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

[Carsten Dominik <carsten.dominik@gmail.com>]

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