gdk-Input-Devices: Input Devices
Description
Functions for handling extended input devicesMethods and Functions
gdkDevicesList()
gdkDeviceSetSource(object, source)
gdkDeviceSetMode(object, mode)
gdkDeviceSetKey(object, index, keyval, modifiers)
gdkDeviceSetAxisUse(object, index, use)
gdkDeviceGetCorePointer()
gdkDeviceGetState(object, window)
gdkDeviceGetHistory(object, window, start, stop)
gdkDeviceGetAxis(object, axes, use)
gdkInputSetExtensionEvents(object, mask, mode)Detailed Description
In addition to the normal keyboard and mouse input devices, GTK+ also
contains support for extended input devices. 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
XInput extension.
Because handling extended input devices may involve considerable
overhead, they need to be turned on for each GdkWindow
individually using gdkInputSetExtensionEvents.
(Or, more typically, for GtkWidgets, using gtkWidgetSetExtensionEvents).
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
gdkInputSetExtensionEvents. Otherwise, the application
must retrieve the device information using gdkDevicesList,
check the has_cursor field, and,
if it is FALSE, draw a cursor itself when it receives
motion events.
Each pointing device is assigned a unique integer ID; events from a
particular device can be identified by the
deviceid field in the event structure. The
events generated by pointer devices have also been extended to contain
pressure, xtilt
and ytilt fields which contain the extended
information reported as additional valuators
from the device. The pressure 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 tilt to the left or up, and 1.0 representing the maximum
tilt to the right or down.)
One additional field in each event is the
source 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.
Various aspects of each device may be configured. The easiest way of
creating a GUI to allow the user to configure such a device
is 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 gdkDevicesList.
Each device must be activated using gdkDeviceSetMode, 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
gdkDeviceSetAxisUse. And the source type for each device
can be set with gdkDeviceSetSource.
Devices may also have associated keys
or function buttons. Such keys can be globally set to map
into normal X keyboard events. The mapping is set using
gdkDeviceSetKey.
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.References
http://developer.gnome.org/doc/API/2.0/gdk/gdk-Input-Devices.html