[pango/broken-underlines] fc: Handle fonts with broken metrics better

[Matthias Clasen <matthiasc src gnome org>]

commit 2502562dd9ba30fd746bdf54a01e54dd11f87f30
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Dec 8 06:44:29 2021 -0500

    fc: Handle fonts with broken metrics better
    
    It seems that some fonts don't have meaningful
    values for underline and strikethrough metrics.
    
    Ignore these font-provided values if they are zero.
    
    Fixes: #616

 pango/pangofc-font.c | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)
---
diff --git a/pango/pangofc-font.c b/pango/pangofc-font.c
index 5635e0be..f29580c3 100644
--- a/pango/pangofc-font.c
+++ b/pango/pangofc-font.c
@@ -365,22 +365,29 @@ get_face_metrics (PangoFcFont      *fcfont,
       metrics->height = extents.ascender - extents.descender + extents.line_gap;
     }
 
-  metrics->underline_thickness = PANGO_SCALE;
-  metrics->underline_position = - PANGO_SCALE;
-  metrics->strikethrough_thickness = PANGO_SCALE;
-  metrics->strikethrough_position = metrics->ascent / 2;
-
-  if (hb_ot_metrics_get_position (hb_font, HB_OT_METRICS_TAG_UNDERLINE_SIZE, &position))
+  if (hb_ot_metrics_get_position (hb_font, HB_OT_METRICS_TAG_UNDERLINE_SIZE, &position) &&
+      position != 0)
     metrics->underline_thickness = position;
+  else
+    metrics->underline_thickness = PANGO_SCALE;
 
-  if (hb_ot_metrics_get_position (hb_font, HB_OT_METRICS_TAG_UNDERLINE_OFFSET, &position))
+  if (hb_ot_metrics_get_position (hb_font, HB_OT_METRICS_TAG_UNDERLINE_OFFSET, &position) &&
+      position != 0)
     metrics->underline_position = position;
+  else
+    metrics->underline_position = - PANGO_SCALE;
 
-  if (hb_ot_metrics_get_position (hb_font, HB_OT_METRICS_TAG_STRIKEOUT_SIZE, &position))
+  if (hb_ot_metrics_get_position (hb_font, HB_OT_METRICS_TAG_STRIKEOUT_SIZE, &position) &&
+      position != 0)
     metrics->strikethrough_thickness = position;
+  else
+    metrics->strikethrough_thickness = PANGO_SCALE;
 
-  if (hb_ot_metrics_get_position (hb_font, HB_OT_METRICS_TAG_STRIKEOUT_OFFSET, &position))
+  if (hb_ot_metrics_get_position (hb_font, HB_OT_METRICS_TAG_STRIKEOUT_OFFSET, &position) &&
+      position != 0)
     metrics->strikethrough_position = position;
+  else
+    metrics->strikethrough_position = metrics->ascent / 2;
 }
 
 PangoFontMetrics *