Current Value ttk.Scales

Command Option

Adding Current Value

Using command to show current values.

Some parts of these scripts are common to both vertical and horizontal scales.

The example 01ttk_tkinter.py can be used as a basis with which to start. The most obvious shortcoming is that there is no value shown for the cursor position. Use the method get() to obtain this value and place it in a Label. The problem with this method is that as it stands it only gives the first position of the cursor. If a button is used to query the scale then the current cursor position will be shown. Compared to the tkinter option this method is not dynamic enough. Our problem lies with the command sequence, so get() is doing its job, but the Scale needs to be first redrawn then the Label text updated before get() returns the correct answer. We can use the command option, then update the Label from the relevant function.

Show/Hide Code 02ttk_tkinter_value.py

import tkinter as tk
import tkinter.ttk as ttk

def selh(val):
    labh.config(text=round(float(val)+0.0049,2))

def selv(val):
    labv.config(text=round(float(val)+0.0049,2))

root = tk.Tk()
s = ttk.Style()
s.theme_use('default')

sch = tk.Scale(root, from_=-1.0, to=1.0, label='Bogusstuinuous', orient='horizontal',
            resolution=0.02, showvalue=1, tickinterval=0.5, digits=3,
            length=200)
sch.grid()

scv = tk.Scale(root, from_=-0, to=10, label='Fun', orient='vertical',
            resolution=1, showvalue=1, tickinterval=2,
            length=200)
scv.grid(row=0, column=1)

sep = ttk.Separator(root, orient='horizontal')
sep.grid(row=1, column=0, columnspan=2)

scth = ttk.Scale(root, from_=-1.0, to=1.0, length=200, command=selh)
scth.grid(row=2, column=0)

labh = ttk.Label(root, text=str(scth.get()))
labh.grid(row=2, column=1)

sctv = ttk.Scale(root, from_=0, to=10, length=200, orient='vertical', command=selv)
sctv.grid(row=3, column=0)

labv = ttk.Label(root, text=str(sctv.get()))
labv.grid(row=3, column=1)

root.mainloop()

The simplest method of displaying the current value is to place the result in a Label. Later on in Colour Picker a Spinbox is used, which allows the slider to position itself according to the Spinbox entry and not just positioned by the cursor, in this case a FloatVar or IntVar is used. It is also possible to position the current value just above the slider.

Bind to Mouse Button

There may be occasions when the command option is required for other actions than showing the current value. In this case bind to the mouse cursor the result is much the same as with command. The bind can be when the mouse is pressed or preferably when the mouse is released while using the method get(). This is because when clicking on the slider it normally is not in the position we are interested in, when the mouse is released the slider is in position and the value obtained by get() is more pertinent. This is still not as dynamic as the tkinter option and will be addressed later.

When binding we can pick up the current x-position of the cursor, note the x-position values at the two extremes. The vertical scale shows the current y-position. Remember the bind gives the actual position for the cursor rather than the centre of the slider.

Show/Hide Code 03ttk_tkinter_bind.py

import tkinter as tk
import tkinter.ttk as ttk

def selh(val):
    labh.config(text=round(float(scth.get())+0.0049,2))
    print('horiz', scth.get(), val.x)

def selv(val):
    labv.config(text=round(float(sctv.get())+0.0049,2))
    print('vert', sctv.get(), val.y)

root = tk.Tk()
s = ttk.Style()
s.theme_use('default')

sch = tk.Scale(root, from_=-1.0, to=1.0, label='Bogusstuinuous', orient='horizontal',
            resolution=0.02, showvalue=1, tickinterval=0.5, digits=3,
            length=200)
sch.grid()

scv = tk.Scale(root, from_=-0, to=10, label='Fun', orient='vertical',
            resolution=1, showvalue=1, tickinterval=2,
            length=200)
scv.grid(row=0, column=1)

sep = ttk.Separator(root, orient='horizontal')
sep.grid(row=1, column=0, columnspan=2)

scth = ttk.Scale(root, from_=-1.0, to=1.0, length=200)
scth.bind("<ButtonRelease-1>", selh)
scth.grid(row=2, column=0)

labh = ttk.Label(root, text=str(scth.get()))
labh.grid(row=2, column=1)

sctv = ttk.Scale(root, from_=0, to=10, length=200, orient='vertical')
sctv.bind("<ButtonRelease-1>", selv)
sctv.grid(row=3, column=0)

labv = ttk.Label(root, text=str(sctv.get()))
labv.grid(row=3, column=1)

root.mainloop()