[Tkinter] How to get the accurate end of the tex widget for highligtng

[ImportRobertPy]

Hello, I have been struggling with this problem for some time now. The code below is supposed to highlight text added to the text widget if the "bg_color" parameter is not None. No coloring appears, but if additional lines are added afterward, color may fill the remainder of the last line. I have determined that this occurs because the self.text_area.index(tk.END) erroneously displays the end of the text as being at the beginning of the next line, even if there is no next line. How do I modify this function to highlight the text correctly?

    def update_text(self, text, clear_first, bg_color=None):
        if clear_first:
            self.text_area.delete(1.0, tk.END)  # Clear the text area

        # Capture the starting index
        start_index = self.text_area.index(tk.END)
        print(self.text_area.index(tk.END))

        # Insert the new text
        self.text_area.insert(tk.END, text)

        # Capture the ending index
        end_index = self.text_area.index(tk.END)
        print(self.text_area.index(tk.END))

        if bg_color:
            # Apply a tag with the background color
            tag_name = f"bg_color_{randint(1, 10000)}"  # Create a unique tag name
            self.text_area.tag_add(tag_name, start_index, end_index)
            self.text_area.tag_config(tag_name, background=bg_color)