diff --git a/src/libdraw/stringwidth.c b/src/libdraw/stringwidth.c
new file mode 100644
index 0000000..c487791
--- /dev/null
+++ b/src/libdraw/stringwidth.c
@@ -0,0 +1,97 @@
+#include <u.h>
+#include <libc.h>
+#include <draw.h>
+
+static Rune empty[] = { 0 };
+int
+_stringnwidth(Font *f, char *s, Rune *r, int len)
+{
+	int wid, twid, n, max, l;
+	char *name;
+	enum { Max = 64 };
+	ushort cbuf[Max];
+	Rune rune, **rptr;
+	char *subfontname, **sptr;
+	Font *def;
+
+	if(s == nil){
+		s = "";
+		sptr = nil;
+	}else
+		sptr = &s;
+	if(r == nil){
+		r = empty;
+		rptr = nil;
+	}else
+		rptr = &r;
+	twid = 0;
+	while((*s || *r) && len){
+		max = Max;
+		if(len < max)
+			max = len;
+		n = 0;
+		while((l = cachechars(f, sptr, rptr, cbuf, max, &wid, &subfontname)) <= 0){
+			if(++n > 10){
+				if(*r)
+					rune = *r;
+				else
+					chartorune(&rune, s);
+				if(f->name != nil)
+					name = f->name;
+				else
+					name = "unnamed font";
+				fprint(2, "stringwidth: bad character set for rune 0x%.4ux in %s\n", rune, name);
+				return twid;
+			}
+			if(subfontname){
+				if(_getsubfont(f->display, subfontname) == 0){
+					def = f->display->defaultfont;
+					if(def && f!=def)
+						f = def;
+					else
+						break;
+				}
+			}
+		}
+		agefont(f);
+		twid += wid;
+		len -= l;
+	}
+	return twid;
+}
+
+int
+stringnwidth(Font *f, char *s, int len)
+{
+	return _stringnwidth(f, s, nil, len);
+}
+
+int
+stringwidth(Font *f, char *s)
+{
+	return _stringnwidth(f, s, nil, 1<<24);
+}
+
+Point
+stringsize(Font *f, char *s)
+{
+	return Pt(_stringnwidth(f, s, nil, 1<<24), f->height);
+}
+
+int
+runestringnwidth(Font *f, Rune *r, int len)
+{
+	return _stringnwidth(f, nil, r, len);
+}
+
+int
+runestringwidth(Font *f, Rune *r)
+{
+	return _stringnwidth(f, nil, r, 1<<24);
+}
+
+Point
+runestringsize(Font *f, Rune *r)
+{
+	return Pt(_stringnwidth(f, nil, r, 1<<24), f->height);
+}