PsL Monthly 1993 December/PSL Monthly Shareware CD-ROM (December 1993).iso/prgmming/dos/pascal/futils.com/FWRITE.DOC

Text File | 1989-09-30 | 7.8 KB | 268 lines

********************************************************************
************************ FWRITE by Rex Kerr ************************
************************ Copyright (C) 1989 ************************
********************************************************************

This is a Turbo Pascal 5.5 unit written mostly in assembly
language.  It has 12 routines for reading/writing and 7 that
affect how the 12 other routines work.

***

VramCh(x,y : byte; ch : char; attr : byte);

This writes the character ch in attribute attr at X,Y on the screen.
Note that VramCh pays no attention to any windows that might be
on the screen--all coordinates are absolute screen coordinates.
If you use the CRT unit in your program, you can write in the
current text color using the CRT variable TextAttr (like this:)

vramch(xpos,ypos,ch,textattr);  { Only textattr needs to stay the same
                                  to write in TP's text color }

***

GetVramCh(x,y : byte; var ch : char; attr : byte);

This reads the character and attribute at X,Y.  See VramCh.

***

VramCharRpt(count : byte; x,y : byte; ch : char; attr : byte);

This repeats one character and attribute starting at x,y and
repeating count times.  It is useful for clearing a portion of
the screen, for example:

program clearwindow(windowx,windowy,windowx2,windowy2 : byte);
var tempbyte : byte;
    i : integer;
begin
     for i := windowy to windowy2 do
     begin
          tempbyte := (windowx2 - windowx) + 1;
          vramcharrpt(tempbyte,windowx,i,' ',textattr);
     end;
end;

That procedure will fill the window (defined by windowx, windowy,
windowx2, windowy2) with spaces in the current text attribute.

***

VramLineCopy(count : byte; x,y : byte; x2,y2 : byte);

This copies count characters (and attributes) starting at X,Y
and going to X2,Y2.  It works about the same as

procedure false_vramlcopy(count,x,y,x2,y2 : byte);
var i,atr : byte;
    ch : char;
begin
     for i := 0 to count-1 do
     begin
          getvramch(x+i,y,ch,attr);
          vramch(x2+i,y2,ch,attr);
     end;
end;

except it is much much faster.

***

VramWrit(x,y : byte; attr : byte; st : string);

This writes the string st in attribute attr starting at X,Y.

It will NOT scroll the screen up when it goes off the end of the
last line, and it does not interpret chars #7,8,10 and 13.

***

ClrVramLine(line : byte; attr : byte);

This clears the line specified with the attribute specified.

***

ClrVram(attr : byte);

This clears the whole screen with the attribute specified.

***

VramScroll(lines : shortint; x,y,w,h : byte; attr : byte);

This scrolls the defined window (that is, a window the same size as
you would get with window(x,y,w,h); ) up the indicated number of
lines.  New lines will be blank in the attribute attr.  To scroll
the screen down, pass a negative number.

Note:  To save speed, scroll as many lines as possible at one time.

Instead of writing

vramscroll(1,1,1,80,25,7);
vramwrit(1,25,7,'This is the');
vramscroll(1,1,1,80,25,7);
vramwrit(1,25,7,'slow way to');
vramscroll(1,1,1,80,25,7);
vramwrit(1,25,7,'scroll this.');

you should write

vramscroll(3,1,1,80,25,7);
vramwrit(1,23,7,'This is the');
vramwrit(1,24,7,'fast way to');
vramwrit(1,25,7,'do this.');

***

VramLine(x,y : byte; start,count : byte; var lin);

This is meant to write count chars and attrs (starting at X,Y on the
screen (and start in lin)) from the predefined type, vram_line, which
is defined as:

type vram_line = array[1..80][1..2] of byte;

in FWRITE.
However, you can pass any variable you want...but be sure you don't
overrun it.

***

GetVramLine(x,y : byte; start,count : byte; var lin);

This does the same thing as VramLine, except it reads into lin
instead of writing from it.

***

PutVramSec(var scrn; x,y,w,h : byte; x2,y2 : byte);

This is meant to copy a window on the screen (x,y,w,h) from scrn
(starting at x2,y2 in scrn).  Scrn is meant to be the predefined
type Vram_ScrBuf, which is defined as

type Vram_ScrBuf = array[1..25] of Vram_Line;

but any variable large enough can be used.

***

GetVramSec(var scrn; x,y,w,h : byte; x2,y2 : byte);

This is putvramsec's twin.  It does the same as putvramsec, except
it reads from the screen instead of writes to it.

***

Get_Display(var screenseg : word);

This returns $B000 if the monitor is monochrome, otherwise it
assumes CGA and returns $B800.  It is normally used on the
variable Vid_Mem_Start.  You can set Vid_Mem_Start yourself if
you want to write to an EGA or VGA display, for example.
      Card             Segment
     Monochrome         $B000
     CGA                $B800
     EGA                $A000
     VGA                $A000

Note: EGAs and VGAs start at $A000 in graphics mode.  I am not sure
      where they start in "large" mode.  In CGA mode (80*25), they
      start at $B800.

***

SetVramOfs(ofst : word);

This sets the offset of screen memory.  For the real screen, it
should always be 0.  However, you may want to define a "fake" screen.
Assuming FakeBuf is an array at least 4000 bytes long, you can do
this to set up a fake screen to read from and write to:

     vid_mem_start := seg(fakebuf);
     setvramofs(ofs(fakebuf));

Now, all reads and writes will be to and from fakebuf, just like it
was the real screen.  To write back to the old screen (assuming
Get_Display works for you) you simply do:

     get_display(vid_mem_start);
     setvramofs(0);

If get_display doesn't work, you'll have to save the old mode in
a variable:

var a : word;
    b : vram_scrbuf;

begin
     vid_mem_start := $B500;   { Wierd display, but...           }
     ( . . . )                 { Do some stuff                   }
     a := vid_mem_start;       { Save the address                }
     vid_mem_start := seg(b);  { Set the segment address         }
     setvramofs(ofs(b));       { Set the offset address          }
     ( . . . )                 { Write to b instead of screen    }
     vid_mem_start := a;       { Get the old address back again  }
     setvramofs(0);            { Now you can write to the screen }
end.

***

GetVramOfs : word;

This gets the current offset.

***

SetVramMaxX(lines : byte);

This sets the length of the lines on the screen.  Useful for both
"fake" screens which are smaller (50*20, maybe) or EGA and VGA modes
where the lines are longer than normal.

***

GetVramMaxX : byte;

This gets the set length of the lines on the screen.

***

SetVramMaxY(lines : byte);

This sets the length of the screen in lines.  It isn't really used
except in ClrVram.  The others never check to see if they are going
off the end of the screen.

***

GetVramMaxY : byte;

This gets the set length of the screen in lines.

***

Two warnings:

1) FWRITE will cause snow on snowy CGAs.  I haven't yet found out
how to not cause snow and not slow down good monitors too much.
2) FWRITE never checks to see that you have valid parameters.  If
your screen is 80*25 and to do vramch(90,30,ch,textattr), It will
write the character out anyway.  This is usually fine for the real
screen.  However, when you are writing to a "fake" screen, you have
to be careful, because if you run over the end of the buffer, you
will most likely be overwriting something you didn't want to.

Also note that FWRITE never moves the cursor, and always reads from
absolute screen coordinates (i.e. 1,1 is always the top left corner
of the screen, no matter what windows you set).

This is version 1.2 of FWRITE.  Version 1.0 had a bug in the
scrolling routine.  The scrolling is now faster, and it works the
right way, too.  To my knowledge, FWRITE is faster than any other
units for Turbo Pascal that write directly to screen memory.