"Keith OHara" <k-ohara5...@oco.net> writes:
> On Fri, 13 Dec 2013 23:05:49 -0800, David Kastrup <d...@gnu.org> wrote:
>
>> That does not make sense. If you want call-once behavior, you can just
>> use a callback.
>
> At the moment, the decision on whether to preserve the callback
> pointer in the grob property, or fill the property with the returned
> value, depends on the method used to request the property,
> get_pure_property() versus get_property(). A callback would be called
> multiple times (and it would have to support the unpure-pure calling
> convention).
>
> The information of whether the callback is providing a value that
> /should/ be kept as final is better stored in the Grob itself, so I am
> thinking of ways to reorganize.
>
> The way stencil callbacks are evaluated now is interesting. The
> stencil callback itself is a simple callback, but when the layout
> engine wants to know the size of a stencil it does
> get_pure_property("Y-extent"). Y-extent property is set to either
> execute the stencil callback, or estimate a height without building
> the final stencil, as appropriate for each Grob.
If you are thinking of reorganizing: the current state is a mess.
I still have not figured out what ly:make-simple-closure is supposed to
do.
Most of the contortions seem focused about when or when not and how to
pass begin/end columns. It would seem to make sense to turn them into
dynamic parameters *begin* *end* that you can then query with (*begin*)
and (*end*). If (*begin*) returns ##f, we can assume being in a pure
calculation.
That would seem to get rid of most of the current interface
complications.
--
David Kastrup
_______________________________________________
lilypond-devel mailing list
lilypond-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/lilypond-devel
