Combobox

A combobox widget combines an entry with a list of choices. This lets users either choose from a set of values you've provided (e.g., typical settings), but also put in their own value (e.g., for less common cases).

Combobox widgets

Comboboxes are created using the ttk_combobox command:

#![allow(unused)]
fn main() {
parent.add_ttk_combobox( "country" -textvariable("country") )?;
}

Like entries, the textvariable option links a variable in your program to the current value of the combobox. As with other widgets, you should initialize the linked variable in your own code.

A combobox will generate a event::virtual_event( "ComboboxSelected" ) that you can bind to whenever its value changes. (You could also trace changes on the textvariable, as we've seen in the previous few widgets we covered. Binding to the event is more straightforward, and so tends to be our preferred choice.)

#![allow(unused)]
fn main() {
country.bind( event::virtual_event( "ComboboxSelected" ), script )?;
}

Predefined Values

You can provide a list of values that users can choose from using the values configuration option:

#![allow(unused)]
fn main() {
country.configure( -values([ "USA","Canada","Australia" ].as_slice() ))?;
}

If set, the TtkState::ReadOnly state flag will restrict users to making choices only from the list of predefined values, but not be able to enter their own (though if the current value of the combobox is not in the list, it won't be changed).

#![allow(unused)]
fn main() {
country.set_state( TtkState::ReadOnly )?;
}

If you're using the combobox in TtkState::ReadOnly mode, I'd recommend that when the value changes (i.e., on a event::virtual_event("ComboboxSelected")), that you call the selection_clear method. It looks a bit odd visually without doing that.

You can also get the current value using the get method, and change the current value using the set method (which takes a single argument, the new value).

As a complement to the get and set methods, you can also use the current method to determine which item in the predefined values list is selected. Call current with no arguments; it will return a 0-based index into the list, or -1 if the current value is not in the list. You can select an item in the list by calling current with a single 0-based index argument.

Want to associate some other value with each item in the list so that your program can use one value internally, but it gets displayed in the combobox as something else? You'll want to have a look at the section entitled "Keeping Extra Item Data" when we get to the discussion of listboxes in a couple of chapters from now.

Run Example

cargo run --example combobox