我想自己做一个文字处理软件，但我不知道如何按下按钮，只加粗用户接下来要输入的内容，而不是整个文本框。

# from tkinter import *  # PEP8: `import *` is not preferred`
import customtkinter as tk
#from docx import Document


class TextWindow(tk.CTkToplevel):  # still use `Toplevel`

    def __init__(self, master):  # send main window as master/parent
        super().__init__(master)  # it will also set `self.master = master`

        ws = self.winfo_screenwidth()  # width of the screen
        hs = self.winfo_screenheight()  # height of the screen

        # calculate x and y coordinates for the Tk root window
        x = (ws / 2) - (300 / 2)
        y = (hs / 2) - (200 / 2)

        self.geometry('%dx%d+%d+%d' % (300, 200, x, y))
        self.title("New World Documents")
        tk.set_appearance_mode("system")
        tk.set_default_color_theme("green")

        self.grid_rowconfigure(0, weight=1)
        self.grid_columnconfigure((0, 1), weight=1)

        self.textbox = tk.CTkTextbox(self, width=400, corner_radius=0, font=("roboto", 12), wrap="word")
        self.textbox.grid(row=0, column=0, padx=20, pady=20, sticky="nsew", columnspan=2)

        self.button = tk.CTkButton(self, text="Save and quit", command=self.go_back)
        self.button.grid(row=1, column=0, padx=20, pady=20, sticky="ew")

        self.button1 = tk.CTkButton(self, text="Bold", command=self.bolden)
        self.button1.grid(row=1, column=1, padx=20, pady=20, sticky="ew")

        self.wm_protocol("WM_DELETE_WINDOW", self.on_close)

    def bolden(self):
        #Function to bolden what the user will type.
        self.textbox.configure(font=("roboto", 12, "bold"))

    def go_back(self):
        # Work in Progress.
        #document = Document()
        #text = self.textbox.get("1.0", "end-1c")
        #document.add_paragraph(text)
        #document.save("test.docx")
        #with open("filepy.txt", "a") as outf:
        #    outf.write(text)
        self.destroy()  # destroy only current window
        self.master.deiconify()  # show again main window

    def on_close(self):
        self.destroy()  # destroy current window
        self.master.destroy()  # destroy main window

class MainScreen(tk.CTk):

    def __init__(self):
        super().__init__()

        ws = self.winfo_screenwidth()  # width of the screen
        hs = self.winfo_screenheight()  # height of the screen

        # calculate x and y coordinates for the Tk root window
        x = (ws / 2) - (300 / 2)
        y = (hs / 2) - (200 / 2)

        self.geometry('%dx%d+%d+%d' % (300, 200, x, y))
        self.title("New World Documents")
        tk.set_appearance_mode("system")
        tk.set_default_color_theme("green")

        self.label = tk.CTkLabel(self, text="New World Documents", font=("roboto",25), width=200, height=25)
        self.label.pack()

        self.button = tk.CTkButton(self, text="New Document", command=self.StartWriting)
        self.button.pack()

    def StartWriting(self):
        self.withdraw()
        self.app = TextWindow(self)  # send main window as argument

    def start(self):
        self.mainloop()

MainScreen().start()

目前，当我按下粗体按钮时，代码所做的唯一事情就是将文本框中的所有内容都加粗，我只想将下一个要输入的单词加粗，就像word、libreoffice、google docs等。
我试过查找答案，但每次我接近标签时，答案都无济于事，因为它只适用于从代码中插入的单词，而不适用于从键入的单词，它也不起作用，因为我无法指定为空格或未来将要键入的单词添加标签。