Eliminate one terminal copy per frame (20% speedup on benchmark)

src/examples/benchmark.cc

@@ -50,12 +50,17 @@ extern "C" {
 
 const int ITERATIONS = 1000;
 
+using namespace Terminal;
+
 int main( void )
 {
-  Terminal::Framebuffer local_framebuffer( 80, 24 );
+  int fbmod = 0;
+  Framebuffer local_framebuffers[ 2 ] = { Framebuffer(80,24), Framebuffer(80,24) };
+  Framebuffer *local_framebuffer = &(local_framebuffers[ fbmod ]);
+  Framebuffer *new_state = &(local_framebuffers[ !fbmod ]);
   Overlay::OverlayManager overlays;
-  Terminal::Display display( true );
+  Display display( true );
-  Terminal::Complete local_terminal( 80, 24 );
+  Complete local_terminal( 80, 24 );
 
   /* Adopt native locale */
   if ( NULL == setlocale( LC_ALL, "" ) ) {
@@ -71,25 +76,27 @@ int main( void )
 
   for ( int i = 0; i < ITERATIONS; i++ ) {
     /* type a character */
-    overlays.get_prediction_engine().new_user_byte( i + 'x', local_framebuffer );
+    overlays.get_prediction_engine().new_user_byte( i + 'x', *local_framebuffer );
 
     /* fetch target state */
-    Terminal::Framebuffer new_state( local_terminal.get_fb() );
+    *new_state = local_terminal.get_fb();
 
     /* apply local overlays */
-    overlays.apply( new_state );
+    overlays.apply( *new_state );
 
     /* calculate minimal difference from where we are */
     const string diff( display.new_frame( false,
-					  local_framebuffer,
+					  *local_framebuffer,
-					  new_state ) );    
+					  *new_state ) );
 
     /* make sure to use diff */
     if ( diff.size() > INT_MAX ) {
       exit( 1 );
     }
 
-    local_framebuffer = new_state;
+    fbmod = !fbmod;
+    local_framebuffer = &(local_framebuffers[ fbmod ]);
+    new_state = &(local_framebuffers[ !fbmod ]);
   }
 
   return 0;

src/frontend/stmclient.cc

@@ -128,6 +128,7 @@ void STMClient::main_init( void )
 
   /* local state */
   local_framebuffer = new Terminal::Framebuffer( window_size.ws_col, window_size.ws_row );
+  new_state = new Terminal::Framebuffer( 1, 1 );
 
   /* initialize screen */
   string init = display.new_frame( false, *local_framebuffer, *local_framebuffer );
@@ -152,19 +153,23 @@ void STMClient::output_new_frame( void )
   }
 
   /* fetch target state */
-  Terminal::Framebuffer new_state( network->get_latest_remote_state().state.get_fb() );
+  *new_state = network->get_latest_remote_state().state.get_fb();
 
   /* apply local overlays */
-  overlays.apply( new_state );
+  overlays.apply( *new_state );
 
   /* calculate minimal difference from where we are */
   const string diff( display.new_frame( !repaint_requested,
 					*local_framebuffer,
-					new_state ) );
+					*new_state ) );
   swrite( STDOUT_FILENO, diff.data(), diff.size() );
-  *local_framebuffer = new_state;
 
   repaint_requested = false;
+
+  /* switch pointers */
+  Terminal::Framebuffer *tmp = new_state;
+  new_state = local_framebuffer;
+  local_framebuffer = tmp;
 }
 
 bool STMClient::process_network_input( void )

src/frontend/stmclient.h

@@ -39,7 +39,7 @@ private:
   int signal_fd;
   struct winsize window_size;
 
-  Terminal::Framebuffer *local_framebuffer;
+  Terminal::Framebuffer *local_framebuffer, *new_state;
   Overlay::OverlayManager overlays;
   Network::Transport< Network::UserStream, Terminal::Complete > *network;
   Terminal::Display display;
@@ -60,6 +60,7 @@ public:
       signal_fd(),
       window_size(),
       local_framebuffer( NULL ),
+      new_state( NULL ),
       overlays(),
       network( NULL ),
       display( true ), /* use TERM environment var to initialize display */
@@ -90,6 +91,10 @@ public:
       delete local_framebuffer;
     }
 
+    if ( new_state != NULL ) {
+      delete new_state;
+    }
+
     if ( network != NULL ) {
       delete network;
     }