Tkinter: How to set relwidth of a Text widget in a Canvas?

Question

In Tkinter, when you place a Text widget in the main window, you can set the relation between the Text widget's width and the main window's width:

text.place(x = 10, y = 10, relwidth = 0.5)

Is it posible to do the same if the Text widget's parent window is a Canvas widget? I tried to use the Canvas itemconfig() method, but it doesn't work:

text = Text(canvas)
canvas.create_window(10, 10, anchor = NW, window = text)
canvas.itemconfig(text, relwidth = 0.5)

Thanks in advance for your help.

Answer 1

No, explicitly setting a relative width is only available when using place. If you are creating an object on a canvas, it is up to you to do the math to configure the width of the object.

It's fairly simple to recompute the width of a text widget by binding to the <Configure> event of the canvas, since that event fires whenever the canvas changes size (among other reasons).

Here's an example that places a text widget on a canvas, and keeps its width at half the width of the canvas. Run the code, and notice that as you resize the window, the text widget is kept at 50% of the width of the canvas.

import tkinter as tk

class Example():
    def __init__(self):
        self.root = tk.Tk()
        self.canvas = tk.Canvas(self.root, background="bisque")
        self.canvas.pack(fill="both", expand=True)

        self.text = tk.Text(self.canvas)
        print("feh:", str(self.text))
        self.canvas.create_window(10, 10, anchor="nw", window=self.text, tags=("text",))

        self.canvas.bind("<Configure>", self._canvas_resize)

    def _canvas_resize(self, event):
        relwidth = event.width / 2
        self.canvas.itemconfigure("text", width=relwidth)

e = Example()
tk.mainloop()