[pango/fix-emoji-scaling] Take font matrix into account

[Matthias Clasen <matthiasc src gnome org>]

commit 775c99e5b8567d0a1773b6ffe6e6d2fd8047d097
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Jul 28 19:09:25 2019 -0400

    Take font matrix into account
    
    When setting up the scale of the hb_font_t, we need
    to take both the pango ctm and the font matrix into
    account - this used to come for free when we were
    calling into cairo for getting glyph metrics. Now,
    we use harfbuzz for glyph metrics, so we need to
    give it the proper scale info.
    
    The symptom of this was Emoji getting an enormous
    width. Curiously, cairo would still render them
    at the expected size.

 pango/pangofc-font.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
---
diff --git a/pango/pangofc-font.c b/pango/pangofc-font.c
index 5ed9b792..a4bf5f61 100644
--- a/pango/pangofc-font.c
+++ b/pango/pangofc-font.c
@@ -1006,11 +1006,30 @@ pango_fc_font_create_hb_font (PangoFont *font)
   key = _pango_fc_font_get_font_key (fc_font);
   if (key)
     {
+      const FcPattern *pattern = pango_fc_font_key_get_pattern (key);
       const PangoMatrix *matrix;
+      PangoMatrix matrix2;
       PangoGravity gravity;
+      FcMatrix fc_matrix, *fc_matrix_val;
+      double x, y;
+      int i;
 
       matrix = pango_fc_font_key_get_matrix (key);
       pango_matrix_get_font_scale_factors (matrix, &x_scale_inv, &y_scale_inv);
+
+      FcMatrixInit (&fc_matrix);
+      for (i = 0; FcPatternGetMatrix (pattern, FC_MATRIX, i, &fc_matrix_val) == FcResultMatch; i++)
+        FcMatrixMultiply (&fc_matrix, &fc_matrix, fc_matrix_val);
+
+      matrix2.xx = fc_matrix.xx;
+      matrix2.yx = fc_matrix.yx;
+      matrix2.xy = fc_matrix.xy;
+      matrix2.yy = fc_matrix.yy;
+      pango_matrix_get_font_scale_factors (&matrix2, &x, &y);
+
+      x_scale_inv /= x;
+      y_scale_inv /= y;
+
       gravity = pango_fc_font_key_get_gravity (key);
       if (PANGO_GRAVITY_IS_IMPROPER (gravity))
         {