Steve Kemp's Blog Writings relating to Debian & Free Software

TAB completion is hard

Sun, 4 Aug 2013 12:32:38 GMT

I've spent the past few days overhauling the TAB-completion which is included in lumail.

Completing a single token is easy, if there is only one match, and you limit yourself to completing at the start of a line. But doing real completion is hard. Consider the case where you want to complete something like this:

unread_message_colour("re[TAB]

Clearly completing the first part "unread_[TAB]" is simple. But to complete "re" to "red" you need to split up your input line into tokens so that you can recognize a quote as a valid completion point.

Similarly you need to split on "(" to allow:

-- show the path to the editor
msg(edit[TAB]

To allow this to be changed/controlled by the user I defined completion_chars() which contains: SPACE, QUOTE, "(", etc.

I'm pleased with the user-callback for offering completion suggestions, my own is pretty basic and just includes all user-defined functions as well as an address book. The latter allows steve.org.uk[TAB] to complete to: "Steve Kemp" <steve@steve.org.uk> - because we allow matches anywhere in the completion string, rather than just prefix-matching.

I struggled with resolving ambiguities, but now that is handled correctly too. Press "TAB" when there are multiple choices available and you can graphically TAB-through the available choices, or press Esc to cancel.

In conclusion I've spent a few days fighting with user-interface stuff and now the mail-client is better, but I've still to tackle RFC 2047 header decoding because that is really hard!

| 1 comments.

 

Comments On This Entry

[gravitar] 7histle

Submitted at 06:47:06 on 5 August 2013

cool

 

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