#103 Access to 'container' id

[Donal K. Fellows]

On my system, if I do
exec xwininfo -tree -id [wm frame .]
I get output something like this:

xwininfo: Window id: 0x3810df9 (has no name)

Root window id: 0x2a (the root window)
(has no name)
Parent window id: 0x2a (the root window)
(has no name)
10 children:
0x3810e03 (has no name): ()
200x200+5+24 +312+72
1 child:
0x5c00004 "wish8.3": ("wish8.3" "Wish8.3")
200x200+0+0 +312+72
1 child:
0x5c00003 (has no name): ()
200x200+0+0 +312+72
[... rest of output elided ...]

Now, the window id of the frame, 0x3810df9, is easily
obtainable with [wm frame] and the window id of the
drawing area is also easily obtainable with [winfo id],
but the window id of the window that comes between them
(present on UNIX/X because the window that implements
the menubar for a window is a sibling of the toplevel
drawing area, not a child of it, so an extra container
is needed to hold them both) is not available without
doing a hack (rummaging through the output of xwininfo
or hacking around with XQueryTree.) Wouldn't it be
better if there was a way to expose this information at
the Tcl and C levels in a cleaner way? (You need it
when you apply a non-rectangular shaping to a window,
for example, because window managers only notice
reshaping events on the container, not its children.)

[Joe English]

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A couple of questions --

Would it suffice to return the X window id of the wrapper
window? (Actually, I think that's about all we can do,
since the wrapper doesn't really have a separate identity as
a Tk window.)
What do you suggest as the command syntax? [wm wrapperid
$toplevel]?
What should it do on non-X platforms?
Should there be a TIP for this?

I think I see how to implement this -- in unix/tkUnixWm.c,
just peek at wmPtr->wrapperPtr->window and do the same
thing as [wm frame].

[Jeffrey Hobbs]

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I like 'winfo id ?-wrapper? $window' best. It uses an
existing command, just adding an easily checked option.

[Joe English]

Patch to unix/tkUnixWm.c, doc/wm.n

[Joe English]

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Please try the attached patch -- this adds [wm wrapper
$toplevel] under Unix.

I made this a subcommand of [wm] instead of [winfo] for two
reasons: the other subcommands of [winfo] work for any
window, whereas all the [wm] subcommands work for toplevels
only; since only toplevels have wrappers this falls into the
latter category. Also, [winfo] is generic, [wm] is
platform-specific, and this feature depends on the
platform-specific parts; there's a lot less plumbing
involved if it's implemented in the [wm] ensemble.

I haven't touched mac/tkMacWm.c or win/tkWinWm.c; not sure
what to do here yet.

Here's the new doc entry:

+ .TP
+ \fBwm wrapper \fIwindow\fR
+ (Unix only.)
+ Under X11, Tk creates a wrapper window around top-level
windows
+ to hold the menu bar.
+ This command returns the platform specific window
identifier
+ for the wrapper window.

[Joe English]

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Old patch has suffered from bit rot; attaching fresh
wm-wrapper-2.patch, made against the current CVS HEAD
(tkUnixWm.c rf1.33)

[Joe English]

updated patch to tkUnixWm.c r1.33, doc/wm.n

[Joe English]

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Reassigning to Jeff so this doesn't get dropped on the
floor.

Remaining questions:
* Should this be integrated into Tcl 8.4?
* Does this change require a TIP?
* Is the documentation clear enough?
* Do we need to add Windows and Mac implementations
(presumably [wm wrapper] would be the same as [winfo id] on
those platforms)?