From 52557c8a1c78ee02bd0eda1c740a37f8d6759b0c Mon Sep 17 00:00:00 2001
From: ubq323 <ubq323@ubq323.website>
Date: Sun, 24 Mar 2024 22:28:12 +0000
Subject: multiple chunks, and drawing works completely correctly with moving
 around

---
 drawing.ha | 32 ++++++++++++++++++++++++--------
 main.ha    | 44 +++++++++++++++++++++++++++++++-------------
 2 files changed, 55 insertions(+), 21 deletions(-)

diff --git a/drawing.ha b/drawing.ha
index 804aee4..5812109 100644
--- a/drawing.ha
+++ b/drawing.ha
@@ -1,4 +1,5 @@
 use sdl2;
+use fmt;
 
 // 2d position, x and y
 type pos = (i32, i32);
@@ -7,13 +8,20 @@ type drawing_state = struct {
 	// is the mouse button held down?
 	drawing: bool,
 	pos: pos,
-	picture: *picture,
+	pictures: []picture,
 };
 
 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.
@@ -33,10 +41,12 @@ fn pidx(pic: *picture, pos: pos) size = {
 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 {
+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,
 };
 
 fn clear_picture(pic: *picture, color: u32) void = {
@@ -57,14 +67,15 @@ fn outline_picture(pic: *picture) void = {
 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 dstate's picture, at given position radius color
+// Draws a circle onto the picture, at given position radius color
 // Clips at the boundaries of the picture to avoid overflow.
-fn circle(dstate: *drawing_state, c: pos, r: i32, color: u32) void = {
+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(dstate.picture.h:i32-1, cy+r);
+	const ymax = min(picture.h:i32-1, cy+r);
 	const xmin = max(0, cx-r);
-	const xmax = min(dstate.picture.w:i32-1, cx+r);
+	const xmax = min(picture.w:i32-1, cx+r);
 
 	const r2 = r*r + r;
 
@@ -73,12 +84,17 @@ fn circle(dstate: *drawing_state, c: pos, r: i32, color: u32) void = {
 		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);
+				pic_set(picture, (x,y), color);
 			};
 		};
 	};
 };
 
 fn do_drawing(dstate: *drawing_state) void = {
-	if (dstate.drawing) circle(dstate, dstate.pos, 20, 0xff0088);
+	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);
+	};
 };
+
diff --git a/main.ha b/main.ha
index 9035053..09fd30f 100644
--- a/main.ha
+++ b/main.ha
@@ -2,6 +2,9 @@ use fmt;
 use sdl2;
 use math;
 
+def CHUNKSIZE = 512;
+def NCHUNKS = 4;
+
 export fn main() void = {
 	sdl2::SDL_Init(sdl2::SDL_INIT_VIDEO)!;
 	defer sdl2::SDL_Quit();
@@ -11,19 +14,30 @@ export fn main() void = {
 
 	const wsurf = sdl2::SDL_GetWindowSurface(win)!;
 
-	const xsurf = sdl2::SDL_CreateRGBSurface(0,
-		512, 512, 32, 0xff0000, 0xff00, 0xff, 0)!;
+	const offs: [_]pos = [
+		(0,0), (0,CHUNKSIZE), (CHUNKSIZE,0), (CHUNKSIZE,CHUNKSIZE),
+	];
+
+	let pictures: []picture = alloc([],NCHUNKS);
+	for (let i = 0z; i < NCHUNKS; i +=1){
+		const surf = sdl2::SDL_CreateRGBSurface(0,
+			CHUNKSIZE, CHUNKSIZE, 32, 0xff0000, 0xff00, 0xff, 0)!;
+		append(pictures, picture_from_surface(surf, offs[i]));
+	};
 
 	let dstate = drawing_state {
 		drawing = false,
 		pos = (0,0),
-		picture = &picture_from_surface(xsurf)
+		pictures = pictures,
 	};
 
 	let camera_pos: pos = (25, 50);
 
-	clear_picture(dstate.picture, 0xffffff);
-	outline_picture(dstate.picture);
+	for (let i = 0z; i < 4; i += 1) {
+		const p = &dstate.pictures[i];
+		clear_picture(p, 0xffffff);
+		outline_picture(p);
+	};
 
 	let quit = false;
 	let n = 0;
@@ -38,22 +52,20 @@ export fn main() void = {
 			case sdl2::SDL_EventType::MOUSEBUTTONDOWN,
 					sdl2::SDL_EventType::MOUSEBUTTONUP =>
 				const edata = ev.button;
-				dstate.pos = (edata.x, edata.y);
+				dstate.pos = (edata.x + camera_pos.0, edata.y + camera_pos.1);
 				if (edata.button == 1)
 					dstate.drawing = (edata.state == 1);
 			case sdl2::SDL_EventType::MOUSEMOTION =>
 				const edata = ev.motion;
-				dstate.pos = (edata.x, edata.y);
+				dstate.pos = (edata.x + camera_pos.0, edata.y + camera_pos.1);
 			case => void;
 		};
 
 		movement(&camera_pos);
-
 		do_drawing(&dstate);
-		
-		sdl2::SDL_BlitSurface(xsurf, null, wsurf, &sdl2::SDL_Rect {
-			x = camera_pos.0, y = camera_pos.1, ...
-		})!;
+
+		for (let i = 0z; i < len(dstate.pictures); i+=1)
+			render_picture(&dstate.pictures[i], wsurf, camera_pos);
 
 		sdl2::SDL_UpdateWindowSurface(win)!;
 		n += 1;
@@ -61,6 +73,13 @@ export fn main() void = {
 	};
 };
 
+fn render_picture(pic: *picture, winsurf: *sdl2::SDL_Surface, camera_pos: pos) void = {
+	sdl2::SDL_BlitSurface(pic.surf, null, winsurf, &sdl2::SDL_Rect{
+		x = pic.pos.0 - camera_pos.0, y = pic.pos.1 - camera_pos.1, ...
+	})!;
+};
+
+
 def SPEED = 17;
 def DIAG_SPEED = 12;  // thereabouts
 
@@ -80,4 +99,3 @@ fn movement(pos: *pos) void = {
 	pos.1 += dy * speed;
 };
 
-
-- 
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