NAME
XGrabPointer, XUngrabPointer, XChangeActivePointerGrab - grab the
pointer
SYNTAX
int XGrabPointer(Display *display, Window grab_window, Bool
owner_events, unsigned int event_mask, int pointer_mode, int
keyboard_mode, Window confine_to, Cursor cursor, Time time);
int XUngrabPointer(Display *display, Time time);
int XChangeActivePointerGrab(Display *display, unsigned int event_mask,
Cursor cursor, Time time);
ARGUMENTS
confine_to
Specifies the window to confine the pointer in or None.
cursor Specifies the cursor that is to be displayed during the grab
or None.
display Specifies the connection to the X server.
event_mask
Specifies which pointer events are reported to the client.
The mask is the bitwise inclusive OR of the valid pointer
event mask bits.
grab_window
Specifies the grab window.
keyboard_mode
Specifies further processing of keyboard events. You can
pass GrabModeSync or GrabModeAsync.
owner_events
Specifies a Boolean value that indicates whether the pointer
events are to be reported as usual or reported with respect
to the grab window if selected by the event mask.
pointer_mode
Specifies further processing of pointer events. You can pass
GrabModeSync or GrabModeAsync.
time Specifies the time. You can pass either a timestamp or
CurrentTime.
DESCRIPTION
The XGrabPointer function actively grabs control of the pointer and
returns GrabSuccess if the grab was successful. Further pointer events
are reported only to the grabbing client. XGrabPointer overrides any
active pointer grab by this client. If owner_events is False, all
generated pointer events are reported with respect to grab_window and
are reported only if selected by event_mask. If owner_events is True
and if a generated pointer event would normally be reported to this
client, it is reported as usual. Otherwise, the event is reported with
respect to the grab_window and is reported only if selected by
event_mask. For either value of owner_events, unreported events are
discarded.
If the pointer_mode is GrabModeAsync, pointer event processing
continues as usual. If the pointer is currently frozen by this client,
the processing of events for the pointer is resumed. If the
pointer_mode is GrabModeSync, the state of the pointer, as seen by
client applications, appears to freeze, and the X server generates no
further pointer events until the grabbing client calls XAllowEvents or
until the pointer grab is released. Actual pointer changes are not
lost while the pointer is frozen; they are simply queued in the server
for later processing.
If the keyboard_mode is GrabModeAsync, keyboard event processing is
unaffected by activation of the grab. If the keyboard_mode is
GrabModeSync, the state of the keyboard, as seen by client
applications, appears to freeze, and the X server generates no further
keyboard events until the grabbing client calls XAllowEvents or until
the pointer grab is released. Actual keyboard changes are not lost
while the pointer is frozen; they are simply queued in the server for
later processing.
If a cursor is specified, it is displayed regardless of what window the
pointer is in. If None is specified, the normal cursor for that window
is displayed when the pointer is in grab_window or one of its
subwindows; otherwise, the cursor for grab_window is displayed.
If a confine_to window is specified, the pointer is restricted to stay
contained in that window. The confine_to window need have no
relationship to the grab_window. If the pointer is not initially in
the confine_to window, it is warped automatically to the closest edge
just before the grab activates and enter/leave events are generated as
usual. If the confine_to window is subsequently reconfigured, the
pointer is warped automatically, as necessary, to keep it contained in
the window.
The time argument allows you to avoid certain circumstances that come
up if applications take a long time to respond or if there are long
network delays. Consider a situation where you have two applications,
both of which normally grab the pointer when clicked on. If both
applications specify the timestamp from the event, the second
application may wake up faster and successfully grab the pointer before
the first application. The first application then will get an
indication that the other application grabbed the pointer before its
request was processed.
XGrabPointer generates EnterNotify and LeaveNotify events.
Either if grab_window or confine_to window is not viewable or if the
confine_to window lies completely outside the boundaries of the root
window, XGrabPointer fails and returns GrabNotViewable. If the pointer
is actively grabbed by some other client, it fails and returns
AlreadyGrabbed. If the pointer is frozen by an active grab of another
client, it fails and returns GrabFrozen. If the specified time is
earlier than the last-pointer-grab time or later than the current X
server time, it fails and returns GrabInvalidTime. Otherwise, the
last-pointer-grab time is set to the specified time (CurrentTime is
replaced by the current X server time).
XGrabPointer can generate BadCursor, BadValue, and BadWindow errors.
The XUngrabPointer function releases the pointer and any queued events
if this client has actively grabbed the pointer from XGrabPointer,
XGrabButton, or from a normal button press. XUngrabPointer does not
release the pointer if the specified time is earlier than the last-
pointer-grab time or is later than the current X server time. It also
generates EnterNotify and LeaveNotify events. The X server performs an
UngrabPointer request automatically if the event window or confine_to
window for an active pointer grab becomes not viewable or if window
reconfiguration causes the confine_to window to lie completely outside
the boundaries of the root window.
The XChangeActivePointerGrab function changes the specified dynamic
parameters if the pointer is actively grabbed by the client and if the
specified time is no earlier than the last-pointer-grab time and no
later than the current X server time. This function has no effect on
the passive parameters of a XGrabButton. The interpretation of
event_mask and cursor is the same as described in XGrabPointer.
XChangeActivePointerGrab can generate a BadCursor and BadValue error.
DIAGNOSTICS
BadCursor A value for a Cursor argument does not name a defined Cursor.
BadValue Some numeric value falls outside the range of values accepted
by the request. Unless a specific range is specified for an
argument, the full range defined by the argument’s type is
accepted. Any argument defined as a set of alternatives can
generate this error.
BadWindow A value for a Window argument does not name a defined Window.
SEE ALSO
XAllowEvents(3), XGrabButton(3), XGrabKey(3), XGrabKeyboard(3)
Xlib - C Language X Interface