Sequencer: Try to avoid excessive double buffer flips when the transport is rolling.

sequencer/src/canvas.C

@@ -483,6 +483,13 @@ Canvas::draw_line ( int x, int flags )
         m.current[ x ][ y ].flags |= flags;
 }
 
+int
+Canvas::playhead_moved ( void )
+{
+    int x = m.grid->ts_to_x( m.grid->index() );
+    
+    return m.playhead != x;
+}
 
 /** draw only the playhead--without reexamining the grid */
 int

sequencer/src/canvas.H

@@ -157,6 +157,7 @@ public:
     void notes ( char *s );
     char * notes ( void );
     void randomize_row ( int y );
+    int playhead_moved ( void );
 
     void start_cursor ( int x, int y );
     void end_cursor ( int x, int y );

sequencer/src/gui/ui.fl

@@ -1591,7 +1591,11 @@ _flags |= FL_DAMAGE_SCROLL;} {}
   }
   Function {draw_playhead( void )} {open return_type void
   } {
-    code {damage( FL_DAMAGE_USER1 );} {}
+    code {
+    if ( _c && _c->playhead_moved() )
+    {
+            damage( FL_DAMAGE_USER1 );
+    }} {}
   }
   Function {draw_border()} {open return_type void
   } {