<!-- ##### 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 
<function>XSendEvent</function>).

<!-- ##### 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 
<function>XSendEvent</function>).
@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 <filename>&lt;gdk/gdkkeysym.h&gt;</filename>
header file for a complete list of GDK key codes.
@length: the length of @string.
@string: a nul-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.
@hardware_keycode: the raw code of the key that was pressed or released.
@group: the keyboard group.

<!-- ##### 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 
<function>XSendEvent</function>).
@time: the time of the event in milliseconds.
@x: the x coordinate of the pointer relative to the window.
@y: the y coordinate of the pointer relative to the window.
@axes: @x, @y translated to the axes of @device, or %NULL if @device is 
  the mouse.
@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: the device where the event originated.
@x_root: the x coordinate of the pointer relative to the root of the screen.
@y_root: the y coordinate of the pointer relative to the root of the screen.

<!-- ##### STRUCT GdkEventScroll ##### -->
<para>
Generated from button presses for the buttons 4 to 7. Wheel mice are 
usually configured to generate button press events for buttons 4 and 5
when the wheel is turned.
</para>

@type: the type of the event (%GDK_SCROLL).
@window: the window which received the event.
@send_event: %TRUE if the event was sent explicitly (e.g. using 
<function>XSendEvent</function>).
@time: the time of the event in milliseconds.
@x: the x coordinate of the pointer relative to the window.
@y: the y coordinate of the pointer relative to the window.
@state: a bit-mask representing the state of the modifier keys (e.g. Control,
Shift and Alt) and the pointer buttons. See #GdkModifierType.
@direction: the direction to scroll to (one of %GDK_SCROLL_UP, 
  %GDK_SCROLL_DOWN, %GDK_SCROLL_LEFT and %GDK_SCROLL_RIGHT).
@device: the device where the event originated.
@x_root: the x coordinate of the pointer relative to the root of the screen.
@y_root: the y coordinate of the pointer relative to the root of the screen.

<!-- ##### STRUCT GdkEventMotion ##### -->
<para>
Generated when the pointer moves.
</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 
<function>XSendEvent</function>).
@time: the time of the event in milliseconds.
@x: the x coordinate of the pointer relative to the window.
@y: the y coordinate of the pointer relative to the window.
@axes: @x, @y translated to the axes of @device, or %NULL if @device is 
  the mouse.
@state: a bit-mask representing the state of the modifier keys (e.g. Control,
  Shift and Alt) and the pointer buttons. See #GdkModifierType.
@is_hint: 
@device: the device where the event originated.
@x_root: the x coordinate of the pointer relative to the root of the screen.
@y_root: the y coordinate of the pointer relative to the root of the screen.

<!-- ##### 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 
<function>XSendEvent</function>).
@area: bounding box of @region.
@region: the region 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 
<function>XSendEvent</function>).
@state: the new visibility state (%GDK_VISIBILITY_FULLY_OBSCURED,
%GDK_VISIBILITY_PARTIAL or %GDK_VISIBILITY_UNOBSCURED).

<!-- ##### STRUCT GdkEventCrossing ##### -->
<para>
Generated when the pointer enters or leaves a window.
</para>

@type: the type of the event (%GDK_ENTER_NOTIFY or %GDK_LEAVE_NOTIFY).
@window: the window which received the event.
@send_event: %TRUE if the event was sent explicitly (e.g. using 
<function>XSendEvent</function>).
@subwindow: the window that was entered or left.
@time: the time of the event in milliseconds.
@x: the x coordinate of the pointer relative to the window.
@y: the y coordinate of the pointer relative to the window.
@x_root: the x coordinate of the pointer relative to the root of the screen.
@y_root: the y coordinate of the pointer relative to the root of the screen.
@mode: the crossing mode (%GDK_CROSSING_NORMAL, %GDK_CROSSING_GRAB or
  %GDK_CROSSING_UNGRAB).
@detail: the kind of crossing that happened (%GDK_NOTIFY_INFERIOR,
  %GDK_NOTIFY_ANCESTOR, %GDK_NOTIFY_VIRTUAL, %GDK_NOTIFY_NONLINEAR or
  %GDK_NOTIFY_NONLINEAR_VIRTUAL).
@focus: %TRUE if @window is the focus window or an inferior.
@state: a bit-mask representing the state of the modifier keys (e.g. Control,
  Shift and Alt) and the pointer buttons. See #GdkModifierType.

<!-- ##### 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 <function>XSendEvent</function>).
@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 <function>XSendEvent</function>).
@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 <function>XSendEvent</function>).
@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>
Generated when a selection is requested or ownership of a selection 
is taken over by another client application. 
</para>

@type: the type of the event (%GDK_SELECTION_CLEAR, %GDK_SELECTION_NOTIFY or 
%GDK_SELECTION_REQUEST).
@window: the window which received the event.
@send_event: %TRUE if the event was sent explicitly (e.g. using <function>XSendEvent</function>).
@selection: the selection.
@target: the target to which the selection should be converted.
@property: the property in which to place the result of the conversion.
@time: the time of the event in milliseconds.
@requestor: the native window on which to place @property.

<!-- ##### TYPEDEF GdkNativeWindow ##### -->
<para>
Used to represent native windows (<type>Window</type>s for the X11 backend, 
<type>HWND</type>s for Win32).
</para>


<!-- ##### STRUCT GdkEventDND ##### -->
<para>
Generated during DND operations. 
</para>

@type: the type of the event (%GDK_DRAG_ENTER, %GDK_DRAG_LEAVE,
  %GDK_DRAG_MOTION, %GDK_DRAG_STATUS, %GDK_DROP_START or %GDK_DROP_FINISHED).
@window: the window which received the event.
@send_event: %TRUE if the event was sent explicitly (e.g. using <function>XSendEvent</function>).
@context: the #GdkDragContext for the current DND operation.
@time: the time of the event in milliseconds.
@x_root: the x coordinate of the pointer relative to the root of the screen,
  only set for %GDK_DRAG_MOTION and %GDK_DROP_START.
@y_root: the y coordinate of the pointer relative to the root of the screen,
  only set for %GDK_DRAG_MOTION and %GDK_DROP_START.

<!-- ##### STRUCT GdkEventProximity ##### -->
<para>
Proximity events are generated when using GDK's wrapper for the
XInput extension. The XInput extension is an add-on for standard X
that allows you to use nonstandard devices such as graphics tablets.
A proximity event indicates that the stylus has moved in or out of
contact with the tablet, or perhaps that the user's finger has moved
in or out of contact with a touch screen.
</para>

@type: the type of the event (%GDK_PROXIMITY_IN or %GDK_PROXIMITY_OUT).
@window: the window which received the event.
@send_event: %TRUE if the event was sent explicitly (e.g. using <function>XSendEvent</function>).
@time: the time of the event in milliseconds.
@device: the device where the event originated.

<!-- ##### 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 <function>XSendEvent</function>).
@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_drawable()
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 <function>XSendEvent</function>).

<!-- ##### STRUCT GdkEventWindowState ##### -->
<para>
Generated when the state of a toplevel window changes.
</para>

@type: the type of the event (%GDK_WINDOW_STATE).
@window: the window which received the event.
@send_event: %TRUE if the event was sent explicitly (e.g. using <function>XSendEvent</function>).
@changed_mask: mask specifying what flags have changed.
@new_window_state: the new window state, a combination of #GdkWindowState bits.

<!-- ##### STRUCT GdkEventSetting ##### -->
<para>
Generated when a setting is modified.
</para>

@type: the type of the event (%GDK_SETTING).
@window: the window which received the event.
@send_event: %TRUE if the event was sent explicitly (e.g. using <function>XSendEvent</function>).
@action: what happened to the setting (%GDK_SETTING_ACTION_NEW,
  %GDK_SETTING_ACTION_CHANGED or %GDK_SETTING_ACTION_DELETED).
@name: the name of the setting.

<!-- ##### ENUM GdkScrollDirection ##### -->
<para>
Specifies the direction for #GdkEventScroll. 
</para>

@GDK_SCROLL_UP: the window is scrolled up.
@GDK_SCROLL_DOWN: the window is scrolled down.
@GDK_SCROLL_LEFT: the window is scrolled to the left.
@GDK_SCROLL_RIGHT: the window is scrolled to the 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>
Specifies the crossing mode for #GdkEventCrossing.
</para>

@GDK_CROSSING_NORMAL: crossing because of pointer motion.
@GDK_CROSSING_GRAB: crossing because a grab is activated.
@GDK_CROSSING_UNGRAB: crossing because a grab is deactivated.

<!-- ##### ENUM GdkNotifyType ##### -->
<para>
Specifies the kind of crossing for #GdkEventCrossing.
</para>
<para>
See the X11 protocol specification of <type>LeaveNotify</type> for
full details of crossing event generation.
</para>

@GDK_NOTIFY_ANCESTOR: the window is entered from an ancestor or 
   left towards an ancestor.
@GDK_NOTIFY_VIRTUAL: the pointer moves between an ancestor and an 
    inferior of the window.
@GDK_NOTIFY_INFERIOR: the window is entered from an inferior or 
   left towards an inferior.
@GDK_NOTIFY_NONLINEAR:  the window is entered from or left towards 
   a window which is neither an ancestor nor an inferior.
@GDK_NOTIFY_NONLINEAR_VIRTUAL: the pointer moves between two windows 
   which are not ancestors of each other and the window is part of
   the ancestor chain between one of these windows and their least
   common ancestor.
@GDK_NOTIFY_UNKNOWN: 

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

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

<!-- ##### ENUM GdkWindowState ##### -->
<para>
Specifies the state of a toplevel window.
</para>

@GDK_WINDOW_STATE_WITHDRAWN: the window is not shown.
@GDK_WINDOW_STATE_ICONIFIED: the window is minimized.
@GDK_WINDOW_STATE_MAXIMIZED: the window is maximized.
@GDK_WINDOW_STATE_STICKY: the window is sticky.

<!-- ##### ENUM GdkSettingAction ##### -->
<para>
Specifies the kind of modification applied to a setting in a #GdkEventSetting.
</para>

@GDK_SETTING_ACTION_NEW: a setting was added.
@GDK_SETTING_ACTION_CHANGED: a setting was changed.
@GDK_SETTING_ACTION_DELETED: a setting was deleted.

