DLIs... Again

[xzerix]

Hi all,

 

I'm back to messing around with DLIs again, and trying to figure out how to change colour on every scanline.

 

Say for a graphics 1 screen you can set each line of text to be a different colour, but not every scanline *within* that line of text - I'm thinking something like the "tiger attack" title screen.

 

I guess one way would be to have a graphics mode where you can change every scanline and draw the characters in but is there a simpler way I'm missing?

 

I hope this makes sense!

 

[Rybags]

Graphics mode just puts constraints on how often a DLI can occur. In some cases it's not desirable for a DLI every line anyway because the overhead is such that you're not left with much time left to do stuff.

 

In Gr. 1 it's easy enough - just use a store to WSYNC to skip ahead to the end of the visible display. So for striped text you'd just setup a table with the colour values then read them in a loop.

 

e.g.

 

dli  pha
  tya
  pha
  ldy #7
docolour  lda ctable,y
  sta wsync 
  sta colpf1
  dey
  bpl docolour
  pla
  tay
  pla
  rti
ctable .byte $a4,$a6,$a8,$aa,$aa,$a8,$a6,$a4

 

Note in this case the colours should be stored in reverse order that they appear.

This should work OK - you have to be careful with the amount of stuff that goes on before the first WSYNC otherwise you miss a line.

[xzerix]

Thanks Rybags - I'd almost had it after all.

 

I'd done the sta wsync before the lda ctable,y which seems to be ok, but the bpl i'd screwed up when I hand-assembled the routine and it was jumping to the wrong place, but not crashing!

 

I think I understand now - Thanks a million

 

-Peter.