Re: Fill column indicator functionality

[Mattias Engdegård]

15 mars 2019 kl. 14.00 skrev Alp Aker <address@hidden>:
> 
>> That's a good question.  Indeed, it would be possible to implement
>> this with a single thin line being drawn, but I think such an
>> implementation would have several disadvantages:
>> 
>>  . It will need to be implemented separately for each window-system
>>    (X, w32, NS), and for TTY frames.  By contrast, the implementation
>>    discussed here is in a single place, is independent of the display
>>    kind, and is very simple and localized.
> 
> I believe a simpler implementation is possible:  Where Ergus's implementation 
> uses a char glyph, it could also use a line-height image glyph.

Terminal emulators often treat box-drawing characters specially, either drawing 
the lines themselves or extending parts of the glyphs in case there would be 
gaps. Even XTerm does this, mainly to supplement missing glyphs.

Being its own terminal emulator, Emacs could do the same to avoid gaps in 
horizontal and vertical lines that should connect. Box-drawing characters are 
attractive for use in tables, diagrams and user interfaces, and work in both 
TTYs and window systems. They are sometimes seen in ASCII+ art in source code 
comments.

The details are fairly window-system-specific but do not have to be implemented 
everywhere at once.