Celluloid becomes unresponsive when opening or enqueuing many (200+) files

[estorok]

Overview Description: Celluloid takes a very long time to open or enqueue a playlist of many files (200+) and become responsive again. Also, the video timestamp / scrubber bar spends a long time erratically jumping between 0:00 and the current video time.

timestamp-issue.webm

Steps to Reproduce:

1. Open an instance of celluloid
2. Enqueue 1000 video or audio files with celluloid --enqueue

Actual Results:
Celluloid is unresponsive for about 20 seconds. Then, audio starts playback. Another 10 seconds later, images appear. Another 10 seconds later, the main window is mostly responsive.

Expected Results:
Celluloid begins playback and becomes responsive within a couple seconds.

Version: 0.24, also git master.

Additional Information:
I have changes that I think fix the issue. (a777a7e) I will submit a pull request. Essentially there are two handlers, playlist_handler and metadata_cache_update_handler that seem to run once for every loaded file, except the playlist update that they call itself builds every playlist entry for the widget from scratch using the internal playlist. So opening multiple files is O(n^2) in the number of files when it should only be O(n).

[jannuary]

With regards to the playlist panel, we should consider switching to the ListView widget instead of a ListBox, since that handles large variable lists of items better, while the ListBox has a cap on 200ish items.
Amberol uses that and handles my entire music folder without a sweat, while displaying thumbnails and metadata: