[luatex] LuaTeX v1: Two questions from testing

[Joseph Wright]

On 13/10/2016 09:51, Hans Hagen wrote:
> On 10/13/2016 8:33 AM, Joseph Wright wrote:
>> Hello,
>>
>> Testing LuaTeX v1, there are relatively few changes from v0.95. However,
>> I've found one logging (?) change and one hyphenation change I didn't
>> expect. With example
>>
>>     \hsize 15em
>>     This is a supercalifragilisticexpialidocious%
>>      \hbox to 1em{}
>>      sentence.
>>     \tracingall
>>     \belowdisplayskip=0pt %
>>     $$
>>     y = mx + c
>>     $$
>>      \bye
>>
>> The results are different from pdfTeX in two ways. The empty \hbox does
>> not prevent hyphenation, which it has to-date (so this is not a result
>> of other hyphenation changes). The log also lacks the zero skip after
>> the display.
>>
>> It's not clear to me if either of these changes is deliberate: what's
>> the situation?
> 
> The criteria for not hyphenating are somewhat arbitrary esp since
> engines started adding features (literals, whatsits, etc). So, why stop
> at a whatsit that in fact could be a box (ximage) but not at a hbox and
> what about rules (ximages are no longer whatsits but a kind of rule). So
> this is what happens now:
> 
> \hyphenationbounds:
> 
> 0 : not strict
> 1 : strict start
> 2 : strict end
> 3 : strict start and strict end
> 
> So the rules are (i'll add the next info to the manual):
> 
> start:
> 
> boundary  : yes when wordboundary
> hlist     : when hyphenationbounds 1 or 3
> vlist     : when hyphenationbounds 1 or 3
> rule      : when hyphenationbounds 1 or 3
> dir       : when hyphenationbounds 1 or 3
> whatsit   : when hyphenationbounds 1 or 3
> glue      : yes
> math      : skipped
> glyph     : exhyphenchar (one only) : yes (so no -- ---)
> otherwise : yes
> 
> end:
> 
> boundary  : yes
> glyph     : yes when different language
> glue      : yes
> penalty   : yes
> kern      : yes when not italic (for some historic reason)
> hlist     : when hyphenationbounds 2 or 3
> vlist     : when hyphenationbounds 2 or 3
> rule      : when hyphenationbounds 2 or 3
> dir       : when hyphenationbounds 2 or 3
> whatsit   : when hyphenationbounds 2 or 3
> ins       : when hyphenationbounds 2 or 3
> adjust    : when hyphenationbounds 2 or 3
> 
> So you can decide to default to \hyphenationbounds=3
> 
> Hans

Thanks: works as you suggest.

Joseph