NavigationToolbar2Tk behave unexpected when using it in with Tkinter Canvas

[andreys42]

Bug report

Bug summary

NavigationToolbar2Tk behave unexpected when using it in with Tkinter Canvas(see attached gif for more details). When scroll a little bit my Canvas then tools like zoom, move (e.t.c) works like canvas area still locate on the previous position.

import tkinter
from tkinter import *

from matplotlib.backends.backend_tkagg import (
    FigureCanvasTkAgg, NavigationToolbar2Tk)
from matplotlib.backend_bases import key_press_handler
from matplotlib.figure import Figure

import numpy as np

root = tkinter.Tk()
root.wm_title("Embedding in Tk")

fig = Figure(figsize=(5, 40), dpi=100)
t = np.arange(0, 3, .01)
fig.add_subplot(111).plot(t, 2 * np.sin(2 * np.pi * t))

canvas = FigureCanvasTkAgg(fig, master=root)  # A tk.DrawingArea.
canvas.draw()

scroll_y = Scrollbar(canvas.get_tk_widget(),orient="vertical", command=canvas.get_tk_widget().yview)
scroll_y.grid(row=0, column=1, sticky="ns")

canvas.get_tk_widget().configure(yscrollcommand=scroll_y.set, scrollregion=canvas.get_tk_widget().bbox("all"))

toolbar = NavigationToolbar2Tk(canvas, root)
toolbar.update()

canvas.get_tk_widget().pack(side=tkinter.TOP, fill=tkinter.BOTH, expand=1)

tkinter.mainloop()

Actual outcome

``

Expected outcome
NavigationToolbar2Tk update its action area with new Scrollbar status

Matplotlib version
3.1.3

• Operating system: Windows 10
• Matplotlib version: 3.1.3
• Matplotlib backend (print(matplotlib.get_backend())): TkAgg
• Python version: 3.7
• Other libraries: Tkinter version 8.6

All packages installed using updated pip

[anntzer]

Looks like the trick is to use self._tkcanvas.canvasx(event.x) and self._tkcanvas.canvasy(event.y) everywhere instead of event.x and event.y (https://effbot.org/tkinterbook/canvas.htm#Tkinter.Canvas.canvasx-method).

[andreys42]

@antzer Are you talking about matplotlib embedding code or my little snippet? If last, then I do not really inderstand where actually I used some "event" features in my snippet...

[anntzer]

I mean that Matplotlib should do so, not you.

[andreys42]

Strange that no one still met same troubles

[andreys42]

@anntzer any ideas for hot fix ?

[anntzer]

As I said the correct patch to Matplotlib is probably along the lines of what I wrote above, but you'll have to check that by yourself.

[timhoffm]

Strange that no one still met same troubles

I'm not surprised that this has not been reported before, as it's a very specific use case:

• Most people do not embed matplotlib in applications, but either use the popup window or notebooks.
• Tk is only one of the supported GUI toolkits.
• You made the canvas scrollable; I assume that most of the time people let the graph scale to the available canvas space.
• Zooming and scrolling is not strictly uncommon, but only used in a minority of cases.

The bug is only visible if all of the above comes together.

[andreys42]

@timhoffm Agree. Do this circumstances mean that this "bug" is low-priority for MPL support team?

[andreys42]

• You made the canvas scrollable; I assume that most of the time people let the graph scale to the available canvas space.

Is there any other options to fit elongated graph (w = 100, h = 1000) in fixed size Tk canvas and to be able scale, move and so on? I mean I think it's really wide-spread task and I thought its solution already implemented in MatPlotLib. ...

[timhoffm]

Do this circumstances mean that this "bug" is low-priority for MPL support team?

We do not formally have "low-priority" as most of the development is done by volunteers. It really depends case-by-case. If somebody picks this up, it might be fixed quickly, if not it might stay open for a long time. That said, Matplotlib is an open source project and pull requests are always welcome.

Is there any other options [...]

I'm not aware of any.

[andreys42]

@timhoffm btw @anntzer 's suggestion about replacement was right. At least it solved my (topic) problem )
Thank you, mr @anntzer :)

[andreys42]

noticed one more strange thing : size of FigureCanvasTkAgg (which is set as "t1, t2, w, h = self.figure.bbox.bounds" ) is not match with allocated by Tkinter area
(If we firstly create Frame, and then fullfill it with FigureCanvasTkAgg object using place(relheight = 1, relwidth = 1) then size of mpl figure canvas can be bigger than it's parent widget - Frame)