Fix calculation of kerning values.

QuLogic · QuLogic · commit 7f57740a62b1 · 2019-08-23T04:04:43.000-04:00
For the straight `get_kerning` call, the result should be in subpixels,
since the callers (in Python) correctly scale it by 64 themselves.

For the glyph advancement calculation, both `pen` (used for glyph
transform and with content boxes) and kerning are in 26.6 fractional
pixels.

Therefore, there's no need to scale either case by 2**6 (64).
diff --git a/src/ft2font.cpp b/src/ft2font.cpp
@@ -602,7 +602,7 @@ int FT2Font::get_kerning(FT_UInt left, FT_UInt right, FT_UInt mode)
     FT_Vector delta;
 
     if (!FT_Get_Kerning(face, left, right, mode, &delta)) {
-        return (int)(delta.x) / (hinting_factor << 6);
+        return (int)(delta.x) / hinting_factor;
     } else {
         return 0;
     }
@@ -640,7 +640,7 @@ void FT2Font::set_text(
         if (use_kerning && previous && glyph_index) {
             FT_Vector delta;
             FT_Get_Kerning(face, previous, glyph_index, FT_KERNING_DEFAULT, &delta);
-            pen.x += (delta.x << 10) / (hinting_factor << 16);
+            pen.x += delta.x / hinting_factor;
         }
         if (FT_Error error = FT_Load_Glyph(face, glyph_index, flags)) {
             throw_ft_error("Could not load glyph", error);
