DP Tool Club 17/CD_ASCQ_17_101194.iso/vrac/edgar.zip/EDGVID.DOC

Text File | 1993-02-19 | 14KB | 350 lines

                   Changing Edgar's Video Operation

Document No. ds-dk9d1-n2j
First Release: October 29, 1990
This Revision: February 19, 1993
Copyright 1990-1993 Duxbury Systems, Inc.
All rights reserved.


                            ABSTRACT

The Duxbury Braille Editor and Braille Previewer, hereinafter
collectively referred to as Edgar, have been developed to work
with a wide range of video graphics adapters available for IBM-PC
and PC-compatible machines.  In most cases, Edgar automatically
detects and supports whatever adapter is installed.  This
behavior is referred to as autodetect.  Edgar also automatically
selects a color scheme appropriate for the particular display
adapter.

This document, intended primarily for the advanced user or
technician, gives further details about Edgar's video adapter
support.  It is possible to tailor this support for unusual
environments or needs by editing Duxbury's parameter-list file. A
a general description of this file is given, followed by
descriptions of specific modifications to make to it to get Edgar
to work with your video board even if autodetect fails, to
eliminate bothersome flicker on EGA/VGA/MCGA displays, and to
change Edgar's color scheme and braille dot size.


                             NOTICES

Information in this and other documents with this product is
subject to change without notice and does not represent a
commitment on the part of Duxbury Systems, Inc. Duxbury Systems
assumes no responsibility for any errors that may appear, other
than to provide corrected information in response to inquiry.


                     THE PARAMETER-LIST FILE

Duxbury's parameter-list file is an ASCII text file named
DXPRLS.DXR, which, if it exists, will be found in the Duxbury
working directory (most often C:\DUXBURY).  The file is optional
and likely will not exist on your system.  You can easily create
or modify this file with an ordinary text editor, such as EDLIN.

The parameter-list file is line oriented.  All lines beginning
with a semicolon are considered comments and are ignored.  The
first non-comment line must read exactly:

for dxc 1

and is used as an "interlock" to ensure that the file was written


                                2

to specifications referred to as dxc (Duxbury "C" language)
version 1.

If you are creating a new DXPRLS file, the next non-comment line
should read:

...101

to begin section 101, the named parameter section.  This is the
only section needed to manipulate Edgar's video support, and so
it is the only portion described here.  (If you are a user of the
Duxbury Translator, a file that comes with that product, DXC.TXT,
contains additional information about the DXPRLS.DXR file.)  The
named-parameter list is similar in function to DOS' environment
variables.  It is used to specify values for optional program
parameters, such as screen colors.  Duxbury's programs check this
list for specific named parameters before resorting to default
values.  Each line following the section header (...101) until
the end of file or the next section header should appear as
follows:

PROGRAM-NAME.PARAMETER-NAME:VALUE

For example, the line:

edgar.video:4

will set the value of the "video" named parameter, used by edgar
and described later, to 4 -- which, as listed later, would force
EGA mode.  In general, parameter values may be numbers, as in
this example; text; or boolean (true/false) values, indicated by
using + (plus) for true and - (minus) for false.

If you do already have a DXPRLS file, you can modify it by adding
section 101 (if necessary) just before any higher-numbered
sections, or at the end of file if no such sections exist.  Once
you have found or created the named-parameter section, it is
quite simple to add, modify, or remove named-parameter
definitions.


                       SUPPORTED VIDEO ADAPTERS

Following is a list of all video adapter standards supported by
the current version of Edgar running on an IBM family
microcomputer or compatible:


                                3

        CGA ....... Color Graphics Adapter
        EGA ....... Enhanced Graphics Adapter
        VGA ....... Video Graphics Array
        MCGA ...... Multicolor Graphics Adapter
        Hercules .. including Hercules Plus and InColor

No other video adapters are supported at this time, except insofar
as they are capable of emulating one of the above.  In
particular, the original IBM Monochrome Display Adapter (MDA) is
not supported.  If Edgar is run on a computer with a
non-supported video adapter, it should simply exit with an error
message.  However, the user is cautioned that under unusual
circumstances, Edgar may cause the machine to freeze up or crash
if run on a machine without one of the supported video cards.


                  COPING WITH AN AUTODETECT FAILURE

On occasion, Edgar might fail to detect the installed video card
correctly, even if that card is otherwise capable of supporting
the program.  Symptoms of this problem include the
above-mentioned error message or mysterious crashes.

At other times, Edgar will function properly even if autodetect
has failed.  For example, if a VGA card is installed but is seen
by Edgar as a CGA card, the program will function, but the
quality of the display will be diminished.  You can easily check
for this kind of problem by using Edgar's version information
command (Alt-v), which will display the type of video adapter on
which Edgar thinks it is operating.

If you are convinced that Edgar's autodetect is not functioning
properly, it is possible to force Edgar to drive your display as
whatever supported adapter you wish.  The technique for doing
this is referred to as autodetect override, and may be useful
even if Edgar's autodetect is working, if you wish to drive your
display in some special manner.  For example, some users may
prefer for Edgar to treat an EGA or VGA display as CGA, since the
latter display type will have larger, bolder dots.  As another
example, some users with Hercules boards may prefer a 40
cell/line display to the default 45 cells/line.

Autodetect override is accomplished by specifying one of the
following numeric values for Edgar's "video" named parameter:

        2 for CGA
        4 for EGA with color (Color or Enhanced Color Display)
        5 for EGA with monochrome display
        7 for VGA
       10 for MCGA


                                4

      256 for Hercules if 40 cell/line display is desired
      257 for Hercules if 45 cell/line display is desired
      258 for EGA with Color Display (640x200 maximum resolution)
      259 for EGA with Enhanced Color Display (640x350 maximum)


                  CHANGING THE BRAILLE DOT SIZE

On all supported adapters except the CGA, braille is normally
drawn using "bold" dots, so called because they are larger than
the dots used in previous versions of Edgar.  The larger dots
allow low-vision users easier access to the screen, and were
requested by many early Edgar users for this purpose.  It is
possible to reduce the dot size to match earlier Edgar versions
by inserting the line:

edgar.bolddot:-

into section 101 of the DXPRLS file.  Note that the character
following the colon is a minus sign, indicating boolean false.

The CGA driver uses larger, coarser dots to draw braille.  These
dots are not adjustable in size.  As described in the previous
section, it is possible to force Edgar to treat an EGA, VGA, or
MCGA display as CGA, if extremely bold dots are desired.


                          REDEFINING COLORS

Similarly, named parameters are used to specify non-default
colors for Edgar's display.  However, due to the varying
capabilities of displays, both the parameter names and the
potential values differ depending on what kind of video hardware
is installed.  In all, Edgar recognizes three different levels of
color capability:

  For COLOR displays, including all VGA and MCGA systems as well
  as EGA systems running with a color monitor, Edgar allows you
  to choose from a palette of 16 colors.  For each element that
  appears on screen, separate foreground and background colors
  should be specified.

  For MONOCHROME displays, specifically EGA cards with a
  monochrome monitor, Edgar allows each element to be displayed
  as white on black, black on white, or bright white on black.

  For BLACK & WHITE displays, such as Hercules and CGA systems,
  Edgar allows each element to be displayed as white on black or
  vice-versa.


                                5

Table I summarizes the named parameters used to specify color
redefinitions for each of the above categories of display.

        Table I - Named Parameters for Color Redefinition

                  Color (EGA/VGA/MCGA)     Monochrome  B & W
                  Foreground  Background   (EGA Mono)  (CGA/Herc)
                  ==========  ==========   ==========  =========
Text:             cstxf       cstxb        mstx        bwstx
Selected Block:   cshlf       cshlb        (1)         (1)
Status Line:      csslf       csslb        mssl        bwssl
  Highlights:     csslh       (2)          (3)         (3)
Dialog Boxes:     csdbf       csdbb        msdb        bwsdb
  Borders:        csdbbf      csdbbb       msdbb       bwsdbb
Menu Boxes:       csmf        csmb         msm         bwsm
  Borders:        csmbf       csmbb        msmb        bwsmb
  Titles:         csmtf       csmtb        msmt        bwsmt
  Selection:      csmsf       csmsb        msms        bwsms

(1) - On monochrome and black and white systems, the selected
block is always shown as the inverse of normal text.

(2) - On color systems, the backgrounds of highlighted characters
is always the same as the backgrounds of non-highlighted
characters within the same element.

(3) - On monochrome and black and white systems, status line
highlights are not shown.

For color systems, the value for each parameter should be one of
the following: BLACK, BLUE, GREEN, CYAN, RED, MAGENTA, BROWN,
WHITE, GRAY, LBLUE, LGREEN, LCYAN, LRED, LMAGENTA, YELLOW, or
LWHITE. Names beginning with an "L" indicate the light, or
intense version of the color.  (Note: both parameter names and
values are case-insensitive.)

On monochrome systems, each parameter should be one of the
following: NORMAL (white on black), INVERSE (black on white),
UNDERLN (white on black with underline), or INTENSE (bright white
on black).

Black and white systems allow only NORMAL and INVERSE.


             ELIMINATING FLICKER ON THE EGA/VGA/MCGA

In order to maintain compatibility with the widest possible range
of video hardware, Edgar makes as few assumptions about that
hardware as possible.  In particular, Edgar performs functions
such as screen mode changes and font downloads to the


                                6

EGA/VGA/MCGA strictly through the video BIOS if at all possible.
This may cause a mildly annoying flicker on your display whenever
the cursor changes or when you toggle shadow dots on/off.

Edgar can be configured to eliminate flicker on compatible
hardware by waiting for the vertical retrace period (the time
during which the monitor's cathode ray is repositioned from the
bottom to the top of the screen) before downloading any font
information.  Since retrace typically occurs 60 times per second,
no noticeable slowdown occurs.  However, in order to determine
the point at which retrace begins, Edgar needs to be sure it is
operating on a genuine IBM EGA/VGA/MCGA or a register compatible
clone.  While most clones are in fact register compatible, you
may wish to check with your manufacturer for this feature before
following the steps below.  Use of Edgar's flicker-elimination
feature on non register-compatible equipment may cause
unpredictable results.

Enabling flicker elimination is accomplished simply by adding the
line:

edgar.vgawvr:+

to section 101 of the DXPRLS file, as described above.  This
assigns a value of "True" to the vgawvr (VGA Wait for Vertical
Retrace) named-parameter.  The parameter is named vgawvr
regardless of whether Edgar is actually running on and EGA, VGA,
or MCGA system.

               STARTING EDGAR WITH AN ASCII DISPLAY

Normally Edgar starts up with a graphics braille dot display.
Users who want to view the braille as ASCII characters can toggle
that mode on with a Ctrl-D.  It is possible to get Edgar to start
up with the ASCII display by default.  Simply place the following
line in section 101 of the DXPRLS file, as described above:

edgar.txmode:+

                    FORCING DISPLAY LINE COUNT

On certain VGA cards, such as the SpeedSTAR Plus, Edgar can
display more than the usual seventeen lines of braille.  However,
on some of these cards, Edgar is unable to detect the presence of
this capability.  If you notice that Edgar's display does not
fill all of your VGA screen, you may wish to try forcing Edgar to
use more lines of the display.  Try the following line in
DXPRLS.DXR:

edgar.rows:19


                                7

If this succeeds, you may wish to try increasing the number to 20
and beyond.  In general, there is no harm in trying this
procedure.  However, you should always verify that you can
actually see the number of rows specified; for this purpose,
Edgar's status line DOES count as a row.  If you cannot see all
of the rows, reduce the edgar.rows setting to avoid operational
problems.


                            AN EXAMPLE

The following is the DXPRLS.DXR file we use to optimize the
display on a Toshiba 3100SX (a portable with a gas plasma VGA
gray-scaled screen):

; dxprls.dxr for Edgar on Toshiba 3100SX
for dxc 1
...101
edgar.vgawvr:+
edgar.cstxb:black
edgar.cstxf:lwhite
edgar.csslb:black
edgar.csslf:white
edgar.csdbb:black
edgar.csdbf:lwhite