Centering a Tkinter Toplevel window in both windows and remote X11?

Question

I know Tkinter can be an exercise in frustration at times, but I am stumped on the "correct" sequence of calls to a Tkinter/ttk Toplevel widget/window that will:

1. Display the window in the center of the screen WITHOUT drawing it off-center and THEN moving it.

2. Size the window properly.

3. Make the window toplevel to the parent form, but not system modal (that is, not toplevel to ALL apps/windows on the system).

4. Optionally create a taskbar button on Windows.

This is the current code that I have so far, with some unrelated bits removed for simplicity's sake:

def __init_ui__(self):
    #// Basic setup.
    self.wm_overrideredirect(False)
    self.wm_resizable(False, False)
    self.configure(relief=FLAT, borderwidth=4)

    #// <Some extraneous widget-creation here>

    #// Done!
    self.update()
    self.withdraw()
    self.update_idletasks()
    self.grid()
    self.transient(self._parent)
    self.grab_set()
    self.form.initial_focus()  #// sets initial focus before the window is displayed
    center(self)  #// https://stackoverflow.com/a/10018670
    self.deiconify()
    self._parent._parent.wait_window(self) #// Reaches back to the root Tk() obj.
    # ENDIF
# END __init_ui__

This form inherits from a custom class I created that wraps a bunch of widget-creation calls, and the class inherits down from object. A second inheritance comes from ttk.Toplevel, to give it access to the various self.wm_* calls and other Tkinter goodies.

That said, I am certain some of my function calls are unneeded. But this particular call order seems to mostly work well on Windows 7. Under X11-over-ssh (using Xming for the X server in Windows), however, things get a bit weirder. In that case, if I move self.update() to be after self.withdraw(), then the window is centered correctly w/o redraw on Windows 7, but on X11, it is drawn and properly centered whilst hidden, but has ZERO geometry (only the compressed window border/decorations are shown). It's as-if grid propagation didn't fire or such.

But where self.update() is right now, it properly sizes and centers the window on both windows and X11 - but you can see the window getting created off-center THEN moved to center on both.

If I use self.wm_attributes("-toolwindow", 1) on Windows, then the windows gets centered without me seeing it, but -toolwindow only works on Windows system. It's an invalid command to both X11 and Aqua.

I'd like to avoid calls to tk::windowingsystem all the time to determine what my window manager is and having to apply different hacks for Windows and X11. And I can't test Mac/Aqua (don't own one, not going to buy), so I'll just have to hope the end look is somewhat functional on that platform.

Additionally, if I click away to another window/app under both Windows and remote X11, clicking back on the main form via the taskbar button only displays the main form -- the child Toplevel window only pops back up when you click anywhere inside the main form. Fixed: (kinda) -- I forgot that adding an argument to self._transient() kinda fixed that by specifying the parent. Earlier tonight, I didn't pass the parent argument in, thus the focusing wasn't right.

So is there some kind of tried-and-true magik recipe or invocation to the Priests of Ancient Mu to get a Tkinter/ttk Toplevel window to size, center, and properly get focus if it's not the root window? Using minimal X11, Motif-look, btw.

And no, I am not using PyGTK, PyQT, wxPython, or some other toolkit. It's standard Tkinter/ttk or bust, since that's what I've spent the last few weeks learning and writing wrapper functions for. The autocomplete combobox I worked up is a cute little contraption. Still slightly buggy, but that's a topic for another SO question...

PS, The Tkinter cookbook on Effbot is down. Looks like a server crash. Did anyone happen to mirror that site by chance?

Answer 1

Solved! Had to tweak the order of the calls a little bit:

#// Done!
self.withdraw()
self.grid()
self.transient(self._parent)
self.grab_set()
self.form.initial_focus()
center(self)
self.deiconify()
self._parent._parent.wait_window(self)

But the real fix was in the center() function I lifted from this answer, by changing the calls to winfo_width()/winfo_height() to winfo_reqwidth()/winfo_reqheight() and adding a call to update() as the first call in center(). Now I get my dialog windows to pop up in the center without seeing them move, focus is applied correctly, and it works on both Windows and remote X11. Maybe one day, I'll find out how well it works on Mac OS X/Aqua.