From f2e76e835645e8771a59404c27ef7546ba4cfb37 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alexei=20Podtelezhnikov=20=28=D0=90=D0=BB=D0=B5=D0=BA?=
 =?UTF-8?q?=D1=81=D0=B5=D0=B9=20=D0=9F=D0=BE=D0=B4=D1=82=D0=B5=D0=BB=D0=B5?=
 =?UTF-8?q?=D0=B6=D0=BD=D0=B8=D0=BA=D0=BE=D0=B2=29?= <apodtele@gmail.com>
Date: Thu, 2 Nov 2023 22:08:04 -0400
Subject: [PATCH] [raster] Remove the jitter exception.

The jitter exception used to be applied when two neighboring pixels
were barely inside the outline. One the left one was turned on then,
which contradicts the OpenType specifications.  Intended to remove
glitches, it caused disappearing lines and was softened by adding an
exception to the exception (#54589).

* src/raster/ftraster.c (Vertical_Sweep_Span): Drop the jitter exception.
---
 src/raster/ftraster.c | 37 ++++++-------------------------------
 1 file changed, 6 insertions(+), 31 deletions(-)

diff --git a/src/raster/ftraster.c b/src/raster/ftraster.c
index 6343e902e..a77b57fd1 100644
--- a/src/raster/ftraster.c
+++ b/src/raster/ftraster.c
@@ -448,7 +448,6 @@
     Int         precision_half;
     Int         precision_scale;
     Int         precision_step;
-    Int         precision_jitter;
 
     PLong       buff;               /* The profiles buffer                 */
     PLong       sizeBuff;           /* Render pool size                    */
@@ -549,27 +548,17 @@
      *
      *   256 / (1 << 12) = 0.0625 pixels.
      *
-     * `precision_jitter' is an epsilon threshold used in
-     * `Vertical_Sweep_Span' to deal with small imperfections in the Bezier
-     * decomposition (after all, we are working with approximations only);
-     * it avoids switching on additional pixels which would cause artifacts
-     * otherwise.
-     *
-     * The value of `precision_jitter' has been determined heuristically.
-     *
      */
 
     if ( High )
     {
       ras.precision_bits   = 12;
       ras.precision_step   = 256;
-      ras.precision_jitter = 30;
     }
     else
     {
       ras.precision_bits   = 6;
       ras.precision_step   = 32;
-      ras.precision_jitter = 2;
     }
 
     ras.precision       = 1 << ras.precision_bits;
@@ -2139,9 +2128,7 @@
                                 PProfile    left,
                                 PProfile    right )
   {
-    Long  e1, e2;
-
-    Int  dropOutControl = left->flags & 7;
+    Int  e1, e2;
 
     FT_UNUSED( y );
     FT_UNUSED( left );
@@ -2153,20 +2140,8 @@
                 ras.precision_bits, (double)x1 / (double)ras.precision,
                 ras.precision_bits, (double)x2 / (double)ras.precision ));
 
-    /* Drop-out control */
-
-    e1 = CEILING( x1 );
-    e2 = FLOOR( x2 );
-
-    /* take care of the special case where both the left */
-    /* and right contour lie exactly on pixel centers    */
-    if ( dropOutControl != 2                             &&
-         x2 - x1 - ras.precision <= ras.precision_jitter &&
-         e1 != x1 && e2 != x2                            )
-      e2 = e1;
-
-    e1 = TRUNC( e1 );
-    e2 = TRUNC( e2 );
+    e1 = (Int)TRUNC( CEILING( x1 ) );
+    e2 = (Int)TRUNC( FLOOR( x2 ) );
 
     if ( e2 >= 0 && e1 < ras.bWidth )
     {
@@ -2180,10 +2155,10 @@
       if ( e2 >= ras.bWidth )
         e2 = ras.bWidth - 1;
 
-      FT_TRACE7(( " -> x=[%ld;%ld]", e1, e2 ));
+      FT_TRACE7(( " -> x=[%d;%d]", e1, e2 ));
 
-      c1 = (Int)( e1 >> 3 );
-      c2 = (Int)( e2 >> 3 );
+      c1 = e1 >> 3;
+      c2 = e2 >> 3;
 
       f1 =  0xFF >> ( e1 & 7 );
       f2 = ~0x7F >> ( e2 & 7 );