User selectable prediction mode (fixes #9 github issue)

scripts/mosh

@@ -26,16 +26,31 @@ $|=1;
 
 my $client = 'mosh-client';
 my $server = 'mosh-server';
+my $predict = 'adaptive';
 
 my $usage =
 qq{Usage: $0 [options] [user@]host
     --client=PATH        mosh client on local machine  (default: "mosh-client")
-   --server=PATH        mosh server on remote machine (default: "mosh-server")\n};
+    --server=PATH        mosh server on remote machine (default: "mosh-server")
+
+    --predict=adaptive   local echo for slower links [default]
+-a  --predict=always     use local echo even on fast links
+-n  --predict=never      never use local echo
+
+Please report bugs to mosh-devel\@mit.edu.
+Mosh home page: http://mosh.mit.edu\n};
 
 GetOptions( 'client=s' => \$client,
 	    'server=s' => \$server,
+	    'predict=s' => \$predict,
+	    'a' => sub { $predict = 'always' },
+	    'n' => sub { $predict = 'never' },
 	    'fake-proxy!' => \my $fake_proxy ) or die $usage;
 
+if ( not exists { adaptive => 0, always => 0, never => 0 }->{ $predict } ) {
+  die $usage;
+}
+
 if ( defined $fake_proxy ) {
   use Errno qw(EINTR);
   use IO::Socket::INET;
@@ -122,5 +137,5 @@ if ( $pid == 0 ) { # child
 
   # Now start real mosh client
   $ENV{ 'MOSH_KEY' } = $key;
-  exec {$client} ($client, $ip, $port);
+  exec {$client} ($client, $ip, $port, $predict);
 }

src/frontend/mosh-client.cc

@@ -22,14 +22,24 @@
 #include "stmclient.h"
 #include "crypto.h"
 
+void usage( const char *argv0 ) {
+  fprintf( stderr, "Usage: %s IP PORT [always|never|adaptive]\n", argv0 );
+}
+
 int main( int argc, char *argv[] )
 {
   /* Get arguments */
   char *ip;
   int port;
 
-  if ( argc != 3 ) {
+  char *predict_mode = NULL;
-    fprintf( stderr, "Usage: %s IP PORT\n", argv[ 0 ] );
+
+  if ( argc == 4 ) {
+    predict_mode = argv[ 3 ];
+  } else if ( argc == 3 ) {
+    /* do nothing */
+  } else {
+    usage( argv[ 0 ]);
     exit( 1 );
   }
 
@@ -61,7 +71,7 @@ int main( int argc, char *argv[] )
   }
 
   try {
-    STMClient client( ip, port, key );
+    STMClient client( ip, port, key, predict_mode );
     client.init();
 
     try {

src/frontend/stmclient.h

@@ -53,7 +53,7 @@ private:
   void output_new_frame( void );
 
 public:
-  STMClient( const char *s_ip, int s_port, const char *s_key )
+  STMClient( const char *s_ip, int s_port, const char *s_key, const char *predict_mode )
     : ip( s_ip ), port( s_port ), key( s_key ),
       saved_termios(), raw_termios(),
       winch_fd(), shutdown_signal_fd(),
@@ -63,7 +63,20 @@ public:
       network( NULL ),
       repaint_requested( false ),
       quit_sequence_started( false )
-  {}
+  {
+    if ( predict_mode ) {
+      if ( !strcmp( predict_mode, "always" ) ) {
+	overlays.get_prediction_engine().set_display_preference( Overlay::PredictionEngine::Always );
+      } else if ( !strcmp( predict_mode, "never" ) ) {
+	overlays.get_prediction_engine().set_display_preference( Overlay::PredictionEngine::Never );
+      } else if ( !strcmp( predict_mode, "adaptive" ) ) {
+	overlays.get_prediction_engine().set_display_preference( Overlay::PredictionEngine::Adaptive );
+      } else {
+	fprintf( stderr, "Unknown prediction mode %s.\n", predict_mode );
+	exit( 1 );
+      }
+    }
+  }
 
   void init( void );
   void shutdown( void );

src/frontend/terminaloverlay.cc

@@ -315,7 +315,9 @@ void ConditionalOverlayRow::apply( Framebuffer &fb, uint64_t confirmed_epoch, bo
 
 void PredictionEngine::apply( Framebuffer &fb ) const
 {
-  bool show = srtt_trigger || glitch_trigger;
+  bool show = (display_preference != Never) && ( srtt_trigger
+						 || glitch_trigger
+						 || (display_preference == Always) );
 
   if ( show ) {
     for_each( cursors.begin(), cursors.end(), [&]( const ConditionalCursorMove &x ) { x.apply( fb, confirmed_epoch ); } );
@@ -377,6 +379,10 @@ void PredictionEngine::init_cursor( const Framebuffer &fb )
 
 void PredictionEngine::cull( const Framebuffer &fb )
 {
+  if ( display_preference == Never ) {
+    return;
+  }
+
   uint64_t now = timestamp();
 
   /* control srtt_trigger with hysteresis */
@@ -547,6 +553,10 @@ ConditionalOverlayRow & PredictionEngine::get_or_make_row( int row_num, int num_
 
 void PredictionEngine::new_user_byte( char the_byte, const Framebuffer &fb )
 {
+  if ( display_preference == Never ) {
+    return;
+  }
+
   cull( fb );
 
   uint64_t now = timestamp();

src/frontend/terminaloverlay.h

@@ -185,6 +185,18 @@ namespace Overlay {
     unsigned int send_interval;
 
   public:
+    enum DisplayPreference {
+      Always,
+      Never,
+      Adaptive
+    };
+
+  private:
+    DisplayPreference display_preference;
+
+  public:
+    void set_display_preference( DisplayPreference s_pref ) { display_preference = s_pref; }
+
     void apply( Framebuffer &fb ) const;
     void new_user_byte( char the_byte, const Framebuffer &fb );
     void cull( const Framebuffer &fb );
@@ -208,7 +220,8 @@ namespace Overlay {
 			       glitch_trigger( 0 ),
 			       last_quick_confirmation( 0 ),
 			       last_scheduled_timeout( 0 ),
-			       send_interval( 250 )
+			       send_interval( 250 ),
+			       display_preference( Adaptive )
     {
     }
   };