Adding a scrollbar to a group of widgets in Tkinter

Question:

I am using Python to parse entries from a log file, and display the entry contents using Tkinter and so far it’s been excellent. The output is a grid of label widgets, but sometimes there are more rows than can be displayed on the screen. I’d like to add a scrollbar, which looks like it should be very easy, but I can’t figure it out.

The documentation implies that only the List, Textbox, Canvas and Entry widgets support the scrollbar interface. None of these appear to be suitable for displaying a grid of widgets. It’s possible to put arbitrary widgets in a Canvas widget, but you appear to have to use absolute co-ordinates, so I wouldn’t be able to use the grid layout manager?

I’ve tried putting the widget grid into a Frame, but that doesn’t seem to support the scrollbar interface, so this doesn’t work:

mainframe = Frame(root, yscrollcommand=scrollbar.set)

Can anyone suggest a way round this limitation? I’d hate to have to rewrite in PyQt and increase my executable image size by so much, just to add a scrollbar!

Asked By: Simon Hibbs

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Source

Answers:

Overview

You can only associate scrollbars with a few widgets, and the root widget and Frame aren’t part of that group of widgets.

There are at least a couple of ways to do this. If you need a simple vertical or horizontal group of widgets, you can use a text widget and the window_create method to add widgets. This method is simple, but doesn’t allow for a complex layout of the widgets.

A more common general-purpose solution is to create a canvas widget and associate the scrollbars with that widget. Then, into that canvas embed the frame that contains your label widgets. Determine the width/height of the frame and feed that into the canvas scrollregion option so that the scrollregion exactly matches the size of the frame.

Why put the widgets in a frame rather than directly in the canvas? A scrollbar attached to a canvas can only scroll items created with one of the create_ methods. You cannot scroll items added to a canvas with pack, place, or grid. By using a frame, you can use those methods inside the frame, and then call create_window once for the frame.

Drawing the text items directly on the canvas isn’t very hard, so you might want to reconsider that approach if the frame-embedded-in-a-canvas solution seems too complex. Since you’re creating a grid, the coordinates of each text item is going to be very easy to compute, especially if each row is the same height (which it probably is if you’re using a single font).

For drawing directly on the canvas, just figure out the line height of the font you’re using (and there are commands for that). Then, each y coordinate is row*(lineheight+spacing). The x coordinate will be a fixed number based on the widest item in each column. If you give everything a tag for the column it is in, you can adjust the x coordinate and width of all items in a column with a single command.

Object-oriented solution

Here’s an example of the frame-embedded-in-canvas solution, using an object-oriented approach:

import tkinter as tk

class Example(tk.Frame):
    def __init__(self, parent):

        tk.Frame.__init__(self, parent)
        self.canvas = tk.Canvas(self, borderwidth=0, background="#ffffff")
        self.frame = tk.Frame(self.canvas, background="#ffffff")
        self.vsb = tk.Scrollbar(self, orient="vertical", command=self.canvas.yview)
        self.canvas.configure(yscrollcommand=self.vsb.set)

        self.vsb.pack(side="right", fill="y")
        self.canvas.pack(side="left", fill="both", expand=True)
        self.canvas.create_window((4,4), window=self.frame, anchor="nw",
                                  tags="self.frame")

        self.frame.bind("<Configure>", self.onFrameConfigure)

        self.populate()

    def populate(self):
        '''Put in some fake data'''
        for row in range(100):
            tk.Label(self.frame, text="%s" % row, width=3, borderwidth="1",
                     relief="solid").grid(row=row, column=0)
            t="this is the second column for row %s" %row
            tk.Label(self.frame, text=t).grid(row=row, column=1)

    def onFrameConfigure(self, event):
        '''Reset the scroll region to encompass the inner frame'''
        self.canvas.configure(scrollregion=self.canvas.bbox("all"))

if __name__ == "__main__":
    root=tk.Tk()
    example = Example(root)
    example.pack(side="top", fill="both", expand=True)
    root.mainloop()

Procedural solution

Here is a solution that doesn’t use a class:

import tkinter as tk

def populate(frame):
    '''Put in some fake data'''
    for row in range(100):
        tk.Label(frame, text="%s" % row, width=3, borderwidth="1", 
                 relief="solid").grid(row=row, column=0)
        t="this is the second column for row %s" %row
        tk.Label(frame, text=t).grid(row=row, column=1)

def onFrameConfigure(canvas):
    '''Reset the scroll region to encompass the inner frame'''
    canvas.configure(scrollregion=canvas.bbox("all"))

root = tk.Tk()
canvas = tk.Canvas(root, borderwidth=0, background="#ffffff")
frame = tk.Frame(canvas, background="#ffffff")
vsb = tk.Scrollbar(root, orient="vertical", command=canvas.yview)
canvas.configure(yscrollcommand=vsb.set)

vsb.pack(side="right", fill="y")
canvas.pack(side="left", fill="both", expand=True)
canvas.create_window((4,4), window=frame, anchor="nw")

frame.bind("<Configure>", lambda event, canvas=canvas: onFrameConfigure(canvas))

populate(frame)

root.mainloop()
Answered By: Bryan Oakley

Make it scrollable

Use this handy class to make the frame containing your widgets scrollable. Follow these steps:

  1. create the frame
  2. display it (pack, grid, etc)
  3. make it scrollable
  4. add widgets inside it
  5. call the update() method
import tkinter as tk
from tkinter import ttk

class Scrollable(tk.Frame):
    """
       Make a frame scrollable with scrollbar on the right.
       After adding or removing widgets to the scrollable frame,
       call the update() method to refresh the scrollable area.
    """

    def __init__(self, frame, width=16):

        scrollbar = tk.Scrollbar(frame, width=width)
        scrollbar.pack(side=tk.RIGHT, fill=tk.Y, expand=False)

        self.canvas = tk.Canvas(frame, yscrollcommand=scrollbar.set)
        self.canvas.pack(side=tk.LEFT, fill=tk.BOTH, expand=True)

        scrollbar.config(command=self.canvas.yview)

        self.canvas.bind('<Configure>', self.__fill_canvas)

        # base class initialization
        tk.Frame.__init__(self, frame)

        # assign this obj (the inner frame) to the windows item of the canvas
        self.windows_item = self.canvas.create_window(0,0, window=self, anchor=tk.NW)


    def __fill_canvas(self, event):
        "Enlarge the windows item to the canvas width"

        canvas_width = event.width
        self.canvas.itemconfig(self.windows_item, width = canvas_width)

    def update(self):
        "Update the canvas and the scrollregion"

        self.update_idletasks()
        self.canvas.config(scrollregion=self.canvas.bbox(self.windows_item))

Usage example

root = tk.Tk()

header = ttk.Frame(root)
body = ttk.Frame(root)
footer = ttk.Frame(root)
header.pack()
body.pack()
footer.pack()

ttk.Label(header, text="The header").pack()
ttk.Label(footer, text="The Footer").pack()


scrollable_body = Scrollable(body, width=32)

for i in range(30):
    ttk.Button(scrollable_body, text="I'm a button in the scrollable frame").grid()

scrollable_body.update()

root.mainloop()
Answered By: Tarqez

Extends class tk.Frame to support a scrollable Frame
This class is independent from the widgets to be scrolled and can be used to replace a standard tk.Frame.

enter image description here

import tkinter as tk

class ScrollbarFrame(tk.Frame):
    """
    Extends class tk.Frame to support a scrollable Frame 
    This class is independent from the widgets to be scrolled and 
    can be used to replace a standard tk.Frame
    """
    def __init__(self, parent, **kwargs):
        tk.Frame.__init__(self, parent, **kwargs)

        # The Scrollbar, layout to the right
        vsb = tk.Scrollbar(self, orient="vertical")
        vsb.pack(side="right", fill="y")

        # The Canvas which supports the Scrollbar Interface, layout to the left
        self.canvas = tk.Canvas(self, borderwidth=0, background="#ffffff")
        self.canvas.pack(side="left", fill="both", expand=True)

        # Bind the Scrollbar to the self.canvas Scrollbar Interface
        self.canvas.configure(yscrollcommand=vsb.set)
        vsb.configure(command=self.canvas.yview)

        # The Frame to be scrolled, layout into the canvas
        # All widgets to be scrolled have to use this Frame as parent
        self.scrolled_frame = tk.Frame(self.canvas, background=self.canvas.cget('bg'))
        self.canvas.create_window((4, 4), window=self.scrolled_frame, anchor="nw")

        # Configures the scrollregion of the Canvas dynamically
        self.scrolled_frame.bind("<Configure>", self.on_configure)

    def on_configure(self, event):
        """Set the scroll region to encompass the scrolled frame"""
        self.canvas.configure(scrollregion=self.canvas.bbox("all"))

Usage: 

class App(tk.Tk):
    def __init__(self):
        super().__init__()

        sbf = ScrollbarFrame(self)
        self.grid_rowconfigure(0, weight=1)
        self.grid_columnconfigure(0, weight=1)
        sbf.grid(row=0, column=0, sticky='nsew')
        # sbf.pack(side="top", fill="both", expand=True)

        # Some data, layout into the sbf.scrolled_frame
        frame = sbf.scrolled_frame
        for row in range(50):
            text = "%s" % row
            tk.Label(frame, text=text,
                     width=3, borderwidth="1", relief="solid") 
                .grid(row=row, column=0)

            text = "this is the second column for row %s" % row
            tk.Label(frame, text=text,
                     background=sbf.scrolled_frame.cget('bg')) 
                .grid(row=row, column=1)


if __name__ == "__main__":
    App().mainloop()
Answered By: stovfl