Components and classes

This section describes the attributes of each components.

Be sure to read YAPG template syntax before continuing your reading.

In the attribute's tables below:

  • the "U" column tells if the attributes can be unserialized from YAPG templates files
  • the "R" column tells if the attributes can be received or changed at runtime with a_component(entity).attr_name and a_component(entity).attr_name = value syntaxes. See Lua runtime to see how to get/change attributes' values of components during runtime.
  • the "P" column tells if the attributes can be used as a template parameter.

"✓" means "yes", "…" means that it will be included in a future version (planned) and nothing means "no".

Currently, the game has the following components:

collidable_component

Component that allows an entity to react to collisions with multiple polygons.

Name Type Description U R
polygons Map associating string to polygon_callback The string is the polygon's name. ✓

polygon_callback class

Represents a polygon with its associated callbacks (used by Collidable_component to allow scripting on collisions)

Attributes

Name Type Description U R
polygon polygon The polygon ✓ ✓
exclusive boolean Whether all the following polygon_callback will be ignored if this one collides ✓
on_collision_begin A function, two args: the entity itself and the other colliding entity A function called when the collision starts ✓
on_collision_end A function, two args: the entity itself and the other colliding entity A function called when the collision ends ✓
collides A function, two args: the entity itself and the other colliding entity A function called each frame while the collision still exists. ✓

collider_component

Component that allows the object to trigger collisions with entities with Collidable_component.

Alone, it will not work as it needs the entity to have a Collidable_component to store at least one hitbox

custom_behavior_component

Component that allows a lua callback function to be called at each frames.

Attributes

Name Type Description U R P
on_update function A function called each frame with two arguments : entity and dt (the time since the previous frame). ✓ 
components = {
    --The custom_behavior_component
    ["custom_behavior"] = {
        on_update = function(entity, dt)
            --act on the entity
        end,
    },
}

custom_data_component

This is a special component, see Lua runtime > Per entity instance storage to understand how it should be used.

health_component

Component that allows an entity to have an health. The entity is killed when its health falls to 0.

Attributes

Name Type Description U R
health int The current health ✓ ✓ (read-only)
max_health int The maximum health ✓ ✓

Methods

Methods that can be called on the health_component in scripts (runtime).

  • kill() : put the entity's health to 0. Will be killed next frame.
  • loose_pv(nbr_hp) : remove nbr_hp to the entity (without going under 0).
  • gain_pv(nbr_hp) : add nbr_hp to the entity (without exceeding max_health).

Example: an enemy that instant kills the player lua --This is the callback called when the enemy polygon is collided by an entity on_collision_begin = function(entity, other) if(player(other) ~= nil and health(other) ~= nil) then --Tests if it's a player and it has a health_component health(other):loose_pv(1) --Remove one hp to it end end,

platform_component

Declares and entity as a platform on which the entities with the Platformer_component can walk and jump.

Attributes

Name Type Description U R P
activated bool activates or not the platform collision with entities ✓ ✓ ✓
platform_type string "Platform" for solid platforms or "Jumpthru" for platforms that the platformer entities can pass through from underneath. ✓

platformer_component

Declares an entity as affected by the gravity and that it can walk and jump on platforms.

Note: it doesn't mean the entity is controlled by a player, need to use Player_component in addition for that. So, items moving on the ground can use the Platformer_component too.

Warning: when trying to move an entity with this component in a lua callback function, consider setting wants_to_jump, wants_to_go_left and wants_to_go_right attributes of this component to make it move (instead of changing it position).

Attributes

Name Type Description U R P
max_walking_speed float The maximum walking speed (pixels/s) ✓ ✓ ✓
max_jumping_speed float The maximum jumping speed (pixels/s) ✓ ✓ ✓
max_falling_speed float The maximum falling speed (pixels/s) ✓ ✓ ✓
acceleration float The walking acceleration of the entity (jumping and falling are affected by gravity, not acceleration) (pixels/s^2). ✓ ✓ ✓
deceleration float The walking deceleration of the entity (pixels/s^2) ✓ ✓ ✓
gravity float The gravity. The jumping and falling acceleration (pixels/s^2) ✓ ✓ ✓
wants_to_jump bool If true, the player will try to jump as soon as possible (the value is not reset by the engine each frame, so don't forget to turn it back to false after). ✓ ✓ ✓
wants_to_go_left bool If true, the player will try to go left (the value is not reset by the engine each frame, so don't forget to turn it back to false after). ✓ ✓ ✓
wants_to_go_right bool If true, the player will try to go right (the value is not reset by the engine each frame, so don't forget to turn it back to false after). ✓ ✓ ✓
on_idle function Function with the current entity as its single argument. Called when the entity stops moving. ✓ ✓ ✓
on_start_walking function Function with the current entity as its single argument. Called when the entity starts walking (on a platform). ✓ ✓ ✓
on_start_jumping function Function with the current entity as its single argument. Called when the entity starts jumping. ✓ ✓ ✓
on_start_falling function Function with the current entity as its single argument. Called when the entity starts falling (from a platform or when going down after a jump). ✓ ✓ ✓
on_turn_right function Function with the current entity as its single argument. Called when the entity turns towards the right direction. ✓ ✓ ✓
on_turn_left function Function with the current entity as its single argument. Called when the entity turns towards the left direction. ✓ ✓ ✓

platformer_hitbox_component

Contains an polygonal hitbox (must be convex). Used to detect collisions between platformer entities and platforms (not used by the CollisionSystem however).

Attributes

Name Type Description U R P
polygon polygon The hitbox convex polygon ✓ ✓ 
components = {
    --The platformer_hitbox_component
    ["platformer_hitbox"] = {
        --this is a square hitbox
        polygon = {
            points = {
                {
                    x = 0,
                    y = 0
                },
                {
                    x = 64,
                    y = 0
                },
                {
                    x = 64,
                    y = 64
                },
                {
                    x = 0,
                    y = 64
                },
            }
        },
    },
}

player_component

Declare an entity as a player. It will allow the player's controls to make the entity walk and jump using the Platformer_component.

Attributes

Name Type Description U R P
player_number int The player number (starting from 0) ✓ (read-only)

position_component

Component containing position and size data of an entity.

Attributes

Name Type Description U R P
x float ✓ ✓ ✓
y float ✓ ✓ ✓
width float ✓ ✓ ✓
height float ✓ ✓ ✓ 
components = {
    --The position_component
    ["position"] = {
        x = 10,
        y = 20,
        width = 64,
        height = 128,
    },
}

render_component

Stores the animations of an entity and tells the render engine which one to render.

Attributes

Name Type Description U R P
texture string The filepath to the texture picture ✓ ✓ ✓
animations map associating string to animation Associates the animation name with the animation. ✓ …
current_animation string The current animation's name ✓ ✓ ✓ 
components = {
    --The render_component
    ["render"] = {
        texture = "myTexture.png",
        animations = {
            default_animation = {
                duration = 1, --See the doc of the Animation class to see how Animations are serialized.
            },
            alternative_animation = {
                duration = 2,
            },
        },
    },
}