[HarfBuzz] Arabic shaping questions

[Deron Kazmaier]

Hi,

Playing with harfbuzz this evening and I'm not getting what I expected. 
The string I am trying to render is:

‎الاثنين ظهرا

And the font I'm using is Frutiger LT Arabic 55 Roman (if some other 
font might work better, I'm happy to try it, but this one worked on Mac 
and Windows in various apps so I figured all was good with it).

hb_buffer_set_direction (hb_buffer, HB_DIRECTION_RTL);
hb_buffer_set_script (hb_buffer, HB_SCRIPT_ARABIC);
hb_buffer_set_language (hb_buffer, hb_language_from_string ("ar"));

Not 100% about the set_language call. That was the best I could suse out.

I've cobbled together my own implementation of the unicode functions, 
and dumped the requests. They match the Unicode database so that is not 
the problem.

Here is the output I have put in. It should be clear what is going on, 
but if not just ask. The important part is that the letters get 
reversed, but no actual joining is performed.

Thanks for any ideas on what I've got going wrong!

Deron

/* calling hb_buffer_add_glyph, number is decimal unicode */
add_glyph 1575
add_glyph 1604
add_glyph 1575
add_glyph 1579
add_glyph 1606
add_glyph 1610
add_glyph 1606
add_glyph 32
add_glyph 1592
add_glyph 1607
add_glyph 1585
add_glyph 1575
get_general_category 1604 (644) ->7 /* decimal unicode, hex unicode, 
general category */
get_combining_class 1604 (644) ->0 /* decimal unicode, hex unicode, 
combing class */
get_general_category 1575 (627) ->7
get_combining_class 1575 (627) ->0
get_general_category 1579 (62B) ->7
get_combining_class 1579 (62B) ->0
get_general_category 1606 (646) ->7
get_combining_class 1606 (646) ->0
get_general_category 1610 (64A) ->7
get_combining_class 1610 (64A) ->0
get_general_category 1606 (646) ->7
get_combining_class 1606 (646) ->0
get_general_category 32 (20) ->29
get_combining_class 32 (20) ->0
get_general_category 1592 (638) ->7
get_combining_class 1592 (638) ->0
get_general_category 1607 (647) ->7
get_combining_class 1607 (647) ->0
get_general_category 1585 (631) ->7
get_combining_class 1585 (631) ->0
get_general_category 1575 (627) ->7
get_combining_class 1575 (627) ->0
get_mirroring 1575 (627) -> 1575
get_mirroring 1604 (644) -> 1604
get_mirroring 1575 (627) -> 1575
get_mirroring 1579 (62B) -> 1579
get_mirroring 1606 (646) -> 1606
get_mirroring 1610 (64A) -> 1610
get_mirroring 1606 (646) -> 1606
get_mirroring 32 (20) -> 32
get_mirroring 1592 (638) -> 1592
get_mirroring 1607 (647) -> 1607
get_mirroring 1585 (631) -> 1585
get_mirroring 1575 (627) -> 1575
get_glyph 1575 -> 275
get_glyph 1604 -> 355
get_glyph 1575 -> 275
get_glyph 1579 -> 287
get_glyph 1606 -> 363
get_glyph 1610 -> 378
get_glyph 1606 -> 363
get_glyph 32 -> 1
get_glyph 1592 -> 331
get_glyph 1607 -> 367
get_glyph 1585 -> 307
get_glyph 1575 -> 275
get_glyph_advance 275: 84352
get_glyph_advance 355: 207040
get_glyph_advance 275: 84352
get_glyph_advance 287: 281536
get_glyph_advance 363: 204544
get_glyph_advance 378: 231552
get_glyph_advance 363: 204544
get_glyph_advance 1: 88896
get_glyph_advance 331: 238272
get_glyph_advance 367: 139840
get_glyph_advance 307: 100160
get_glyph_advance 275: 84352
get_kerning 275 307: 0
get_kerning 307 367: 0
get_kerning 367 331: 0
get_kerning 331 1: 0
get_kerning 1 363: 0
get_kerning 363 378: 0
get_kerning 378 363: 0
get_kerning 363 287: 0
get_kerning 287 275: 0
get_kerning 275 355: 0
get_kerning 355 275: 0

/* hb_shape results */

outputchar 275 (1575) offset:0,0 advance:84352,0
outputchar 307 (1585) offset:0,0 advance:100160,0
outputchar 367 (1607) offset:0,0 advance:139840,0
outputchar 331 (1592) offset:0,0 advance:238272,0
outputchar 1 (32) offset:0,0 advance:88896,0
outputchar 363 (1606) offset:0,0 advance:204544,0
outputchar 378 (1610) offset:0,0 advance:231552,0
outputchar 363 (1606) offset:0,0 advance:204544,0
outputchar 287 (1579) offset:0,0 advance:281536,0
outputchar 275 (1575) offset:0,0 advance:84352,0
outputchar 355 (1604) offset:0,0 advance:207040,0
outputchar 275 (1575) offset:0,0 advance:84352,0