Juri Linkov wrote:
> There is a task in etc/TODO:
> 
>   ** Compilation error navigation bar, parallel to the scroll bar,
>   indicating where in the buffer there are compilation errors.
>   Perhaps we could arrange to display these error indications on top
>   of the scroll bar itself.  That depends on to what extent toolkit
>   scroll bars are extensible.
> 
> If it's possible to display such tab-like indications
> on the scroll bar, is it still called a scroll bar?
> 
> If it's not possible, then what is an alternative?
> Maybe, 1-column side bar windows?

WinMerge and KDiff3 have a "sort of" scrollbar with transparent thumb
used to indicate (and jump to) the regions with differences.

See picture.