96 lines
1.9 KiB
Forth
96 lines
1.9 KiB
Forth
fn draw-line screen: (addr screen), x0: int, y0: int, x1: int, y1: int, color: int {
|
|
var dx: int
|
|
var dy: int
|
|
var sx: int
|
|
var sy: int
|
|
var err: int
|
|
# dx = abs(x1-x0)
|
|
var tmp2/ecx: int <- copy x1
|
|
tmp2 <- subtract x0
|
|
var tmp/eax: int <- abs tmp2
|
|
copy-to dx, tmp
|
|
# sx = sgn(x1-x0)
|
|
tmp <- sgn tmp2
|
|
copy-to sx, tmp
|
|
# dy = -abs(y1-y0)
|
|
tmp2 <- copy y1
|
|
tmp2 <- subtract y0
|
|
tmp <- abs tmp2
|
|
tmp <- negate
|
|
copy-to dy, tmp
|
|
# sy = sgn(y1-y0)
|
|
tmp <- sgn tmp2
|
|
copy-to sy, tmp
|
|
# err = dx + dy
|
|
tmp <- copy dy
|
|
tmp <- add dx
|
|
copy-to err, tmp
|
|
#
|
|
var x/ecx: int <- copy x0
|
|
var y/edx: int <- copy y0
|
|
$draw-line:loop: {
|
|
pixel screen, x, y, color
|
|
# if (x == x1 && y == y1) break
|
|
{
|
|
compare x, x1
|
|
break-if-!=
|
|
compare y, y1
|
|
break-if-!=
|
|
break $draw-line:loop
|
|
}
|
|
# e2 = err*2
|
|
var e2/ebx: int <- copy err
|
|
e2 <- shift-left 1
|
|
# if (e2 >= dy) { err += dy; x += sx; }
|
|
{
|
|
compare e2, dy
|
|
break-if-<
|
|
tmp <- copy dy
|
|
add-to err, tmp
|
|
x <- add sx
|
|
}
|
|
# if (e2 <= dx) { err += dx; y += sy; }
|
|
{
|
|
compare e2, dx
|
|
break-if->
|
|
tmp <- copy dx
|
|
add-to err, tmp
|
|
y <- add sy
|
|
}
|
|
loop
|
|
}
|
|
}
|
|
|
|
fn draw-horizontal-line screen: (addr screen), y: int, x0: int, x1: int, color: int {
|
|
var x/eax: int <- copy x0
|
|
{
|
|
compare x, x1
|
|
break-if->=
|
|
pixel screen, x, y, color
|
|
x <- increment
|
|
loop
|
|
}
|
|
}
|
|
|
|
fn draw-vertical-line screen: (addr screen), x: int, y0: int, y1: int, color: int {
|
|
var y/eax: int <- copy y0
|
|
{
|
|
compare y, y1
|
|
break-if->=
|
|
pixel screen, x, y, color
|
|
y <- increment
|
|
loop
|
|
}
|
|
}
|
|
|
|
fn draw-rect screen: (addr screen), xmin: int, ymin: int, xmax: int, ymax: int, color: int {
|
|
var y/eax: int <- copy ymin
|
|
{
|
|
compare y, ymax
|
|
break-if->=
|
|
draw-horizontal-line screen, y, xmin, xmax, color
|
|
y <- increment
|
|
loop
|
|
}
|
|
}
|