tkinter画布滚动，但滚动条未调整以显示画布大小

import tkinter as tk

def scroll_canvas(event):
    canvas.yview_scroll(int(-1*(event.delta/120)), "units")

root = tk.Tk()
root.geometry("400x300")

# 创建Canvas组件
canvas = tk.Canvas(root, width=400, height=300)
canvas.pack(side=tk.LEFT, fill=tk.BOTH, expand=True)

# 创建Scrollbar组件
scrollbar = tk.Scrollbar(root, command=canvas.yview)
scrollbar.pack(side=tk.RIGHT, fill=tk.Y)

# 将Scrollbar与Canvas关联
canvas.configure(yscrollcommand=scrollbar.set)

# 绑定滚轮事件
canvas.bind_all("<MouseWheel>", scroll_canvas)

# 创建一个大的矩形，用于演示滚动效果
canvas.create_rectangle(0, 0, 1000, 1000, fill="red")

# 设置可滚动的区域大小
canvas.config(scrollregion=canvas.bbox("all"))

root.mainloop()