gtk/docs/reference/gdk/tmpl/input_devices.sgml

<!-- ##### SECTION Title ##### -->
Input Devices

<!-- ##### SECTION Short_Description ##### -->
Functions for handling extended input devices.

<!-- ##### SECTION Long_Description ##### -->
<para>
In addition to the normal keyboard and mouse input devices, GTK+ also
contains support for <firstterm>extended input devices</firstterm>. In
particular, this support is targeted at graphics tablets. Graphics
tablets typically return sub-pixel positioning information and possibly
information about the pressure and tilt of the stylus. Under
X, the support for extended devices is done through the 
<firstterm>XInput</firstterm> extension.
</para>
<para>
Because handling extended input devices may involve considerable
overhead, they need to be turned on for each #GdkWindow
individually using gdk_input_set_extension_events().
(Or, more typically, for GtkWidgets, using gtk_widget_set_extension_events()).
As an additional complication, depending on the support from
the windowing system, its possible that a normal mouse
cursor will not be displayed for a particular extension
device. If an application does not want to deal with displaying
a cursor itself, it can ask only to get extension events
from devices that will display a cursor, by passing the
%GDK_EXTENSION_EVENTS_CURSOR value to
gdk_input_set_extension_events(). Otherwise, the application
must retrieve the device information using gdk_input_list_devices(),
check the <structfield>has_cursor</structfield> field, and, 
if it is %FALSE, draw a cursor itself when it receives 
motion events.
</para>
<para>
Each pointing device is assigned a unique integer ID; events from a
particular device can be identified by the
<structfield>deviceid</structfield> field in the event structure. The
events generated by pointer devices have also been extended to contain
<structfield>pressure</structfield>, <structfield>xtilt</structfield>
and <structfield>ytilt</structfield> fields which contain the extended
information reported as additional <firstterm>valuators</firstterm>
from the device. The <structfield>pressure</structfield> field is a 
a double value ranging from 0.0 to 1.0, while the tilt fields are
double values ranging from -1.0 to 1.0. (With -1.0 representing the
maximum title to the left or up, and 1.0 representing the maximum
tilt to the right or down.)
</para>
<para>
One additional field in each event is the
<structfield>source</structfield> field, which contains an
enumeration value describing the type of device; this currently
can be one of 
%GDK_SOURCE_MOUSE,
 %GDK_SOURCE_PEN,
%GDK_SOURCE_ERASER,
or %GDK_SOURCE_CURSOR. This field is present to allow simple
applications to (for instance) delete when they detect eraser
devices without having to keep track of complicated per-device
settings.
</para>
<para>
Various aspects of each device may be configured. The easiest way of
creating a GUI to allow the user to conifigure such a device
is to use to use the #GtkInputDialog widget in GTK+. 
However, even when using this widget, application writers
will need to directly query and set the configuration parameters
in order to save the state between invocations of the application.
The configuration of devices is queried using gdk_input_list_devices.
Each device must is activated using gdk_input_set_mode(), which
also controls whether the device's range is mapped to the
entire screen or to a single window. The mapping of the valuators of
the device onto the predefined valuator types is set using
gdk_input_set_axes. And the source type for each device
can be set with gdk_input_set_source().
</para>
<para>
Devices may also have associated <firstterm>keys</firstterm>
or macro buttons. Such keys can be globally set to map
into normal X keyboard events. The mapping is set using
gdk_input_set_key().
</para>
<para>
The interfaces in this section will most likely be considerably
modified in the future to accomodate devices that may have different
sets of additional valuators than the pressure xtilt and ytilt.
</para>

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

</para>

<!-- ##### MACRO GDK_CORE_POINTER ##### -->
<para>
This macro contains an integer value representing
the device ID for the core pointer device.
</para>



<!-- ##### FUNCTION gdk_input_list_devices ##### -->
<para>
Lists all available input devices, along with their
configuration information.
</para>

@Returns: A #GList of #GdkDeviceInfo structures. This list
          is internal data of GTK+ and should not be modified 
          or freed.


<!-- ##### STRUCT GdkDeviceInfo ##### -->
<para>
The #GdkDeviceInfo structure contains information about a 
device. It has the following fields:
</para>

@deviceid: a unique integer ID for this device.
@name: the human-readable name for the device.
@source: the type of device.
@mode: a value indicating whether the device is enabled and
       how the device coordinates map to the screen.
@has_cursor: if %TRUE, a cursor will be displayed indicating 
             the current on-screen location to the user. Otherwise,
             the application is responsible for drawing a cursor 
             itself.
@num_axes: the number of axes for this device.
@axes: a pointer to an array of GdkAxisUse values which
       give the mapping of axes onto the possible valuators
       for a GDK device.
@num_keys: the number of macro buttons.
@keys: a pointer to an array of #GdkDeviceKey structures  
       which describe what key press events are generated
       for each macro button.

<!-- ##### STRUCT GdkDeviceKey ##### -->
<para>
The #GdkDeviceKey structure contains information
about the mapping of one device macro button onto
a normal X key event. It has the following fields:
</para>

@keyval: the keyval to generate when the macro button is pressed.
         If this is 0, no keypress will be generated.
@modifiers: the modifiers set for the generated key event.

<!-- ##### FUNCTION gdk_input_set_extension_events ##### -->
<para>
Turns extension events on or off for a particular window,
and specifies the event mask for extension events.
</para>

@window: a #GdkWindow.
@mask: the event mask
@mode: the type of extension events that are desired.


<!-- ##### ENUM GdkExtensionMode ##### -->
<para>
An enumeration used to specify which extension events
are desired for a particular widget.
</para>

@GDK_EXTENSION_EVENTS_NONE: no extension events are desired.
@GDK_EXTENSION_EVENTS_ALL: all extension events are desired.
@GDK_EXTENSION_EVENTS_CURSOR: extension events are desired only if a cursor
                              will be displayed for the device.

<!-- ##### FUNCTION gdk_input_set_source ##### -->
<para>
Sets the source type for a device.
</para>

@deviceid: the device to configure
@source: the new source type.


<!-- ##### ENUM GdkInputSource ##### -->
<para>
An enumeration describing the type of an input device
in general terms.
</para>

@GDK_SOURCE_MOUSE: the device is a mouse. (This will be reported for the core
                    pointer, even if it is something else, such as a trackball.)
@GDK_SOURCE_PEN: the device is a stylus of a graphics tablet or similar device.
@GDK_SOURCE_ERASER: the device is an eraser. Typically, this would be the other end
                    of a stylus on a graphics tablet.
@GDK_SOURCE_CURSOR: the device is a graphics tablet "puck" or similar device.

<!-- ##### FUNCTION gdk_input_set_mode ##### -->
<para>
Enables or disables a device, and determines how the
device maps onto the screen.
</para>

@deviceid: the device to configure.
@mode: the new mode.
@Returns: %TRUE if the device supports the given mode, otherwise 
          %FALSE and the device's mode is unchanged.


<!-- ##### ENUM GdkInputMode ##### -->
<para>
An enumeration that describes the mode of an input device.
</para>

@GDK_MODE_DISABLED: the device is disabled and will not report any events.
@GDK_MODE_SCREEN: the device is enabled. The device's coordinate space
                    maps to the entire screen.
@GDK_MODE_WINDOW: the device is enabled. The device's coordinate space
                    is mapped to a single window. The manner in which this window
                    is chosen is undefined, but it will typically be the same
                    way in which the focus window for key events is determined.

<!-- ##### FUNCTION gdk_input_set_axes ##### -->
<para>
Sets the mapping of the axes (valuators) of a device
onto the predefined valuator types that GTK+ understands.
</para>

@deviceid: the device to configure.
@axes: an array of GdkAxisUse. This length of this array
       must match the number of axes for the device.


<!-- ##### ENUM GdkAxisUse ##### -->
<para>
An enumeration describing the way in which a device
axis (valuator) maps onto the predefined valuator
types that GTK+ understands.
</para>

@GDK_AXIS_IGNORE: the axis is ignored.
@GDK_AXIS_X: the axis is used as the x axis.
@GDK_AXIS_Y: the axis is used as the y axis.
@GDK_AXIS_PRESSURE: the axis is used for pressure information.
@GDK_AXIS_XTILT: the axis is used for x tilt information.
@GDK_AXIS_YTILT: the axis is used for x tilt information.
@GDK_AXIS_LAST: a constant equal to the numerically highest axis value.

<!-- ##### FUNCTION gdk_input_set_key ##### -->
<para>
Sets the key event generated when a macro button is pressed.
</para>

@deviceid: the device to configure.
@index: the index of the macro button.
@keyval: the key value for the #GdkKeypressEvent to generate.
         (a value of 0 means no event will be generated.)
@modifiers: the modifier field for the generated 
            #GdkKeyPressEvent.


<!-- ##### FUNCTION gdk_input_window_get_pointer ##### -->
<para>
Returns information about the current position of the pointer
within a window, including extended device information.
Any of the return parameters may be %NULL, in which case,
they will be ignored.
</para>

@window: a #GdkWindow.
@deviceid: a device ID.
@x: location to store current x postion.
@y: location to store current y postion.
@pressure: location to store current pressure.
@xtilt: location to store current tilt in the x direction.
@ytilt: location to store current tilt in the y direction.
@mask: location to store the current modifier state.


<!-- ##### FUNCTION gdk_input_motion_events ##### -->
<para>
Retrieves the motion history for a given device/window pair.
</para>

@window: a #GdkWindow.
@deviceid: the device for which to retrieve motion history.
@start: the start time.
@stop: the stop time.
@nevents_return: location to store the number of events returned.
@Returns: a newly allocated array containing all the events
          from @start to @stop. This array should be freed
          with g_free() when you are finished using it.


<!-- ##### STRUCT GdkTimeCoord ##### -->
<para>
The #GdkTimeCoord structure stores a single event in a
motion history. It contains the following fields:
</para>

@time: The timestamp for this event.
@x: the x position.
@y: the y position.
@pressure: the pressure.
@xtilt: the tilt in the x direction.
@ytilt: the tilt in the y direction.