[luatex] the son of trouble in the output routine.

[Taco Hoekwater]

Taco Hoekwater wrote:
> Paul Isambert wrote:
>> Damn. I forgot to mention one important thing: if you turn the 4-line 
>> paragraph into a 5-line one, i.e. if you kill the widow, everything 
>> works fine (the title appears after the paragraph, etc.)
>> Paul
> 
> Thanks for the report, I will look into this.

Found and fixed (took me a long time to find it). The bug was introduced
during commit #3417: * Some experimental tweaking of buildpage_filter.

What this experiment actually did was: it split the adding of a new
(line) box to the vertical list into separate steps for

a. the already waiting contributions
b. any \adjust pre stuff from the box
c. the box
d. any \adjust stuff from the box

This split introduced extra calls to the page builder, which then
resulted in the bug. So, the experiment is now reverted.

Best wishes,
Taco