Put the real terminal in alternate screen mode

Closes #2

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

src/terminal/terminaldisplay.cc

@@ -46,12 +46,12 @@ static const Renditions & initial_rendition( void )
 
 std::string Display::open() const
 {
-  return std::string( "\033[?1h" );
+  return std::string( smcup ? smcup : "" ) + std::string( "\033[?1h" );
 }
 
 std::string Display::close() const
 {
-  return std::string( "\033[?1l\033[0m\033[?25h" );
+  return std::string( "\033[?1l\033[0m\033[?25h" ) + std::string( rmcup ? rmcup : "" );
 }
 
 std::string Display::new_frame( bool initialized, const Framebuffer &last, const Framebuffer &f ) const

src/terminal/terminaldisplay.h

@@ -78,6 +78,8 @@ namespace Terminal {
 
     int posterize_colors; /* downsample input colors >8 to [0..7] */
 
+    const char *smcup, *rmcup; /* enter and exit alternate screen mode */
+
     void put_cell( bool initialized, FrameState &frame, const Framebuffer &f ) const;
 
   public:

src/terminal/terminaldisplayinit.cc

@@ -89,7 +89,7 @@ const char *Display::ti_str( const char *capname ) const
 }
 
 Display::Display( bool use_environment )
-  : has_ech( true ), has_bce( true ), has_title( true ), posterize_colors( false )
+  : has_ech( true ), has_bce( true ), has_title( true ), posterize_colors( false ), smcup( NULL ), rmcup( NULL )
 {
   if ( use_environment ) {
     int errret = -2;
@@ -145,5 +145,8 @@ Display::Display( bool use_environment )
     /*
     posterize_colors = ti_num( "colors" ) < 256;
     */
+
+    smcup = ti_str("smcup");
+    rmcup = ti_str("rmcup");
   }
 }