diff --git a/src/character.c b/src/character.c
index e0978bb39fa..5753e883c32 100644
--- a/src/character.c
+++ b/src/character.c
@@ -34,6 +34,7 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */
 #include "lisp.h"
 #include "character.h"
 #include "buffer.h"
+#include "frame.h"
 #include "dispextern.h"
 #include "composite.h"
 #include "disptab.h"
@@ -343,6 +344,14 @@ lisp_string_width (Lisp_Object string, ptrdiff_t from, ptrdiff_t to,
   ptrdiff_t from_byte = i_byte;
   ptrdiff_t width = 0;
   struct Lisp_Char_Table *dp = buffer_display_table ();
+#ifdef HAVE_WINDOW_SYSTEM
+  struct frame *f =
+    (FRAMEP (selected_frame) && FRAME_LIVE_P (XFRAME (selected_frame)))
+    ? XFRAME (selected_frame)
+    : NULL;
+  int font_width = -1;
+  Lisp_Object default_font, frame_font;
+#endif
 
   eassert (precision <= 0 || (nchars && nbytes));
 
@@ -361,23 +370,40 @@ lisp_string_width (Lisp_Object string, ptrdiff_t from, ptrdiff_t to,
 	  chars = end - i;
 	  bytes = string_char_to_byte (string, end) - i_byte;
 	}
-      else if (!NILP (BVAR (current_buffer, enable_multibyte_characters))
-	       && ! NILP (Vauto_composition_mode)
+#ifdef HAVE_WINDOW_SYSTEM
+      else if (f && FRAME_WINDOW_P (f)
+	       && multibyte
 	       && find_automatic_composition (i, -1, &ignore, &end, &val, string)
 	       && end > i)
 	{
-	  int j;
-	  for (thiswidth = 0, j = 0; j < LGSTRING_GLYPH_LEN (val); j++)
+	  int pixelwidth = composition_gstring_width (val, 0,
+						      LGSTRING_GLYPH_LEN (val),
+						      NULL);
+	  /* The below is somewhat expensive, so compute it only once
+	     for the entire loop, and only if needed.  */
+	  if (font_width < 0)
 	    {
-	      Lisp_Object g = LGSTRING_GLYPH (val, j);
+	      font_width = FRAME_COLUMN_WIDTH (f);
+	      default_font = Fface_font (Qdefault, Qnil, Qnil);
+	      frame_font = Fframe_parameter (Qnil, Qfont);
 
-	      if (NILP (g))
-		break;
-	      thiswidth += char_width (LGLYPH_CHAR (g), dp);
+	      if (STRINGP (default_font) && STRINGP (frame_font)
+		  && (SCHARS (default_font) != SCHARS (frame_font)
+		      || SBYTES (default_font) != SBYTES (frame_font)
+		      || memcmp (SDATA (default_font), SDATA (frame_font),
+				 SBYTES (default_font))))
+		{
+		  Lisp_Object font_info = Ffont_info (default_font, Qnil);
+		  font_width = AREF (font_info, 11);
+		  if (font_info <= 0)
+		    font_width = AREF (font_info, 10);
+		}
 	    }
+	  thiswidth = (double) pixelwidth / font_width + 0.5;
 	  chars = end - i;
 	  bytes = string_char_to_byte (string, end) - i_byte;
 	}
+#endif	/* HAVE_WINDOW_SYSTEM */
       else
 	{
 	  int c;