Author image Kevin Ryde
and 1 contributors


X11::Protocol::ChooseWindow -- user click to choose window


 use X11::Protocol::ChooseWindow;
 my $client_window = X11::Protocol::ChooseWindow->choose (X => $X);


This spot of code lets the user click on a toplevel window to choose it, in a similar style to the xwininfo or xkill programs.


The choose is implemented in a similar way to the xwininfo etc programs. It consists of GrabPointer() on the root window, wait for a ButtonPress and ButtonRelease from the user, get the frame window from the ButtonPress event, then the client window under there from frame_window_to_client() of X11::Protocol::WM.

KeyPress events are not used and they go to the focus window in the usual way. This can be good in a command line program since it lets the user press ^C (SIGINT) in an xterm or similar. Perhaps in the future there could be an option to watch for Esc to cancel or some such.

A virtual root per root_to_virtual_root() in X11::Protocol::WM is used if present. This helps ChooseWindow work with amiwm and similar virtual root window managers.


The following choose() is in class method style with the intention of perhaps in the future having objects of type X11::Protocol::ChooseWindow holding state and advanced by events supplied by an external main loop.


$window = X11::Protocol::ChooseWindow->choose (key=>value,...)

Read a user button press to choose a toplevel window. The key/value options are as follows,

    X        => X11::Protocol object
    display  => string ":0:0" etc

    screen   => integer, eg. 0
    root     => XID of root window

    time     => integer server timestamp
    event    => hashref of event initiating the choose

    cursor       => XID of cursor
    cursor_glyph => integer glyph for cursor font
    cursor_name  => string name from cursor font

X or display gives the server, or the default is to open the DISPLAY environment variable. X for an X11::Protocol object is usual, but sometimes it can make sense to open a new connection just to choose.

root or screen gives the root window to choose on, or the default is the current screen of $X, which in turn defaults to the screen part of the display name. If there's a window manager virtual root then that's automatically used as necessary.

time or the time field in event is a server timestamp for the GrabPointer(). This guards against stealing a grab from another client if badly lagged. Omitted or undef means CurrentTime. In a command line program there might be no initiating event, making CurrentTime all that's possible.

cursor etc is the mouse pointer cursor to show during the choose, as a visual indication to the user. The default is a "crosshair". cursor_name or cursor_glyph are from the usual cursor font. See X11::CursorFont for available names. For example perhaps the "exchange" cursor to choose a window for some sort of swap or flip,

    $window = X11::Protocol::ChooseWindow->choose
                (X => $X,
                 cursor_name => "exchange");

A cursor XID can be created by any client as usual. Don't forget to flush if creating a cursor from one connection, so it's ready for use from another.


X11::Protocol, X11::Protocol::WM, X11::CursorFont

xwininfo(1), xkill(1), and their dsimple.c Select_Window() code

"Inter-Client Communication Conventions Manual" section "WM_STATE Property" for notes on using WM_STATE to identify client windows.



Copyright 2010, 2011, 2012, 2013, 2014, 2016, 2017, 2019 Kevin Ryde

X11-Protocol-Other is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version.

X11-Protocol-Other is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

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