From dc53a2d8deb41c583c985e274b766b4c61d5f0bb Mon Sep 17 00:00:00 2001
From: Camden Dixie O'Brien <cdo@wip.sh>
Date: Wed, 1 Jan 2025 21:31:29 +0000
Subject: [PATCH] Snap view and entity positions to grid when not in motion

This fixes some chunky movement badness.
---
 app/main.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/app/main.c b/app/main.c
index 0e3d096..f9efee5 100644
--- a/app/main.c
+++ b/app/main.c
@@ -340,8 +340,8 @@ static void mapdraw(void)
 					.h = TILESIZE,
 				};
 				const SDL_Rect dest = {
-					.x = SCALE * (int)round(x - vpos.x),
-					.y = SCALE * (int)round(y - vpos.y),
+					.x = (int)rint(SCALE * (x - vpos.x)),
+					.y = (int)rint(SCALE * (y - vpos.y)),
 					.w = SCALE * TILESIZE,
 					.h = SCALE * TILESIZE,
 				};
@@ -353,8 +353,12 @@ static void mapdraw(void)
 
 static void entityupdate(entity_t *e, double dt)
 {
-	if (0 == e->speed)
+	if (0 == e->speed) {
+		// Round position to nearest integer to align with pixel grid.
+		e->pos.x = rint(e->pos.x);
+		e->pos.y = rint(e->pos.y);
 		return;
+	}
 
 	// Update sprite variant
 	if (e->dir.y >= 0) {
@@ -395,8 +399,8 @@ static void entitydraw(entity_t *e, uint64_t t)
 	e->src.x = e->animstep.x * frame + e->svarstep.x * e->svar;
 	e->src.y = e->animstep.y * frame + e->svarstep.y * e->svar;
 	SDL_Rect dest = {
-		.x = SCALE * (int)round(e->pos.x - e->src.w / 2 - vpos.x),
-		.y = SCALE * (int)round(e->pos.y - e->src.h / 2 - vpos.y),
+		.x = (int)rint(SCALE * (e->pos.x - e->src.w / 2 - vpos.x)),
+		.y = (int)rint(SCALE * (e->pos.y - e->src.h / 2 - vpos.y)),
 		.w = SCALE * e->src.w,
 		.h = SCALE * e->src.h,
 	};
@@ -413,8 +417,8 @@ static void objsdraw(uint64_t t)
 		SDL_Rect src = type->src;
 		src.x += type->src.w * ((t / BASEANIMPERIOD) % type->animframes);
 		SDL_Rect dest = {
-			.x = SCALE * (int)round(obj->pos.x - vpos.x),
-			.y = SCALE * (int)round(obj->pos.y - vpos.y - type->src.h),
+			.x = (int)rint(SCALE * (obj->pos.x - vpos.x)),
+			.y = (int)rint(SCALE * (obj->pos.y - vpos.y - type->src.h)),
 			.w = SCALE * type->src.w,
 			.h = SCALE * type->src.h,
 		};
@@ -552,6 +556,11 @@ int main(int argc, char *argv[])
 		} else {
 			p.tex = pidle;
 			p.speed = 0;
+
+			// Round view position to nearest integer to align with
+			// pixel grid.
+			vpos.x = rint(vpos.x);
+			vpos.y = rint(vpos.y);
 		}
 		entityupdate(&p, dt);