GRAB(9) GRAB(9)
NAME
grab - Confine pointer and keyboard events to a window sub-
tree
SYNOPSIS
grab what ?arg arg ...?
DESCRIPTION
This command implements simple pointer and keyboard grabs
for Tk. When a grab is set for a particular window, Tk
restricts all pointer events to the grab window and its
descendants in Tk's window hierarchy. Whenever the pointer
is within the grab window's subtree, the pointer will behave
exactly the same as if there had been no grab at all and all
events will be reported in the normal fashion. When the
pointer is outside window's tree, button presses and
releases and mouse motion events are reported to window, and
window entry and window exit events are ignored. The grab
subtree ``owns'' the pointer: windows outside the grab
subtree will be visible on the screen but they will be
insensitive until the grab is released. The tree of windows
underneath the grab window can include top-level windows, in
which case all of those top-level windows and their
descendants will continue to receive mouse events during the
grab.
A grab locks out all applications on the screen, so that
only the given subtree of the grabbing application will be
sensitive to pointer events (mouse button presses, mouse
button releases, pointer motions, window entries, and window
exits). During grabs the window manager will not receive
pointer events either (which means that if the grab is not
released the whole GUI will freeze, so be careful!).
During a grab Tk grabs the keyboard so that all keyboard
events are always sent to the grabbing application. The
focus command is still used to determine which window in the
application receives the keyboard events. The keyboard grab
is released when the grab is released.
The grab command can take any of the following forms:
grab release window
Releases the grab on window if there is one, otherwise
does nothing. Returns an empty string.
grab set window
If a grab was already in effect for this application on
window's display then it is automatically released. If
there is already a grab on window then the command does
GRAB(9) GRAB(9)
nothing. Returns an empty string.
grab ifunset window
Same as grab set except that window is only grabbed if
there is no other grab currently in effect.
grab status window
Returns none if no grab is currently set on window, or
window if it has the grab.
BUGS
The current application-exclusive nature of grab is a prob-
lem which will be adressed in the future.