Re: Bored at work....

[Antoine Vignau <antoine.vignau@laposte.net>]

OK OK. If you want to save some cycles, begin from the last line and DEX BPL VERTLOOP.

Another option would still be the use of absolute addressing: the idea is to:

 LDX £0
VERTLOOP
 LDA THI,X
 ORA $E6    ; another trick for fun, PAGE1 or PAGE2 ???
 STA HORZLOOP2+2
 STA HORZLOOP+2
 LDA TLO,X
 STA HORZLOOP2+1
 ORA £1
 STA HORZLOOP+1 

 LDY £0
HORZLOOP
 LDA $2001,y
HORZLOOP2
 STA $2000,y
 INY
 CPY £40
 BNE HORZLOOP

 DEX
 BPL HORZLOOP
 RTS   ; just for fun ;-)

I think you will save some cycles.

####

I thought you would have used a screen buffer of 40*20/24 (depending on the size of your tiles) and scroll that buffer internally and then refresh on screen what was necessary by comparing the buffer before scrolling and the new buffer.

Let's try some algorithm:

oldMAPBUFFER <= currentMAPBUFFER
scrollLEFT(currentMAPBUFFER)
for y=0 to 23
 for x=0 to 39
  if currentMAPBUFFER(x, y) =! oldMAPBUFFER(x, y)
    drawTILEONSCREEN(currentMAPBUFFER(x, y))
 next x
next y
RTS ; for fun ;-)

Antoine