Backport --predict-overwrite from upstream

man/mosh-client.1

@@ -49,6 +49,38 @@ directly.
 With the \-c option, \fBmosh-client\fP instead prints the number of colors
 of the terminal given by the TERM environment variable.
 
+The \-v option will print some debugging information on standard
+error.  More instances of this flag will result in more debugging
+information.  If standard error is not redirected from the terminal,
+the display will be corrupted and quickly become unusable.
+
+.SH ENVIRONMENT VARIABLES
+
+.TP
+.B MOSH_KEY
+This variable must be set, and must contain a Base64-encoded cryptographic key from
+.BR mosh-server (1).
+
+.TP
+.B MOSH_ESCAPE_KEY
+See
+.BR mosh (1).
+
+.TP
+.B MOSH_PREDICTION_DISPLAY
+Controls local echo as described in
+.BR mosh (1).
+
+.TP
+.B MOSH_PREDICTION_OVERWRITE
+Controls local echo insert/overwrite as described in
+.BR mosh (1).
+
+.TP
+.B MOSH_TITLE_NOPREFIX
+See
+.BR mosh (1).
+
 .SH SEE ALSO
 .BR mosh (1),
 .BR mosh-server (1).

man/mosh.1

@@ -121,8 +121,67 @@ Synonym for \-\-predict=always
 Synonym for \-\-predict=never
 
 .TP
+
 .B \-p \fINUM\fP, \-\-port=\fINUM\fP
 Use a particular server-side UDP port, for example, if this is the
+
+.B \-\-predict\-overwrite\fP
+When prediction is enabled, do not insert speculative local echo
+before existing text, but overwrite it instead.
+
+The MOSH_PREDICTION_OVERWRITE environment variable also enables this
+if its value is 'yes'.
+
+.TP
+.B \-o
+Synonym for \-\-predict\-overwrite
+
+.TP
+.B \-\-family=inet
+Only use IPv4 for the SSH connection and Mosh session.
+
+.TP
+.B \-\-family=inet6
+Only use IPv6 for the SSH connection and Mosh session.  This and the
+following modes require Perl's IO::Socket::IP or IO::Socket::INET6
+modules.
+
+.TP
+.B \-\-family=auto
+Autodetect IPv4 or IPv6 for hosts that only have addresses
+in a single family.  Hosts with both IPv4 and IPv6 addresses will
+raise an error, and require re-invocation of \fBmosh\fP with another
+\fB\-\-family\fP option.
+
+.TP
+.B \-\-family=all
+Choose an address from all available IPv4 or IPv6 address, even for
+dual-stack hosts.  This is the most convenient option, but requires
+dual-stack connectivity, and Mosh 1.2.5 or later on the server, when
+roaming with dual-stack servers.
+
+.TP
+.B \-\-family=prefer-inet
+Similar to \fB\-\-family=all\fP, but attempt connects to the IPv4
+addresses first.  This is the default.
+
+.TP
+.B \-\-family=prefer-inet6
+Similar to \fB\-\-family=all\fP, but attempt connects to the IPv6
+addresses first.
+
+.TP
+.B \-4
+Synonym for \-\-family=inet
+
+.TP
+.B \-6
+Synonym for \-\-family=inet6
+
+.TP
+.B \-p \fIPORT\fP[:\fIPORT2\fP], \-\-port=\fIPORT\fP[:\fIPORT2\fP]
+Use a particular server-side UDP port or port range,
+for example, if this is the
 only port that is forwarded through a firewall to the
 server. Otherwise, \fBmosh\fP will choose a port between 60000 and
 61000.

scripts/mosh

@@ -46,6 +46,8 @@ my $server = 'mosh-server';
 
 my $predict = undef;
 
+my $overwrite = 0;
+
 my $port_request = undef;
 
 my $ssh = 'ssh';
@@ -67,6 +69,8 @@ qq{Usage: $0 [options] [--] [user@]host [command...]
 -n      --predict=never         never use local echo
         --predict=experimental  aggressively echo even when incorrect
 
+-o      --predict-overwrite             prediction overwrites instead of inserting
+
 -p NUM  --port=NUM           server-side UDP port
 
         --ssh=COMMAND        ssh command to run when setting up session
@@ -126,6 +130,7 @@ sub ip_and_sockaddr {
 GetOptions( 'client=s' => \$client,
 	    'server=s' => \$server,
 	    'predict=s' => \$predict,
+	    'predict-overwrite|o!' => \$overwrite,
 	    'port=i' => \$port_request,
 	    'a' => sub { $predict = 'always' },
 	    'n' => sub { $predict = 'never' },
@@ -148,6 +153,10 @@ if ( defined $predict ) {
   predict_check( $predict, 0 );
 }
 
+if ( $overwrite ) {
+    $ENV{ "MOSH_PREDICTION_OVERWRITE" } = "yes";
+}
+
 if ( defined $port_request ) {
   if ( $port_request =~ m{^[0-9]+$}
        and $port_request >= 0

src/frontend/mosh-client.cc

@@ -126,6 +126,10 @@ int main( int argc, char *argv[] )
   char *predict_mode = getenv( "MOSH_PREDICTION_DISPLAY" );
   /* can be NULL */
 
+  /* Read prediction insertion preference */
+  char *predict_overwrite = getenv( "MOSH_PREDICTION_OVERWRITE" );
+  /* can be NULL */
+
   char *key = strdup( env_key );
   if ( key == NULL ) {
     perror( "strdup" );
@@ -141,7 +145,7 @@ int main( int argc, char *argv[] )
   set_native_locale();
 
   try {
-    STMClient client( ip, port, key, predict_mode );
+    STMClient client( ip, port, key, predict_mode, predict_overwrite );
     client.init();
 
     try {

src/frontend/stmclient.h

@@ -75,7 +75,7 @@ class STMClient {
   }
 
 public:
-  STMClient( const char *s_ip, int s_port, const char *s_key, const char *predict_mode )
+  STMClient( const char *s_ip, int s_port, const char *s_key, const char *predict_mode, const char *predict_overwrite )
     : ip( s_ip ), port( s_port ), key( s_key ),
       saved_termios(), raw_termios(),
       window_size(),
@@ -103,6 +103,9 @@ class STMClient {
 	exit( 1 );
       }
     }
+    if ( predict_overwrite && !strcmp( predict_overwrite, "yes" ) ) {
+      overlays.get_prediction_engine().set_predict_overwrite( true );
+    } 
   }
 
   void init( void );

src/frontend/terminaloverlay.cc

@@ -662,32 +662,45 @@ void PredictionEngine::new_user_byte( char the_byte, const Framebuffer &fb )
 	  cursor().col--;
 	  cursor().expire( local_frame_sent + 1, now );
 
-	  for ( int i = cursor().col; i < fb.ds.get_width(); i++ ) {
-	    ConditionalOverlayCell &cell = the_row.overlay_cells[ i ];
-
+	  if ( predict_overwrite ) {
+	    ConditionalOverlayCell &cell = the_row.overlay_cells[ cursor().col ];
 	    cell.reset_with_orig();
 	    cell.active = true;
 	    cell.tentative_until_epoch = prediction_epoch;
 	    cell.expire( local_frame_sent + 1, now );
-	    cell.original_contents.push_back( *fb.get_cell( cursor().row, i ) );
+	    const Cell orig_cell = *fb.get_cell();
+	    cell.original_contents.push_back( orig_cell );
+	    cell.replacement = orig_cell;
+	    cell.replacement.clear();
+	    cell.replacement.append(' ');
+	  } else {
+	    for ( int i = cursor().col; i < fb.ds.get_width(); i++ ) {
+	      ConditionalOverlayCell &cell = the_row.overlay_cells[ i ];
+
+	      cell.reset_with_orig();
+	      cell.active = true;
+	      cell.tentative_until_epoch = prediction_epoch;
+	      cell.expire( local_frame_sent + 1, now );
+	      cell.original_contents.push_back( *fb.get_cell( cursor().row, i ) );
 
-	    if ( i + 2 < fb.ds.get_width() ) {
-	      ConditionalOverlayCell &next_cell = the_row.overlay_cells[ i + 1 ];
-	      const Cell *next_cell_actual = fb.get_cell( cursor().row, i + 1 );
-
-	      if ( next_cell.active ) {
-		if ( next_cell.unknown ) {
-		  cell.unknown = true;
+	      if ( i + 2 < fb.ds.get_width() ) {
+		ConditionalOverlayCell &next_cell = the_row.overlay_cells[ i + 1 ];
+		const Cell *next_cell_actual = fb.get_cell( cursor().row, i + 1 );
+
+		if ( next_cell.active ) {
+		  if ( next_cell.unknown ) {
+		    cell.unknown = true;
+		  } else {
+		    cell.unknown = false;
+		    cell.replacement = next_cell.replacement;
+		  }
 		} else {
 		  cell.unknown = false;
-		  cell.replacement = next_cell.replacement;
+		  cell.replacement = *next_cell_actual;
 		}
 	      } else {
-		cell.unknown = false;
-		cell.replacement = *next_cell_actual;
+		cell.unknown = true;
 	      }
-	    } else {
-	      cell.unknown = true;
 	    }
 	  }
 	}
@@ -710,7 +723,8 @@ void PredictionEngine::new_user_byte( char the_byte, const Framebuffer &fb )
 	}
 
 	/* do the insert */
-	for ( int i = fb.ds.get_width() - 1; i > cursor().col; i-- ) {
+	int rightmost_column = predict_overwrite ? cursor().col + 1 : fb.ds.get_width() - 1;
+	for ( int i = rightmost_column; i > cursor().col; i-- ) {
 	  ConditionalOverlayCell &cell = the_row.overlay_cells[ i ];
 	  cell.reset_with_orig();
 	  cell.active = true;

src/frontend/terminaloverlay.h

@@ -251,6 +251,7 @@ namespace Overlay {
 
   private:
     DisplayPreference display_preference;
+    bool predict_overwrite;
 
     bool active( void ) const;
 
@@ -261,6 +262,7 @@ namespace Overlay {
 
   public:
     void set_display_preference( DisplayPreference s_pref ) { display_preference = s_pref; }
+    void set_predict_overwrite( bool overwrite ) { predict_overwrite = overwrite; }
 
     void apply( Framebuffer &fb ) const;
     void new_user_byte( char the_byte, const Framebuffer &fb );
@@ -291,7 +293,8 @@ namespace Overlay {
 			       last_quick_confirmation( 0 ),
 			       send_interval( 250 ),
 			       last_height( 0 ), last_width( 0 ),
-			       display_preference( Adaptive )
+			       display_preference( Adaptive ),
+			       predict_overwrite( false )
     {
     }
   };