fix VTE. only remove surrogate double chars.

lib/unicode.js

@@ -567,13 +567,18 @@ exports.chars.wide = new RegExp('(['
   + '\\uffe0-\\uffe6'
   + '])', 'g');
 
-// All wide chars including surrogate pairs.
-exports.chars.all = new RegExp('('
+// All surrogate pair wide chars.
+exports.chars.swide = new RegExp('('
   // 0x20000 - 0x2fffd:
   + '[\\ud840-\\ud87f][\\udc00-\\udffd]'
   + '|'
   // 0x30000 - 0x3fffd:
   + '[\\ud880-\\ud8bf][\\udc00-\\udffd]'
+  + ')', 'g');
+
+// All wide chars including surrogate pairs.
+exports.chars.all = new RegExp('('
+  + exports.chars.swide.source.slice(1, -1)
   + '|'
   + exports.chars.wide.source.slice(1, -1)
   + ')', 'g');

lib/widget.js

@@ -2428,10 +2428,7 @@ Element.prototype.parseContent = function(noTags) {
       // VTE cannot display double-width chars that are also
       // surrogate pairs: It miscalculates the width of the chars.
       if (this.screen.program.isVTE) {
-        // In reality we should only drop double-width surrogate pairs,
-        // but we don't have a regex for that yet.
-        // content = content.replace(unicode.chars.surrogateDoubleWidth, '?');
-        content = content.replace(unicode.chars.surrogate, '?');
+        content = content.replace(unicode.chars.swide, '?');
       }
     } else {
       // no double-width: replace them with question-marks.