The tkinter canvas background color does not change

Question

I have 2 seperate files and trying to make a sort of 'module' with this one file. But it does not work.

The background color is still this weird gray color even if I set it to say, black. Here is the 'module' file:

import tkinter as tk
class TUICanv:
 global screenWidth, screenHeight
 def __init__(self,win,bg="#232627"):
 self.screenWidth = win.winfo_screenwidth()
 self.screenHeight = win.winfo_screenheight()
 self.canvas = tk.Canvas(win,width=self.screenWidth,height=self.screenHeight,background=bg)
 self.background = bg
 self.width = self.canvas.winfo_width()
 self.height = self.canvas.winfo_height()

And here is the other file:

import tkinter as tk
import terkinter as tr
import os
import re
win = tk.Tk()
allowedChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz_"
win.title("Terminos")
canv = tr.TUICanv(win)
win.geometry(f'{canv.screenWidth}x{canv.screenHeight}')
canv.canvas.create_text(100,10,fill="darkblue",font="Times 20 italic bold",text="Click the bubbles that are multiples of two.")
win.mainloop()

The background does not change. It may be that the window in the other file is different, because I have only started tkinter 2 weeks ago.

• acw1668: You have not applied any layout manager (pack, grid or place) on the canvas, so it is hidden. Also the line global screenWidth, screenHeight is not necessary and better be removed. Another suggestion is to inherit TUICanv from tk.Canvas.
• Felix508: EDIT: Resolved: I added self.canvas.pack()
• acw1668: From design point of view, it is not recommended to call layout function inside child class because child does not know which layout manager is used in parent. So it is the responsibility of the parent to layout its children.

Answer 1

Your canvas is not visible. One way to make it visible is to pack it by by adding

self.canvas.pack(fill="both", expand=True)

to your terkinter.py __init__ method.

• Bryan Oakley: It's not a good practice for the class to call pack on itself. That limits its usabiliity to only an application using pack. If the application switched to grid, this class would have to be modified.

Answer 2

As others have pointed out, the problem is that you aren't making the widget visible by calling pack, place, or grid, or adding to the screen in some other method.

The simple solution is for your app to call one of those methods. For example:

...
win.title("Terminos")
canv = tr.TUICanv(win)
canv.cavas.pack(side="top", fill="both", expand=True)
...

That's not the best solution though, since it depends on the calling app to know that it implements an inner canvas. A better solution would be for your class to inherit from tk.Canvas. In that way it behaves just like the canvas.

For example:

import tkinter as tk
class TUICanv(tk.Canvas):
 global screenWidth, screenHeight
 def __init__(self,win,bg="red"):
 self.screenWidth = win.winfo_screenwidth()
 self.screenHeight = win.winfo_screenheight()
 super().__init__(win,width=self.screenWidth, height=self.screenHeight,background=bg)
 self.width = self.winfo_width()
 self.height = self.winfo_height()
root = tk.Tk()
c = TUICanv(root)
c.pack(side="top", fill="both", expand=True)
root.mainloop()

• user30412914: Typo error canv.cavas should be canv.canvas