From e7a19b7d91ebf94b2a354271f7de968a21ca6f1c Mon Sep 17 00:00:00 2001
From: Camden Dixie O'Brien <cdo@wip.sh>
Date: Sun, 29 Dec 2024 18:49:04 +0000
Subject: [PATCH] Fix camera when at edge of map

---
 app/main.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/app/main.c b/app/main.c
index 4e2551a..5d8a91b 100644
--- a/app/main.c
+++ b/app/main.c
@@ -25,6 +25,10 @@
 #define MAPHEIGHT 64
 #define MAPSHIFTX 32
 #define MAPSHIFTY 32
+#define MAPMINX (TILESIZE * (-32))
+#define MAPMAXX (TILESIZE * 32)
+#define MAPMINY (TILESIZE * (-32))
+#define MAPMAXY (TILESIZE * 32)
 
 #define TSASSET "/overworld.png"
 #define TSCOLS 40
@@ -75,6 +79,11 @@ static inline double mag(dvec_t v)
 	return sqrt(v.x * v.x + v.y * v.y);
 }
 
+static inline double dot(dvec_t v, dvec_t u)
+{
+	return v.x * u.x + v.y * u.y;
+}
+
 static inline unsigned tileat(double x, double y)
 {
 	const unsigned row = (unsigned)floor(x / TILESIZE) + MAPSHIFTX;
@@ -317,9 +326,15 @@ int main(int argc, char *argv[])
 			.x = ppos.x - (vpos.x + VIEWWIDTH / 2),
 			.y = ppos.y - (vpos.y + VIEWHEIGHT / 2),
 		};
-		if (mag(pvdisp) > 72) {
-			vpos.x += (double)dt / 1000.0 * pvel.x;
-			vpos.y += (double)dt / 1000.0 * pvel.y;
+		if (mag(pvdisp) > 72 && dot(pvdisp, pvel) > 0) {
+			const double nextx = vpos.x + (double)dt / 1000.0 * pvel.x;
+			const double nexty = vpos.y + (double)dt / 1000.0 * pvel.y;
+			const bool validx = nextx >= MAPMINX && nextx < MAPMAXX;
+			const bool validy = nexty >= MAPMINY && nexty < MAPMAXY;
+			if (validx && validy) {
+				vpos.x = nextx;
+				vpos.y = nexty;
+			}
 		}
 
 		SDL_RenderClear(renderer);