Support scroll up / scroll down (fixes bug w/nano reported by Anders Kaseorg)

terminalframebuffer.hpp

@@ -153,14 +153,13 @@ namespace Terminal {
     std::deque<Row> rows;
     std::vector<wchar_t> window_title;
 
-    void scroll( int N );
-
     Row newrow( void ) { return Row( ds.get_width(), ds.get_background_rendition() ); }
 
   public:
     Framebuffer( int s_width, int s_height );
     DrawState ds;
 
+    void scroll( int N );
     void move_rows_autoscroll( int rows );
 
     Row *get_row( int row )

terminalfunctions.cpp

@@ -474,3 +474,19 @@ void Dispatcher::OSC_dispatch( Parser::OSC_End *act, Framebuffer *fb )
     }
   }
 }
+
+/* scroll down or terminfo indn */
+void CSI_SD( Framebuffer *fb, Dispatcher *dispatch )
+{
+  fb->scroll( dispatch->getparam( 0, 1 ) );
+}
+
+static Function func_CSI_SD( CSI, "S", CSI_SD );
+
+/* scroll up or terminfo rin */
+void CSI_SU( Framebuffer *fb, Dispatcher *dispatch )
+{
+  fb->scroll( -dispatch->getparam( 0, 1 ) );
+}
+
+static Function func_CSI_SU( CSI, "T", CSI_SU );