Scroll bar moves by pixels, not samples. This eliminates rounding errors while scrolling.

Region.C

@@ -260,7 +260,7 @@ Region::draw_box( int X, int Y, int W, int H )
     fl_push_clip( x(), Y, w(), H );
 
     if ( _selected )
-        fl_draw_box( FL_DOWN_BOX, x() - 10, Y, w() + 50, H, _selection_color );
+        fl_draw_box( fl_down( box() ), x() - 10, Y, w() + 50, H, _selection_color );
     else
         fl_draw_box( box(), x() - 10, Y, w() + 50, H, _box_color );
 

main.C

@@ -72,7 +72,7 @@ cb_zoom ( Fl_Widget *w, void *v )
 void
 cb_scroll ( Fl_Widget *w, void *v )
 {
-    timeline.xoffset = ((Fl_Slider*)w)->value();
+    timeline.xoffset = timeline.x_to_ts( ((Fl_Slider*)w)->value() );
     //  timeline.tracks->redraw();
     timeline.scroll->redraw();