[freetype2-demos] master 46b5ae2: [ftmulti] Enable overlap flag testing.

[Werner Lemberg]

branch: master
commit 46b5ae2d034395470b439d2a28d63731383107ab
Author: Alexei Podtelezhnikov <apodtele@gmail.com>
Commit: Alexei Podtelezhnikov <apodtele@gmail.com>

    [ftmulti] Enable overlap flag testing.
    
    Variation fonts often relay on overlapping contours, which require
    oversampling to render properly. FreeType relies on FT_OUTLINE_OVERLAP
    to trigger the expensive mitigation algorithm. This commit enables
    tinkering with the overlap flags and, therefore, the oversampling.
    Normally, the flags should be set by the font designers sparingly.
    
    The bitmap strike toggle is no longer available, which has never
    been important for the variation font testing.
    
    * src/ftmulti.c (Process_Event): Reassign F4 to overlap toggle.
    (Render_Glyph): Tinker with the overlap flags before rendering.
---
 src/ftmulti.c | 25 +++++++++++--------------
 1 file changed, 11 insertions(+), 14 deletions(-)

diff --git a/src/ftmulti.c b/src/ftmulti.c
index de05802..bfbfbe6 100644
--- a/src/ftmulti.c
+++ b/src/ftmulti.c
@@ -94,7 +94,7 @@
   static int  hinted    = 1;         /* is glyph hinting active?    */
   static int  grouping  = 1;         /* is axis grouping active?    */
   static int  antialias = 1;         /* is anti-aliasing active?    */
-  static int  use_sbits = 1;         /* do we use embedded bitmaps? */
+  static int  overlaps  = 0x0;       /* flip overlap flags or not?  */
   static int  Num;                   /* current first glyph index   */
 
   static int  res       = 72;
@@ -103,8 +103,6 @@
 
   static int  Fail;
 
-  static int  graph_init  = 0;
-
   static int  render_mode = 1;
 
   static FT_MM_Var    *multimaster   = NULL;
@@ -305,8 +303,6 @@
     bit = (grBitmap*)surface;
 
     fore_color = grFindColor( bit, 255, 255, 255, 255 );  /* white */
-
-    graph_init = 1;
   }
 
 
@@ -322,6 +318,10 @@
     /* first, render the glyph image into a bitmap */
     if ( glyph->format != FT_GLYPH_FORMAT_BITMAP )
     {
+      /* overlap flags mitigate AA rendering artifacts in overlaps */
+      /* by oversampling, toggle the flag to test the effect       */
+      glyph->outline.flags ^= overlaps;
+
       error = FT_Render_Glyph( glyph, antialias ? FT_RENDER_MODE_NORMAL
                                                 : FT_RENDER_MODE_MONO );
       if ( error )
@@ -373,14 +373,11 @@
     int  flags;
 
 
-    flags = FT_LOAD_DEFAULT;
+    flags = FT_LOAD_NO_BITMAP;
 
     if ( !hint )
       flags |= FT_LOAD_NO_HINTING;
 
-    if ( !use_sbits )
-      flags |= FT_LOAD_NO_BITMAP;
-
     return FT_Load_Glyph( face, idx, flags );
   }
 
@@ -558,7 +555,7 @@
     grWriteln( "q, ESC      quit ftmulti" );
     grWriteln( "F2          toggle axis grouping" );
     grWriteln( "F3          toggle outline hinting" );
-    grWriteln( "F4          toggle embedded bitmaps" );
+    grWriteln( "F4          toggle overlap flags" );
     grWriteln( "F5          toggle anti-aliasing" );
     grWriteln( "F6          cycle through hinting engines (if available)" );
     grLn();
@@ -645,10 +642,10 @@
       break;
 
     case grKeyF4:
-      use_sbits  = !use_sbits;
-      new_header = use_sbits
-                     ? "embedded bitmaps are now used if available"
-                     : "embedded bitmaps are now ignored";
+      overlaps  ^= FT_OUTLINE_OVERLAP;
+      new_header = overlaps
+                     ? "overlap flags are flipped"
+                     : "overlap flags are unchanged";
       break;
 
     case grKEY( ',' ):