How to set a canvas into the main window?

Question

I was trying to put a Canvas into the main window.

But although the master is the main window and I pack it like every other widget, it doesn't work as expected:

A second Tk opens, which is the Canvas, separate from the root.

Why does this happen and is it somehow possible to do what I want instead?

Answer 1

HonFu I’m pretty sure that canvas should work like every other widget so it shouldn’t open a new window. Copy this code and run it:
from tkinter import *
master = Tk()

canvas_width = 80
canvas_height = 40
w = Canvas(master,
width=canvas_width,
height=canvas_height)
w.pack()

y = int(canvas_height / 2)
w.create_line(0, y, canvas_width, y, fill="#476042")

mainloop()

What happens when you run it?

Answer 2

I'm just starting out with tkinter.

My understanding was that there is a 'mommy', that Tk-object, and that every widget declaring her master will be part of that mommy window.

And that is true for Lable, Button, RadioButton, Entry, Checkbutton, Frame, Scale...

Only Canvas is being a spoilsport starting a thing of her own.

Answer 3

HonFu (Incase you’re still having problems with the program) I just ran your code on my pc and it worked like I expected. So it opened a new window and packed the canvas on there and it didn’t open any new windows.

Answer 4

Hm, interesting...

I am not close to my PC right now, but I will copypaste this into there later and report.

Answer 5

HonFu No problem :)

Answer 6

Can you share your code, please?

Answer 7

I appreciate the spirit of letting people show code; in this case I'll just be spelling out what I already wrote though.

from tkinter import *
m = Tk()
c = Canvas(master=m)
c.pack()
m.mainloop()

What I expect: A canvas as one element of the main window.

What I get: Two separate windows.

Any way around this?

Answer 8

HonFu Maybe the m in m.mainloop() calls Tk() again and it opens a new window

Answer 9

Goodester, have you worked with tkinter?

Answer 10

HonFu Yep, a little bit.

Answer 11

HonFu I don’t see anything wrong with your code though and I can’t really debug it right now because I can’t use my pc.

Answer 12

Have you used Canvas yourself?

Answer 13

HonFu Yes like a year ago I don’t use it very often

Answer 14

HonFu Have you tried to pack some other widget instead of Canvas on the master so you could see if Canvas is causing the bug?

Answer 15

It works perfectly fine with everything else.

Answer 16

Goodester, I just tried your example...

... and it worked. oO

Now I am relieved that everything is as it should be, but the question, what the heck I was doing differently, will be haunting me for a while...

Anyway, thanks a lot for your help! :)