Arjen Markus I have combined the advice by Marty Backe and Erik Leunissen into a small receipe for creating modal dialog(ue)s.
I felt a receipe was needed as the proper implementation requires:
both of which are somewhat obscure commands.
I have tested the code on UNIX (Sun Solaris with CDE window manager, Tcl/Tk 8.3.1) and Windows NT, Tcl/Tk 8.3.4). I have not paid any attention to the layout of the two windows :-)
#
# Create a button in the . window that displays a message box when pressed
#
button .hi -text Hi -command {tk_messageBox -message "Hi"}
pack .hi
#
# Create a second window which acts as modal dialogue:
# - make sure it is on top (first wait for the . window!)
# - grab the display (locally)
# - wait for the dialogue to disappear
#
# Note: the implementation is fairly rigorous. Leaving out
# some of the [wm] commands may work on a particular platform,
# but this way it works well on both UNIX and Windows)
# Leaving out [wm transient] gives a different appearance
# on Windows.
#
tkwait visibility .
toplevel .f
button .f.b -text Close -command {destroy .f}
pack .f.b
grab .f
wm transient .f .
wm protocol .f WM_DELETE_WINDOW {grab release .f; destroy .f}
raise .f
tkwait window .f