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 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 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 title 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 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().
Devices may also have associated keys
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().
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.
Details
GDK_CORE_POINTER
#define GDK_CORE_POINTER 0xfedc |
This macro contains an integer value representing
the device ID for the core pointer device.
gdk_input_list_devices ()
GList* gdk_input_list_devices (void); |
Lists all available input devices, along with their
configuration information.
struct GdkDeviceInfo
struct GdkDeviceInfo
{
guint32 deviceid;
gchar *name;
GdkInputSource source;
GdkInputMode mode;
gint has_cursor; /* TRUE if the X pointer follows device motion */
gint num_axes;
GdkAxisUse *axes; /* Specifies use for each axis */
gint num_keys;
GdkDeviceKey *keys;
}; |
The GdkDeviceInfo structure contains information about a
device. It has the following fields:
struct GdkDeviceKey
struct GdkDeviceKey
{
guint keyval;
GdkModifierType modifiers;
}; |
The GdkDeviceKey structure contains information
about the mapping of one device macro button onto
a normal X key event. It has the following fields:
gdk_input_set_extension_events ()
Turns extension events on or off for a particular window,
and specifies the event mask for extension events.
enum GdkExtensionMode
typedef enum
{
GDK_EXTENSION_EVENTS_NONE,
GDK_EXTENSION_EVENTS_ALL,
GDK_EXTENSION_EVENTS_CURSOR
} GdkExtensionMode; |
An enumeration used to specify which extension events
are desired for a particular widget.
gdk_input_set_source ()
Sets the source type for a device.
enum GdkInputSource
typedef enum
{
GDK_SOURCE_MOUSE,
GDK_SOURCE_PEN,
GDK_SOURCE_ERASER,
GDK_SOURCE_CURSOR
} GdkInputSource; |
An enumeration describing the type of an input device
in general terms.
gdk_input_set_mode ()
Enables or disables a device, and determines how the
device maps onto the screen.
enum GdkInputMode
typedef enum
{
GDK_MODE_DISABLED,
GDK_MODE_SCREEN,
GDK_MODE_WINDOW
} GdkInputMode; |
An enumeration that describes the mode of an input device.
gdk_input_set_axes ()
Sets the mapping of the axes (valuators) of a device
onto the predefined valuator types that GTK+ understands.
enum GdkAxisUse
typedef enum
{
GDK_AXIS_IGNORE,
GDK_AXIS_X,
GDK_AXIS_Y,
GDK_AXIS_PRESSURE,
GDK_AXIS_XTILT,
GDK_AXIS_YTILT,
GDK_AXIS_LAST
} GdkAxisUse; |
An enumeration describing the way in which a device
axis (valuator) maps onto the predefined valuator
types that GTK+ understands.
gdk_input_set_key ()
Sets the key event generated when a macro button is pressed.
gdk_input_window_get_pointer ()
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.
gdk_input_motion_events ()
Retrieves the motion history for a given device/window pair.
struct GdkTimeCoord
struct GdkTimeCoord
{
guint32 time;
gdouble x;
gdouble y;
gdouble pressure;
gdouble xtilt;
gdouble ytilt;
}; |
The GdkTimeCoord structure stores a single event in a
motion history. It contains the following fields: