Thanks for the deeper details. The example code I've looked at (pango
and firefox) do not use the unset call. I know your time is limited, and
I appreciate the info.
Deron
On 2/1/11 12:03 PM, Behdad Esfahbod wrote:
On 02/01/11 09:56, Tom Hacohen wrote:
Dear all,
I ran a test application in callgrind and noticed that the calls to
FT_Load_Glyph are what slows everything down. We already have glyph
cache in EFL and I would really like to be able to use it with harfbuzz.
At first glance, it seems like I can't override harfbuzz's
hb_ft_get_glyph_advance from the outside, but I have to implement my own
class and put it in harfbuzz, which is less than convinient.
The way this is supposed to work is that you create your own font callbacks
that *wrap* the original ones. You
hb_font_funcs_t *new_funcs, *orig_funcs;
hb_destroy_func_t orig_destroy;
void *orig_user_data;
new_funcs = hb_font_funcs_create ();
/* set funcs in new_funcs */
hb_font_unset_funcs (font,&orig_funcs,&orig_destroy,&orig_user_data);
/* save orig_funcs, orig_destroy, and orig_user_data in new_user_data */
hb_font_set_funcs (font, new_funcs, new_user_data, new_destroy);
Then in your callbacks, you can use orig_funcs and orig_user_data to call into
harfbuzz to get the value, and cache it.
I'm not quite satisfied with this scheme. The problem with it is that if/when
new callbacks are added to hb_font_funcs_t, your code needs to be updated to
relay those. Would have been much nicer if they falled through automatically
(so you could in essence really subclass a font_funcs_t). I'll think more
about it to see if I can make that happen.
behdad
I'd very much like to be able to do that, because using my cache will
make everything a lot faster.
Are my observations correct?
How do you guys (that use harfbuzz in other projects) solve it?
Thanks,
Tom.
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