Adding a playlist

We're now ready to add the playlist widget to our music player.

We'll use new crates, so add the following to the main.rs file:

extern crate gdk_pixbuf;
extern crate id3;

The crate gdk_pixbuf will be used to show and manipulate the cover and the id3 crate to get the metadata from MP3 files.

Also, add the following to Cargo.toml:

gdk-pixbuf = "^0.3.0"
id3 = "^0.2.0"

Next, we'll create a new module to contain this new widget:

mod playlist;

We'll start this module by adding a bunch of use statements:

use std::path::Path;

use gdk_pixbuf::{InterpType, Pixbuf, PixbufLoader};
use gtk::{
    CellLayoutExt,
    CellRendererPixbuf,
    CellRendererText,
    ListStore,
    ListStoreExt,
    ListStoreExtManual,
    StaticType,
    ToValue,
    TreeIter,
    TreeModelExt,
    TreeSelectionExt,
    TreeView,
    TreeViewColumn,
    TreeViewColumnExt,
    TreeViewExt,
    Type,
    WidgetExt,
};
use id3::Tag;

These will be followed by some constants:

const THUMBNAIL_COLUMN: u32 = 0;
const TITLE_COLUMN...