{$X+} (* This is a handy little trick to know. If you put this at the top
of your program, you do not have to set a variable when calling
a function, i.e. you may just say 'READKEY' instead of
'CH:=READKEY' *)
USES Crt; (* This has a few nice functions in it, such as the
READKEY command. *)
CONST VGA = $a000; (* This sets the constant VGA to the segment of the
VGA screen. *)
Type Virtual = Array [1..64000] of byte; { The size of our Virtual Screen }
VirtPtr = ^Virtual; { Pointer to the virtual screen }
VAR Virscr : VirtPtr; { Our first Virtual screen }
Vaddr : word; { The segment of our virtual screen}
{ДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДД}
Procedure SetMCGA; { This procedure gets you into 320x200x256 mode. }
BEGIN
asm
mov ax,0013h
int 10h
end;
END;
{ДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДД}
Procedure SetText; { This procedure returns you to text mode. }
BEGIN
asm
mov ax,0003h
int 10h
end;
END;
{ДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДД}
Procedure Cls (Col : Byte; Where:Word);
{ This clears the screen to the specified color, on the VGA or on the
virtual screen }
BEGIN
Fillchar (Mem [where:0],64000,col);
END;
{ДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДД}
procedure WaitRetrace; assembler;
{ This waits until you are in a Verticle Retrace ... this means that all
screen manipulation you do only appears on screen in the next verticle
retrace ... this removes most of the "fuzz" that you see on the screen
when changing the pallette. It unfortunately slows down your program
by "synching" your program with your monitor card ... it does mean
that the program will run at almost the same speed on different
speeds of computers which have similar monitors. In our SilkyDemo,
we used a WaitRetrace, and it therefore runs at the same (fairly
fast) speed when Turbo is on or off. }
label
l1, l2;
asm
mov dx,3DAh
l1:
in al,dx
and al,08h
jnz l1
l2:
in al,dx
and al,08h
jz l2
end;
{ДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДД}
Procedure SetUpVirtual;
{ This sets up the memory needed for the virtual screen }
BEGIN
GetMem (VirScr,64000);
vaddr := seg (virscr^);
END;
{ДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДД}
Procedure ShutDown;
{ This frees the memory used by the virtual screen }
BEGIN
FreeMem (VirScr,64000);
END;
{ДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДД}
Procedure PutPixel (X,Y : Integer; Col : Byte; Where : Word);
{ This puts a pixel at X,Y using color col, on VGA or the Virtual Screen}
BEGIN
Mem [Where:X+(Y*320)]:=col;
END;
{ДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДД}
Procedure Flip;
{ This flips the virtual screen to the VGA screen. }
BEGIN
Move (Virscr^,mem [VGA:0],64000);
END;
{ДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДД}
Procedure BlockMove;
{ This tests various ways of moving a block around the screen }
VAR loop1,loop2,loop3:Integer;
BEGIN
For loop1:=1 to 50 do BEGIN { This draw a block }
for loop2:=1 to 50 do { directly to VGA, no }
for loop3:=1 to 50 do { flipping }
putpixel (loop1+loop2,loop3,32,VGA);
cls (0,VGA);
END;
For loop1:=1 to 50 do BEGIN { This draws a block }
for loop2:=1 to 50 do { to the virtual screen, }
for loop3:=1 to 50 do { then flips it to VGA }
putpixel (loop1+loop2,loop3,32,Vaddr);
flip;
cls (0,Vaddr);
END;
For loop1:=1 to 50 do BEGIN { This draws a block }
for loop2:=1 to 50 do { to the virtual screen, }
for loop3:=1 to 50 do { waits for a retrace, }
putpixel (loop1+loop2,loop3,32,Vaddr); { then flips it to VGA }
waitretrace;
flip;
cls (0,Vaddr);
END;
END;
{ДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДДД}
Procedure PatternDraw;
{ This test the speed of flipping by drawing two patterns and flipping
them }
VAR loop1,loop2:integer;
BEGIN
for loop1:=1 to 100 do { This draws pattern one }
for loop2:=1 to 100 do { to the virtual screen }
putpixel (loop1,loop2,loop1,Vaddr); { then flips it to VGA }
flip;
for loop1:=1 to 100 do { This draws pattern two }
for loop2:=1 to 100 do { to the virtual screen }
putpixel (loop1,loop2,loop2,Vaddr); { then flips it to VGA }
flip;
END;
BEGIN
ClrScr;
Writeln ('This program will demonstrate the power of virtual screens.');
Writeln ('A block will firstly move across the screen, being drawn and');
Writeln ('erased totally on the VGA. Then the same block will move');
Writeln ('across, but will be drawn on the virtual screen and flipped');
Writeln ('to the VGA screen without a retrace (see part 2). The the');
Writeln ('block will go again, with flipping and a retrace.');
Writeln;
Writeln ('I will then draw a pattern, flip it to VGA, draw another');
Writeln ('pattern, flip it to VGA, and repeat that until a key is pressed.');
Writeln ('This will demonstrate that even when I put down 10000 pixels,');
Writeln ('then flip them to the VGA, it is still relatively fast. ');
Writeln; Writeln;
Writeln ('Hit any key to continue ...');
readkey;
setmcga;
setupvirtual;
cls (0,vaddr); { After you have got the memory for the virtual screen,
it is usually filled with random garbage. It is always
wise to clear the virtual screen directly afterwards }
BlockMove;
Repeat
PatternDraw;
Until keypressed;
Readkey;
settext;
shutdown;
Writeln ('All done. This concludes the fourth sample program in the ASPHYXIA');
Writeln ('Training series. You may reach DENTHOR under the name of GRANT');
Writeln ('SMITH on the MailBox BBS, or leave a message to ASPHYXIA on the');
Writeln ('ASPHYXIA BBS. Get the numbers from Roblist, or write to :');
Writeln (' Grant Smith');
Writeln (' P.O. Box 270');
Writeln (' Kloof');
Writeln (' 3640');
Writeln ('I hope to hear from you soon!');
Writeln; Writeln;
Write ('Hit any key to exit ...');
Readkey;
END.