Don't send empty HostBytes strings.

This allows more Resize instructions to be elided.  It also keeps the
server from sending empty updates when the screen has been written but
not changed.

1 files changed, 5 insertions, 2 deletions

diff --git a/src/statesync/completeterminal.cc b/src/statesync/completeterminal.cc
index d65ff9d..c22c6d0 100644
--- a/src/statesync/completeterminal.cc
+++ b/src/statesync/completeterminal.cc
@@ -87,8 +87,11 @@ string Complete::diff_from( const Complete &existing ) const
       new_res->MutableExtension( resize )->set_width( terminal.get_fb().ds.get_width() );
       new_res->MutableExtension( resize )->set_height( terminal.get_fb().ds.get_height() );
     }
-    Instruction *new_inst = output.add_instruction();
-    new_inst->MutableExtension( hostbytes )->set_hoststring( display.new_frame( true, existing.get_fb(), terminal.get_fb() ) );
+    string update = display.new_frame( true, existing.get_fb(), terminal.get_fb() );
+    if ( !update.empty() ) {
+      Instruction *new_inst = output.add_instruction();
+      new_inst->MutableExtension( hostbytes )->set_hoststring( update );
+    }
   }
   
   return output.SerializeAsString();