Add kerning toggle for HarfBuzz shaping

Make the "Kerning" track property toggle the OpenType feature "kern".
The old TrueType kerning code won't come back.

3 files changed, 13 insertions, 1 deletions

diff --git a/libass/ass_render.c b/libass/ass_render.c
index 81dadb9..40923ba 100644
--- a/libass/ass_render.c
+++ b/libass/ass_render.c
@@ -1719,7 +1719,6 @@ ass_render_event(ASS_Renderer *render_priv, ASS_Event *event,
     int MarginL, MarginR, MarginV;
     int last_break;
     int alignment, halign, valign;
-    int kern = render_priv->track->Kerning;
     double device_x = 0;
     double device_y = 0;
     TextInfo *text_info = &render_priv->text_info;
@@ -2265,6 +2264,8 @@ ass_start_frame(ASS_Renderer *render_priv, ASS_Track *track,
     else
         render_priv->border_scale = 1.;
 
+    ass_shaper_set_kerning(render_priv->shaper, track->Kerning);
+
     // PAR correction
     render_priv->font_scale_x = render_priv->settings.aspect /
                                 render_priv->settings.storage_aspect;
diff --git a/libass/ass_shaper.c b/libass/ass_shaper.c
index 816674c..802f118 100644
--- a/libass/ass_shaper.c
+++ b/libass/ass_shaper.c
@@ -239,6 +239,16 @@ static void shape_fribidi(ASS_Shaper *shaper, size_t len)
 }
 
 /**
+ * \brief Toggle kerning for HarfBuzz shaping.
+ * NOTE: currently only works with OpenType fonts, the TrueType fallback *always*
+ * kerns. It's a bug in HarfBuzz.
+ */
+void ass_shaper_set_kerning(ASS_Shaper *shaper, int kern)
+{
+    shaper->features[KERN].value = !!kern;
+}
+
+/**
  * \brief Find shape runs according to the event's selected fonts
  */
 void ass_shaper_find_runs(ASS_Shaper *shaper, ASS_Renderer *render_priv,
diff --git a/libass/ass_shaper.h b/libass/ass_shaper.h
index e067d3f..cbfcdd7 100644
--- a/libass/ass_shaper.h
+++ b/libass/ass_shaper.h
@@ -27,6 +27,7 @@
 void ass_shaper_info(ASS_Library *lib);
 ASS_Shaper *ass_shaper_new(size_t prealloc);
 void ass_shaper_free(ASS_Shaper *shaper);
+void ass_shaper_set_kerning(ASS_Shaper *shaper, int kern);
 void ass_shaper_find_runs(ASS_Shaper *shaper, ASS_Renderer *render_priv,
                           GlyphInfo *glyphs, size_t len);
 void ass_shaper_shape(ASS_Shaper *shaper, TextInfo *text_info);