Avoid assertion violations when rendering some fonts

* src/dispextern.h (FONT_TOO_HIGH): Don't consider a font "too
high" if its pixel_size value is zero.  This avoids assertion
violations at the end of x_produce_glyphs.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/dispextern.h b/src/dispextern.h
index 70358724024..7b9ae78dcd3 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -1541,7 +1541,8 @@ struct glyph_string
    large vertical space.  The heuristics is in the factor of 3.  We
    ignore the ascent and descent values reported by such fonts, and
    instead go by the values reported for individual glyphs.  */
-#define FONT_TOO_HIGH(ft)  ((ft)->ascent + (ft)->descent > 3*(ft)->pixel_size)
+#define FONT_TOO_HIGH(ft)                                               \
+  ((ft)->pixel_size > 0 && (ft)->ascent + (ft)->descent > 3*(ft)->pixel_size)
 
 
 /***********************************************************************