<!-- ##### SECTION Title ##### -->
Event Structures

<!-- ##### SECTION Short_Description ##### -->
data structures specific to each type of event.

<!-- ##### SECTION Long_Description ##### -->
<para>
The event structs contain data specific to each type of event in GDK.
</para>
<note>
<para>
A common mistake is to forget to set the event mask of a widget so that the
required events are received. See gtk_widget_set_events().
</para>
</note>

<!-- ##### SECTION See_Also ##### -->
<para>

</para>

<!-- ##### UNION GdkEvent ##### -->
<para>
The #GdkEvent struct contains a union of all of the event structs,
and allows access to the data fields in a number of ways.
</para>
<para>
The event type is always the first field in all of the event structs, and
can always be accessed with the following code, no matter what type of event
it is:
<informalexample>
<programlisting>
  GdkEvent *event;  
  GdkEventType type;

  type = event->type;
</programlisting>
</informalexample>
</para>

<para>
To access other fields of the event structs, the pointer to the event can be
cast to the appropriate event struct pointer, or the union member name can be
used. For example if the event type is %GDK_BUTTON_PRESS then the x coordinate
of the button press can be accessed with:
<informalexample>
<programlisting>
  GdkEvent *event;  
  gdouble x;

  x = ((GdkEventButton*)event)->x;
</programlisting>
</informalexample>
or:
<informalexample>
<programlisting>
  GdkEvent *event;  
  gdouble x;

  x = event->button.x;
</programlisting>
</informalexample>
</para>


<!-- ##### STRUCT GdkEventAny ##### -->
<para>
Contains the fields which are common to all event structs.
Any event pointer can safely be cast to a pointer to a #GdkEventAny to access
these fields.
</para>

@type: the type of the event.
@window: the window which received the event.
@send_event: TRUE if the event was sent explicitly (e.g. using XSendEvent).

<!-- ##### STRUCT GdkEventKey ##### -->
<para>
Describes a key press or key release event.
</para>

@type: the type of the event (%GDK_KEY_PRESS or %GDK_KEY_RELEASE).
@window: the window which received the event.
@send_event: TRUE if the event was sent explicitly (e.g. using XSendEvent).
@time: the time of the event in milliseconds.
@state: a bit-mask representing the state of the modifier keys (e.g. Control,
Shift and Alt) and the pointer buttons. See #GdkModifierType.
@keyval: the key that was pressed or released. See the &lt;gdk/gdkkeysym.h&gt;
header file for a complete list of GDK key codes.
@length: the length of @string.
@string: a null-terminated multi-byte string containing the composed characters
resulting from the key press. When text is being input, in a GtkEntry for
example, it is these characters which should be added to the input buffer.
When using <link linkend="gdk-Input-Methods"> Input Methods</link> to support
internationalized text input, the composed characters appear here after the
pre-editing has been completed.

<!-- ##### STRUCT GdkEventButton ##### -->
<para>
Used for button press and button release events. The
<structfield>type</structfield> field will be one of %GDK_BUTTON_PRESS,
%GDK_2BUTTON_PRESS, %GDK_3BUTTON_PRESS, and %GDK_BUTTON_RELEASE.
</para>
<para>
Double and triple-clicks result in a sequence of events being received.
For double-clicks the order of events will be:
<orderedlist>
<listitem><para>%GDK_BUTTON_PRESS</para></listitem>
<listitem><para>%GDK_BUTTON_RELEASE</para></listitem>
<listitem><para>%GDK_BUTTON_PRESS</para></listitem>
<listitem><para>%GDK_2BUTTON_PRESS</para></listitem>
<listitem><para>%GDK_BUTTON_RELEASE</para></listitem>
</orderedlist>
Note that the first click is received just like a normal
button press, while the second click results in a %GDK_2BUTTON_PRESS being
received just after the %GDK_BUTTON_PRESS.
</para>
<para>
Triple-clicks are very similar to double-clicks, except that %GDK_3BUTTON_PRESS
is inserted after the third click. The order of the events is:
<orderedlist>
<listitem><para>%GDK_BUTTON_PRESS</para></listitem>
<listitem><para>%GDK_BUTTON_RELEASE</para></listitem>
<listitem><para>%GDK_BUTTON_PRESS</para></listitem>
<listitem><para>%GDK_2BUTTON_PRESS</para></listitem>
<listitem><para>%GDK_BUTTON_RELEASE</para></listitem>
<listitem><para>%GDK_BUTTON_PRESS</para></listitem>
<listitem><para>%GDK_3BUTTON_PRESS</para></listitem>
<listitem><para>%GDK_BUTTON_RELEASE</para></listitem>
</orderedlist>
</para>
<para>
For a double click to occur, the second button press must occur within 1/4 of
a second of the first. For a triple click to occur, the third button press
must also occur within 1/2 second of the first button press.
</para>

@type: the type of the event (%GDK_BUTTON_PRESS, %GDK_2BUTTON_PRESS,
%GDK_3BUTTON_PRESS or %GDK_BUTTON_RELEASE).
@window: the window which received the event.
@send_event: TRUE if the event was sent explicitly (e.g. using XSendEvent).
@time: the time of the event in milliseconds.
@x: the x coordinate of the mouse relative to the window.
@y: the y coordinate of the mouse relative to the window.
@axes: 
@state: a bit-mask representing the state of the modifier keys (e.g. Control,
Shift and Alt) and the pointer buttons. See #GdkModifierType.
@button: the button which was pressed or released, numbered from 1 to 5.
Normally button 1 is the left mouse button, 2 is the middle button,
and 3 is the right button. On 2-button mice, the middle button can often
be simulated by pressing both mouse buttons together.
@device: 
@x_root: the x coordinate of the mouse relative to the root of the screen.
@y_root: the y coordinate of the mouse relative to the root of the screen.

<!-- ##### STRUCT GdkEventScroll ##### -->
<para>

</para>

@type: 
@window: 
@send_event: 
@time: 
@x: 
@y: 
@state: 
@direction: 
@device: 
@x_root: 
@y_root: 

<!-- ##### STRUCT GdkEventMotion ##### -->
<para>

</para>

@type: the type of the event.
@window: the window which received the event.
@send_event: TRUE if the event was sent explicitly (e.g. using XSendEvent).
@time: 
@x: 
@y: 
@axes: 
@state: 
@is_hint: 
@device: 
@x_root: 
@y_root: 

<!-- ##### STRUCT GdkEventExpose ##### -->
<para>
Generated when all or part of a window becomes visible and needs to be
redrawn.
</para>

@type: the type of the event (%GDK_EXPOSE).
@window: the window which received the event.
@send_event: TRUE if the event was sent explicitly (e.g. using XSendEvent).
@area: the area that needs to be redrawn.
@count: the number of contiguous %GDK_EXPOSE events following this one.
The only use for this is "exposure compression", i.e. handling all contiguous
%GDK_EXPOSE events in one go, though GDK performs some exposure compression
so this is not normally needed.

<!-- ##### STRUCT GdkEventVisibility ##### -->
<para>
Generated when the window visibility status has changed.
</para>

@type: the type of the event (%GDK_VISIBILITY_NOTIFY).
@window: the window which received the event.
@send_event: TRUE if the event was sent explicitly (e.g. using XSendEvent).
@state: the new visibility state (%GDK_VISIBILITY_FULLY_OBSCURED,
%GDK_VISIBILITY_PARTIAL or %GDK_VISIBILITY_UNOBSCURED).

<!-- ##### STRUCT GdkEventCrossing ##### -->
<para>

</para>

@type: the type of the event.
@window: the window which received the event.
@send_event: TRUE if the event was sent explicitly (e.g. using XSendEvent).
@subwindow: 
@time: the time of the event in milliseconds.
@x: 
@y: 
@x_root: 
@y_root: 
@mode: 
@detail: 
@focus: 
@state: 

<!-- ##### STRUCT GdkEventFocus ##### -->
<para>
Describes a change of keyboard focus.
</para>

@type: the type of the event (%GDK_FOCUS_CHANGE).
@window: the window which received the event.
@send_event: TRUE if the event was sent explicitly (e.g. using XSendEvent).
@in: TRUE if the window has gained the keyboard focus, FALSE if it has lost
the focus.

<!-- ##### STRUCT GdkEventConfigure ##### -->
<para>
Generated when a window size or position has changed.
</para>

@type: the type of the event (%GDK_CONFIGURE).
@window: the window which received the event.
@send_event: TRUE if the event was sent explicitly (e.g. using XSendEvent).
@x: the new x coordinate of the window, relative to its parent.
@y: the new y coordinate of the window, relative to its parent.
@width: the new width of the window.
@height: the new height of the window.

<!-- ##### STRUCT GdkEventProperty ##### -->
<para>
Describes a property change on a window.
</para>

@type: the type of the event (%GDK_PROPERTY_NOTIFY).
@window: the window which received the event.
@send_event: TRUE if the event was sent explicitly (e.g. using XSendEvent).
@atom: the property that was changed.
@time: the time of the event in milliseconds.
@state: whether the property was changed (%GDK_PROPERTY_NEW_VALUE) or
deleted (%GDK_PROPERTY_DELETE).

<!-- ##### STRUCT GdkEventSelection ##### -->
<para>

</para>

@type: the type of the event.
@window: the window which received the event.
@send_event: TRUE if the event was sent explicitly (e.g. using XSendEvent).
@selection: 
@target: 
@property: 
@time: the time of the event in milliseconds.
@requestor: 

<!-- ##### TYPEDEF GdkNativeWindow ##### -->
<para>

</para>


<!-- ##### STRUCT GdkEventDND ##### -->
<para>

</para>

@type: the type of the event.
@window: the window which received the event.
@send_event: TRUE if the event was sent explicitly (e.g. using XSendEvent).
@context: 
@time: the time of the event in milliseconds.
@x_root: 
@y_root: 

<!-- ##### STRUCT GdkEventProximity ##### -->
<para>

</para>

@type: the type of the event.
@window: the window which received the event.
@send_event: TRUE if the event was sent explicitly (e.g. using XSendEvent).
@time: the time of the event in milliseconds.
@device: 

<!-- ##### STRUCT GdkEventClient ##### -->
<para>
An event sent by another client application.
</para>

@type: the type of the event (%GDK_CLIENT_EVENT).
@window: the window which received the event.
@send_event: TRUE if the event was sent explicitly (e.g. using XSendEvent).
@message_type: the type of the message, which can be defined by the
application.
@data_format: the format of the data, given as the number of bits in each
data element, i.e. 8, 16, or 32. 8-bit data uses the b array of the data
union, 16-bit data uses the s array, and 32-bit data uses the l array.

<!-- ##### STRUCT GdkEventNoExpose ##### -->
<para>
Generated when the area of a #GdkDrawable being copied, with gdk_draw_pixmap()
or gdk_window_copy_area(), was completely available.
</para>
<para>
FIXME: add more here.
</para>

@type: the type of the event (%GDK_NO_EXPOSE).
@window: the window which received the event.
@send_event: TRUE if the event was sent explicitly (e.g. using XSendEvent).

<!-- ##### ENUM GdkScrollDirection ##### -->
<para>

</para>

@GDK_SCROLL_UP: 
@GDK_SCROLL_DOWN: 
@GDK_SCROLL_LEFT: 
@GDK_SCROLL_RIGHT: 

<!-- ##### ENUM GdkVisibilityState ##### -->
<para>
Specifies the visiblity status of a window for a #GdkEventVisibility.
</para>

@GDK_VISIBILITY_UNOBSCURED: the window is completely visible.
@GDK_VISIBILITY_PARTIAL: the window is partially visible.
@GDK_VISIBILITY_FULLY_OBSCURED: the window is not visible at all.

<!-- ##### ENUM GdkCrossingMode ##### -->
<para>

</para>

@GDK_CROSSING_NORMAL: 
@GDK_CROSSING_GRAB: 
@GDK_CROSSING_UNGRAB: 

<!-- ##### ENUM GdkNotifyType ##### -->
<para>

</para>

@GDK_NOTIFY_ANCESTOR: 
@GDK_NOTIFY_VIRTUAL: 
@GDK_NOTIFY_INFERIOR: 
@GDK_NOTIFY_NONLINEAR: 
@GDK_NOTIFY_NONLINEAR_VIRTUAL: 
@GDK_NOTIFY_UNKNOWN: 

<!-- ##### ENUM GdkPropertyState ##### -->
<para>
Specifies the type of a property change for a #GdkEventProperty.
</para>

@GDK_PROPERTY_NEW_VALUE: the property value wan changed.
@GDK_PROPERTY_DELETE: the property was deleted.

