According to bug 325159, Ctrl+Click should unselect the selected item in a richlistbox. The keyboard equivalent to this is Ctrl+Space which in this case doesn't work. OTOH listbox doesn't allow an item to be deselected (nor does tree nor does HTMLSelect) in single-select mode.
Should this behavior really be expected of richlistbox, Ctrl+Space must be added. However I'd rather vote for listbox/tree/HTMLSelect consistency and remove Ctrl+Click - since this is no necessary functionality for the Extensions/Themes/Downloads managers and since in the future it might be desirable to force a richlistbox to have one (and only one) item selected - as currently done by HTMLSelect on e.g. this "Enter Bug" page for component selection (think listbox as radio options vs. listbox as checkbox options).
If however Ctrl+Space should be added, please file a seperate bug for listbox for adding the same functionality (since I currently don't see substantial enough a difference between listbox and richlistbox for allowing such unexpected differences). Of course, I'm biased - I wrote the patch for bug 298371 to make richlistbox inherit directly from listbox for improved feature parity.
I'm replying to your comment in bug 325159 here, since that bug is closed up and the relevant place for discussion is here.
IMO, the Ctrl+click behavior to deselect is perfectly consistent. <richlistbox> doesn't support multiple selection; however, <listbox> does support multiple selection, and you do use Ctrl+click to both select and deselect items. So, to me, it logically follows that Ctrl+click would deselect the selected item in <richlistbox>, its lack of multiple selection support notwithstanding.
How useful is it to deselect a richlistitem? Admittedly, not very. However, the code is there and, I agree, that <richlistbox> and <listbox> should work as similarly as possible. So, I think that Ctrl+space should be added as a way to deselect a <richlistitem> on top of the Ctrl+click functionality. As I see it, that would be the most consistent implementation.
And thank you for being willing to address this issue in your next version of Console², as unimportant as it may be.
To make the point clear: listbox does support item deselecting only in multiple-select mode and *not* in single-select mode. For consistency, I'd expect the same behavior of richlistbox (where multiple-selection is coming in the mentioned bug 298371).
And should you add Ctrl+click deselecting, you'd severly hinder the mentioned functionality of using (rich)listboxes as a radio-style element. IMO this is not worth it.
Can the bug be closed?
WORKSFORME as of 2007-01-17 thanks to the fix for bug 298371.