How to make a polygon change it's height depending on the amount of text that needs to fit in there in Python Tkinter?

I've been trying to make a chat like UI in python using Tkinter. I've made some progress but for some reason, the height of my polygon isn't changing enough to fit the whole text. After a few lines the text overspills outside of the polygon, usually after 3 or 4. I've tried various things to get it to work, but it still doesn't? I would like the polygon to be able to change size depending on the amount of text that is inside, width wise it works, but height wise it doesn't? Could anyone help me figure out why and how to fix it? Any suggestions is helpful? Also? Feel free to give me any advice/help on how to make my code better and more efficient?

from tkinter import *

root = Tk()
root.config(bg="lightblue")

canvas = Canvas(root, width=600, height=600,bg="grey")
canvas.grid(row=0,column=0,columnspan=2)

bubbles = []

def round_rectangle(x1, y1, x2, y2, radius=25, **kwargs):
        points = [x1+radius, y1,
                  x1+radius, y1,
                  x2-radius, y1,
                  x2-radius, y1,
                  x2, y1,
                  x2, y1+radius,
                  x2, y1+radius,
                  x2, y2-radius,
                  x2, y2-radius,
                  x2, y2,
                  x2-radius, y2,
                  x2-radius, y2,
                  1+radius, y2,
                  x1+radius, y2,
                  x1, y2,
                  x1, y2-radius,
                  x1, y2-radius,
                  x1, y1+radius,
                  x1, y1+radius,
                  x1, y1]

        return canvas.create_polygon(points, **kwargs, smooth=True)
    

class RoundBubble:
    def __init__(self,master,message=""):
        self.master = master
        self.canvas = canvas
        resize = canvas.create_text(15, 15, text=message, width=300, anchor="w")
        x, y, w, h = canvas.bbox(resize)
        self.chonk = round_rectangle(x-5, y-5, x+w, y+h, radius=25, fill="light blue")
        canvas.move(self.chonk, 0, 530)
        self.canvas.tag_lower(self.chonk)
        canvas.move(resize, 0, 530)
        root.update_idletasks()

def send_message():
    
    if bubbles:
        canvas.move(ALL, 0, -50)
    a = RoundBubble(canvas,message=entry.get())
    bubbles.append(a)

entry = Entry(root,width=26)
entry.grid(row=1,column=0)
Button(root,text="Send",command=send_message).grid(row=1,column=1)
root.mainloop()

I've tried using len() and splitlines() to count the number of lines to adjust for the height but that didn't seem to work?

Here is a partial solution that adds a Scrollbar and a scrollregion to canvas then keeps track of the location of each bubble and uses that to calculate the next message position. I've used tags to move both text and bubble together. Scrolling messages is performed by supplying canvas.yview_scroll with location data.

root = Tk()
root.config(bg="lightblue")
canvas = Canvas(
root, width = 600, height = 600,
xscrollincrement = 1, yscrollincrement = 1,
bg = "grey", scrollregion = "0 0 600 4000")
canvas.grid(columnspan=2, sticky = "nsew")
vert = Scrollbar(root, orient = "vertical", command = canvas.yview)
vert.grid(row = 0, column = 3, sticky = "ns")
canvas["yscrollcommand"] = vert.set
bubbles = []
location = [15]
def round_rectangle(x1, y1, x2, y2, radius=25, **kwargs):
points = [x1+radius, y1,
x1+radius, y1,
x2-radius, y1,
x2-radius, y1,
x2, y1,
x2, y1+radius,
x2, y1+radius,
x2, y2-radius,
x2, y2-radius,
x2, y2,
x2-radius, y2,
x2-radius, y2,
1+radius, y2,
x1+radius, y2,
x1, y2,
x1, y2-radius,
x1, y2-radius,
x1, y1+radius,
x1, y1+radius,
x1, y1]
return canvas.create_polygon(points, **kwargs, smooth=True)
class RoundBubble:
def __init__(self,master,message=""):
self.master = master
self.canvas = canvas
text = canvas.create_text(
15, location[~0], text=message,width=300, anchor="nw", tags = "A")
x, y, w, h = canvas.bbox(text)
chonk = round_rectangle(
x-5, y-5, w+5, h+5, radius=25, fill="light blue", tags = "A")
x1, y1, w1, h1 = canvas.bbox(chonk)
location.append(h1 + 5)
self.canvas.tag_lower(chonk, text)
self.canvas.dtag("A")
def send_message(e = None):
if len(location) > 1:
canvas.yview_scroll(location[1]- location[0], "units")
a = RoundBubble(canvas,message=entry.get())
bubbles.append(a)
entry = Entry(root,width=26)
entry.grid(row=1,column=0)
entry.bind("<Return>", send_message)
Button(root,text="Send",command=send_message).grid(row=1,column=1)
root.mainloop()

Note that .bbox() returns the coordinates of the top-left and bottom-right corners of the bounding box, so the line

self.chonk = round_rectangle(x-5, y-5, x+w, y+h, radius=25, fill="light blue")

should be as below instead:

self.chonk = round_rectangle(x-5, y-5, w+5, h+5, radius=25, fill="light blue")

Note that you can simply create the bubble just below the bottom of the canvas and then move all messages up by the height (and some vertical space) of the newly created bubble. Also suggest to put the function round_rectangle() inside the RoundBubble class:

...
class RoundBubble:
    def __init__(self, master, message=""):
        self.canvas = master
        # create the text and bubble at the position just below the viewable area
        resize = self.canvas.create_text(15, self.canvas.winfo_height()+5, text=message, width=300, anchor="nw")
        x1, y1, x2, y2 = self.canvas.bbox(resize)
        self.chonk = self.round_rectangle(x1-5, y1-5, x2+5, y2+5, radius=25, fill="light blue")
        self.canvas.tag_lower(self.chonk)
        self.canvas.update_idletasks()
        # move all messages up to see the just added message
        self.canvas.move(ALL, 0, -(y2-y1+10)-10)

    def round_rectangle(self, x1, y1, x2, y2, radius=25, **kwargs):
        points = [x1+radius, y1,
                  x1+radius, y1,
                  x2-radius, y1,
                  x2-radius, y1,
                  x2, y1,
                  x2, y1+radius,
                  x2, y1+radius,
                  x2, y2-radius,
                  x2, y2-radius,
                  x2, y2,
                  x2-radius, y2,
                  x2-radius, y2,
                  1+radius, y2,
                  x1+radius, y2,
                  x1, y2,
                  x1, y2-radius,
                  x1, y2-radius,
                  x1, y1+radius,
                  x1, y1+radius,
                  x1, y1]

        return self.canvas.create_polygon(points, **kwargs, smooth=True)


def send_message():
    a = RoundBubble(canvas, message=entry.get())
    bubbles.append(a)
...