (the maximun W95 will give to a DOS task).
  Mouse:
    Full support.
  Note: I think all of it applies to Windows 98, if you see any difference
        please tell me.

Windows NT:
  This platform isn't fully supported by the DOS target. I think NT's support
  for DOS applications is completly broken so I don't care about it. If you
  have patches I'll receive it.



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Foot notes:


[1] Note that the driver ever takes the keyboard keystrokes from BIOS, it
can be using the BIOS interrupt or simply removing the key from the BIOS'
buffer.
  The last approach reports much more keys but not all, in particular:

* Control + `1457890=;,./
* Macro key (I have it in one of my keyboards)

  To workaround it I created a small TSR (hacking another TSR and rewriting
the code inside the ISR ;-). This TSR is included with the sources
distribution in the extra/doskeys directory, you can distribute it with
your program if you want, just don't remove my copyright.


