XIGrabEnter and XIGrabFocusIn establish a passive grab. The
modifier device for a enter grab is the paired master device if
deviceid specifies a master pointer. Otherwise, the modifier
device is the device specified with deviceid.

For XIGrabEnter and XIGrabFocusIn, in the future, the device is
actively grabbed (as for XIGrabDevice, the last-grab time is
set to the time at which the pointer/focus entered window) if
the device is not grabbed and the pointer has entered the
grab_window or the focus has been set to the grab_window when
the specified modifier keys are logically down on the modifier
device and no other buttons or modifier keys are logically
down.

The interpretation of the remaining arguments is as for
XIGrabDevice. The active grab is terminated automatically when
the pointer leaves the window or the focus is set to a
different window (independent of the logical state of the
modifier keys).

If the device is an attached slave device, the device is
automatically detached from the master device when the grab
activates and reattached to the same master device when the
grab deactivates. If the master device is removed while the
device is floating as a result of a grab, the device remains
floating once the grab deactivates.

Note that the logical state of a device (as seen by client
applications) may lag the physical state if device event
processing is frozen.

This request overrides all previous grabs by the same client of
the same type and modifier combinations on the same window. A
modifiers of XIAnyModifier is equivalent to issuing the grab
request for all possible modifier combinations (including the
combination of no modifiers). It is not required that all
modifiers specified have currently assigned KeyCodes.

If some other client has already issued a XIGrabEnter or
XIGrabFocusIn  on the same window, a BadAccess error results.
When using XIAnyModifier, the request fails completely, and a
XIBadAccess error results (no grabs are established) if there
is a conflicting grab for any combination. XIGrabEnter and
XIGrabFocusIn have no effect on an active grab.

On success, XIGrabEnter and XIGrabFocusIn return 0;
If one or more modifier combinations could not be grabbed,
XIGrabEnter and XIGrabFocusIn return the number of failed
combinations and modifiers_inout contains the failed combinations
and their respective status codes.

XIGrabEnter and XIGrabFocusIn can generate BadDevice,
BadMatch, BadValue, and BadWindow errors.

XIUngrabEnter and XIUngrabFocusIn releases the passive grab on
the specified window if it was grabbed by this client. A
modifier of XIAnyModifier is equivalent to issuing the ungrab
request for all possible modifier combinations, including the
combination of no modifiers. XIUngrabEnter and XIUngrabFocusIn
have no effect on an active grab.

XIUngrabEnter and XIUngrabFocusIn can generate BadDevice,
BadMatch, BadValue and BadWindow errors.

XIGrabEnter and XIGrabFocusIn return the number of modifier combination
that could not establish a passive grab. The modifiers are returned in
modifiers_inout, along with the respective error for this modifier
combination. If XIGrabEnter or XIGrabFocusIn return zero, passive grabs
with all requested modifier combinations were established successfully.

BadDevice
       An invalid deviceid was specified.

BadMatch
       This error may occur if XIGrabEnter specified a device
       that has no valuators, or XIGrabFocusIn specified a device
       that has no keys.

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.

The protocol headers for XI 2.0 did not provide
XIGrabModeAsync or XIGrabModeSync. Use GrabModeSync and
GrabModeAsync instead, respectively.

XIAllowEvents(3)