different behavior of hb_ft_font_set_funcs vs hb_ot_font_set_funcs in vertical, one of them is broken

[HinTak]

288 vs 216 is a lot of difference - one of them is broken (actually I know which one...):

hb-view --font-funcs=ft --direction=ttb  -o a.png -O png  msmincho.ttc   '《日本ょ》'
$ file a.png
a.png: PNG image data, 288 x 1312, 8-bit grayscale, non-interlaced

$ hb-view --font-funcs=ot --direction=ttb  -o a.png -O png  msmincho.ttc   '《日本ょ》'
$ file a.png
a.png: PNG image data, 216 x 1312, 8-bit grayscale, non-interlaced

[khaledhosny]

Duplicate of #537.

[khaledhosny]

Reopening per #537 (comment)

[HinTak]

Here is from the latest code (49bdb54):

ft:

ascender/descender/line_gap= 128 -128 0
h ascender/descender/line_gap= 256 -64 -64
v ascender/descender/line_gap= 0 0 0

ot:

ascender/descender/line_gap= 220 36 0
h ascender/descender/line_gap= 220 -36 0
v ascender/descender/line_gap= 220 36 0

The values from the ft routines seems to be the behaving one. The md5sum of the font used is:

ea3f8835f67b492a0740ac34e1e807f8  msmincho.ttc

I seem to have a case of the opposite situation , with horizontal layout and mongolian/phags pa. I guess I'll file a different bug if I need to.

[HinTak]

Note the sign swap of the descender from -36 to +36 in the ot funcs output - the groups of 3 lines are from get_font_extents(..., direction), get_h_extents and get_v_extents, btw.

[behdad]

ascender/descender/line_gap= 220 36 0 h ascender/descender/line_gap= 220 -36 0 v ascender/descender/line_gap= 220 36 0

What are these printouts of?

[behdad]

So, msmincho has descent -36 in hhea table and +36 in vhea table. That's what HB is returning. One can argue that the way vhea descent is written is consistent with it needing a negation... FreeType doesn't seem to use that value whatsoever.

I like to see the values in a few other fonts before doing anything here.

[behdad]

NotoSansCJK-Regular has, in hhea:

    <ascent value="880"/> 
    <descent value="-120"/> 
    <lineGap value="500"/> 

and vhea:

    <ascent value="500"/> 
    <descent value="-500"/> 
    <lineGap value="500"/> 

This is consistent with what I would have expected.

@kenlunde have you seen the issue in previous comment in many fonts?