[HarfBuzz] Mixing HB_SCRIPT_INVALID with HB_SCRIPT_HANI in TTB direction

[Eduardo Castiñeyra]

Hi,

I have a run of text consisting of three japanese Kanjis and one CJK 
punctuation symbol (0x3002). I gave HB the whole block and let it guess 
the script with hb_buffer_guess_segment_properties which detects script 
= HB_SCRIPT_HANI

However, the punctuation symbol (a HB_SCRIPT_INVALID symbol), doesn't 
seem to be shaped by the vertical (TTB) direction setting unless I 
modify the script in the properties to HB_SCRIPT_INVALID.

I know we should have separated that run into different scripts but, 
even for a single punctuation symbol ? Also it is a little weird that we 
have to use something called "INVALID" to make it work properly.

Is there any alternative to splitting this paragraph ? I have set the 
whole run as "INVALID", and it works, but it doesn't look very elegant.

Thanks!