Bug 341481 - pangocairo kerning problem with nonidentity scaling

Finally fix this embarrassing bug.  The fix is a kludge, but it will
be redone for 1.28 (harfbuzz-ng) anyway.

1 files changed, 50 insertions, 6 deletions

diff --git a/pango/pango-ot-buffer.c b/pango/pango-ot-buffer.c
index 533c3102..f5a68512 100644
--- a/pango/pango-ot-buffer.c
+++ b/pango/pango-ot-buffer.c
@@ -207,6 +207,9 @@ pango_ot_buffer_get_glyphs (const PangoOTBuffer  *buffer,
 static void
 apply_gpos_ltr (PangoGlyphString    *glyphs,
 		hb_glyph_position_t *positions,
+		gboolean             scale,
+		double               xscale,
+		double               yscale,
 		gboolean             is_hinted)
 {
   int i;
@@ -224,6 +227,8 @@ apply_gpos_ltr (PangoGlyphString    *glyphs,
 
       if (is_hinted)
 	adjustment = PANGO_UNITS_ROUND (adjustment);
+      if (G_UNLIKELY (scale))
+	adjustment *= xscale;
 
       if (positions[i].new_advance)
 	glyphs->glyphs[i].geometry.width  = adjustment;
@@ -241,14 +246,25 @@ apply_gpos_ltr (PangoGlyphString    *glyphs,
       for (j = back; j < i; j++)
 	glyphs->glyphs[i].geometry.x_offset -= glyphs->glyphs[j].geometry.width;
 
-      glyphs->glyphs[i].geometry.x_offset += PANGO_UNITS_26_6(x_pos);
-      glyphs->glyphs[i].geometry.y_offset -= PANGO_UNITS_26_6(y_pos);
+      if (G_UNLIKELY (scale))
+        {
+	  glyphs->glyphs[i].geometry.x_offset += xscale * PANGO_UNITS_26_6(x_pos);
+	  glyphs->glyphs[i].geometry.y_offset -= yscale * PANGO_UNITS_26_6(y_pos);
+	}
+      else
+        {
+	  glyphs->glyphs[i].geometry.x_offset += PANGO_UNITS_26_6(x_pos);
+	  glyphs->glyphs[i].geometry.y_offset -= PANGO_UNITS_26_6(y_pos);
+	}
     }
 }
 
 static void
 apply_gpos_rtl (PangoGlyphString    *glyphs,
 		hb_glyph_position_t *positions,
+		gboolean             scale,
+		double               xscale,
+		double               yscale,
 		gboolean             is_hinted)
 {
   int i;
@@ -268,6 +284,8 @@ apply_gpos_rtl (PangoGlyphString    *glyphs,
 
       if (is_hinted)
 	adjustment = PANGO_UNITS_ROUND (adjustment);
+      if (G_UNLIKELY (scale))
+	adjustment *= xscale;
 
       if (positions[i_rev].new_advance)
 	glyphs->glyphs[i].geometry.width  = adjustment;
@@ -287,8 +305,16 @@ apply_gpos_rtl (PangoGlyphString    *glyphs,
       for (j = i; j < back; j++)
 	glyphs->glyphs[i].geometry.x_offset += glyphs->glyphs[j].geometry.width;
 
-      glyphs->glyphs[i].geometry.x_offset += PANGO_UNITS_26_6(x_pos);
-      glyphs->glyphs[i].geometry.y_offset -= PANGO_UNITS_26_6(y_pos);
+      if (G_UNLIKELY (scale))
+        {
+	  glyphs->glyphs[i].geometry.x_offset += xscale * PANGO_UNITS_26_6(x_pos);
+	  glyphs->glyphs[i].geometry.y_offset -= yscale * PANGO_UNITS_26_6(y_pos);
+	}
+      else
+        {
+	  glyphs->glyphs[i].geometry.x_offset += PANGO_UNITS_26_6(x_pos);
+	  glyphs->glyphs[i].geometry.y_offset -= PANGO_UNITS_26_6(y_pos);
+	}
     }
 }
 
@@ -376,10 +402,28 @@ pango_ot_buffer_output (const PangoOTBuffer *buffer,
   positions = hb_buffer_get_glyph_positions (buffer->buffer);
   if (buffer->applied_gpos)
     {
+      gboolean scale = FALSE;
+      double xscale = 1, yscale = 1;
+      PangoFcFontKey *key = _pango_fc_font_get_font_key (buffer->font);
+
+      /* This is a kludge, and dupped in pango_fc_font_kern_glyphs().
+       * Should move the scale factor to PangoFcFont layer. */
+      if (key) {
+	const PangoMatrix *matrix = pango_fc_font_key_get_matrix (key);
+	PangoMatrix identity = PANGO_MATRIX_INIT;
+	if (G_UNLIKELY (matrix && 0 != memcmp (&identity, matrix, 4 * sizeof (double))))
+	  {
+	    scale = TRUE;
+	    pango_matrix_get_font_scale_factors (matrix, &xscale, &yscale);
+	    if (xscale) xscale = 1 / xscale;
+	    if (yscale) yscale = 1 / yscale;
+	  }
+      }
+
       if (buffer->rtl)
-	apply_gpos_rtl (glyphs, positions, buffer->font->is_hinted);
+	apply_gpos_rtl (glyphs, positions, scale, xscale, yscale, buffer->font->is_hinted);
       else
-	apply_gpos_ltr (glyphs, positions, buffer->font->is_hinted);
+	apply_gpos_ltr (glyphs, positions, scale, xscale, yscale, buffer->font->is_hinted);
     }
   else
     {