[HarfBuzz] No kerning?

[Konstantin Ritt]

Did you enable 'kern' feature? Something like that:

            const hb_feature_t features[1] = {

                { HB_TAG('k','e','r','n'), !!kerningEnabled, 0, uint(-1) }

            };

            const int num_features = 1;


            bool shapedOk = hb_shape_full(hb_font, buffer, features,
num_features, 0);



Regards,
Konstantin

2015-10-05 23:32 GMT+04:00 Jamie Dale <jamiedale88+harfbuzz at gmail.com>:

> Hey all,
>
> In our application we have two text shaping backends; a simple "kerning
> only" implementation using our existing font rendering code (fast, but
> can't handle complex languages), and a HarfBuzz based implementation for
> when we need to support complex languages (although ideally the
> HarfBuzz implementation should be able to produce mostly equivalent results
> when compared to our existing font rendering when dealing with languages
> like English).
>
> If you've seen my previous email entitled "Using FreeType load flags",
> then you'll know I'm using some custom font functions to try and ensure
> HarfBuzz uses the correct FreeType hinting flags, as well as cache a lot of
> FreeType calls, and use the correct scale.
>
> So far this has worked out really well, however I've noticed that the
> HarfBuzz implementation isn't applying kerning when shaping English text
> (probably other languages too).
>
> The images below are using the Roboto font, and show the output from each
> implementation.
> The top image is using our "kerning only" implementation, and the bottom
> image is using HarfBuzz. Note that the "T" and "e" characters are further
> apart in the bottom image.
> [image: Inline images 2]
> [image: Inline images 1]
>
> Here's the (slightly cut down) code I'm using to create my HarfBuzz font:
>
> hb_font_t* CreateHarfBuzzFont(FT_Face InFace, const uint32 InGlyphFlags,
> const int32 InFontSize, const float InFontScale)
> {
> hb_font_t* HarfBuzzFont = nullptr;
>
> // Set the character size to render at (needs to be in 1/64 of a "point")
> FT_Set_Char_Size(InFace, 0, InFontSize * 64, 96, 96);
>
> if (InFontScale != 1.0f)
> {
> FT_Matrix ScaleMatrix;
> ScaleMatrix.xy = 0;
> ScaleMatrix.xx = (FT_Fixed)(InFontScale * 65536);
> ScaleMatrix.yy = (FT_Fixed)(InFontScale * 65536);
> ScaleMatrix.yx = 0;
> FT_Set_Transform(InFace, &ScaleMatrix, nullptr);
> }
> else
> {
> FT_Set_Transform(InFace, nullptr, nullptr);
> }
>
> {
> // Create a sub-font from the default FreeType implementation so we can
> override some font functions to provide low-level caching
> hb_font_t* HarfBuzzFTFont = hb_ft_font_create(InFace, nullptr);
> HarfBuzzFont = hb_font_create_sub_font(HarfBuzzFTFont);
> hb_font_destroy(HarfBuzzFTFont);
> }
>
> hb_font_set_funcs(...); // Sets functions that use the user-data below,
> implementations are mostly default, but with a caching layer, and usage of
> FreeType hinting flags
> hb_font_set_user_data(...); // Ensures we have access to InGlyphFlags and
> the low-level caches
> hb_font_set_scale(HarfBuzzFont, InFontScale, InFontScale);
>
> return HarfBuzzFont;
> }
>
> Am I just missing something simple? I tried calling hb_font_set_ppem but
> that didn't seem to make any difference.
>
> Thanks,
> Jamie.
>
> _______________________________________________
> HarfBuzz mailing list
> HarfBuzz at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/harfbuzz
>
>
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