The scale applied to the hb_font seems to affect how badly this breaks (it's currently less bad, but still broken).
It is possible that I was just never setting the hb_font scale correctly as I was handling scaling internally from my user-data and ignoring the font setting. -Jamie. On 8 May 2017 at 21:15, Jamie Dale <[email protected]> wrote: > Something is definitely causing it to change when the font is scaled > though: > > Scale | x_offset > ~0.666 | 2141 > ~0.832 | 340 > ~1.000 | -1461 > ~1.165 | -3262 > ~1.332 | -5063 > > -Jamie. > > On 8 May 2017 at 20:45, Jamie Dale <[email protected]> wrote: > >> Hey all, >> >> I'm running HarfBuzz 1.2.4 with a modified hb_font implementation based >> on the FreeType implementation in the vanilla version. >> >> One of the differences is that I pass through the FreeType scale as >> user-data and apply it when getting the metrics from FreeType (via >> FT_Set_Transform). >> >> We've been running with this for a while, and haven't noticed any issues >> until today when we tried it with some Thai text and found that the >> hb_glyph_position_t::x_offset was coming back wrong once the text was >> scaled (weirdly this same issue doesn't seem to affect >> hb_glyph_position_t::y_offset). >> >> When the scale is 1, everything is fine, but when the scale is <1 the >> glyph is too far right (suggesting that the offset is too large), and when >> the scale is >1 the glyph is too far left (suggesting that the offset is >> too small). >> >> That would suggest to me that the value I'm getting back hasn't been >> scaled appropriately for the actual FreeType glyph. Unfortunately I'm not >> familiar enough with how HarfBuzz calculates that value to know where that >> lack of scale is happening. >> >> I do notice that there's no FreeType override for the >> set_glyph_h_origin_func from hb_font. Could that be the issue? >> >> The Thai text being used is ฝึ (U+0E1D, U+0E36) and the font is Tahoma >> (available in Windows). >> >> Has anyone else attempted something like this? >> >> Thanks, >> Jamie. >> > >
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