NAME

SDL::EventHandler - base class for application-specific SDL event handlers

SYNOPSIS

        # load the event class and this library
        load_bytecode 'library/SDL/Event.pir'
        load_bytecode 'library/SDL/EventHandler.pir'

        # subclass this class
        .local pmc parent_class
        .local pmc class_type

        getclass parent_class, 'SDL::EventHandler'
        subclass class_type, parent_class, 'My::Event::Handler'

        # define your overridden methods
        .sub key_down_down method
                .param pmc event
                .param pmc event_args

                # ...

        .end

        # create an event handler object
        .local pmc event_handler
        .local int handler_type

        find_type handler_type, 'My::Event::Handler'
        event_handler = new handler_type

        # create and populate some event_arguments
        .local pmc event_args

        new event_args, .PerlHash
        event_args[ 'main_surface' ] = main_surface
        event_args[ 'sprite_list'  ] = sprites

        # create a new event object
        .local pmc event
        .local int event_type

        find_type event_type, 'SDL::Event'
        event = new event_type

        # ... and wait for events
        event.wait_event( event_handler, handler_args )

DESCRIPTION

SDL::EventHandler is a parent class for all event handlers in SDL Parrot programs. Subclass this class and override the methods that correspond to the events you want to handle.

METHODS

SDL::EventHandler provides the following methods:

key_down( event, event_args ): Dispatches a key down event to the appropriate key_down_keyname method, if one exists. Otherwise, does nothing.; Override this if you want to change the way dispatching happens or to do something different for all key down events. In general, you will probably want to override the key_down_* methods instead.
key_up( event, event_args ): Dispatches a key up event to the appropriate key_upkeyname method, if one exists. Otherwise, does nothing.; Override this if you want to change the way dispatching happens or to do something different for all key up events. In general, you will probably want to override the key_up_* methods instead.

Key Event Methods

Key event methods have names of the form key_eventtype_keyname. That is, to handle a key down event for the Escape key, override the method key_down_escape. Key names follow the SDL naming convention, except that key names are in all lowercase.

Unless you override key_down or key_up and do something different, all of these methods will receive one argument, the event_args hash passed to SDL::Event::wait_event(). Use this hash to store and to retrieve data between events, particularly your main surface and any sprites or other surfaces.

Other Event Methods

In addition, you can override the following methods to handle their event types.

active_event

mouse_motion

mouse_button_down

mouse_button_up

joy_axis_motion

joy_ball_motion

joy_hat_motion

joy_button_down

joy_button_up

quit

sys_wm_event

video_resize

video_expose

event_reserved_a

event_reserved_b

event_reserved_2

event_reserved_3

event_reserved_4

event_reserved_5

event_reserved_6

event_reserved_7

By default, these methods do nothing. They all take two arguments, the SDL::Event object representing the incoming event and the event_args hash storing data between events.

At the very least, you should override quit().

AUTHOR

Written and maintained by chromatic, <chromatic at wgz dot org>. Designed by Allison Randal. Please send patches, feedback, and suggestions to the Perl 6 Internals mailing list.

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