It looks like the Mac client is already doing this and it's clearly the trend in other apps as well. Even apt-get is using kB/s, ferchrissake... :)
Flame away.
Use gtk_tree_model_iter_nth_child() instead of gtk_tree_model_get_iter_first() to avoid an unnecessary gtk_tree_path object being created and destroyed. This is a very minor change and I'm not sure how useful it really is, but it doesn't hurt.
According to the GTK+ documentation, this "can be an advantage in situations where resizing the label because of text changes would be distracting, e.g. in a statusbar." It doesn't seem to prevent relayout in GTK+ 2.20.1, but maybe other versions of GTK+ will make better use of the flag.
The main window called gtk_tree_model_filter_refilter() once per second to refresh the torrent list's filtering. This is not an efficient approach: gtk_tree_model_filter_refilter() emits a "row changed" event for every row, causing unnecessary re-rendering.
I've removed the call to gtk_tree_model_filter_refilter() and expanded the model to includes all the fields necessary for filtering. That way we only fire "row changed" events for rows that actually change.
By reducing the number of renders in steady state, this might ameliorate https://bugs.launchpad.net/ubuntu/+source/transmission/+bug/655024
However it will *not* help the related "CPU spikes to 100% on scrolling" ticket at https://trac.transmissionbt.com/ticket/3887 because rendering paused torrents is still exceptionally expensive in the murrine theme.
Some of the refresh events to the main window's torrent list are caused by main window relayout caused by the toolbar's GtkLabels recalculating their size after being updated once per second. To prevent relayout in some trivial cases, I'm replacing the gtk_label_set_text() calls with gtr_label_set_text() because the latter doesn't update the label widget if the old and new text strings are the same.
There are other changes that can handle more important cases -- I'll test those out next.
The Berne Convention says that the copyright year is moot, so instead of adding another year to each file as in previous years, I've removed the year altogether from the source code comments in libtransmission, gtk, qt, utils, daemon, and cli.
Juliusz's copyright notice in tr-dht and Johannes' copyright notice in tr-lpd have been left alone; it didn't seem appropriate to modify them.
