Improve play buttons and the playlists they load

[oskarrough]

We use <r4-play-button> in different contexts. On channels, on cards, on track page, on a track list item. Our play() method accepts channel, tracks and track.. Depending on the combination, we load a certain playlist in the player.

It doesn't feel quite right what we do at the moment. I'd like to review it and see if it can feel more natural.

Question 1

On the channel page we show a list of most recent tracks. Should playing load all tracks, or just the recent ones?

Question 2

Another example, when filtering on /tracks and you play a track, does it update the playlist to the current filter?

Related #125

[oskarrough]

For 1) it should load all tracks, at least that's what I would expect.

For 2) it depends. There are three ways you can play on that page:

• "play selection" button (should set tracks to the current filtered tracks)
• "play all" button (should reset tracks back to all)
• "play" button on a track (should not set tracks, but keep current player.tracks. if no tracks, load all?