Underline when empirical delay gets >500ms, even if SRTT hasn't (fixes #35)

src/frontend/terminaloverlay.cc

@@ -382,13 +382,18 @@ void PredictionEngine::cull( const Framebuffer &fb )
     srtt_trigger = false;
   }
 
-  /* control flagging with hysteresis */
+  /* control underlining with hysteresis */
   if ( send_interval > FLAG_TRIGGER_HIGH ) {
     flagging = true;
   } else if ( send_interval <= FLAG_TRIGGER_LOW ) {
     flagging = false;
   }
 
+  /* really big glitches also activate underlining */
+  if ( glitch_trigger > GLITCH_REPAIR_COUNT ) {
+    flagging = true;
+  }
+
   /* go through cell predictions */
 
   BOOST_AUTO( i, overlays.begin() );
@@ -473,8 +478,11 @@ void PredictionEngine::cull( const Framebuffer &fb )
       case Pending:
 	/* When a prediction takes a long time to be confirmed, we
 	   activate the predictions even if SRTT is low */
-	if ( (now - j->prediction_time) >= GLITCH_THRESHOLD ) {
-	  glitch_trigger = GLITCH_REPAIR_COUNT;
+	if ( (now - j->prediction_time) >= GLITCH_FLAG_THRESHOLD ) {
+	  glitch_trigger = GLITCH_REPAIR_COUNT * 2; /* display and underline */
+	} else if ( ((now - j->prediction_time) >= GLITCH_THRESHOLD)
+		    && (glitch_trigger < GLITCH_REPAIR_COUNT) ) {
+	  glitch_trigger = GLITCH_REPAIR_COUNT; /* just display */
 	}
 
 	break;

src/frontend/terminaloverlay.h

@@ -152,6 +152,8 @@ namespace Overlay {
     static const uint64_t GLITCH_REPAIR_COUNT = 10; /* non-glitches required to cure glitch trigger */
     static const uint64_t GLITCH_REPAIR_MININTERVAL = 150; /* required time in between non-glitches */
 
+    static const uint64_t GLITCH_FLAG_THRESHOLD = 500; /* prediction outstanding this long => underline */
+
     char last_byte;
     Parser::UTF8Parser parser;
 
@@ -172,7 +174,7 @@ namespace Overlay {
 
     bool flagging; /* whether we are underlining predictions */
     bool srtt_trigger; /* show predictions because of slow round trip time */
-    int glitch_trigger; /* show predictions temporarily because of long-pending prediction */
+    unsigned int glitch_trigger; /* show predictions temporarily because of long-pending prediction */
     uint64_t last_quick_confirmation;
 
     ConditionalCursorMove & cursor( void ) { assert( !cursors.empty() ); return cursors.back(); }