[type42] Fix auto-hinting.

The autohinter could not access the base (unscaled) outline in the
child TrueType glyph slot. We now share the internal parts between
the parent and child glyph slots. Fixes #1057.

* src/type42/t42objs.c (T42_GlyphSlot_Init): Remove the internal parts
of `T42_GlyphSlot' and replace it with the child TrueType structure.
(T42_GlyphSlot_Done): Updated accordingly.

ChangeLog

@@ -1,3 +1,15 @@
+2021-05-27  Alexei Podtelezhnikov  <apodtele@gmail.com>
+
+	[type42] Fix auto-hinting.
+
+	The autohinter could not access the base (unscaled) outline in the
+	child TrueType glyph slot. We now share the internal parts between
+	the parent and child glyph slots. Fixes #1057.
+
+	* src/type42/t42objs.c (T42_GlyphSlot_Init): Remove the internal parts
+	of `T42_GlyphSlot' and replace it with the child TrueType structure.
+	(T42_GlyphSlot_Done): Updated accordingly.
+
 2021-05-25  Werner Lemberg  <wl@gnu.org>
 
 	[psaux] Guard and trace AFM kern data allocation.

src/type42/t42objs.c

@@ -583,6 +583,7 @@
     FT_Face        face    = t42slot->face;
     T42_Face       t42face = (T42_Face)face;
     FT_GlyphSlot   ttslot;
+    FT_Memory      memory  = face->memory;
     FT_Error       error   = FT_Err_Ok;
 
 
@@ -598,6 +599,11 @@
         slot->ttslot = ttslot;
     }
 
+    /* share the loader so that the autohinter can see it */
+    FT_GlyphLoader_Done( t42slot->internal->loader );
+    FT_FREE( t42slot->internal );
+    t42slot->internal = slot->ttslot->internal;
+
     return error;
   }
 
@@ -609,6 +615,7 @@
 
 
     FT_Done_GlyphSlot( slot->ttslot );
+    t42slot->internal = NULL;
   }