[VarC] Change rotation/skew representation

Fixes https://github.com/harfbuzz/boring-expansion-spec/issues/77

src/OT/glyf/VarCompositeGlyph.hh

@@ -197,11 +197,11 @@ struct VarCompositeGlyphRecord
 
     if (flags & HAVE_TRANSLATE_X)	translateX = * (const FWORD *) p++;
     if (flags & HAVE_TRANSLATE_Y)	translateY = * (const FWORD *) p++;
-    if (flags & HAVE_ROTATION)		rotation = * (const F2DOT14 *) p++;
+    if (flags & HAVE_ROTATION)		rotation = * (const F4DOT12 *) p++;
     if (flags & HAVE_SCALE_X)		scaleX = * (const F6DOT10 *) p++;
     if (flags & HAVE_SCALE_Y)		scaleY = * (const F6DOT10 *) p++;
-    if (flags & HAVE_SKEW_X)		skewX = * (const F2DOT14 *) p++;
-    if (flags & HAVE_SKEW_Y)		skewY = * (const F2DOT14 *) p++;
+    if (flags & HAVE_SKEW_X)		skewX = * (const F4DOT12 *) p++;
+    if (flags & HAVE_SKEW_Y)		skewY = * (const F4DOT12 *) p++;
     if (flags & HAVE_TCENTER_X)		tCenterX = * (const FWORD *) p++;
     if (flags & HAVE_TCENTER_Y)		tCenterY = * (const FWORD *) p++;
 
@@ -270,7 +270,7 @@ struct VarCompositeGlyphRecord
     }
     if (flags & HAVE_ROTATION)
     {
-      rotation = rec_points[0].x / (1 << 14);
+      rotation = rec_points[0].x / (1 << 12);
       rec_points++;
     }
     if (flags & (HAVE_SCALE_X | HAVE_SCALE_Y))
@@ -281,8 +281,8 @@ struct VarCompositeGlyphRecord
     }
     if (flags & (HAVE_SKEW_X | HAVE_SKEW_Y))
     {
-      skewX = rec_points[0].x / (1 << 14);
-      skewY = rec_points[0].y / (1 << 14);
+      skewX = rec_points[0].x / (1 << 12);
+      skewY = rec_points[0].y / (1 << 12);
       rec_points++;
     }
     if (flags & (HAVE_TCENTER_X | HAVE_TCENTER_Y))

src/hb-open-type.hh

@@ -156,8 +156,7 @@ struct HBFixed : Type
 
 /* 16-bit signed fixed number with the low 14 bits of fraction (2.14). */
 using F2DOT14 = HBFixed<HBINT16, 14>;
-
-/* 16-bit signed fixed number with the low 10 bits of fraction (6.10). */
+using F4DOT12 = HBFixed<HBINT16, 12>;
 using F6DOT10 = HBFixed<HBINT16, 10>;
 
 /* 32-bit signed fixed-point number (16.16). */