From a5c414dd4cdd8ac04e28fa40b8d4d092a2f805fe Mon Sep 17 00:00:00 2001
From: KikooDX <kikoodx@paranoici.org>
Date: Wed, 23 Dec 2020 23:22:02 +0100
Subject: [PATCH] Jump (yay) and grace frames support.

---
 include/input.h  |  3 ++-
 include/player.h |  3 +++
 src/input.c      |  1 +
 src/main.c       |  3 ++-
 src/player.c     | 25 ++++++++++++++++++++++++-
 5 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/include/input.h b/include/input.h
index e31087b..dc2c13d 100644
--- a/include/input.h
+++ b/include/input.h
@@ -4,13 +4,14 @@
 #include <gint/defs/types.h>
 #include <stdbool.h>
 
-#define KEYS_COUNT 5
+#define KEYS_COUNT 6
 
 enum {
 	K_LEFT,
 	K_RIGHT,
 	K_UP,
 	K_DOWN,
+	K_JUMP,
 	K_EXIT
 };
 
diff --git a/include/player.h b/include/player.h
index 31f1671..186a8ee 100644
--- a/include/player.h
+++ b/include/player.h
@@ -1,6 +1,8 @@
 #ifndef _DEF_PLAYER
 #define _DEF_PLAYER
 
+#include <stdbool.h>
+
 #include "vec.h"
 
 typedef struct Player {
@@ -9,6 +11,7 @@ typedef struct Player {
 	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) */
+	uint grace; /* coyot jump */
 } Player;
 
 #include "level.h"
diff --git a/src/input.c b/src/input.c
index 3912cb2..cf5581a 100644
--- a/src/input.c
+++ b/src/input.c
@@ -28,6 +28,7 @@ void input_init(Input *input) {
 	input->keys[K_RIGHT] = KEY_RIGHT;
 	input->keys[K_UP] = KEY_UP;
 	input->keys[K_DOWN] = KEY_DOWN;
+	input->keys[K_JUMP] = KEY_SHIFT;
 	input->keys[K_EXIT] = KEY_EXIT;
 	for (int i = 0; i < KEYS_COUNT; ++i) {
 		input->states[i] = S_UP;
diff --git a/src/main.c b/src/main.c
index a25783b..7129ce4 100644
--- a/src/main.c
+++ b/src/main.c
@@ -33,7 +33,8 @@ int play_level(uint level_id) {
 		.spd = {0, 0},
 		.hbox = {TILE_SIZE - 1, TILE_SIZE - 1},
 		.vbox = {7, 7},
-		.origin = {0 * VEC_PRECISION, 0 * VEC_PRECISION}
+		.origin = {0 * VEC_PRECISION, 0 * VEC_PRECISION},
+		.grace = 0
 	};
 	vec_cpy(&player.pos, player.origin); /* place the player at "0/0"*/
 
diff --git a/src/player.c b/src/player.c
index a876f83..ec5dd09 100644
--- a/src/player.c
+++ b/src/player.c
@@ -1,4 +1,5 @@
 #include <gint/display.h>
+#include <stdbool.h>
 
 #include "player.h"
 #include "vec.h"
@@ -12,6 +13,8 @@
 #define FRICTION 0.9
 #define ACCELERATION (MAX_SPD * (1 - FRICTION))
 #define GRAVITY PXS
+#define JUMP_SPD (-128 * PXS)
+#define GRACE_UNITS (int)(UPS / 5)
 #define SGN(x) ((x > 0) ? (1) : ((x < 0) ? (-1) : (0)))
 #define PLAYER_COLLIDE(pos) player_collide(player, pos, level, level->solid_layer)
 
@@ -42,6 +45,9 @@ void player_move(Player *player, const Level *level) {
 			destination.y += TILE_SIZE * sgn_spd_y;
 		}
 		destination.y -= TILE_SIZE * sgn_spd_y;
+		if (sgn_spd_y > 0) { /* the player was falling */
+			player->grace = GRACE_UNITS;
+		}
 		player->spd.y = 0;
 	}
 	/* move the player to their new position */
@@ -49,15 +55,32 @@ void player_move(Player *player, const Level *level) {
 }
 
 void player_step(Player *player, Input *input, const Level *level) {
+	/* Get directionnal input and assign it to move.x/move.y:
+	 * i.e., if the player hold left and down move will have
+	 * move.x = -1 and move.y = 1. */
 	Vec move = {
 		(input_is_down(input, K_RIGHT) - input_is_down(input, K_LEFT)),
 		(input_is_down(input, K_DOWN) - input_is_down(input, K_UP))
 	};
+	/* other keys */
+	bool kp_jump = input_is_pressed(input, K_JUMP);
 	int xacc = move.x * ACCELERATION; /* calculate horizontal acceleration */
 	player->spd.x *= FRICTION; /* apply horizontal friction */
 	player->spd.x += xacc; /* apply horizontal acceleration */
 	player->spd.y += GRAVITY; /* apply gravity */
-	player_move(player, level);
+	/* Grace frames allow the player to jump a short
+	 * time after leaving a platform. */
+	if (player->grace) {
+		player->grace -= 1;
+		if (kp_jump) {
+			/* If the player try to jump and can, prevent
+			 * them to do it again and assign them the
+			 * corresponding y speed. */
+			player->grace = 0;
+			player->spd.y = JUMP_SPD;
+		}
+	}
+	player_move(player, level); /* move the player according to their speed */
 }
 
 void player_draw(Player *player, Camera *camera) {