Frescobaldi external PDF viewer not updating

[Andrew Bernard]

HI Keiren,

I have unhijacked the thread with a new subject.

OK.  Mac up and running:

Mac OS 10.13.4
Frescobaldi 2.20.0
Lilypond 2.19.80
Skim 1.4.34

All works fine. I am unable to duplicate your problem. I do note that I have 
explicitly turned on 'check for file changes' and 'reload automatically' in the 
Sync tab of Skim preferences.

Preview seems erratic.

I am loading the named output file.

Speaking as UNIX programmer with 40 year plus experience, I would tend not to 
rely on loading a temp file autogenerated, Who knows how this is implemented? 
The tmp file may not be fully written out to disk by the time the PDF viewer 
looks at it as this can be asynchronous and so on, and updates may be missed. 
Writing this down I am aware this sounds like nonsense, but the fact is that 
tmp files can have different semantics to disk files and you just don’t know 
enough about how it all works. Sometimes tmp file systems are in RAM and this 
can change things in subtle ways. Given this, it sounds dodgy to me to be 
reading the temp file into a viewer. I know that Mac writes to /var/folders but 
again I do not know enough about how these files are buffered to disk to be 
prepared to be using these as an authoritative source for the PDF viewer. I 
think this goes partly toward explaining the erratic behaviour you are seeing. 
Restarting F obviously works because all is redone afresh. Then after a while 
it will go bung again.

Andrew