Re: report a programming error when trying to align on empty parent(issue 7533046)

[Trevor Daniels]

address@hidden wrote Saturday, March 23, 2013 3:44 PM

> If i got everything right, you'll see in that explanation that an empty
> extent isn't harmful (at least in self-alignment) - it just results in
> offset being 0.
> So, the question is: in general, is it ok if a grob has empty extent?
> Or should extent always be some Interval (possibly zero)?
> In other words: if an alignment method is called on an empty grob (see
> example below), should it just say "well, i received an empty object, so
> what?  I can't do anything with it, so i'll move on", or shout "hey,
> there are empty grobs flying around!  Do something about it!".
> 
> Example: if we override grob's stencil to #f, the extent will be #f as
> well:
> 
> \version "2.17.12"
> { c' e' f' d' }
> \addlyrics { la le \override LyricText #'stencil = ##f li lo }
> 
> - the above code reports "programming error: cannot align on self: empty
> element".  Do we consider above code (and the use of \omit as currently
> defined) a good practice?  

A 'programming error' should be issued only when an internal inconsistency
in LilyPond's code or data structures is detected.  Any such message should
always result in a bug being reported and tracked.  If the problem is due to
suspect user code a warning or error should be issued.  In this case maybe
a warning is appropriate.

Trevor