= TKInter Calc II

== Themed Widgets
Use ttk.button() //etc.// whenever possible. That's because ttk is the newest version. tk.button() and others are old, don't use them unless ttk. doesn't work.

== Binding
For example, you may wish to bind a key to a button. This helps you streamline the control of an application. If you just have two input methods there could be a problem with things like arrows and backspace or delete messing up the calculator window.

<Code:Python>
import tkinter as tk
from tkinter import ttk

def press_eq(event):
    print('Equals key pressed.')

root = tk.Tk()

button1 = ttk.Button(root, text='=')
button1.bind('<KeyPress-Return>', press_eq)


button1.focus()
button1.pack(expand=True)

root.mainloop()
</Code>

=== Binding Mouse
Observe carefully that <Button> and <Button-1> events are both the same event, but one has a specifier. Events such as <KeyPress> and <KeyPress-Enter> are discussed on some sites such as [[https://www.pythontutorial.net/tkinter/tkinter-event-binding/]].

<Code:Python>
import tkinter

root = tkinter.Tk()

def right_click_handler(event):
    # event.num == 2 is MOUSE.
    if event.num == 2:
        print("RIGHT CLICK")

root.bind("<Button-1>", lambda x: print("LEFT CLICK"))
root.bind("<Button>", right_click_handler)

root.mainloop()
</Code>

Here, a lambda is used to handle left clicks with <Button-1> while the more general <Button> handles both left and right, but uses <Code:Python>event.num == 2</Code> to determine right click vs. left click, so it could handle both if needed.

== Dragging
To capture a click-and-drag event use any of the <B1-Motion> (left-click), <B2-Motion> (right click) or <B3-Motion> (middle mouse button click). Note that Note that when dragging outside of an element the event still fires.

<Code:Python>
import tkinter

root = tkinter.Tk()
label = tkinter.Label(root, text="HEY")
label.pack()

def drag_handler(event):
print(event.x, event.y)

label.bind("<B1-Motion>", drag_handler)

root.mainloop()
</Code>

=== Hovering
Hovering over an element sends out two events in sequence, <Enter> and <Leave>

<Code:Python>
import tkinter

root = tkinter.Tk()

label = tkinter.Label(root, text="HELLO", bg="white", fg="navy")
label.bind("<Enter>", lambda event: event.widget.config(bg="navy", fg="white"))
label.bind("<Leave>", lambda event: event.widget.config(bg="white", fg="navy"))
label.pack()

root.mainloop()
</Code>