Implementing the View menu

Tkinter offers the following three varieties of menu items:

• Checkbutton menu items: These let you make a yes/no choice by checking/unchecking the menu item
• Radiobutton menu items: These let you choose an option from many different options
• Cascade menu items: These menu items only opens up to show another list of choices

The following View menu shows all of these three types of menu items in action:

The first three menu items in the View menu let users make a definite yes or no choice by checking or unchecking them. These are examples of the Checkbutton menu.

The Themes menu item in the preceding screenshot is an example of a Cascade menu. Hovering over this cascade menu simply opens another list of menu items. However, we can also bind a menu item by using the postcommand=callback option. This can be used to manage something just before bringing up the cascading menu item's contents and is often used for dynamic list creation.

Within the cascade menu, you are presented with a list of choices for your editor's theme. However, you can only select one theme. Selecting one theme unselects the previous selection, if any exists. This is an example of the Radiobutton menu.

We will not present the entire code here (refer to the 2.03.py code in the code bundle). However, the example code used to add these three types of menu items is as follows:

view_menu.add_checkbutton(label="Show Line Number", variable=show_line_no)
view_menu.add_cascade(label="Themes", menu=themes_menu)
themes_menu.add_radiobutton(label="Default", variable=theme_name)

Now, we need to track whether a selection has been made by adding a variable, which can be BooleanVar(), IntVar(), or Stringvar(), as discussed in Chapter 1, Meet Tkinter.

This concludes our first iteration. In this iteration, we laid down the majorities of the visual elements of the text editor. Now, it's time to add some functionality to the editor.