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1992-07-08
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This is the documentation for SCRUTIL.EXE and SCRBLANK.DLL, an
OS/2 Presentation Manager screen saver for OS/2 1.3 and 2.0.
Kai Uwe Rommel,
Zennerstrasse 1
D-8000 Muenchen 70
Germany
Phone: +49 89 723 4101
Fax: +49 89 723 7889
email: rommel@jonas.bofe.sub.org (preferred)
or: rommel@informatik.tu-muenchen.de
May 26 1992
---------------------
0. Overview
This small program is a screen saver for OS/2 Presentation Manager
and in addition shows a small window with the current date and
time and amount of free memory.
1. Installation
Put SCRUTIL.EXE somewhere in your PATH or where you keep your
utility programs and SCRBLANK.DLL somewhere in your LIBPATH.
SCRBLANK.DLL needs IOPL because it uses hardware features of the
video cards to blank the screen(s). Set either IOPL=YES in CONFIG.SYS
or add SCRBLANK to your IOPL list.
2. Start
You can start the program by entering the command "START SCRUTIL"
but you better put it in a program group (1.3) or folder (2.0).
You can mark it as "Open when system is started" (1.3) or put a
shadow of it in the startup folder (2.0).
3. Usage
Initially, the program puts it's window in the upper right screen
corner, but you can move it wherever you want it. Under 1.3, you
can then choose "Save" from the desktop manager's "Desktop" menu
to let it save it's screen position. Under 2.0, the position is
saved, when the screen saver is terminated or the system is shut
down.
The window shows the current time and date in the format defined
in the PM control panel (1.3) or country settings box in the
system setup folder (2.0) in the first line.
In the second line, the current amount of free memory is shown in
kilobytes. Under 2.0, this value always shows the combined size of
all currently unused memory pages.
Under 1.3 it usually shows the largest contiguous segment of
memory currently available. This does not always represent the
total amount of free memory, especially not after some time of
system usage when memory became fragmented (which is not a bad
thing at all, because the system compacts memory as needed, but
only when it is needed, not for the free memory display by this
program). However, there exists an option to let it more precisely
display available memory, called "bean count" (see below). But use
this option with care because it can seriously degrade system
performance and should only be used when really needed (for
example, when you want to debug a program and you don't trust it's
memory usage).
After some period of user inactivity (no keyboard or mouse input)
the screen is blanked. You can blank the screen immediately by
moving the mouse pointer into the upper right screen corner and
you can prevent the screen from being blanked by moving the mouse
pointer into the lower right screen corner.
You can bring up the screen saver's configuration box by double
clicking on the window.
4. Configuration
The configuration box is different under 1.3 and 2.0. Under both
systems, it shows a title and copyright and version number and
three buttons, "Ok", "Cancel", and "Terminate". You of course know
what the purpose of these buttons is.
Under 2.0, a group of controls are showed to adjust the screen
saver. You can specify the saver delay time, if it should blank
your screen at all and which display cards are in your computer.
If you disable the screen saver, it will not blank the screen(s)
after the specified period of inactivity, but you can still blank
it manually by moving the mouse pointer into the upper right
screen corner.
The possible cards are 8514/A, VGA, EGA and Monochrome. This screen
saver does not use any Presentation Manager functions to perform
the screen blanking but rather uses hardware capabilities of the
display cards to blank the screen. This has the advantage that no
screen redraw has to be done when the screen is switched back on.
In addition, it cannot interfere with running programs (as long as
they do not change the current screen palette).
But for the screen saver to function properly, you must correctly
set what kind of display adaptor(s) you have. You can check more
than one adaptor, if you have a secondary screen attached to your
computer, for debugging programs, for example. In such cases, the
screen saver can blank the debug screen too. Possible combinations
are VGA and Monochrome, 8514/A and VGA or even 8514/A, VGA and
Monochrome all together.
If you should have problems that your VGA does not get blanked
properly although you have chosen VGA in the configuration box,
you can try to choose EGA instead, which should work with all VGA
cards too.
Under 1.3 the configuration box shows another group of controls
to let you adjust the free memory display. You can choose bean
count if you need to (see warning above) and if you enable the
bean count, you can adjust the minimum size of the segments which
should be counted for the total free memory and the interval at
which the total free memory amount should be recalculated.
5. Future enhancements
Perhaps newer display cards can be supported as they become
available and if I get access to one. For example, I would like
to hear from XGA users, if the screen saver works with it and
with which setting (8514/A or VGA).