Consistently round glyph advances in the SFNT font backend

* src/sfnt.h (SFNT_ROUND_FIXED): New macro.

* src/sfntfont.c (sfntfont_get_glyph_outline): Don't apply
advance width distortion before the glyph is instructed or
decomposed.  Round advance width as measured between both
phantom points subsequent to instruction code execution.
(sfntfont_draw): Don't take the advance's ceiling when advancing
origin point.

2 files changed, 12 insertions, 7 deletions

diff --git a/src/sfnt.h b/src/sfnt.h
index 7baed372212..576d287e8e6 100644
--- a/src/sfnt.h
+++ b/src/sfnt.h
@@ -1455,6 +1455,7 @@ struct sfnt_post_table
 
 
 #define SFNT_CEIL_FIXED(fixed)  (((fixed) + 0177777) & 037777600000)
+#define SFNT_ROUND_FIXED(fixed) (((fixed) + 0100000) & 037777600000)
 #define SFNT_FLOOR_FIXED(fixed) ((fixed) & 037777600000)
 
 
diff --git a/src/sfntfont.c b/src/sfntfont.c
index c626e76b52b..b20a7c91115 100644
--- a/src/sfntfont.c
+++ b/src/sfntfont.c
@@ -2257,9 +2257,6 @@ sfntfont_get_glyph_outline (sfnt_glyph glyph_code,
                                  head, maxp))
     goto fail;
 
-  /* Add the advance width distortion.  */
-  temp.advance += distortion.advance;
-
   if (interpreter)
     {
       if (glyph->simple)
@@ -2295,8 +2292,11 @@ sfntfont_get_glyph_outline (sfnt_glyph glyph_code,
 
           if (outline)
             {
-              /* Save the new advance width.  */
-              temp.advance = advance;
+              /* Save the new advance width.  This advance width is
+                 rounded again, as the instruction code executed might
+                 have moved both phantom points such that they no
+                 longer measure a fractional distance.  */
+              temp.advance = SFNT_ROUND_FIXED (advance);
 
               /* Finally, adjust the left side bearing of the glyph
                  metrics by the origin point of the outline, should a
@@ -2319,6 +2319,11 @@ sfntfont_get_glyph_outline (sfnt_glyph glyph_code,
                                           sfntfont_get_metrics,
                                           &dcontext);
 
+      /* Add the advance width distortion, which is not applied to
+         glyph metrics in advance of their being instructed, and thus
+         has to be applied before the metrics are.  */
+      temp.advance += distortion.advance;
+
       /* At this point, the glyph metrics are unscaled.  Scale them
          up.  If INTERPRETER is set, use the scale placed within.  */
       sfnt_scale_metrics (&temp, scale);
@@ -2328,7 +2333,6 @@ sfntfont_get_glyph_outline (sfnt_glyph glyph_code,
          been applied by either instruction code or glyph variation.
          The left side bearing is the distance from the origin point
          to the left most point on the X axis.  */
-
       if (index != -1)
         temp.lbearing = outline->xmin - outline->origin;
     }
@@ -3707,7 +3711,7 @@ sfntfont_draw (struct glyph_string *s, int from, int to,
       if (s->padding_p)
         current_x += 1;
       else
-        current_x += SFNT_CEIL_FIXED (metrics.advance) / 65536;
+        current_x += metrics.advance / 65536;
     }
 
   /* Call the window system function to put the glyphs to the