我正在尝试制作一个具有设定高度的框架，并带有垂直滚动条来响应鼠标滚动事件。框架需要包含框架，因此没有可以使用的内置Tk小部件。这是我正在使用的Python 3代码，源于此处的几个相关答案：

import tkinter as tk

class VertScrollingFrame(tk.Frame):
    def __init__(self,root):
        super().__init__(root)
        self.canvas = tk.Canvas(root)
        self.frame = tk.Frame(self.canvas)
        self.bar = tk.Scrollbar(root,orient = "vertical",command = self.canvas.yview)
        self.bar.lift(self.frame)
        self.canvas.configure(yscrollcommand = self.bar.set)

        self.bar.pack(side = "right",fill = "y")
        self.canvas.pack(side = "left",fill = 'both',expand = True)
        self.canvas.create_window(
            (4,4),window = self.frame,anchor = "nw",tags = "self.frame",)
        #self.frame.pack()

        def on_cfg(_):
            self.canvas.configure(scrollregion = self.canvas.bbox("all"))
        self.frame.bind('<Configure>',on_cfg)

        def on_scroll(event):
            if event.delta:
                amount = round(-event.delta / 120)
            else:
                amount = {4: -1,5: 1}[event.num] * 2
            self.canvas.yview_scroll(amount,"units")

        bind_keys = {'<MouseWheel>','<Button-4>','<Button-5>'}
        def scroll_bind(_):
            for key in bind_keys:
                self.canvas.bind_all(key,on_scroll)
        def scroll_unbind(_):
            for key in bind_keys:
                self.canvas.unbind_all(key)

        self.frame.bind('<Enter>',scroll_bind)
        self.frame.bind('<Leave>',scroll_unbind)

root = tk.Tk()
win = tk.Toplevel(root)
sf = VertScrollingFrame(win)
for _ in range(20):
    f = tk.Frame(sf.frame)
    for x in range(12):
        tk.Button(f,text = str(x)).pack(side = 'left')
    f.pack()
sf.pack()
root.mainloop()

我在滚动框架中填充了宽阔的按钮网格，并且画布似乎在水平调整大小以适合它们，但是ScrollingFrame不是。它只是切断了内容的右侧。如何使框架展开以使其内容水平放置？

在未注释self.frame.pack()的情况下，我得到了另一个不同的错误结果：奇怪的是，垂直和水平方向都裁剪了按钮网格，并且没有滚动的内容。