diff --git a/uppsrc/Core/CharSet.cpp b/uppsrc/Core/CharSet.cpp
index cb99d73a4..ee50a6132 100644
--- a/uppsrc/Core/CharSet.cpp
+++ b/uppsrc/Core/CharSet.cpp
@@ -2296,4 +2296,25 @@ String ToLowerAscii(const String& s, byte charset)
 	return r;
 }
 
+bool IsDoubleWidth(int c)
+{
+	// This function is taken from Markus Kuhn's wcwidth implementation.
+	// For license and implementation details, see:
+	// https://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c
+	
+	return  c >= 0x1100
+		&& (c <= 0x115F										// Hangul Jamo init. consonants
+			||  c == 0x2329
+			||  c == 0x232A
+			|| (c >= 0x2E80 && c <= 0xA4CF && c != 0x303F)	// CJK ... Yi
+			|| (c >= 0xAC00 && c <= 0xD7A3)					// Hangul syllables
+			|| (c >= 0xF900 && c <= 0xFAFF)					// CJK compatibility ideographs
+			|| (c >= 0xFE10 && c <= 0xFE19)					// Vertical forms
+			|| (c >= 0xFE30 && c <= 0xFE6F)					// CJK compatibility forms
+			|| (c >= 0xFF00 && c <= 0xFF60)					// Fullwidth forms
+			|| (c >= 0xFFE0 && c <= 0xFFE6)
+			|| (c >= 0x20000 && c <= 0x2FFFD)
+			|| (c >= 0x30000 && c <= 0x3FFFD)
+			);
+}
 }
diff --git a/uppsrc/Core/CharSet.h b/uppsrc/Core/CharSet.h
index f74ed812a..a467275c5 100644
--- a/uppsrc/Core/CharSet.h
+++ b/uppsrc/Core/CharSet.h
@@ -190,7 +190,7 @@ inline bool IsPunct(int c)         { return c != ' ' && !IsAlNum(c); }
 inline bool IsSpace(int c)         { return c == ' ' || c == '\f' || c == '\n' || c == '\r' || c == '\v' || c == '\t'; }
 inline bool IsXDigit(int c)        { return IsDigit(c) || c >= 'A' && c <= 'F' || c >= 'a' && c <= 'f'; }
 
-inline bool IsCJKIdeograph(int c)  { return c >= 0x2e80 && c <= 0xdfaf || c >= 0xf900 && c <= 0xfaff; }
+bool IsDoubleWidth(int c);
 
 word UnicodeCombine(word chr, word combine);
 
@@ -253,6 +253,8 @@ bool    SaveFileBOMUtf8(const char *path, const String& data);
 
 // Deprecated
 
+inline bool IsCJKIdeograph(int c)  { return c >= 0x2e80 && c <= 0xdfaf || c >= 0xf900 && c <= 0xfaff; }
+
 int  ToUnicode(int chr, byte charset);
 int  FromUnicode(wchar wchr, byte charset, int defchar = DEFAULTCHAR);
 
diff --git a/uppsrc/Core/src.tpp/CharSet_en-us.tpp b/uppsrc/Core/src.tpp/CharSet_en-us.tpp
index e6d4ba313..96adbe035 100644
--- a/uppsrc/Core/src.tpp/CharSet_en-us.tpp
+++ b/uppsrc/Core/src.tpp/CharSet_en-us.tpp
@@ -393,10 +393,11 @@ character.&]
 [s5;:IsXDigit`(int`): [@(0.0.255) bool]_[* IsXDigit]([@(0.0.255) int]_[*@3 c])&]
 [s2;%% Returns true [%-*@3 c].is hexadecimal digit (0`-9, a`-f, A`-F).&]
 [s3;%% &]
-[s4;%% &]
-[s5;:IsCJKIdeograph`(int`): [@(0.0.255) bool]_[* IsCJKIdeograph]([@(0.0.255) int]_[*@3 c])&]
-[s2;%% Returns true if [%-*@3 c].is in UNICODE code`-point for CJK 
-ideogram.&]
+[s4; &]
+[s5;:Upp`:`:IsDoubleWidth`(int`): [@(0.0.255) bool]_[* IsDoubleWidth]([@(0.0.255) int]_[*@3 c
+])&]
+[s2;%% Returns true if [%-*@3 c] is a double`-width UNICODE character 
+(like CJK ideograph).&]
 [s3;%% &]
 [s4;%% &]
 [s5;:UnicodeCombine`(word`,word`): [_^word^ word]_[* UnicodeCombine]([_^word^ word]_[*@3 chr],
diff --git a/uppsrc/CtrlLib/LineEdit.cpp b/uppsrc/CtrlLib/LineEdit.cpp
index ccb54fc97..a96bc1a8c 100644
--- a/uppsrc/CtrlLib/LineEdit.cpp
+++ b/uppsrc/CtrlLib/LineEdit.cpp
@@ -480,7 +480,7 @@ void   LineEdit::Paint0(Draw& w) {
 							x = fsz.cx * gp;
 						}
 						else
-						if(IsCJKIdeograph(chr)) {
+						if(IsDoubleWidth(chr)) {
 							x += 2 * fsz.cx;
 							gp += 2;
 						}
@@ -508,7 +508,7 @@ void   LineEdit::Paint0(Draw& w) {
 							h.ink = color[INK_SELECTED];
 						}
 						int x = gp * fsz.cx - scx;
-						bool cjk = IsCJKIdeograph(h.chr);
+						bool cjk = IsDoubleWidth(h.chr);
 						int xx = x + (gp + 1 + cjk) * fsz.cx;
 						if(h.chr == '\t') {
 							int ngp = (gp + tabsize) / tabsize * tabsize;
@@ -679,7 +679,7 @@ int64  LineEdit::GetGPos(int ln, int cl) const {
 				if(*s == '\t')
 					gl = (gl + tabsize) / tabsize * tabsize;
 				else
-					gl += 1 + IsCJKIdeograph(*s);
+					gl += 1 + IsDoubleWidth(*s);
 				if(cl < gl) break;
 				s++;
 			}
@@ -704,7 +704,7 @@ Point LineEdit::GetColumnLine(int64 pos) const {
 		if(*s == '\t')
 			p.x = (p.x + tabsize) / tabsize * tabsize;
 		else
-			p.x += 1 + IsCJKIdeograph(*s);
+			p.x += 1 + IsDoubleWidth(*s);
 		s++;
 	}
 	return p;
@@ -1125,7 +1125,7 @@ void LineEdit::SetHBar()
 				if(*s == '\t')
 					pos = (pos + tabsize) / tabsize * tabsize;
 				else
-					pos += 1 + IsCJKIdeograph(*s);
+					pos += 1 + IsDoubleWidth(*s);
 				s++;
 			}
 			mpos = max(mpos, pos);