advanced text editor

from guizero import App, TextBox, PushButton, Box, Combo, Slider, MenuBar, CheckBox, info

app = App(title="Colins Text Editor")


# function for reading files
def opt_darkmode ():
    if darkmode.value == True:
        app.bg = "black"
        app.text_color = "white"
    else:
        app.bg = "white"
        app.text_color = "black"

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)
    save_button.disable() # disables the save button after saving
    btn_ltr_cnt.disable() # enables the letter count button

def enable_save():
    save_button.enable() # enables the save button
    btn_ltr_cnt.enable() # enables the letter count button

def change_font():
    editor.font = font.value

def exit_app ():
    if save_button.enabled == True:
        app.warn("Your Attention please!", "You have not saved the changes")
    else:
        app.destroy()

def change_font_size():
    editor.text_size = txtsize.value
    # resize the widget because if the text is made bigger, this might affect the size of the TextBox so guizero needs to know how to maintain the intended layout
    editor.resize(1, 1)
    editor.resize("fill", "fill")

def change_font_colour():
    editor.text_color = txtcol.value

def count_letters():
    ltr_cnt.value = len(editor.value)-1

menubar = MenuBar(app, toplevel = ["File","Font","Count"],
            options = [
            [["open", open_file], ["save", save_file], ["exit", exit_app]],
            [["size", change_font_size],["colour", change_font_colour],["style",change_font]],
            [["count", count_letters]]
            ])



# create a box to house the controls, we want the box to span the entire width of the app

file_controls = Box(app, align="top", width="fill")

# a padder to pull it away form the edge
pad = Box(file_controls,align = "left", width=5, height=5)

# preference controls
pref_controls = Box(app,align="bottom",width = "fill", border = True)

#change font
font = Combo(pref_controls,options=["courier", "times new roman", "verana","arial"], align="left", command=change_font)
# change font size
txtsize = Slider(pref_controls, start = 8, end = 30, command = change_font_size, align = "left")
#change font colour
txtcol = Combo(pref_controls, options=["green","blue","black","grey"], command = change_font_colour, align = "left")
#count number of letters
ltr_cnt = TextBox(pref_controls, align ="left")
btn_ltr_cnt = PushButton(pref_controls, command= count_letters, text = "Count", align ="left", enabled = False )
#enable / disable dark mode
darkmode = CheckBox(pref_controls, text = "darkmode", command = opt_darkmode, align="left")

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

# create a save button which uses the save_file function
save_button = PushButton(file_controls, text="Save", command = save_file,  align="right", enabled = False)

# create an open button which uses the open_file function
open_button = PushButton(file_controls, text="Open", command = open_file, align="right")

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



app.display()