Re: Screen Handling packages!

[Richard Riehle <richard@adaworks.com>]

Henrik Quintel wrote:

> Hello everybody,
> I am looking for Ada95 packages which can do the following operations:

  [ description of requirement snipped ]

For MS-DOS you may want to use a package supported
by ANSI.SYS.    I believe the contributions by Michael
Feldman in the Ada Software Repository support that.

Another approach, not for the faint of heart, but one I have
seen used successfully is to access Hex B800 directly. At
B800, you have a mapping to the screen at the pixel level.
If you have a system address capability in your compiler
to access B800, you can actually peek and poke with Ada
into that area of memory.

Yoshimi Fujii, formerly of Alsys, wrote a very nice little
Tetris program using the Alsys Ada 83 compiler many
years ago, and he used this trick.   We tried to convert it to
Meridian, but Meridian had a signed integer for System.Address,
and it could not reach data in the high-order part of
DOS memory.

By tweaking the pixels directly, along with their associated
attributes, you can gain enormous speed in your program.

I suppose you could use this trick even with a Windows system,
but I have not tried it  -- and probably would avoid doing it
since there is no end to mischief it could bring upon you.

Probably better off using the ANSI.SYS trick, after all.

Richard Riehle