Source

pygame / docs / _sources / ref / event.txt

.. include:: common.txt

:mod:`pygame.event`
===================

.. module:: pygame.event
   :synopsis: pygame module for interacting with events and queues

| :sl:`pygame module for interacting with events and queues`

Pygame handles all it's event messaging through an event queue. The routines in
this module help you manage that event queue. The input queue is heavily
dependent on the pygame display module. If the display has not been initialized
and a video mode not set, the event queue will not really work.

The queue is a regular queue of Event objects, there are a variety of ways to
access the events it contains. From simply checking for the existance of
events, to grabbing them directly off the stack.

All events have a type identifier. This event type is in between the values of
``NOEVENT`` and ``NUMEVENTS``. All user defined events can have the value of
``USEREVENT`` or higher. It is recommended make sure your event id's follow
this system.

To get the state of various input devices, you can forego the event queue and
access the input devices directly with their appropriate modules; mouse, key,
and joystick. If you use this method, remember that pygame requires some form
of communication with the system window manager and other parts of the
platform. To keep pygame in synch with the system, you will need to call
``pygame.event.pump()`` to keep everything current. You'll want to call this
function usually once per game loop.

The event queue offers some simple filtering. This can help performance
slightly by blocking certain event types from the queue, use the
``pygame.event.set_allowed()`` and ``pygame.event.set_blocked()`` to work with
this filtering. All events default to allowed.

The event subsystem should be called from the main thread.  If you want to post
events into the queue from other threads, please use the fastevent package.

Joysticks will not send any events until the device has been initialized.

An Event object contains an event type and a readonly set of member data. The
Event object contains no method functions, just member data. Event objects are
retrieved from the pygame event queue. You can create your own new events with
the ``pygame.event.Event()`` function.

Your program must take steps to keep the event queue from overflowing. If the
program is not clearing or getting all events off the queue at regular
intervals, it can overflow. When the queue overflows an exception is thrown.

All Event objects contain an event type identifier in the ``Event.type``
member. You may also get full access to the Event's member data through the
``Event.dict`` method. All other member lookups will be passed through to the
Event's dictionary values.

While debugging and experimenting, you can print the Event objects for a quick
display of its type and members. Events that come from the system will have a
guaranteed set of member items based on the type. Here is a list of the Event
members that are defined with each type.

::

    QUIT	     none
    ACTIVEEVENT	     gain, state
    KEYDOWN	     unicode, key, mod
    KEYUP	     key, mod
    MOUSEMOTION	     pos, rel, buttons
    MOUSEBUTTONUP    pos, button
    MOUSEBUTTONDOWN  pos, button
    JOYAXISMOTION    joy, axis, value
    JOYBALLMOTION    joy, ball, rel
    JOYHATMOTION     joy, hat, value
    JOYBUTTONUP      joy, button
    JOYBUTTONDOWN    joy, button
    VIDEORESIZE      size, w, h
    VIDEOEXPOSE      none
    USEREVENT        code

Events support equality comparison. Two events are equal if they are the same
type and have identical attribute values. Inequality checks also work.

.. function:: pump

   | :sl:`internally process pygame event handlers`
   | :sg:`pump() -> None`

   For each frame of your game, you will need to make some sort of call to the
   event queue. This ensures your program can internally interact with the rest
   of the operating system. If you are not using other event functions in your
   game, you should call ``pygame.event.pump()`` to allow pygame to handle
   internal actions.

   This function is not necessary if your program is consistently processing
   events on the queue through the other :mod:`pygame.event` functions.

   There are important things that must be dealt with internally in the event
   queue. The main window may need to be repainted or respond to the system. If
   you fail to make a call to the event queue for too long, the system may
   decide your program has locked up.

   .. ## pygame.event.pump ##

.. function:: get

   | :sl:`get events from the queue`
   | :sg:`get() -> Eventlist`
   | :sg:`get(type) -> Eventlist`
   | :sg:`get(typelist) -> Eventlist`

   This will get all the messages and remove them from the queue. If a type or
   sequence of types is given only those messages will be removed from the
   queue.

   If you are only taking specific events from the queue, be aware that the
   queue could eventually fill up with the events you are not interested.

   .. ## pygame.event.get ##

.. function:: poll

   | :sl:`get a single event from the queue`
   | :sg:`poll() -> Event`

   Returns a single event from the queue. If the event queue is empty an event
   of type ``pygame.NOEVENT`` will be returned immediately. The returned event
   is removed from the queue.

   .. ## pygame.event.poll ##

.. function:: wait

   | :sl:`wait for a single event from the queue`
   | :sg:`wait() -> Event`

   Returns a single event from the queue. If the queue is empty this function
   will wait until one is created. The event is removed from the queue once it
   has been returned. While the program is waiting it will sleep in an idle
   state. This is important for programs that want to share the system with
   other applications.

   .. ## pygame.event.wait ##

.. function:: peek

   | :sl:`test if event types are waiting on the queue`
   | :sg:`peek(type) -> bool`
   | :sg:`peek(typelist) -> bool`

   Returns true if there are any events of the given type waiting on the queue.
   If a sequence of event types is passed, this will return True if any of
   those events are on the queue.

   .. ## pygame.event.peek ##

.. function:: clear

   | :sl:`remove all events from the queue`
   | :sg:`clear() -> None`
   | :sg:`clear(type) -> None`
   | :sg:`clear(typelist) -> None`

   Remove all events or events of a specific type from the queue. This has the
   same effect as ``pygame.event.get()`` except nothing is returned. This can
   be slightly more effecient when clearing a full event queue.

   .. ## pygame.event.clear ##

.. function:: event_name

   | :sl:`get the string name from and event id`
   | :sg:`event_name(type) -> string`

   Pygame uses integer ids to represent the event types. If you want to report
   these types to the user they should be converted to strings. This will
   return a the simple name for an event type. The string is in the WordCap
   style.

   .. ## pygame.event.event_name ##

.. function:: set_blocked

   | :sl:`control which events are allowed on the queue`
   | :sg:`set_blocked(type) -> None`
   | :sg:`set_blocked(typelist) -> None`
   | :sg:`set_blocked(None) -> None`

   The given event types are not allowed to appear on the event queue. By
   default all events can be placed on the queue. It is safe to disable an
   event type multiple times.

   If None is passed as the argument, this has the opposite effect and ``ALL``
   of the event types are allowed to be placed on the queue.

   .. ## pygame.event.set_blocked ##

.. function:: set_allowed

   | :sl:`control which events are allowed on the queue`
   | :sg:`set_allowed(type) -> None`
   | :sg:`set_allowed(typelist) -> None`
   | :sg:`set_allowed(None) -> None`

   The given event types are allowed to appear on the event queue. By default
   all events can be placed on the queue. It is safe to enable an event type
   multiple times.

   If None is passed as the argument, ``NONE`` of the event types are allowed
   to be placed on the queue.

   .. ## pygame.event.set_allowed ##

.. function:: get_blocked

   | :sl:`test if a type of event is blocked from the queue`
   | :sg:`get_blocked(type) -> bool`

   Returns true if the given event type is blocked from the queue.

   .. ## pygame.event.get_blocked ##

.. function:: set_grab

   | :sl:`control the sharing of input devices with other applications`
   | :sg:`set_grab(bool) -> None`

   When your program runs in a windowed environment, it will share the mouse
   and keyboard devices with other applications that have focus. If your
   program sets the event grab to True, it will lock all input into your
   program.

   It is best to not always grab the input, since it prevents the user from
   doing other things on their system.

   .. ## pygame.event.set_grab ##

.. function:: get_grab

   | :sl:`test if the program is sharing input devices`
   | :sg:`get_grab() -> bool`

   Returns true when the input events are grabbed for this application. Use
   ``pygame.event.set_grab()`` to control this state.

   .. ## pygame.event.get_grab ##

.. function:: post

   | :sl:`place a new event on the queue`
   | :sg:`post(Event) -> None`

   This places a new event at the end of the event queue. These Events will
   later be retrieved from the other queue functions.

   This is usually used for placing ``pygame.USEREVENT`` events on the queue.
   Although any type of event can be placed, if using the sytem event types
   your program should be sure to create the standard attributes with
   appropriate values.

   .. ## pygame.event.post ##

.. function:: Event

   | :sl:`create a new event object`
   | :sg:`Event(type, dict) -> Event`
   | :sg:`Event(type, **attributes) -> Event`

   Creates a new event with the given type. The event is created with the given
   attributes and values. The attributes can come from a dictionary argument
   with string keys, or from keyword arguments. The event object exposes its
   dictionary as attribute __dict__, and also as dict for backward
   compatibility.

   Attributes type, __dict__, and dict are readonly. Other attributes are
   mutable. There are no methods attached to an Event object.

   Mutable attributes are new to Pygame 1.9.2.

   .. ## pygame.event.Event ##

.. ## pygame.event ##
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