1 files changed, 100 insertions, 0 deletions
diff --git a/client/drawing.ha b/client/drawing.ha
new file mode 100644
index 0000000..e164d33
--- /dev/null
+++ b/client/drawing.ha
@@ -0,0 +1,100 @@
+use sdl2;
+use fmt;
+
+// 2d position, x and y
+export type pos = (i32, i32);
+
+export type drawing_state = struct {
+	// is the mouse button held down?
+	drawing: bool,
+	pos: pos,
+	pictures: []picture,
+};
+
+export type picture = struct {
+	// the surface data as u32s
+	d: *[*]u32,
+	w: size,
+	h: size,
+
+	// backreference to the surface whose data we're using
+	surf: *sdl2::SDL_Surface,
+
+	pos: pos,
+
+};
+
+// 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.
+export 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;
+};
+
+export fn pic_set(pic: *picture, pos: pos, val: u32) void =
+	pic.d[pidx(pic,pos)] = val;
+
+export fn picture_from_surface(surf: *sdl2::SDL_Surface, pos: pos) picture = picture {
+	w = surf.w: size,
+	h = surf.h: size,
+	d = (surf.pixels as *opaque: *[*]u32),
+	surf = surf,
+	pos = pos,
+};
+
+export fn clear_picture(pic: *picture, color: u32) void = {
+	for (let i = 0z; i < pic.w*pic.h; i+=1) pic.d[i] = color;
+};
+
+export fn outline_picture(pic: *picture) void = {
+	for (let x = 0; x:size < pic.w; x+=1) {
+		pic_set(pic, (x, 0), 0);
+		pic_set(pic, (x, pic.h:int-1), 0);
+	};
+	for (let y = 0; y:size < pic.h; y+=1) {
+		pic_set(pic, (0, y), 0);
+		pic_set(pic, (pic.w:int-1, y), 0);
+	};
+};
+
+fn min(a: i32, b: i32) i32 = if (a<b) a else b;
+fn max(a: i32, b: i32) i32 = if (a<b) b else a;
+
+// Draws a circle onto the picture, at given position radius color
+// Clips at the boundaries of the picture to avoid overflow.
+export fn circle(picture: *picture, c: pos, r: i32, color: u32) void = {
+	// fmt::printfln("C {} {} {} {:x}",c.0,c.1,r,color)!;
+	const (cx,cy) = c;
+	const ymin = max(0, cy-r);
+	const ymax = min(picture.h:i32-1, cy+r);
+	const xmin = max(0, cx-r);
+	const xmax = min(picture.w:i32-1, 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(picture, (x,y), color);
+			};
+		};
+	};
+};
+
+export fn do_drawing(dstate: *drawing_state) void = {
+	if (dstate.drawing) for (let i = 0z; i < 4; i+=1) {
+		const pic = &dstate.pictures[i];
+		const p = (dstate.pos.0 - pic.pos.0, dstate.pos.1 - pic.pos.1);
+		circle(pic, p, 20, 0xff0088);
+	};
+};
+