From: Po Lu <luangruo@yahoo.com>
Date: Mon, 25 Dec 2023 07:38:15 +0000 (+0800)
Subject: Apply TTF advance width rounding to uninstructed glyphs
X-Git-Url: http://git.eshelyaron.com/gitweb/?a=commitdiff_plain;h=1be132731d31c3752b275735e5dbe1f60d1988c3;p=emacs.git

Apply TTF advance width rounding to uninstructed glyphs

* src/sfnt.c (sfnt_scale_metrics):

* src/sfntfont.c (sfntfont_get_glyph_outline): Round advance and
floor lbearing scaling glyph metrics.
(sfntfont_measure_pcm): Don't round or truncate metrics which
have already been.
---

diff --git a/src/sfnt.c b/src/sfnt.c
index d945342c264..b67377ad064 100644
--- a/src/sfnt.c
+++ b/src/sfnt.c
@@ -5656,18 +5656,21 @@ sfnt_lookup_glyph_metrics (sfnt_glyph glyph, int pixel_size,
   return 0;
 }
 
-/* Scale the specified glyph metrics by FACTOR.
-   Set METRICS->lbearing and METRICS->advance to their current
-   values times factor.  */
+/* Scale the specified glyph metrics by FACTOR.  Set METRICS->lbearing
+   and METRICS->advance to their current values times factor; take the
+   floor of the left bearing and round the advance width.  */
 
 MAYBE_UNUSED TEST_STATIC void
 sfnt_scale_metrics (struct sfnt_glyph_metrics *metrics,
 		    sfnt_fixed factor)
 {
-  metrics->lbearing
-    = sfnt_mul_fixed (metrics->lbearing * 65536, factor);
-  metrics->advance
-    = sfnt_mul_fixed (metrics->advance * 65536, factor);
+  sfnt_fixed lbearing, advance;
+
+  lbearing = sfnt_mul_fixed (metrics->lbearing * 65536, factor);
+  advance = sfnt_mul_fixed (metrics->advance * 65536, factor);
+
+  metrics->lbearing = sfnt_floor_fixed (lbearing);
+  metrics->advance = sfnt_round_fixed (advance);
 }
 
 /* Calculate the factor used to convert em space to device space for a
diff --git a/src/sfntfont.c b/src/sfntfont.c
index 078fe6083a6..c626e76b52b 100644
--- a/src/sfntfont.c
+++ b/src/sfntfont.c
@@ -2304,7 +2304,8 @@ sfntfont_get_glyph_outline (sfnt_glyph glyph_code,
 		 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.  */
-	      temp.lbearing = outline->xmin - outline->origin;
+	      temp.lbearing
+		= SFNT_FLOOR_FIXED (outline->xmin - outline->origin);
 	    }
 	}
     }
@@ -3497,12 +3498,12 @@ sfntfont_measure_pcm (struct sfnt_font_info *font, sfnt_glyph glyph,
   if (!outline)
     return 1;
 
-  /* Round the left side bearing down.  */
-  pcm->lbearing = SFNT_FLOOR_FIXED (metrics.lbearing) / 65536;
+  /* The left side bearing has already been floored.  */
+  pcm->lbearing = metrics.lbearing / 65536;
   pcm->rbearing = SFNT_CEIL_FIXED (outline->xmax) / 65536;
 
-  /* Round the advance, ascent and descent upwards.  */
-  pcm->width = SFNT_CEIL_FIXED (metrics.advance) / 65536;
+  /* The advance is already rounded; ceil the ascent and descent.  */
+  pcm->width = metrics.advance / 65536;
   pcm->ascent = SFNT_CEIL_FIXED (outline->ymax) / 65536;
   pcm->descent = SFNT_CEIL_FIXED (-outline->ymin) / 65536;