improve screen.setTerminal.

lib/widgets/screen.js

@@ -261,7 +261,21 @@ Screen.prototype.__defineSetter__('terminal', function(terminal) {
 });
 
 Screen.prototype.setTerminal = function(terminal) {
-  return this.program.setTerminal(terminal);
+  var entered = !!this.program.isAlt
+    , result;
+
+  if (entered) {
+    this.program._buf = '';
+    this.leave();
+  }
+
+  result = this.program.setTerminal(terminal);
+
+  if (entered) {
+    this.enter();
+  }
+
+  return result;
 };
 
 Screen.prototype.enter = function() {