Category : Alternate Operating Systems - Quarterdeck DesqView, CP/M, etc
Archive   : QWAUG92.ZIP
Filename : VGA.TEC

 
Output of file : VGA.TEC contained in archive : QWAUG92.ZIP

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.


************************************************************************
*This technical note may be copied and distributed freely as long as it*
*is distributed in its entirety and it is not distributed for profit. *
* Copyright (C) 1990-2 by Quarterdeck Office Systems *
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