some additions for the tutorial

[Mathis C]

Hi, I'm currently reading your tutorial on tk (which is awesome) and I have a few things to add if it can help :

On the page http://www.tkdocs.com/tutorial/menus.html we can get the windowing system in Python with

root._windowingsystem

In fact it can be used on any widget and that works.

The themed spinbox can also be used be the class doesn't exist in the framework so I wrote it based on the other ttk classes :

class Spinbox(ttk.Widget, tkinter.Spinbox):
    """Spinbox widget, themed !"""
    def __init__(self, master=None, **kw):
        ttk.Widget.__init__(self, master, 'ttk::spinbox', kw)

    def configure(self, cnf=None, **kw):
        if cnf:
            kw.update(cnf)
        ttk.Widget.configure(self, **kw)
        if any(['from' in kw, 'from_' in kw, 'to' in kw]):
            self.event_generate('<<RangeChanged>>')

And finally to get things like %d %i etc (tcl substitutions) in Python programs, we have to use a tuple with a registered command and substitions that we want, and the command will be called with the substitions as arguments in the order, ex :

cmd = widget.register(real_command)
cmd = (cmd, '%d', '%i', '%P', '%s', '%S', '%v', '%V') # add tk params
widget['validatecommand'] = cmd

Real example : I made an Entry subclass to facilitate validation :

ACTION_CODES = {'-1': 'other', '0': 'delete', '1': 'insert'}
vcmd_event = namedtuple('ValidateCommandEvent',
    'action index text_after text_before text_change validate reason')

class Entry(ttk.Entry):
    """Helper for ttk.Entry, particularly to validate commands"""

    def __init__(self, master=None, validate='none', validatecommand=None, **kw):
        # get the validate command
        self._vcmd = validatecommand
        # defaults validate on key if vcmd set
        if self._vcmd is not None and validate == 'none':
            validate = 'key'

        super().__init__(master, validate=validate, **kw)

        cmd = self.register(self._vcmd_impl)
        cmd = (cmd, '%d', '%i', '%P', '%s', '%S', '%v', '%V') # add tk params
        self['validatecommand'] = cmd

    def _vcmd_impl(self, action, index, t_after, t_before, t_change, validate, reason):
        ret = self._vcmd(self, vcmd_event(
            ACTION_CODES[action],
            int(index), # beginning of insertion/deletion
            t_after, t_before, t_change, validate, reason,
        ))
        assert ret in (True, False), 'The return value of the validation callback must be True or False\nThe validation on %s has been disabled, set validate to none|key|focus|focusin|focusout|all to re-enable it.' % self
        return ret