fix disappearing double-width chars on scroll up.

lib/widget.js

@@ -1111,6 +1111,9 @@ Screen.prototype.draw = function(start, end) {
       // Optimize by comparing the real output
       // buffer to the pending output buffer.
       if (data === o[x][0] && ch === o[x][1]) {
+        // if (unicode.charWidth(ch, 0) === 2) {
+        //   x++;
+        // }
         if (lx === -1) {
           lx = x;
           ly = y;
@@ -1209,9 +1212,17 @@ Screen.prototype.draw = function(start, end) {
             // Might also need: `line[x + 1][0] !== line[x][0]`
             // for borderless boxes?
             if (x === line.length - 1 || angles[line[x + 1][1]]) {
+              // If we're at the end, we don't have enough space for a
+              // double-width. Overwrite it with a space and ignore.
               ch = ' ';
               o[x][1] = ' ';
             } else {
+              // ALWAYS refresh double-width chars because this special cursor
+              // behavior is needed. There may be a more efficient way of doing
+              // this. See above.
+              o[x][1] = ' ';
+              // Eat the next character by moving forward and marking as a
+              // space (which it is).
               o[++x][1] = ' ';
             }
           }

test/widget-eaw.js

@@ -5,7 +5,7 @@ screen = blessed.screen({
   dump: __dirname + '/logs/eaw.log',
   smartCSR: true,
   dockBorders: true,
-  fullUnicode: process.argv[2] === '-' ? false : true
+  fullUnicode: ~process.argv.indexOf('-') ? false : true
 });
 
 // screen.options.fullUnicode = false;
@@ -40,7 +40,8 @@ var COMBINE = blessed.unicode.fromCodePoint(0x10A01);
 // At cols=44, the bug that is avoided by this occurs:
 // || angles[line[x + 1][1]]) {
 
-var lorem = 'Non eram nes' + COMBINE + 'cius Brute cum quae summis ingeniis exquisitaque'
+var lorem = 'Non eram nes' + (!~process.argv.indexOf('s') ? COMBINE : '')
++ 'cius Brute cum quae summis ingeniis exquisitaque'
 + ' doctrina philosophi Graeco sermone tractavissent ea Latinis litteris mandaremus'
 + ' fore ut hic noster labor in varias reprehensiones incurreret nam quibusdam et'
 + ' iis quidem non admodum indoctis totum hoc displicet philosophari quidam autem'
@@ -88,10 +89,13 @@ var lorem = 'Non eram nes' + COMBINE + 'cius Brute cum quae summis ingeniis exqu
 lorem = lorem.replace(/e/gi, DOUBLE);
 // NOTE: libvte breaks when trying to display
 // this surrogate pair double width character:
-if (process.argv[2] !== 'vte') {
+if (~process.argv.indexOf('vte')) {
   lorem = lorem.replace(/a/gi, SURROGATE_DOUBLE);
 }
 lorem = lorem.replace(/o/gi, SURROGATE_SINGLE);
+if (~process.argv.indexOf('s')) {
+  lorem = lorem.replace(/s/gi, 's' + COMBINE);
+}
 
 var main = blessed.box({
   parent: screen,