From e306da5e4140324f2d5cd85f24bfb302969c4ff8 Mon Sep 17 00:00:00 2001
From: KikooDX <kikoodx@paranoici.org>
Date: Tue, 22 Dec 2020 16:46:00 +0100
Subject: [PATCH] Friction and acceleration (pfiou)

---
 levels/create_demo.lua |  2 +-
 src/player.c           | 27 ++++++++++++++++++++-------
 2 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/levels/create_demo.lua b/levels/create_demo.lua
index cd5b6ec..899203e 100755
--- a/levels/create_demo.lua
+++ b/levels/create_demo.lua
@@ -6,7 +6,7 @@ local function create_random_level(width, height, layers)
   io.write(height, "\n")
   for i = 1, layers, 1 do
     for r = 1, width * height, 1 do
-      io.write(math.floor(math.random() * 2)) --random 0 (2/3) or 1 (1/3)
+     io.write(math.floor(math.random() * 1.5)) --random 0 (2/3) or 1 (1/3)
       io.write("\n")
     end
     if i ~= layers then
diff --git a/src/player.c b/src/player.c
index e7bdd5a..167cef1 100644
--- a/src/player.c
+++ b/src/player.c
@@ -7,27 +7,39 @@
 #include "input.h"
 #include "collide.h"
 
+/* TODO: Determine FRICTION and ACCELERATION from UPS. */
+#define FRICTION 0.9
+#define ACCELERATION 64
 #define SGN(x) ((x > 0) ? (1) : ((x < 0) ? (-1) : (0)))
 #define PLAYER_COLLIDE(pos) player_collide(player, pos, level, level->solid_layer)
 
 void player_move(Player *player, const Level *level) {
-	/* TODO: Take into account player.origin and allow to snap for
-	 * more than one tile. THIS CODE WILL BREAK IF THE PLAYER SPEED
-	 * IS SUPERIOR THAN TILE_SIZE! */
-	//const int sgn_spd_x = SGN(player->spd.x);
-	//const int sgn_spd_y = SGN(player->spd.y);
+	/* TODO: Take into account player.origin. */ 
+	const int sgn_spd_x = SGN(player->spd.x);
+	const int sgn_spd_y = SGN(player->spd.y);
 	Vec destination;
 	vec_cpy(&destination, player->pos);
 	/* snap the player to the grid if they hit a wall */
 	destination.x += player->spd.x;
 	if (PLAYER_COLLIDE(destination)) {
 		destination.x = player->pos.x - player->pos.x % TILE_SIZE;
+		/* Move the player tile per tile until it enters an
+		 * occuped tile. */
+		while (!PLAYER_COLLIDE(destination)) {
+			destination.x += TILE_SIZE * sgn_spd_x;
+		}
+		/* then, move it back one tile */
+		destination.x -= TILE_SIZE * sgn_spd_x;
 		player->spd.x = 0;
 	}
 	/* do the same for y */
 	destination.y += player->spd.y;
 	if (PLAYER_COLLIDE(destination)) {
 		destination.y = player->pos.y - player->pos.y % TILE_SIZE;
+		while (!PLAYER_COLLIDE(destination)) {
+			destination.y += TILE_SIZE * sgn_spd_y;
+		}
+		destination.y -= TILE_SIZE * sgn_spd_y;
 		player->spd.y = 0;
 	}
 	/* move the player to their new position */
@@ -39,8 +51,9 @@ void player_step(Player *player, Input *input, const Level *level) {
 		(input_is_down(input, K_RIGHT) - input_is_down(input, K_LEFT)),
 		(input_is_down(input, K_DOWN) - input_is_down(input, K_UP))
 	};
-	vec_mul(&move, 32 * PXS); /* calculate speed */
-	vec_cpy(&player->spd, move);
+	vec_mulf(&player->spd, FRICTION); /* apply friction */
+	vec_mul(&move, ACCELERATION); /* apply acceleration */
+	vec_add(&player->spd, move);
 	player_move(player, level);
 }