[comp.lang.pascal] Buffered Graphics for CGA with Turbo Pascal???

terrell@druhi.ATT.COM (TerrellE) (07/21/89)

OK Turbo Pascal Fans:

Here's my problem:  I want to do buffered graphics with Turbo Pascal (v. 5.0).
By buffered graphics I mean that I want to have a program issue many graphics
commands to a memory buffer (but not to the screen).  When the drawing is
complete, I want to blast it to the screen all at once.

I believe that Turbo's BGI driver for EGA allows this (I think that there
is support for multiple pages).  However, I want to do this with CGA.  Since
CGA is memory mapped, if the Turbo graphics commands can be sent to a
memory buffer instead of the screen, it would be easy to dump the buffer
to the screen (by just copying all of the bytes over).

Can I do this???  If so, how does one specify that the output of the Turbo
graphics commands go to a memory buffer rather than the screen???


Thanks in advance,




Eric Terrell	(att!druhi!terrell)

NU113738@NDSUVM1.BITNET (07/25/89)

As far as I know, there is no way to tell the Turbo Pascal Graphics
system to write to a specified memory designation instead of the display
screen in CGA mode.

At one time I wanted to do this also, but as I found out, what you need to
do is basically write your own graphics system and have it write to the
memory.  Its what I ended up doing.  CGA sucks.

Anyway, I suppose you could theoretically go in and debug your compiled
program and manually change the far address of the graphics write but
then you run into the problem of having to use and static memory area
that might trash other areas.  I can't think of any way to use a dynamically
allocated area of memory for graphics writes in CGA.  Sorry.

If anyone else knows a possibility, please jump in.  I'd like a simple way
to do it too.

Jeff Bakke
NU113738@NDSUVM1.BITNET