ttk Opening Secondary Window when Applying Style

Question

Here is my code

from Tkinter import *
import ttk, tkMessageBox
import os

font = ("Avenir", 24)

b = ttk.Style()
b.configure('TButton', font=font)

class LoginScreen(Tk):
    def __init__(self, *args, **kwargs):
        Tk.__init__(self, *args, **kwargs)

        container = Frame(self)
        container.pack(side=TOP, fill=BOTH, expand=True)

        self.frames = {}
        for F in (Login, Register):
            frame = F(container, self)
            self.frames[F] = frame

            frame.grid(row=0, column=0, sticky='nsew')

        self.show_frame(Login)

    def show_frame(self, cont):
        frame = self.frames[cont]
        frame.tkraise()

class Login(Frame):
    def __init__(self, parent, controller):
        Frame.__init__(self, parent)
        label = Label(self, text="screen 1")
        button = Button(self, text="move", font=font, command=lambda: controller.show_frame(Register))

        button.pack()
        label.pack()

class Register(Frame):
    def __init__(self, parent, controller):
        Frame.__init__(self, parent)
        label = Label(self, text="screen 2")
        label.pack()

if __name__ == '__main__':
    app = LoginScreen()
    app.title("Login")
    app.mainloop()

When I run this, I get this screen: Working Screen without ttk

But as soon as I change:

button = Button(self, text="move", font=font, command=lambda: controller.show_frame(Register))

to

button = ttk.Button(self, text="move", style='TButton', command=lambda: controller.show_frame(Register))

A Secondary Window is opened and the font doesn't change.

I'm hoping there is something simple I am overlooking, but this method of styling ttk widgets is the only way I've seen it done online.

I don't want the window, and as I have stated before it seems to magically appear when I apply the 'b' style to a button.

Thanks for reading.

Answer 1

The secondary window is caused by your line 7. When you call ttk.Style it needs a root window to work with, and if one has not been created yet it creates one. To fix this you need to move lines 7 and 8 to a point after creating the root window (calling Tk()).

if __name__ == '__main__':
    app = LoginScreen()
    app.title("Login")
    b = ttk.Style()
    b.configure('TButton', font=font)
    app.mainloop()