[Oberon] PO2013 - CopyBlock

[Tomas Kral]

Hi,

As I have optimised vertical scroll w/ SYSTEM.COPY,
I do horizontal scroll recursive.

IF sx = sy THEN (*horizontal scroll*)
  CopyBlock(sx, sy, w, h, dx, dy-1, mode);
  CopyBlock(dx, dy-1, w, h, dx, dy, mode)
ELSE
 IF dx = sx THEN (*vertical scroll w/ SYSTEM.COPY*)
 ELSIF n <= 0 THEN (*diagonal right*)
 ELSE (*diagonal left*)
 END
END

I have two versions of diagonal shift, 
[a] using ASR LSL, shorter slower code 
[b] using ROR, faster bigger code

Running a little benchmark on moving an arbitrary block of 400x300 pixels (4bit colour) horizontally and diagonally.

[a]
diagonal left 59 ms
diagonal right 58 ms
horizontal left 50 ms
horizontal right 50 ms

[b]
diagonal left 51 ms
diagonal right 48 ms
horizontal left 42 ms
horizontal right 40 ms
 
The recursion has only 8 ms overhead, some 8 ms is also the delta between faster [b] and [a] variant.

-- 
Tomas Kral <thomas.kral at email.cz>