From a8234e35b65402953a735112d854921ad2cc305a Mon Sep 17 00:00:00 2001
From: KikooDX <kikoodx@protonmail.com>
Date: Mon, 21 Sep 2020 14:52:28 +0200
Subject: [PATCH] Better camera offset system

---
 include/camera.h | 1 +
 include/player.h | 3 ++-
 src/camera.c     | 6 ++++++
 src/level.c      | 3 +--
 src/main.c       | 3 ++-
 src/player.c     | 7 +++----
 6 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/include/camera.h b/include/camera.h
index 879808a..ea8c9e8 100644
--- a/include/camera.h
+++ b/include/camera.h
@@ -7,6 +7,7 @@
 typedef struct Camera
 {
 	Vec pos;
+	Vec offset; /* adjusted pixel offset based on pos */
 	Vec *target; /* the target position to lerp on */
 	float speed; /* camera lerp speed with 0 < speed <= 1 */
 } Camera;
diff --git a/include/player.h b/include/player.h
index a8a2729..0b5ea3a 100644
--- a/include/player.h
+++ b/include/player.h
@@ -8,7 +8,8 @@
 typedef struct Player
 {
 	Vec pos;
-	Vec hbox; /* the bottom right corner of the player's hitbox */
+	Vec hbox; /* the bottom left corner of the player's hitbox */
+	Vec vbox; /* the bottom left corner of the player's visual box */
 	Vec origin; /* the origin of the player (offset) */
 } Player;
 
diff --git a/src/camera.c b/src/camera.c
index d7cddad..7cf9fcf 100644
--- a/src/camera.c
+++ b/src/camera.c
@@ -7,7 +7,13 @@
 
 void camera_step(Camera *camera)
 {
+	/* lerp towards target */
 	vec_lerp(&camera->pos, *camera->target, camera->speed);
+	/* calculate pixel offset */
+	Vec * const offset = &camera->offset; /* DRY */
+	vec_cpy(offset, camera->pos);
+	vec_div(offset, VEC_PRECISION);
+	vec_sub(offset, VEC_DCENTER);
 }
 
 void camera_draw_debug(Camera *camera)
diff --git a/src/level.c b/src/level.c
index 4edeb85..c9485e3 100644
--- a/src/level.c
+++ b/src/level.c
@@ -32,9 +32,8 @@ void layer_draw(const Level *level, Camera *camera, uint layer_id)
 				Vec tl = {x, y};
 				Vec br;
 				vec_mul(&tl, VEC_PRECISION * TILE_SIZE);
-				vec_sub(&tl, camera->pos);
 				vec_div(&tl, VEC_PRECISION);
-				vec_sub(&tl, VEC_DCENTER);
+				vec_sub(&tl, camera->offset);
 				vec_cpy(&br, tl);
 				vec_add(&br, (Vec){TILE_SIZE - 1, TILE_SIZE - 1});
 				vec_drect(tl, br, color);
diff --git a/src/main.c b/src/main.c
index 329eca7..4187735 100644
--- a/src/main.c
+++ b/src/main.c
@@ -33,6 +33,7 @@ int play_level(uint level_id)
 	Player player = {
 		.pos = {16 * VEC_PRECISION, 16 * VEC_PRECISION},
 		.hbox = {7 * VEC_PRECISION, 7 * VEC_PRECISION},
+		.vbox = {7, 7},
 		.origin = {4 * VEC_PRECISION, 4 * VEC_PRECISION}
 	};
 
@@ -44,7 +45,7 @@ int play_level(uint level_id)
 	Camera camera = {
 		.pos = {DWIDTH * VEC_PRECISION, DHEIGHT * VEC_PRECISION},
 		.target = &player.pos,
-		.speed = 0.01
+		.speed = 0.02
 	};
 
 	/* create input manager */
diff --git a/src/player.c b/src/player.c
index 472ba5c..fc1302e 100644
--- a/src/player.c
+++ b/src/player.c
@@ -21,15 +21,14 @@ void player_draw(Player *player, Camera *camera)
 	Vec draw_pos_br;
 	vec_cpy(&draw_pos_tl, player->pos);
 	vec_sub(&draw_pos_tl, player->origin);
-	vec_sub(&draw_pos_tl, camera->pos);
 	vec_cpy(&draw_pos_br, draw_pos_tl);
-	vec_add(&draw_pos_br, player->hbox);
 	vec_div(&draw_pos_tl, VEC_PRECISION);
 	vec_div(&draw_pos_br, VEC_PRECISION);
 	vec_mul(&draw_pos_tl, SCALE);
 	vec_mul(&draw_pos_br, SCALE);
-	vec_add(&draw_pos_tl, VEC_DCENTER);
-	vec_add(&draw_pos_br, VEC_DCENTER);
+	vec_sub(&draw_pos_tl, camera->offset);
+	vec_sub(&draw_pos_br, camera->offset);
+	vec_add(&draw_pos_br, player->vbox);
 	vec_drect(draw_pos_tl, draw_pos_br, C_BLACK);
 }