[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?

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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)

[deanhystad]

Text always contains a newline at the end. "end" is the position of this newline. To get the position before the newline use "end -1c".

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import tkinter as tk     class Window(tk.Tk):     def __init__(self):         super().__init__()         self.text_tag = 0         self.text_area = tk.Text(self, wrap="word")         self.text_area.pack(expand=True, fill=tk.BOTH)       def update_text(self, text, clear_first=False, bg_color=None):         if clear_first:             self.text_area.delete(1.0, tk.END)         start_index = self.text_area.index("end - 1c")         self.text_area.insert(tk.END, text)         if bg_color:             tag_name = f"bg_color_{self.text_tag}"             end_index = self.text_area.index("end - 1c")             print(start_index, end_index, bg_color, tag_name)             self.text_tag += 1             self.text_area.tag_add(tag_name, start_index, end_index)             self.text_area.tag_config(tag_name, background=bg_color)     window = Window() window.update_text("This is regular text.") window.update_text(" This is red text.", bg_color="pink") window.update_text(" This is blue text.", bg_color="lightblue") window.update_text(" This is yellow text.", bg_color="yellow") window.update_text(" Back to normal text.")   window.mainloop()

You can learn more about text indexing here:

https://tkdocs.com/tutorial/text.html

You don't need to use add() to add the tag. It is easier to add the tag in the insert.

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import tkinter as tk     class Window(tk.Tk):     def __init__(self):         super().__init__()         self.text_tag = 0         self.text_area = tk.Text(self, wrap="word")         self.text_area.pack(expand=True, fill=tk.BOTH)       def update_text(self, text, clear_first=False, bg_color=None):         if clear_first:             self.text_area.delete(1.0, tk.END)         if bg_color is None:             self.text_area.insert(tk.END, text)         else:             tag_name = f"bg_color_{self.text_tag}"             self.text_tag += 1             self.text_area.insert(tk.END, text, tag_name)             self.text_area.tag_config(tag_name, background=bg_color)     window = Window() window.update_text("This is regular text.") window.update_text(" This is red text.", bg_color="pink") window.update_text(" This is blue text.", bg_color="lightblue") window.update_text(" This is yellow text.", bg_color="yellow") window.update_text(" Back to normal text.")   window.mainloop()

It is unusual to have random tags. I would create a palette of tags that can be used to highlight text.

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import tkinter as tk     class Window(tk.Tk):     def __init__(self):         super().__init__()         self.text_area = tk.Text(self, wrap="word")         self.text_area.pack(expand=True, fill=tk.BOTH)       def update_text(self, text, clear_first=False, tags=None):         if clear_first:             self.text_area.delete(1.0, tk.END)         self.text_area.insert(tk.END, text, tags)       def tag(self, name, **kwargs):         self.text_area.tag_config(name, **kwargs)     window = Window() window.tag("hilite", background="yellow") window.tag("underline", underline=1) window.update_text("This is normal text.") window.update_text(" This is highlited text.", tags=("hilite",)) window.update_text(" This is underlined text.", tags=("underline",)) window.update_text(" This text is hilighted and underlined.", tags=("hilite", "underline")) window.update_text(" Back to normal text.")   window.mainloop()