expose screen.enter and screen.leave. fixes #29.

lib/widget.js

@@ -348,26 +348,12 @@ function Screen(options) {
     self.emit('blur');
   });
 
-  this.program.alternateBuffer();
-  this.program.hideCursor();
-  this.program.cup(0, 0);
-  //this.program.csr(0, this.height - 1);
-  this.alloc();
+  this.enter();
 
   function reset() {
     if (reset.done) return;
     reset.done = true;
-    if (self.program.scrollTop !== 0
-        || self.program.scrollBottom !== self.rows - 1) {
-      self.program.csr(0, self.height - 1);
-    }
-    self.program.clear();
-    self.program.showCursor();
-    self.program.normalBuffer();
-    if (self._listenedMouse) {
-      self.program.disableMouse();
-    }
-    self.program.flush();
+    self.leave();
   }
 
   this._maxListeners = Infinity;
@@ -412,6 +398,31 @@ Screen.prototype.__proto__ = Node.prototype;
 
 Screen.prototype.type = 'screen';
 
+Screen.prototype.enter = function() {
+  if (this.program.isAlt) return;
+  this.program.alternateBuffer();
+  this.program.hideCursor();
+  this.program.cup(0, 0);
+  //this.program.csr(0, this.height - 1);
+  this.alloc();
+};
+
+Screen.prototype.leave = function() {
+  if (!this.program.isAlt) return;
+  if (this.program.scrollTop !== 0
+      || this.program.scrollBottom !== this.rows - 1) {
+    this.program.csr(0, this.height - 1);
+  }
+  // this.program.clear();
+  this.alloc();
+  this.program.showCursor();
+  this.program.normalBuffer();
+  if (this._listenedMouse) {
+    this.program.disableMouse();
+  }
+  this.program.flush();
+};
+
 Screen.prototype.log = function() {
   return this.program.log.apply(this.program, arguments);
 };