Fix display of composite characters with large fonts

* src/xdisp.c (x_produce_glyphs): Call normal_char_ascent_descent
for reasonable values of font ascent and descent.
(get_font_ascent_descent): New function.

* src/composite.c (composition_gstring_width): Call
get_font_ascent_descent for reasonable values of font ascent and
descent.

* dispextern.h: Add prototype for get_font_ascent_descent.

3 files changed, 21 insertions, 5 deletions

diff --git a/src/composite.c b/src/composite.c
index 577b97920f4..e942eef3006 100644
--- a/src/composite.c
+++ b/src/composite.c
@@ -732,9 +732,11 @@ composition_gstring_width (Lisp_Object gstring, ptrdiff_t from, ptrdiff_t to,
       if (FONT_OBJECT_P (font_object))
         {
           struct font *font = XFONT_OBJECT (font_object);
+          int font_ascent, font_descent;
 
-          metrics->ascent = font->ascent;
-          metrics->descent = font->descent;
+          get_font_ascent_descent (font, &font_ascent, &font_descent);
+          metrics->ascent = font_ascent;
+          metrics->descent = font_descent;
         }
       else
         {
diff --git a/src/dispextern.h b/src/dispextern.h
index 1537d44330d..5202142313a 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -3246,6 +3246,8 @@ extern ptrdiff_t compute_display_string_end (ptrdiff_t,
 extern void produce_stretch_glyph (struct it *);
 extern int merge_glyphless_glyph_face (struct it *);
 
+extern void get_font_ascent_descent (struct font *, int *, int *);
+
 #ifdef HAVE_WINDOW_SYSTEM
 
 #ifdef GLYPH_DEBUG
diff --git a/src/xdisp.c b/src/xdisp.c
index 50d7376b28a..53303272e60 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -24079,6 +24079,17 @@ calc_pixel_width_or_height (double *res, struct it *it, Lisp_Object prop,
   return false;
 }
 
+void
+get_font_ascent_descent (struct font *font, int *ascent, int *descent)
+{
+#ifdef HAVE_WINDOW_SYSTEM
+  normal_char_ascent_descent (font, -1, ascent, descent);
+#else
+  *ascent = 1;
+  *descent = 0;
+#endif
+}
+
 
 /***********************************************************************
                              Glyph Display
@@ -26818,9 +26829,10 @@ x_produce_glyphs (struct it *it)
           boff = font->baseline_offset;
           if (font->vertical_centering)
             boff = VCENTER_BASELINE_OFFSET (font, it->f) - boff;
-          font_ascent = FONT_BASE (font) + boff;
-          font_descent = FONT_DESCENT (font) - boff;
-          font_height = FONT_HEIGHT (font);
+          normal_char_ascent_descent (font, -1, &font_ascent, &font_descent);
+          font_ascent +=  boff;
+          font_descent -= boff;
+          font_height = font_ascent + font_descent;
 
           cmp->font = font;