Text Editor with theme and save warning V7

### Text Editor V7 save warning message and cgange theme 06/05/2022
from guizero import App, TextBox, PushButton, Box, Combo, Slider, Text, MenuBar

# A new function that closes the app
def exit_app():
    if text.visible==False:
        text.show()
    else:
        app.destroy()

# function for reading files
def open_file():
    with open(file_name.value, "r") as f:
        editor.value = f.read()

# function for writing files
def save_file():
    with open(file_name.value, "w") as f:
        f.write(editor.value)
        text.hide()

# functions for changing fonts
def change_font():
    editor.font = font.value
def courier_font():
    editor.font = "courier"
def times_font():
    editor.font = "times new roman"
def verdana_font():
    editor.font = "verdana"

def change_text_size():
    editor.text_size = size.value
    editor.resize(1, 1)
    editor.resize("fill", "fill")
    editor.show()

# function for changing text colour
def change_font_color():
    choice = font_color.value
    if choice == "Red":
        editor.text_color = "Red"
    if choice == "Green":
        editor.text_color = "Green"
    if choice == "Blue":
        editor.text_color = "Blue"
    if choice == "Reset":
        editor.text_color = None

# change theme
def change_theme():
    choice = theme.value
    if choice == "Light":
        editor.text_color = "Black"
        editor.bg = "White"
    if choice == "Dark":
        editor.text_color = "White"
        editor.bg = "Black"


app = App(title="texteditor")

menubar = MenuBar(app,
                  # These are the menu options
                  toplevel=["File", "Font"],
                  # The options are file and font style
                  options=[
                      [ ["open",open_file], ["save",save_file], ["exit",exit_app ] ],
                      [ ["courier",courier_font], ["times new roman",times_font], ["verdana",verdana_font ] ]
                  ])

# create a box to house the controls
file_controls = Box(app, align="top", width="fill", border=True)

# create a TextBox for the file name
file_name = TextBox(file_controls, text="text_file.txt", width=50, align="left")

# create a TextBox which is not in the box and fills the rest of the GUI
editor = TextBox(app, multiline=True, height="fill", width="fill")

# create a box to house the controls at the bottom, add a font combobox and size slider
preferences_controls = Box(app, align="bottom", width="fill", border=True)

font = Combo(preferences_controls, options=["courier", "times new roman", "verdana"], align="right", command=change_font)
size = Slider(preferences_controls,  align="right", command=change_text_size, start=8, end=42)
font_color = Combo(preferences_controls, options=["Red", "Green", "Blue", "Reset"], align="left", command=change_font_color)
text = Text(preferences_controls, text="Save changes to this file?", visible=False)
theme = Combo(preferences_controls, align="left", options=["Light","Dark"], command=change_theme)

app.display()