[HarfBuzz] hb_buffer_get_glyph_positions() for NotoColorEmoji.ttf

[Takao Fujiwara]

I'd like to get a character width and height and am thinking to use hb_buffer_get_glyph_positions()->x_advance .

I tried hello-harfbuzz with noto-emoji fonts:
https://github.com/behdad/harfbuzz-tutorial/blob/master/hello-harfbuzz.c
https://github.com/googlei18n/noto-emoji/tree/master/fonts

Seems hello-harfbuzz can get x_advance with NotoEmoji-Reqular.ttf but it failed in FT_Set_Char_Size() or FT_Set_Pixel_Sizes() with NotoColorEmoji.ttf.
Even if I ignore the return value of FT_THROW(Invalid_Pixel_Size) from FT_Set_Pixel_Sizes(), seems hello-harfbuzz does not return the accurate x_advance.

Do you have any ideas to resolve it?

I'm using harfbuzz 1.3.2 and freetype 2.6.5 and testing U+1F469.

% ./hello-harfbuzz \
     /usr/share/fonts/google-noto-emoji/NotoColorEmoji.ttf \
     "👩‍"

Seems NotoEmoji-Reqular.ttf is a scalable font and NotoColorEmoji.ttf is a fixed size font.