🚀 go-pugleaf

 Hello,

 I have a question for all the game programmers that
 use the methode XOR-animation on VGA
 (or even a better methode!):

 Could you please send me a mail about the assembly
 technique. With examples, because the most books
 I've read don't show examples. And probably I
 need some examples to understand the THEORY.

 So far I've got this code:

 Type pic: ARRAY[0..19,0..19] OF BYTE;

 {*
    The colors are restricted to 16 foreground/ 16 background.
    Bit 0..3 are for the background/ 4..8 fore the foreground
    So for example:

        1001|0110 Background
        0110|0101 Foreground
        --------------------
        1111|0011 Xor
        0110|0101 Foreground
        --------------------
        1001|0110 Xor


    I've been told that this should be the fastest way for
    creating smooth animation, because the adapter does
    all the work.
 *}

 Var VideoMem:ARRAY[0..199,0..319] OF BYTE ABSOLUTE $A000h:0000;

 procedure PutXOR(x,y: integer; p: pic);
 var i,t: Integer;
     b: Byte;
     p1: Pointer;

 begin
   port[$3ce]:=3;   {* ... Set dataregister *}
   port[$3cf]:=24;  {* ... to XOR *}

   for t:=0 to 19 do
     for i:=0 to 19 do
        begin
          b:=p[i,t];
          p1:=@VideoMem[y+i,x+t];
          asm
            les di,p1        {* ... load destination adres *}
            mov al,es:[di]   {* ... in al *}
            mov al,b         {* ... load color byte in al  *}
            mov [es:di],al   {* ... write it to the screen *}
            {*
              This all works, but it's to slow,
              I'm looking for something that
            *}
          end;
        end;
  end;

 end;

 Please could someone help me for this, or else I can't
 sleep.

 Cu Robin



********************************************************************

 Robin Leeuwerke
 Noordelijke Hogeschool Leeuwarden
 The Netherlands

 e-mail: R.Leeuwerke@gamma.rug.nl

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