Creating a toolbar

We'll start our music player by adding a toolbar with the buttons needed for such software:

• Open a file
• Play
• Pause
• Stop
• Previous/next song
• Remove song from playlist

That'll be a good start for our first non-empty window.

First of all, we'll need some additional import statements:

use gtk::{
    ContainerExt,
    SeparatorToolItem,
    Toolbar,
    ToolButton,
};

Then, we'll declare a constant because we'll use this value elsewhere:

const PLAY_STOCK: &str = "gtk-media-play";

We'll explain what this is very soon.

We'll now create a toolbar and add it to the window:

fn main() {
    // Same code to initialize gtk, create the window.
    application.connect_startup(|application| {
        // …

        let toolbar = Toolbar::new();
        window.add(&toolbar);

Note: Don't call window.show() yet...