Hi Alex,
On Tue 07 Apr 2026 at 12:28, Alexander Burger <[email protected]> wrote:
> It is based on the new PicoLisp frame buffer library, also separately
> available in
>
> https://software-lab.de/fb.tgz
that line drawing code in fb.tgz/lib.c seems quite complicated.
Here is what I did in forth:
variable x variable y
variable x2 variable y2 variable dx variable dy
variable sx variable sy variable e
: line
x2 @ x @ - abs dx !
x @ x2 @ < if 1 else -1 then sx !
y2 @ y @ - abs negate dy !
y @ y2 @ < if 1 else -1 then sy !
dx @ dy @ + e !
begin
plot
e @ 2* dy @ >= if
x @ x2 @ = if exit then
dy @ e +!
sx @ x +!
else e @ 2* dx @ <= if
y @ y2 @ = if exit then
dx @ e +!
sy @ y +!
then then
again ;
(tested), which could be written in C as (not tested):
void line(int x, int y, int x2, int y2) {
int dx = abs(x2 - x);
int sx = x < x2 ? 1 : -1;
int dy = -abs(y2 - y);
int sy = y < y2 ? 1 : -1;
int e = dx + dy;
for(;;) {
point(x, y);
if((dy << 1) <= e) {
if(x == x2) break;
e += dy;
x += sx;
}
else if((dy << 1) <= e) {
if(y == y2) break;
e += dx;
y += sy;
}
}
}
Cheers,
Tomas
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