Show indicators showing where there are trailing spaces on lines. Especially on lines with no text.
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+1 I think this is a nice feature to have.
You can display whitespaces if this helps.
With "Show white space" and "Show line endings" what more is needed?
The idea would be to ONLY show trailing whitespace. I could also imagine setting a nasty looking color/bg color to help you notice bad whitespace.
Ah, yeah, that would be handy, kind of like `git diff` does.
Personally, I always turn on the "Strip trailing whitespace" feature, but it's a bit destructive when working on files where other people have edited it without an equivalent feature in their editor.
P.S. If anyone feels like implementing this, it should probably be added to Scintilla (where other related whitespace display features come from) and then adding a preference in Geany to control it (IMO).
Personally I don't use strip because I like to "keep the indent" in empty lines (shameless plug for a patch that allows that https://github.com/geany/geany/pull/128\). However I show all whitespace so it doesn't really bother me. And it is definitely nice to not destroy other peoples files/whitespace.
Honestly it's not something I would use but something I used to like quite a bit and something that many editors have. It also seems like a useful feature.
Also, it would be nice to have a custom style and ignore empty (except whitespace) lines so that it could be used to highlight trailing whitespace while show whitespace is turned on (make it extra visible).
To take Matthews point and emphasise it, this not only belongs in Scintilla, it almost certainly has to be implemented there. Scintilla is a separate project that Geany (among others) uses. Submit patches to www.scintilla.org.