[Ttk]'s [panedwindow] [widget].
    :   http://www.tcl.tk/man/tcl8.5/TkCmd/ttk_panedwindow.htm

[WHD] 2010-04-14: Is there a way to get a list of the names of the managed subwindows in index order?  I can refer to managed subwindows from 0 to end, but I don't see any way in the interface to determine how many managed windows there are, nor the order in which they are stacked.  [winfo children] returns the children of the panedwindow in the order of creation, which can be very different.
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[MHo] 2008-04-09: Does someone know if and how it's possible to determine the dimension of a pane inside a panedwindow? I have a canvas inside a pane that holds an image. If resizing / maximizing the top-level windows, everything should grow to use the extra space. But the pane itself says it is has the dimension '''1x1''', and the canvas stays as its initial size (if I don't specify such initial size, something else goes wrong that is beyond the scope of this question...).

[MG] I've noticed with this (and other Tile widgets) in Windows / Tk 8.5 that there's a delay before sizes and things fully update - calling [update] and/or [update idletasks] doesn't resolve the problem. I've had to resort to doing something like

  $widget add $foo
  after 25 [list doStuffWith $widget]

to give the widgets time to update their sizes and report the correct ones back. See if that resolves the problem? In your case, [winfo] width and [winfo height] on the canvas may work, too?
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**Create a custom sash handle bar**
In the default theme the sash handle bar is empty. So it is not obvious that it is a panedwindow. This little piece of code creates a new style for the panedwindow which as a Firefox-like sash handle bar.

======
image create photo img:sash -data {
R0lGODlhBQB5AKECADMzM9TQyP///////yH+EUNyZWF0ZWQgd2l0aCBHSU1QACH5BAEKAAMALAAA
AAAFAHkAAAJOjA95y+0LUAxpUkufboLh1UFPiIyeKTqk8R1rpp5xysk1zbytoaPl/LsFczYiDlRE
Hl1J5pLXhD4DPSDLd7XChFnudgO2KC5izA6sqTQKADs=
}

ttk::style element create Sash.xsash image \
        [list img:sash ] \
        -border {1 1} -sticky ew -padding {1 1}

ttk::style layout TPanedwindow {
        Sash.xsash
}

======
'''Demo code'''
======

package require Ttk

# ttk::setTheme clam

set xf [ttk::frame .f]
set pw [ttk::panedwindow .f.pw -orient horizontal ]

ttk::frame $pw.f1
ttk::label $pw.f1.l -text "Frame 1"
pack $pw.f1.l

ttk::frame $pw.f2
ttk::label $pw.f2.l -text "Frame 2"
pack $pw.f2.l

$pw add $pw.f1
$pw add $pw.f2

pack $pw -expand 1 -fill both
pack $xf -expand 1 -fill both

======

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!!!!!!
%| [Category Widget] |%
!!!!!!