Category : Alternate Operating Systems - Quarterdeck DesqView, CP/M, etc
Archive   : QMTEK601.ZIP
Filename : VGA.TEC

ID:VG DESQview Video Modes
Quarterdeck Technical Note #148
by Joe Wilder

Q: What fonts are available to me in DESQview?

The available font sizes from the DESQview menu are: 25, 30, 50,
and 60 lines maximum per screen. Fonts displayed on the screen
can be of two types, text fonts and graphic fonts.

The text fonts available are 25 or 50 lines per screen. Graphic
fonts are 30 or 60 lines per screen. If graphics are being
displayed on the screen, text font sizes won't be available. If
a text mode is selected, DESQview will sometimes draw a curtain
over the graphics programs and the text programs on the screen
will be able to be displayed in a mode. If the graphics program
is set to run in the background and is on the screen in a window,
DESQview will not allow you to switch the display to a text mode.

If a 25 or 50 line program is being displayed in a window on the
screen when a graphic program is started, DESQview will switch
the font size of that program to 30 or 60 lines, because those
are the closest font sizes available when the display is in a
graphic mode. In addition to the graphic font sizes on the
DESQview menu, any number or size of bit-mapped custom fonts can
be displayed on the screen when the display is in a graphic mode.
The only graphical font sizes available from the Desqview menu,
however are 30 or 60 lines per screen.

Q: How do I use different font sizes while in DESQview?

ALT-Rearrange-Video displays font size choices on the DESQview
menu. Setting the program itself to a certain font size should
be respected in DESQview, but you may need to adjust the Maximum
Height field to an appropriate number of lines or Pages to 2 or
greater. If Pages is set to greater than 1, maximum height is
limited to 25 lines on non-direct screen write programs and
programs that are virtualized. If a program writes directly to
the screen and Change a Program is set to write text directly to
the screen and Virtualize text/graphics is set to N, you should
be able to display a 50 line program when Pages is set to 25 even
though maximum height is set to 25. The reason why the Direct
Screen Write programs can display more than 25 lines when Maximum
Height is set to 25 when they are not being virtualized is that
Desqview turns the whole screen over to the program and won't
interfere with whatever it puts on the screen. If the window is
virtualized, typically the program will display more lines, but
only 25 lines worth will be shown in the window. If a program
doesn't have the facility to display more than 25 lines, DESQview
can't help it do that.

Q: How many ways can programs put information on the VGA display?

A program can display text on the screen by asking the System
BIOS to put it there, or by writing directly to video memory.
All graphic programs write directly to the screen (video memory.)
Approximately half of all text programs write directly to the
screen. The VGA display can only display one font at a time, no
matter how many DESQview windows are open. For instance, you
couldn't have a 25 and a 50 line program displayed at the same
time. If the display is in a Graphic mode any number of Graphic
fonts can be displayed simultaneously. Other Graphics images
could also be displayed.

Q: How can I tell if a program writes directly to the screen?

The way to tell if a program writes directly to the screen:
(Remember, if it's a graphics program, it writes directly.) Set
"Writes text directly to screen" to N on the Change a Program
menu. Now start the program and try to run it in a small window.
If it writes outside of its window borders, that means the
program writes directly and "Writes text directly to screen" must
be set to Y.

Q: When do I need to set Virtualize text/graphics (Y,N,T) to Y?

Screen virtualization is only available on machines with 80386 or
80486 processors. You only need to virtualize if the program
writes directly to screen and you want the program to stay
running while it's in the background (without video bleedthrough)
or stay running while it's in a small window. Virtualizing slows
programs down, so if your program doesn't need to stay running in
the background or in a small window, you would want Virtualize
set to N. Virtualizing of graphics requires Expanded memory. If
the machine is too low on Expanded memory to provide screen
virtualization, it will run just like you had NOT set Virtualize
to Y, and if you have forced the program to run in background, it
will bleed through the foreground window.

If a program doesn't write directly to the screen, Writes text
directly and Virtualize should both be set to N. DESQview can
run these programs in a small window and in the background
without any special adjustments.

If a program only does output but nevertheless writes directly to
the screen, it is best to set Virtualize text/graphics to T.
This setting requires much less memory than a setting of Y.

Some progams are written take advantage of DESQview's video
handling (DESQview Aware or DESQview Specific programs) in their
code. Many of these programs can have Writes text directly...
to 'N'.

Q: When I run Graphics programs, my 25 line programs no longer
cover the full screen. How can I correct this?

When switching from a window that is using a Graphic mode to a
window that is using the 25 line font, the program will sometimes
display 25 lines on a 30 line screen. When this happens, the
bottom 5 lines of the screen will display the program that is in
the background and the program you're working in may look
scrunched up. Because there is no 25 line Graphic mode, DESQview
has to do it this way. When the screen is in a graphic mode,
DESQview has to display programs in Graphic mode also. In
graphic mode only 30 and 60 line fonts are available.

One way to run a Graphic program and still have your program
display in a 25 line font is to do ALT-Rearrange-Hide before
switching away from the Graphic program. This will hide it from
the screen and allow the monitor to switch to the 25 line font.
A hidden program that writes directly to the screen will not be
able to run while it is hidden.

Another way to use a Graphic program and switch to a 25 line
program is to run the DESQview Setup program and set Display Text
Graphics at the same time? to N. Now when you switch from the
Graphic program to the program, DESQview will put a curtain over
your Graphic program and allow the monitor to return to the mode.
Virtualization will not be possible when this option is selected.


Q: Is Desqview compatible with Extended VGA Modes?

The highest resolution in the IBM VGA Specification is 640x480.
Some VGA cards have the capability of displaying resolutions of
700X420, 800X600, and 1024X768. Since these modes are not
standardized and most of the manufacturers of these cards
implement these resolutions differently, DESQview cannot fully
support these modes.

DESQview will support 640X480 in that it can save and restore the
screen when programs are switched away from and back to. It can
also virtualize this resolution, meaning it will allow a program
that writes directly to the screen to stay running in a small
window or in the background without bleeding through the
foreground window.

DESQview can Save and Restore 800X600 on some VGA cards if
Graphic Pages in Change a Program is set to 4, but it cannot
Virtualize it. It's sometimes O.K. to set Runs in Background to
Y and Virtualize... to N for purposes of printing in the
background if the program doesn't do screen updates or only does
minor screen updates while it's printing.



Q: Why do my colors sometimes change when I switch windows?

The VGA display in its normal 640X480 mode can display 16 colors
out of a pallette of 256 colors. If for instance, two windows
are being displayed on the screen and the program in each window
is using a different 16 color set, the correct colors can only be
displayed in one window at a time. DESQview will assign the
correct colors to the window you are using. The other window
will have its colors reassigned to use the same color values as
the first window until you switch to it.

Q: Why does only half of my screen get restored in some programs?

When a program is switched away from and another program is put
on the screen, DESQview (not the program) saves that screen away.
When you switch back to that program DESQview redisplays on the
screen what it had saved. This saving and restoring process is
done in Expanded memory if available. Some programs use more
video memory than others. DESQview has to have a larger buffer
available for those programs. If the buffer isn't large enough,
DESQview may only find enough room to save part of the screen.
When restored only part of the screen gets restored. The amount
of memory used for this buffer is set in the Change-a- Programs
Advanced Options. The fields labeled "Text Pages:" and "Graphics
Pages:" may be set from 1 to 4. Each text page takes about 4K of
memory and each graphic page requires 64K of memory. If only
part of your program's display is getting restored, try raising
these numbers.

Copyright (C) 1991 by Quarterdeck Office Systems
* * * E N D O F F I L E * * *