master cd91ecedcbd 1/2: Consistently round glyph advances in the SFNT font backend

[Po Lu]

branch: master
commit cd91ecedcbdf03ae13f45cb173360b11f13a0bc0
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    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.
---
 src/sfnt.h     |  1 +
 src/sfntfont.c | 18 +++++++++++-------
 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