[Python] Tk MouseWheel Support

Middle button is Button-3 IIRC, and I think it'd be MouseUp and
MouseDown. I'm really not sure though.

It's Button-2 rather.

Middle button is button-3 on Mac OS X, and button-2 on Linux and
Windows. Very annoying, to say the least.

For X11, here's a better way to inject MouseWheel events so all
widgets that understand MouseWheel events will work without additional
code:

def mousewheel(e, delta):
try:
w = e.widget.focus_displayof()
except AttributeError:
# e.widget might be string
# if not created by Tkinter (eg., menu tearoff)
return
if w: w.event_generate('<MouseWheel>', delta=delta,
state=e.state, rootx=e.x_root, rooty=e.y_root,
x=e.x, y=e.y, time=e.time)
root.bind_all('<Button-4>', lambda e, mw=mousewheel: mw(e, 120))
root.bind_all('<Button-5>', lambda e, mw=mousewheel: mw(e, -120))

Google found this:

Using the Mouse Wheel with Tkinter (Python)
http://www.daniweb.com/software-development/python/code/217059

which I adapted to get this (tested on XP with Python 2.7):

import Tkinter as tk

def mouse_wheel(event):
dir = 0
# respond to Linux or Windows wheel event
if event.num == 5 or event.delta == -120:
dir = 1
if event.num == 4 or event.delta == 120:
dir = -1
listbox.yview_scroll(dir, "units")

root = tk.Tk()
root.title('turn mouse wheel')
root['bg'] = 'darkgreen'

# with Windows OS
root.bind("<MouseWheel>", mouse_wheel)
# with Linux OS
root.bind("<Button-4>", mouse_wheel)
root.bind("<Button-5>", mouse_wheel)

listbox = tk.Listbox(root)
listbox.pack()
for i in range(100):
listbox.insert(tk.END, str(i))

root.mainloop()

Can you post your code please (if it's too long, strip it down to
the smallest program which still shows the problem.)

On Ubuntu 10.04, Python 2.6.5, the Listbox already recognizes the
mouse wheel. Listbox aside, the following works here:


import Tkinter as tk

def wheel_up(event):
print "wheel_up", event

def wheel_down(event):
print "wheel_down", event

root = tk.Tk()
root.bind("<Button-4>", wheel_up)
root.bind("<Button-5>", wheel_down)
root.mainloop()

First, thanks to MRAB for showing me how to get the wheel working.

In the following code (Windows only), rolling the wheel doesn't invoke
the event method. If I change the mouse wheel binding to
self.master.bind... the event gets called and the scrolling works.
Note that the scrolling occurs even when the mouse is outside the
listbox. I guess I'll have to look at the mouse position when I enter
the wheel_event method to see if the mouse is over the listbox.

# mouse wheel in listbox
import Tkinter as tk

class Application(tk.Frame):
def __init__(self, master=None):
tk.Frame.__init__(self, master)
self.grid()

self.button = tk.Button(self, text='Button')
self.button.grid(row=0, column=0)

self.yscroll = tk.Scrollbar(self, orient=tk.VERTICAL)
self.yscroll.grid(row=1, column=1, sticky=tk.N+tk.S)
self.list = tk.Listbox(self, selectmode=tk.SINGLE, width@,
height=5,
yscrollcommand=self.yscroll.set)
self.list.grid(row=1, column=0, sticky=tk.N+tk.S+tk.E+tk.W)
self.yscroll["command"] = self.list.yview
self.list.bind("<MouseWheel>", self.wheel_event)
for i in xrange(10):
self.list.insert(tk.END, 'line ' + str(i))

def wheel_event(self, evt):
lines = evt.delta // 120
self.list.yview_scroll(-lines, tk.UNITS)

root = tk.Tk()
root.geometry('300x300+400+200')
root.title(' Wheel Test')
app = Application(master = root)
root.mainloop()