font: ignore bearing for strikes

This is more robust and simpler. The bearing calculations initially
were bugged, but getting rid of them completely seems better. It is
consistent with other text renderers as well. To simplify things, also
move striking before the additional scale is applied and get rid of the
half-pixel overlapping thing; it is not needed with additive blending.

Fixes #193.

diff --git a/libass/ass_font.c b/libass/ass_font.c
index 67f8eec4102447d8ad11db3b98ac7e353939976e..b97567f11a4d3bd0b11c3b72ce426a96d1640375 100644 (file)
--- a/libass/ass_font.c
+++ b/libass/ass_font.c
@@ -375,7 +375,7 @@ static int ass_strike_outline_glyph(FT_Face face, ASS_Font *font,
     TT_OS2 *os2 = FT_Get_Sfnt_Table(face, ft_sfnt_os2);
     TT_Postscript *ps = FT_Get_Sfnt_Table(face, ft_sfnt_post);
     FT_Outline *ol = &((FT_OutlineGlyph) glyph)->outline;
-    int bear, advance, y_scale, i, dir;
+    int advance, y_scale, i, dir;
 
     if (!under && !through)
         return 0;
@@ -394,11 +394,7 @@ static int ass_strike_outline_glyph(FT_Face face, ASS_Font *font,
     if (!ASS_REALLOC_ARRAY(ol->contours, ol->n_contours + i))
         return 0;
 
-    // If the bearing is negative, the glyph starts left of the current
-    // pen position
-    bear = FFMIN(face->glyph->metrics.horiBearingX, 0);
-    // We're adding half a pixel to avoid small gaps
-    advance = d16_to_d6(glyph->advance.x) + 32;
+    advance = d16_to_d6(glyph->advance.x);
     y_scale = face->size->metrics.y_scale;
 
     // Reverse drawing direction for non-truetype fonts
@@ -406,24 +402,23 @@ static int ass_strike_outline_glyph(FT_Face face, ASS_Font *font,
 
     // Add points to the outline
     if (under && ps) {
-        int pos = FT_MulFix(ps->underlinePosition, y_scale * font->scale_y);
-        int size = FT_MulFix(ps->underlineThickness,
-                             y_scale * font->scale_y / 2);
+        int pos = FT_MulFix(ps->underlinePosition, y_scale);
+        int size = FT_MulFix(ps->underlineThickness, y_scale / 2);
 
         if (pos > 0 || size <= 0)
             return 1;
 
-        add_line(ol, bear, advance, dir, pos, size);
+        add_line(ol, 0, advance, dir, pos, size);
     }
 
     if (through && os2) {
-        int pos = FT_MulFix(os2->yStrikeoutPosition, y_scale * font->scale_y);
-        int size = FT_MulFix(os2->yStrikeoutSize, y_scale * font->scale_y / 2);
+        int pos = FT_MulFix(os2->yStrikeoutPosition, y_scale);
+        int size = FT_MulFix(os2->yStrikeoutSize, y_scale / 2);
 
         if (pos < 0 || size <= 0)
             return 1;
 
-        add_line(ol, bear, advance, dir, pos, size);
+        add_line(ol, 0, advance, dir, pos, size);
     }
 
     return 0;
@@ -658,6 +653,9 @@ FT_Glyph ass_font_get_glyph(ASS_Font *font, uint32_t ch, int face_index,
         glyph->advance.x = face->glyph->linearVertAdvance;
     }
 
+    ass_strike_outline_glyph(face, font, glyph, deco & DECO_UNDERLINE,
+                             deco & DECO_STRIKETHROUGH);
+
     // Apply scaling and shift
     FT_Matrix scale = { double_to_d16(font->scale_x), 0, 0,
                         double_to_d16(font->scale_y) };
@@ -666,9 +664,6 @@ FT_Glyph ass_font_get_glyph(ASS_Font *font, uint32_t ch, int face_index,
     FT_Outline_Translate(outl, font->v.x, font->v.y);
     glyph->advance.x *= font->scale_x;
 
-    ass_strike_outline_glyph(face, font, glyph, deco & DECO_UNDERLINE,
-                             deco & DECO_STRIKETHROUGH);
-
     return glyph;
 }