From 9d7f111b7d5d882a10f919fcc861efc48ceedff9 Mon Sep 17 00:00:00 2001
From: P. J. McDermott <pj@pehjota.net>
Date: Sat, 27 Mar 2021 17:48:12 -0400
Subject: ball: Collide with walls

---
diff --git a/src/ball.c b/src/ball.c
index 2fd2b97..767b565 100644
--- a/src/ball.c
+++ b/src/ball.c
@@ -111,10 +111,38 @@ _db_ball_bounce(struct db_ball *ball, double col_x, double col_y)
 void
 db_balls_collisions(struct db_ball *ball)
 {
+	SDL_Rect        wall;
+	int             map_tw;
+	int             map_th;
+	int             x_min;
+	int             x_max;
+	int             y_min;
+	int             y_max;
+	int             x;
+	int             y;
 	struct db_ball *other;
 	double          col_x;
 	double          col_y;
 
+	wall.w = map_tw = db_map_get_tilewidth (ball->map);
+	wall.h = map_th = db_map_get_tileheight(ball->map);
+	x_min = floor((ball->x - ball->r) / map_tw);
+	x_max = ceil ((ball->x + ball->r) / map_tw);
+	y_min = floor((ball->y - ball->r) / map_th);
+	y_max = ceil ((ball->y + ball->r) / map_th);
+	for (y = y_min; y < y_max; ++y) {
+		for (x = x_min; x < x_max; ++x) {
+			if (db_map_tile_ball_collides(ball->map, x, y)) {
+				wall.x = x * map_tw;
+				wall.y = y * map_th;
+				if (db_col_cir_rect(ball->x, ball->y, ball->r,
+							&wall, &col_x, &col_y)){
+					_db_ball_bounce(ball, col_x, col_y);
+				}
+			}
+		}
+	}
+
 	/* Spinning balls shouldn't collide with any other balls */
 	if (ball->sr == 0) {
 		for (other = ball->next; other != NULL; other = other->next) {
--
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