Re: Bug: Recurring items NEVER show up in timeline unaccompanied

[Nick Dokos <nicholas.dokos@hp.com>]

Carsten Dominik <carsten.dominik@gmail.com> wrote:

> Dear all,
> 
> Maybe I can add the following background information to Nick's
> amazing analysis.

I wouldn't call it "amazing", but thanks for the kind words!

> 
> - The timeline was the first agenda-like view I implemented,
>   it used to be (many years ago) the only way to see what was
>   coming up.  That is why it only listed the future, and included
>   the past when used with e prefix argument (I believe).
> 
> - Since then the agenda view came along, with vastly better
>   properties for being used as a planning tool for the coming
>   day an d week.  It also included the possibility to look
>   at several files, which made the timelines view of a single
>   file look poor.  Since then, the timeline has been a more
>   or less orphaned feature, and this is why it does not
>   work well with stuff like repeaters (repeaters where added
>   MUCH later).
> 
> - So the use-case of the timeline view became slowly redefined
>   as a way to look at the milestones and events of a single
>   project.  One consequence was to always include the past.
> 
> - For historic reasons, the timeline uses the same mechanics
>   as the agenda:  Pick a date, find everything that is going
>   on on that date, move on to the next date.  Lather, rinse,
>   repeat.  However, when looking at a project that may have
>   dates spread over potentially many years, this mechanics
>   is not very practical.  First, there will be many empty
>   days where nothing is going on.  This will make the view
>   look very boring and will make it hard to find useful
>   dates.  Second, constructing the view in this way
>   takes forever because of the inefficient pick-a-day,
>   scan-entire-file-to-see-what-fits-strategy.
> 
> - To makes things more efficient, the timeline starts by
>   first making a list of relevant days in the project by
>   looking at all explicit dates, and at ranges.  Here is
>   where the repeaters go wrong - they should return a whole
>   list of dates where they are important - but they only
>   add one, the starting date.  With this list of dates,
>   it knows how to skip ranges of dates where nothing is
>   happening.
> 

A very interesting history lesson: thanks very much for that.

> Solutions for this problem are (these are alternatives)
> 
> 1. Be satisfied with the way things are, just realize that
>    repeaters only show up on the first date when the
>    event happens for the first time.
> 
> 2. Use the agenda, restricted to a single file, for a time
>    range you specify.  This has the advantage that also
>    diary sexps will work properly - the timeline currently
>    has no way to deal with these.
> 
> 3. Change the section of the timeline code that produces
>    the list of interesting dates.  One strategy could be
>    to first make a list of explicit dates, in order to
>    define an overall range.  Then find all repeaters and
>    add dates this repeater targets, restricted to
>    the range of explicit dates in the file.  If done
>    like this, you could always put a target date
>    for conclusion of the project into the file, and that
>    far-into-the-future date would define the range of
>    the repeaters automatically.
> 
> 4. Define a variable that will make the timeline always
>    look at *every* date in the range covered by the
>    file.  And live with the fact that constructing the
>    view might take long.  Maybe it will not even to
>    terribly long if you really use this view for single
>    projects.  This would be easy to implement.
> 
> 5. Rebuilt the entire timeline view to not use the
>    agendas mechanics of picking a date, scanning the file,
>    picking a date etc.  Instead, do a single pass over the
>    file and build a list of dates with events in this way
>    and then format and display the list.  Disadvantage
>    here would be that many things which now work easily,
>    like log view to include logging dates, would have to
>    be thought over and reimplemented specially for the
>    timeline.
> 

And a very clear analysis of the situation. In these possibilities,
there is the underlying assumption that the timeline is kept as a
feature. What about the additional possibility of actually declaring it
obsolete and getting rid of it? Can the agenda (possibly with some
extension) cover the need of Mark S for omitting days where nothing
happens?  Is there anything else that the timeline offers?

> Hope this helps.

Extremely helpful, thanks!

Nick