# sdl2.ext.particles - A simple particle system

class `sdl2.ext.particles.``ParticleEngine`

  A simple particle processing system. The `ParticleEngine` takes care of creating, updating and deleting particles via callback functions. It only decreases the life of the particles by itself and marks them as dead, once the particle’s life attribute has reached 0 or below.

  `createfunc`

    Function for creating new particles. The function needs to take two arguments, the `world` argument passed to `process()` and a list of the particles considered dead (`Particle.life` <= 0).

        def creation_func(world, deadparticles):
            ...

  `updatefunc`

    Function for updating existing, living particles. The function needs to take two arguments, the `world` argument passed to `process()` and a `set` of the still living particles.

        def update_func(world, livingparticles):
            ...

  `deletefunc`

    Function for deleting dead particles. The function needs to take two arguments, the `world` argument passed to `process()` and a list of the particles considered dead (`Particle.life` <= 0).

        def deletion_func(world, deadparticles):
            ...

  `process`(world : World, components : iterable) → None

    Processes all particle components, decreasing their life by 1.

    Once the life of all particle components has been decreased properly and the particles considered dead (life <= 0) are identified, the creation, update and deletion callbacks are invoked.

    The creation callback takes the passed world as first and the list of dead particles as second argument.

        def particle_createfunc(world, list_of_dead_ones):
            ...

    Afterwards the still living particles are passed to the update callback, which also take the passed world as first and the living particles as set as second argument.

        def particle_updatefunc(world, set_of_living_ones):
            ...

    Finally, the dead particles need to be deleted in some way or another, which is done by the deletion callback, taking the passed world as first and the list of dead particles as second argument.

        def particle_deletefunc(world, list_of_dead_ones):
            ...

class `sdl2.ext.particles.``Particle`(x, y, life : int)

  A simple particle component type. It only contains information about a x- and y-coordinate and its current life time. The life time will be decreased by 1, every time the particle is processed by the `ParticleEngine`.

  `x`

    The x coordinate of the particle.

  `y`

    The y coordinate of the particle.

  `life`

    The remaining life time of the particle.

  `position`

    The x- and y-coordinate of the particle as tuple.