Why does the tkinter scrollbar on a canvas with inner frame get disabled on declaring pack_propagate(0)?

Question

My code has a Frame, a Canvas inside the Frame, and an inner Frame inside the Canvas. I want to put Entry boxes inside the inner Frame and fit them to the inner Frame via pack_propagate(0) to avoid pixel/font width conversions with the Entry widget's width option. However, this breaks the inner Frame's scroll functionality. I want to add Entry widgets dynamically above and below the first and last Entry widgets in the inner Frame, which I am currently doing using pack(before=). So I would like to stick with the packer if possible.

How can I get the scrollbar working again? The following minimum working example has frame.pack_propagate(0) commented out, so the Entry widgets are not sized to the column correctly:

import tkinter as tk
import tkinter.ttk as ttk

root = tk.Tk()

myframe = ttk.Frame(root)
myframe.pack()
sb = ttk.Scrollbar(myframe)
sb.pack(side=tk.RIGHT, fill=tk.Y, expand=1)

canvas = tk.Canvas(myframe, width=200, height=300,
                   scrollregion=(0, 0, 200, 300), yscrollcommand=sb.set)
canvas.pack()
frame = ttk.Frame(canvas, width=200, height=300) # inner Frame
canvas.create_window((0, 0), window=frame, anchor='nw')
sb.config(command=canvas.yview)

frame.bind("<Configure>", lambda event: canvas.configure(
    scrollregion=canvas.bbox(tk.ALL)))
# frame.pack_propagate(0) # How to enable this and ensure scrollbar works?

s = tk.StringVar()
s.set("I'm a box")
for _ in range(100):
    eb = ttk.Entry(frame, textvariable=s)
    eb.pack()

root.mainloop()

Edit1: Added StringVar() and changed eb.grid() to eb.pack()

Answer 1

See example which resize inner Frame to Canvas - it uses

self._canvas.bind('<Configure>', self.inner_resize)

and inside method inner_resize()

self._canvas.itemconfig(self._window, width=event.width)

Full example

import tkinter as tk
import tkinter.ttk as ttk

class ScrolledFrame(tk.Frame):

    def __init__(self, parent, vertical=True, horizontal=False):
        super().__init__(parent)

        # canvas for inner frame
        self._canvas = tk.Canvas(self, bg='red')
        self._canvas.grid(row=0, column=0, sticky='news') # changed

        # create right scrollbar and connect to canvas Y
        self._vertical_bar = tk.Scrollbar(self, orient='vertical', command=self._canvas.yview)
        if vertical:
            self._vertical_bar.grid(row=0, column=1, sticky='ns')
        self._canvas.configure(yscrollcommand=self._vertical_bar.set)

        # create bottom scrollbar and connect to canvas X
        self._horizontal_bar = tk.Scrollbar(self, orient='horizontal', command=self._canvas.xview)
        if horizontal:
            self._horizontal_bar.grid(row=1, column=0, sticky='we')
        self._canvas.configure(xscrollcommand=self._horizontal_bar.set)

        # inner frame for widgets
        self.inner = tk.Frame(self._canvas)
        self._window = self._canvas.create_window((0, 0), window=self.inner, anchor='nw')

        # autoresize inner frame
        self.columnconfigure(0, weight=1) # changed
        self.rowconfigure(0, weight=1) # changed

        # resize when configure changed
        self.inner.bind('<Configure>', self.resize)

        # resize inner frame to canvas size
        self.resize_width = False
        self.resize_height = False
        self._canvas.bind('<Configure>', self.inner_resize)

    def resize(self, event=None): 
        self._canvas.configure(scrollregion=self._canvas.bbox('all'))

    def inner_resize(self, event):
        # resize inner frame to canvas size
        if self.resize_width:
            self._canvas.itemconfig(self._window, width=event.width)
        if self.resize_height:
            self._canvas.itemconfig(self._window, height=event.height)

# --- main ----

root = tk.Tk()

sf = ScrolledFrame(root)
sf.resize_width = True # it will resize frame to canvas
sf.pack(fill='both', expand=True)

s = tk.StringVar()
s.set("I'm a box")

for _ in range(100):
    eb = ttk.Entry(sf.inner, textvariable=s)
    eb.pack(fill='x', expand=True)

root.mainloop()