Scrollbar of my app is working not correctly when content is large what must I do?

Question

from tkinter import *

#Root
root = Tk()
root.title('A WINDOW')

#Frame
main_frame = Frame(root)
main_frame.pack(fill=BOTH, expand = True)

#Canvas
main_canvas = Canvas(main_frame)
main_canvas.pack(side = LEFT, fill = BOTH, expand = True)

#Scrollbar
scrollbar = Scrollbar(main_frame, orient = VERTICAL, command =  main_canvas.yview)
scrollbar.pack(side = RIGHT, fill = 'y')

#Configure the Canvas
main_canvas.configure(yscrollcommand=scrollbar.set)

#Frame@2
Frame2 = Frame(main_canvas)
main_canvas.create_window((0, 0), window = Frame2, anchor = 'nw')
main_canvas.bind('<Configure>', lambda e :main_canvas.configure(scrollregion=main_canvas.bbox('all')))
for i in range(2000):
    Button(Frame2, text = str(i)).grid(row = i, column = 0)



root.mainloop()

and when I execute the program, it works until the 1080th one then scrollbar moves but buttons don't go down anymore I hope you understood me and have an idea about what must I do...

Answer 1

This is a slight modification of your code. It demonstrates the limitation of the window object in tk.Canvas with a maximum height of 32768. It can be shown by changing variable offset to some arbitrary value and scrolling to the end of canvas. The last button will still be visible even though its position is 32768+offset.

Function bookmark finds frame2 in the window object and finds all objects in frame2 then changes background color. This makes it easy to confirm first and last buttons are visible.

import tkinter as tk

root = tk.Tk()
frame = tk.LabelFrame(root, labelanchor = tk.S, text = '0|0')
frame.grid(row = 0, column = 0, sticky = tk.NSEW)
for a in [root, frame]:
    a.rowconfigure(0, weight = 1)
    a.columnconfigure(0, weight = 1)

main_canvas = tk.Canvas(frame)
main_canvas.grid(row = 0, column = 0, sticky = tk.NSEW)
scrollbar = tk.Scrollbar(frame, orient = tk.VERTICAL, command =  main_canvas.yview)
scrollbar.grid(row = 0, column = 1, sticky = tk.NS)
main_canvas.configure(yscrollcommand = scrollbar.set)

def location(event):
    x, y = main_canvas.canvasx(event.x), main_canvas.canvasy(event.y)
    frame['text'] = f'{x} | {y}'

# bind mouse
main_canvas.bind('<Motion>', location)

frame2 = tk.Frame(main_canvas)
# frame is positioned at offset
offset = 0
main_canvas.create_window(0, offset, window = frame2, anchor = tk.NW)

def bookends(x):
    # Find reference to frame2
    C = main_canvas.winfo_children()[0]
    # find all objects in frame2
    D = C.winfo_children()
    print(len(D))
    # change colors of first and last buttons
    D[0]['background'] = 'red'
    D[x]['background'] = 'red'

for i in range(2000):
    tk.Button(
        frame2,
        text = str(i),
        font = '{Courier New} 6',
        padx=0, pady=0).grid(
            row = i, column = 0, ipadx = 0, ipady = 0)

bookends(1999)

# main_canvas['scrollregion'] = f'0 0 40 {32768+offset}'
main_canvas.bind('<Configure>', lambda e :main_canvas.configure(scrollregion=main_canvas.bbox('all')))

root.mainloop()