"Trevor Daniels" <t.dani...@treda.co.uk> writes: > David Kastrup wrote Wednesday, August 24, 2016 7:48 AM > > >> "Trevor Daniels" <t.dani...@treda.co.uk> writes: >> >>> Prompted by the recent discussion on lute tablature, I tried coding a >>> Scheme engraver to create the duration grobs but quickly ran into a >>> problem. I need to collect information from both a Listener and an >>> Acknowledger so the obvious place to build the grob is in >>> stop-translator-timestep, >> >> No, no, no. stop-translator-timestep really is only for cleanup work. >> Stuff is no longer in working order then. You want process-acknowledged >> here I think. >> >> There will always be a call to process-acknowledged whenever grobs have >> been created, and _reading_ stuff from grobs should be delayed until >> then since other acknowledgers might _write_ stuff into a grob even >> after your personal acknowledger has been called. So the basic workflow >> is to use the various acknowledgers to _record_ the grobs you are >> interested in and _write_ stuff into them (or do read/write stuff that >> more or less is accumulative and/or really unrelated to other >> engravers), and then use the process-acknowledged hook for processing >> (including _reading_) the grobs you had recorded. >> >> You can create new grobs in process-acknowledged. That will lead to a >> new cycle of acknowledger calls followed by process-acknowledged. Only >> when all those cycles are over is stop-translator-timestep called, and >> then creating grobs is no longer an option. > > Thanks David. That's beautifully clear, and much better than the rather > terse sentence in the CG which misled me: > > "If useful things are to be done to the acknowledged grobs, this > should be deferred until all the acknowledging has finished, i.e., > store the acknowledged grobs and process the information in a > process-acknowledged () or stop-translation-timestep () function." > > I took what appeared to be the stop-translation-timestep option.
You can still "process" parts of the grob there (if that means just reading out properties and possibly setting context properties based on them) but stop-translation-timestep is a cleanup hook, and other engravers might have already cleaned up stuff you might have wanted to use. And _creating_ grobs in there is clean out since engravers and other code may no longer be in a state where they could process them. -- David Kastrup _______________________________________________ lilypond-devel mailing list lilypond-devel@gnu.org https://lists.gnu.org/mailman/listinfo/lilypond-devel
