[pango/font-metrics-trouble-in-northwest] wip: Fix up font metrics in improver gravities

[Matthias Clasen <matthiasc src gnome org>]

commit ca217a382d895b68d4c656214665b79a6dd86618
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Nov 19 22:15:06 2021 -0500

    wip: Fix up font metrics in improver gravities
    
    In these gravities, we give the font a negative scale
    to get negative advance widths, but this also makes
    font metrics come out negative, and some of our code
    in pango-layout.c can't deal with that. So flip the
    metrics back.

 pango/pangofc-font.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)
---
diff --git a/pango/pangofc-font.c b/pango/pangofc-font.c
index 74503b91..1e003cf3 100644
--- a/pango/pangofc-font.c
+++ b/pango/pangofc-font.c
@@ -322,6 +322,8 @@ pango_fc_font_get_coverage (PangoFont     *font,
   return coverage;
 }
 
+static PangoGravity pango_fc_font_key_get_gravity (PangoFcFontKey *key);
+
 /* For Xft, it would be slightly more efficient to simply to
  * call Xft, and also more robust against changes in Xft.
  * But for now, we simply use the same code for all backends.
@@ -336,6 +338,8 @@ get_face_metrics (PangoFcFont      *fcfont,
   hb_font_t *hb_font = pango_font_get_hb_font (PANGO_FONT (fcfont));
   hb_font_extents_t extents;
   hb_position_t position;
+  PangoFcFontKey *key = _pango_fc_font_get_font_key (fcfont);
+  PangoGravity gravity;
 
   FcMatrix *fc_matrix;
   gboolean have_transform = FALSE;
@@ -362,6 +366,14 @@ get_face_metrics (PangoFcFont      *fcfont,
       metrics->height = extents.ascender - extents.descender + extents.line_gap;
     }
 
+  gravity = pango_fc_font_key_get_gravity (key);
+  if (PANGO_GRAVITY_IS_IMPROPER (gravity))
+    {
+      metrics->descent = - metrics->descent;
+      metrics->ascent = - metrics->ascent;
+      metrics->height = - metrics->height;
+    }
+
   metrics->underline_thickness = PANGO_SCALE;
   metrics->underline_position = - PANGO_SCALE;
   metrics->strikethrough_thickness = PANGO_SCALE;
@@ -978,6 +990,7 @@ pango_fc_font_create_hb_font (PangoFont *font)
           x_scale_inv = -x_scale_inv;
           y_scale_inv = -y_scale_inv;
         }
+
       get_font_size (key, &pixel_size, &point_size);
     }