1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
|
use sdl2;
// 2d position, x and y
type pos = (int, int);
type drawing_state = struct {
// is the mouse button held down?
drawing: bool,
pos: pos,
picture: picture,
};
type picture = struct {
d: *[*]u32,
w: size,
h: size,
};
// Returns array index of the pixel at position pos.
// Bounds check happens in here instead of using a slice type, so
// that it's easier to remove later.
fn pidx(pic: *picture, pos: pos) size = {
const (x,y) = pos;
const (xs,ys) = (x:size, y:size);
assert(0 <= x, "x position must not be less than 0");
assert(0 <= y, "y position must not be less than 0");
assert(xs < pic.w, "x position must be less than picture width");
assert(ys < pic.h, "y position must be less than picture height");
return xs + pic.w*ys;
};
fn pic_set(pic: *picture, pos: pos, val: u32) void = pic.d[pidx(pic,pos)] = val;
fn picture_from_surface(surf: *sdl2::SDL_Surface) picture = picture {
w = surf.w: size,
h = surf.h: size,
d = (surf.pixels as *opaque: *[*]u32),
};
fn min(a: int, b: int) int = if (a<b) a else b;
fn max(a: int, b: int) int = if (a<b) b else a;
fn circle(dstate: *drawing_state, c: pos, r: int, color: u32) void = {
const (cx,cy) = c;
const ymin = max(0, cy-r);
const ymax = min(dstate.picture.h:int-1, cy+r);
const xmin = max(0, cx-r);
const xmax = min(dstate.picture.w:int-1, cx+r);
const r2 = r*r + r;
for (let y = ymin; y<=ymax; y+=1) {
const yd = y-cy;
for (let x = xmin; x<=xmax; x+=1) {
const xd = x-cx;
if (yd*yd + xd*xd <= r2) {
pic_set(&dstate.picture, (x,y), color);
};
};
};
};
fn do_drawing(dstate: *drawing_state) void = {
if (dstate.drawing) circle(dstate, dstate.pos, 20, 0xff0088);
};
|
