[Tutor] Tkinter OptionMenu question

[Abel Daniel]

On Thu, Jun 05, 2003 at 08:35:07AM -0700 Neil Hodge (hodge3@llnl.gov) wrote:
> I was wondering if anyone here knows how to change the items in a 
> Tkinter OptionMenu after it's initial creation. 

After a quick scan of the tkinter source, I think modifying the list
isn't really supported.

> I have tried everything that I can think of (after reading all of the 
> docs I could find), but nothing works.  Any ideas?  Thanks.

A quick & extremly hackish workaround would be to create another
OptionMenu, with the new options and place it at the same place.
(something like old_menu.grid_forget() and new_menu.grid() could work,
provided you pass the same parameters (row, column, etc.) to
new_menu.grid() ). (This method is so ugly, I don't know why I mentioned it.)

The _real_ solution however, is to 'fix' OptionMenu to allow
modification of the list.
At first i wanted to describe who to do this by subclassing OptionMenu, but
it turns out I'm better at writing code than describing how to write code...
So here it is:

----8<----

import Tkinter

class EditableOptionMenu(Tkinter.OptionMenu):
    """OptionMenu which allows editing of menu items
    
    Differences between this and Tkinter.OptionMenu:
      1) insert_option() and delete_option() methods
      2) self.menu, self.variable, self.callback exposed (as we need them to add
         menu items later) (last 3 lines in __init__ )
      3) some names changed from foo to Tkinter.foo, in __init__
         as we do "import Tkinter"

    By Abel Daniel, under the same licence as Tkinter. (As code was
    copyed from there.)
    """
    def __init__(self, master, variable, value, *values, **kwargs):
        """copy-paste-modified from Tkinter.OptionMenu, works the same way"""
        kw = {"borderwidth": 2, "textvariable": variable,
              "indicatoron": 1, "relief": Tkinter.RAISED, "anchor": "c",
              "highlightthickness": 2}
        Tkinter.Widget.__init__(self, master, "menubutton", kw)
        self.widgetName = 'tk_optionMenu'
        menu = self.__menu = Tkinter.Menu(self, name="menu", tearoff=0)
        self.menuname = menu._w
        # 'command' is the only supported keyword
        callback = kwargs.get('command')
        if kwargs.has_key('command'):
            del kwargs['command']
        if kwargs:
            raise TclError, 'unknown option -'+kwargs.keys()[0]
        menu.add_command(label=value,
                 command=Tkinter._setit(variable, value, callback))
        for v in values:
            menu.add_command(label=v,
                     command=Tkinter._setit(variable, v, callback))
        self["menu"] = menu
        
        self.menu=menu
        self.variable=variable
        self.callback=callback
        
    def insert_option(self, index, text):
        """Insert an option to the menu.
        Handling of index is the same as in Tkinter.Menu.insert_command()
        """
        self.menu.insert_command(index, label=text,
            command=Tkinter._setit(self.variable, text, self.callback))

    def delete_option(self, index1, index2=None):
        """Delete options the same way as Tkinter.Menu.delete()"""
        self.menu.delete(index1, index2)

    def change_option(self, index, new_text):
        """Change to new_text
        Bug: doesn't change the selection if the currently selected option
        is changed, fixing this is left as an exercise to the reader"""
        self.menu.entryconfigure(index, label=new_text,
            command=Tkinter._setit(self.variable, new_text, self.callback))



if __name__ == '__main__':
    r=Tkinter.Tk()
    strvar = Tkinter.StringVar()
    test = ("none", "item1", "item2", "item3")
    strvar.set(test[0])
    om = EditableOptionMenu(r, strvar, *test)
    om.pack()

    om.insert_option(4, 'item4')
    om.delete_option(2)
    om.change_option(0, 'baz') # this nicely exposes the bug :)
    r.mainloop()

----8<---------------------

A bit of commentary: the options are added in __init__, at the
"for v in values:" loop. For adding options later, we have to store
enough information to allow doing what the loop does later, i.e. we
need to store menu, variable, callback somewhere.

As this way we expose the underlying Menu more, we could add extra
features, like adding separators, other menu options (submenus) in the
drop-down list. (I didn't try this, but it might work with a bit of hacking.)

Abel Daniel
abli@freemail.hu