[PATCH v2 6/7] shell32/autocomplete: Use the optional IACList interface and IACList::Expand, if available

[Gabriel Ivăncescu]

On Mon, Oct 15, 2018 at 1:15 PM Huw Davies <huw at codeweavers.com> wrote:
>
> This is going to need some work; trying to follow this code is just too hard.
>
> Huw.

The expand method gets called with the path ending in a slash, but
only if it's needed (the tests show this). For example, if the text is
a\b\c\d and the previous text was a\b\c\e, there's no expansion as
both would expand to a\b\c\ and Windows doesn't do it redundantly
(this is needed for things like paste or replacing selections to work
correctly, we can't just keep track of last character input, again,
the tests show this with selection deletions and caret movements and
others).

Now what the code does is 3 "stages". First it skips all the shared
prefix (case insensitively). So basically the beginning of both
txtbackup and the new txt are skipped if identical (and stops where
they mismatch). At this point we know all characters before i (the
mismatch pos) are identical so no need to check them.

Then, starting from the mismatch position, it looks for a delimiter in
the new text. If it finds one, obviously, it will look for the last
delim and expand the whole text up to that last delim (since they
differ).

If it doesn't find one, it checks if txtbackup (the old text) has a
delim after they mismatch, because if they don't, it means they only
differ by non-delim characters, so no expansion is needed. (e.g.
a\b\c\foo and a\b\c\bar don't need any expansion)

But if there is a delim in txtbackup (e.g. a\b\c\foo and
a\b\c\bar\baz), we need to find the last delim in the shared prefix,
so it scans backwards for the first delim (in this case, to expand
a\b\c\ since otherwise a\b\c\bar\ was expanded before).

I know I could comment it better, but I don't want to be too verbose
so some advice would be appreciated.