Shell Alternative

 BBS: Inland Empire Archive
Date: 03-08-92 (01:52)             Number: 151
From: RICH GELDREICH               Refer#: NONE
  To: TIM FITZGERALD                Recvd: NO  
Subj: Shell Alternative              Conf: (11) Quik_Bas

Well... this is about preventing the user from seeing anything that a
SHELL'd program writes to the screen. I have two ways(off the top of my
head)- one of 'em might not work.

The first method, which probably won't work, is to keep your display and
work screens seperate. For instance:

Screen 0,,1,0   'sets up text mode with work page of 1 and display of 0

Then, shell to your program. This *may* make dos write everything to
page 1 while the user only sees page 0, but I haven't tested this out so
you will have to experiment with that.

The second way is to set all of the palette attributes to black, shell
to dos, and then set the palette back to normal. Setting all of the
screen attributes to 0 will effectively turn off the display so anything
written to it will not be seen. Like this:

pcopy 0,1   'save your clean text screen to a temperary page
for A=0 to 255:palette A,0:next  'this will work with VGA
shell "myprog"
pcopy 1,0
palette   'set palette back to normal

The first pcopy 0,1 copies the normal display page to a temperary place
so it can be restored later. Next, all of the atttributes to the screen
are set to 0. The program is executed, effectively invisible to the
user. Then, the original screen is copied back and the palettes are set
back to normal.

Hope that helps!

Rich Geldreich

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