bug#47012: xref copies keymap properties to minibuffer

[Dmitry Gutov <dgutov@yandex.ru>]

On 01.04.2021 11:43, Juri Linkov wrote:

>> https://altbox.dev/ack/screenshot.png
>> https://spinorlab.wordpress.com/2015/08/15/the-silver-searcher/
> 
> But all of them display green foreground file names
> with yellow background matches.  This is exactly
> what grep.el does by default, so it's the reason
> why output of grep.el is readable, but output of xref.el is not.

3/4 use something yellow-ish, yes (ripgrep in the console uses red 
foreground, for some reason).

> The problem is that currently in xref both file names and matches
> use the same color green.  The only difference is that file names
> are displayed with green foreground, and matches with green background.

Okay. Guess I haven't experienced that because in my theme highlight 
looks grey-ish. *sigh*

> What causes the difficulty in readability is the effect similar to
> https://en.wikipedia.org/wiki/Stroop_effect that causes the
> delay in reaction time between congruent and incongruent stimuli.
> 
> Using exactly the same grep colors in xref by changing
> 'xref-match' to inherit from the 'match' face
> completely solves this problem.

You are right. I could even say "unfortunately", because IMHO the bright 
yellow highlights are too much. Too strong emphasis, visually.

So let's change it to inherit from 'match', because that's what that 
face is documented to be used for.

Additionally, what do you think about toning down 'match''s background 
color? Maybe use some subtler yellow like "lemon chiffon" or "khaki1"? 
Or "light goldenrod".

ag and deadgrep use some darker khaki tones on the screenshots, but both 
probably assume dark background.

>>> Another suggestion how to remove "visual garbage" is to truncate
>>> duplicate prefixes: currently the prefixes of long absolute file names
>>> are repeated for all file names.  It would improve readability
>>> to display shorter relative file names without duplicate project root part.
>>
>> Please try (setq xref-file-name-display 'project-relative).
> 
> Thanks, I didn't know about this.  Shouldn't this be the default value
> since this is what's displayed by grep and ripgrep.

I wouldn't mind, personally.

> Actually,
> there is no exact option for what grep and ripgrep do,
> because they display file names relative to the search directory.
> But currently there is no xref option to display file names
> relative to the subdirectory specified by 'C-u C-x p g'.

This issue is tricky because xref-find-definitions does not assume the 
presence of a project, or even of any kind of containing directory. And 
yet, it's handy to show its results with relative file names when 
possible, too. So I picked "relative to the project" as the option 
value, and the corresponding logic.

I think what you're talking about is only a problem when the directory 
has no containing project at all. In that case we could probably default 
to the value of default-directory as the reference.

Not sure the logic is applicable to general xref output, though (e.g. 
xref-find-definitions search in a directory with TAGS but without .git). 
So perhaps that behavior should be opt-in, e.g. with an extra arg for 
xref--show-xrefs.

Or just keep it an exception, hoping people don't use 'C-u C-x p g' 
outside of projects often enough for this to be a nuisance.