Use Alt+Key for fast alias expansion in index view

[seifferth]

Cf. #31. This commit adds
Alt+Key keybindings to the index view. Pressing Alt+Key will treat
Key as a single letter search alias that is invoked directly without
prompting the user to enter more text. This provides a slightly more
convenient way to switch between frequent queries.

I also decided to keep aliases out of the search history if invoked
via Alt+Key. Having all those implicitly invoked standard searches
in the history would have felt a lot like cluttering it unnecessarily.

[wangp]

Interesting idea. I can't really see a problem with it except that we might want to introduce an Alt key binding one day (probably unlikely), which would potentially conflict with someone's configuration. Well, it would be an easy fix for the user.

Another option is simply a two key sequence, e.g. c x could invoke the search ~x.

[seifferth]

Another option is simply a two key sequence, e.g. c x could invoke the search ~x.

True, but then we do already have a three key sequence that does already this: ~<Key><Enter>.

I can't really see a problem with it except that we might want to introduce an Alt key binding one day (probably unlikely)

True again. But as we don't use Alt yet, I figured that this should be fine for now. As you said, we could still reserve some Alt+Key combinations later on. I don't really think that the need would ever arise, though. Even if we reserve Alt for search term expansion, we are still left with way more unused keys than we should ever need. Also note that this only affects the index view, so Alt is still free for use in all the others.

[wangp]

Merged. Let's try it out.

[seifferth]

Tanks for merging. About commit fc8261f (Restrict Alt+Key to ASCII letters or digits only). I just checked if German non-ASCII characters work with the previous version, and they do. So I am reasonably sure that curses does handle UTF-8 quite well. I guess that the ASCII range should be wide enough anyway, but if this uncertainty is the only reason for the restriction, I'd be happy to take care of testing non-ASCII characters occasionally.

[wangp]

You're right. It was only my intention to filter out control characters, Alt+Backspace, Alt+Enter and so on. I've relaxed it to allow any "printable" character as defined by isprint, which is the same test we use for the text entry module so it should be okay.

[seifferth]

It was only my intention to filter out control characters, Alt+Backspace, Alt+Enter and so on.

That sounds reasonable. I hadn't thought of Enter and Backspace, honestly. Thanks for relaxing the rule.