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12.9 Grabbing a Button

CLX provides the grab-button and ungrab-button functions for passively grabbing and releasing pointer control.


grab-button window button event-mask &key (:modifiers 0) :owner-p :sync-pointer-p :sync-keyboard-p :confine-to :cursor Function
     
window
A window.
button
The button (type card8 ) pressed or :any.
event-mask
A pointer-event-mask.
:modifiers
A modifier-mask .
:owner-p
If true, all client windows receive pointer events normally.
:sync-pointer-p
Indicates whether the pointer is handled in a synchronous or asynchronous fashion.
:sync-keyboard-p
Indicates whether the keyboard is in synchronous or asynchronous mode.
:confine-to
A window to which the pointer is confined.
:cursor
A cursor.

This request establishes a passive grab. If the specified button is pressed when the specified modifier keys are down (and no other buttons or modifier keys are down), and:

  • window contains the pointer
  • The :confine-to window (if any) is viewable
  • These constraints are not satisfied for any ancestor of window

then:

  • The pointer is actively grabbed as described with grab-pointer
  • The last-pointer-grab time is set to the time that the button was pressed (as transmitted in the :button-press event)
  • The :button-press event is reported

The interpretation of the remaining arguments is the same as with grab-pointer. The active grab is terminated automatically when all buttons are released (independent of the state of modifier keys).

A zero modifier mask is equivalent to issuing the request for all possible modifier-key combinations (including the combination of no modifiers). It is not required that all specified modifiers have currently assigned keycodes. A button of :any is equivalent to issuing the request for all possible buttons. Otherwise, it is not required that the specified button currently be assigned to a physical button.


ungrab-button window button &key (:modifiers 0) Function
     
window
A window.
button
The button (type card8 ) that is released or :any.
:modifiers
A modifier-mask .

Releases the passive button/key combination on the specified window if it was grabbed by this client. A zero modifier mask is equivalent to issuing the request for all possible modifier combinations including the combination of no modifiers. A button of :any is equivalent to issuing the request for all possible buttons. This has no effect on an active grab.


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