The function establishes a passive grab. In the future, the pointer is actively grabbed (as for the last-pointer-grab time is set to the time at which the button was pressed (as transmitted in the event), and the event is reported if all of the following conditions are true:
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The pointer is not grabbed, and the specified button is logically pressed when the specified modifier keys are logically down, and no other buttons or modifier keys are logically down.
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The grab_window contains the pointer.
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The confine_to window (if any) is viewable.
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A passive grab on the same button/key combination does not exist on any ancestor of grab_window.
The interpretation of the remaining arguments is as for The active grab is terminated automatically when the logical state of the pointer has all buttons released (independent of the state of the logical modifier keys).
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 on the same button/key combinations on the same window. A modifiers of 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. A button of 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.
If some other client has already issued a with the same button/key combination on the same window, a error results. When using or the request fails completely, and a error results (no grabs are established) if there is a conflicting grab for any combination. has no effect on an active grab.
can generate and errors.
The function releases the passive button/key combination on the specified window if it was grabbed by this client. A modifiers of is equivalent to issuing the ungrab request for all possible modifier combinations, including the combination of no modifiers. A button of is equivalent to issuing the request for all possible buttons. has no effect on an active grab.
can generate and errors.