Re: Feature proposal/request: Indentation driven by display engine

[Carsten Dominik]

Hi Stafan,

On May 26, 2008, at 11:02 PM, Stefan Monnier wrote:

> > > Can't you remove the display property when you fold to avoid the  
> > > problem?
> > I could, but then I would have to add and remove text properties  
> > during
> > each fold/unfold, quite some unnecessary overhead.
>
> Not sure how much of an overhead that would be.  Doesn't seem major.
> It might be inconvenient to code, tho.  Is that what you meant?

Yes, mainly this.  There are many show/hide commands, some in outline  
mode, some in Org, I would need to make sure that each time the right  
thing happens.


> > > > It then occurred to me that it might be useful to support
> > > > such a feature directly in the display engine.
> > > > For example, if the line contains text with an `indentation'
> > > > property, the display engine would add this amount of white
> > > > space to before the beginning of the line, maybe also a vertical
> > > > line indicating the location of the margin.
> > >
> > > This property would still need to be added to every line.  So  
> > > basically
> > > all you're asking is a "before-string" text-property, maybe?
>
> > Hmm, nice translation of my request.  Yes, basically what I am
> > asking for is a working before-string text property.  I know
> > that adding the property sounds like a lot of effort, but I could
> > use the font-lock/jit-lock setup to get this done efficiently,
> > only for the pieces that actually get displayed.
>
> The same has been requested for display properties (e.g. to put
> something in the margin without hiding any of the current text, you
> need an overlay).
>
> A `before-string' text-property might be doable, but I couldn't tell  
> you
> how easy it'd be to add.  If someone wants to implement that, I might
> accept it (e.g., as a form of `display' property), but if I were you
> I wouldn't hold my breath (we have enough bugs to fix and are getting
> close to feature freeze).

Sure, I appreciate that.

> The best I can offer for now, is to use overlays which you add via
> jit-lock and which you eagerly remove in the background (so they don't
> accumulate).


Yes, one possible path.
> Well... patches welcome,

In this case, not from me, not clue where to even start.

Thanks.

- Carsten