space_game/game.h

#include <SDL2/SDL.h>
#include <SDL2/SDL_image.h>
#include <stdbool.h>
#include <stdint.h>
#include <math.h>
#include "vect.h"

#ifndef _DEFGAME
#define _DEFGAME 

#include "garbo.h"
#include "draw.h"

enum motors {
    M_GRAVITY = 0,
    M_FRICTION = 1,
    M_PLAYER_WALK = 2
};

enum world_thing_kind {
    PLAYER_W,
    STATIC_WALL_W, 
    FLOOR
};

// used to exert a force on an object
typedef struct motorstruct {
    double x; // positive is right
    double y; // positive is down
    double torque; // positive is anticlockwise
    double max_velocity; // max motor output velocity
                        // does not apply force if the velocity in the 
                        // direction of the motor vector is greater than
                        // max_velocity
    uint32_t timeout;// absolute time (in ms, from when the program starts) 
                     // for when the motor stops. 
                     // set to -1 for infinity
    void (*update_motor)(struct motorstruct *motor); // function pointer for generating 
                                        // the motor's output curve
} Motor;

typedef struct {
    int x;
    int y;
} Point;

typedef struct BodyStruct{

    // turn on dynamic physics
    // For moving objects.
    // eg. on for payer, off for walls
    bool dynamics;

    // unique identifier
    int uid;

    bool colliding;

    // position in viewport (pixels)
    SDL_Point screen_pos;

    // SI Unit kinematics
    /*------------------*/
    Vect position;
    Vect vel;
    Vect acc;

    // properties
    double obj_mass; // kgs
    double obj_elasticity; // rho

    //float x_vel;
    //float y_vel;

    //float x_acc;
    //float y_acc;
    /*------------------*/


    // constants
    double elasticity;

    // collisions
    Vect *collision_poly;
    Vect *collision_shape;
    int collision_poly_size;
    void (*updateCollisionPoly)(struct BodyStruct *);


    // fields
    double glob_friction;
    bool glob_gravity; // t/f

    uint32_t last_advance_time;

    // applying forces
    int num_motors;
    int max_motors;
    Motor *motors;
} Body;

typedef struct {
    bool has_physics;
    Body *physics;
    int max_walking_speed;
    int colliding;
} player_st;

typedef struct {
    int numNodes;
    SDL_Point *nodes;
    Body *physics;
} Wall;

typedef struct {
    Vect left;
    Vect right;
    Body *physics; 
} FloorPoly;

typedef struct {
    FloorPoly *polys;
    int numPolys;
} Floor;

typedef struct {
    enum world_thing_kind kind;
    int nid;
    bool collisions;
    bool physics;
    union {
        player_st *player;
        Wall *wall;
        Floor *floor;
    };
} world_thing;


/* array of all the things in the world and their kinds */
world_thing *world;

int things_in_world;
int world_size;

void startgame(SDL_Renderer * ren) ;

void process_keydown(SDL_Keysym key);
void process_keyup(SDL_Keysym key);

void step(int interval);

player_st player;

void add_motor(Body *thing, double x, double y); 
#endif