Try to generalize the Track_Widget display calculations.

Region.C

@@ -266,7 +266,15 @@ Region::handle ( int m )
     }
 }
 
+void
+Region::draw_box( int X, int Y, int W, int H )
+{
+    /* dirty hack to keep the box from flipping to vertical at small sizes */
 
+    fl_push_clip( x(), Y, w(), H );
+    fl_draw_box( box(), x() - 10, Y, w() + 50, H, _box_color );
+    fl_pop_clip();
+}
 
 /* Draw (part of) region. OX is pixel offset from start of timeline, X
    Y W and H are the portion of the widget to draw (arrived at by
@@ -281,7 +289,7 @@ Region::draw ( int X, int Y, int W, int H )
     int ox = timeline.ts_to_x( _offset );
 
     if ( ox > OX + _track->w() ||
-         ox < OX && ox + w() < OX )
+         ox < OX && ox + abs_w() < OX )
         return;
 
     int rw = timeline.ts_to_x( _end - _start );
@@ -306,7 +314,7 @@ Region::draw ( int X, int Y, int W, int H )
     fl_push_clip( rx, Y, rw, H );
 
     /* dirty hack to keep the box from flipping to vertical at small sizes */
-    fl_draw_box( box(), rx - 10, Y, rw + 50, H, _box_color );
+//    fl_draw_box( box(), rx - 10, Y, rw + 50, H, _box_color );
 
 
 //    fl_push_clip( x() + Fl::box_dx( box() ), y(), w() - Fl::box_dw( box() ), h() );

Region.H

@@ -69,14 +69,23 @@ public:
 
     int y ( void ) const { return _track->y(); }
     int h ( void ) const { return _track->h(); }
-    int x ( void ) const { return _offset < timeline.xoffset ? -1 : min( 32767, _track->x() + timeline.ts_to_x( _offset - timeline.xoffset ) ); }
-//    int x ( void ) const { return (short)( _track->x() + timeline.ts_to_x( _offset - timeline.xoffset )); }
 
-    virtual int w ( void ) const { return timeline.ts_to_x( _end - _start ); }
-//    int w ( void ) const { return timeline.ts_to_x( (_end - _start) - ( timeline.xoffset - _offset) ); }
+    int x ( void ) const { return _offset < timeline.xoffset ? -1 : min( 32767, _track->x() + timeline.ts_to_x( _offset - timeline.xoffset ) ); }
+    virtual int w ( void ) const
+        {
+            int tx = timeline.ts_to_x( _offset );
+
+            int rw;
+            if ( tx < scroll_x() )
+                rw = abs_w() - (scroll_x() - tx);
+            else
+                rw = abs_w();
+
+            return min( rw, _track->w() );
+        }
 
     int abs_x ( void ) const { return timeline.ts_to_x( timeline.xoffset ); }
-    int abs_w ( void ) const { return timeline.ts_to_x( _end - _start ); }
+    virtual int abs_w ( void ) const { return timeline.ts_to_x( _end - _start ); }
 
 
     Fl_Color color ( void ) { return _color; }
@@ -98,10 +107,17 @@ public:
     virtual Fl_Boxtype box ( void ) const { return FL_UP_BOX; }
 
     /* just draw a simple box */
+
+    virtual void
+    draw_box ( int X, int Y, int W, int H )
+        {
+            fl_draw_box( box(), x(), y(), w(), y(), _box_color );
+        }
+
     virtual void
     draw ( int X, int Y, int W, int H )
         {
-            fl_draw_box( box(), x(), y(), w(), y(), _box_color );
+            draw_box( X, Y, W, H );
         }
 
 
@@ -231,8 +247,8 @@ protected:
 
 public:
 
-    int w ( void ) const { return 10; }
-    nframes_t length ( void ) const { return timeline.x_to_ts( w() ); }
+    int abs_w ( void ) const { return 10; }
+    nframes_t length ( void ) const { return timeline.x_to_ts( abs_w() ); }
 
     Track_Point ( )
         {
@@ -242,9 +258,6 @@ public:
     void
     draw ( int X, int Y, int W, int H )
         {
-            if ( x() < 0 )
-                return;
-
             Track_Widget::draw( x(), Y, w(), H );
 
             draw_label( _label, FL_ALIGN_RIGHT );
@@ -302,6 +315,7 @@ public:
         Region ( Clip *c );
 
         int handle ( int m );
+        void draw_box( int X, int Y, int W, int H );
         void draw ( int X, int Y, int W, int H );
         void resize ( void );
 

Track.C

@@ -47,6 +47,10 @@ Track::draw ( void )
 
     fl_push_clip( x(), y(), w(), h() );
 
+    for ( list <Track_Widget *>::iterator r = _regions.begin();  r != _regions.end(); r++ )
+        (*r)->draw_box( x(), y(), w(), h() );
+
+    /* TODO: detect overlap and draw with transparency/crossfade */
     for ( list <Track_Widget *>::iterator r = _regions.begin();  r != _regions.end(); r++ )
         (*r)->draw( x(), y(), w(), h() );
 

main.C

@@ -123,7 +123,7 @@ main ( int argc, char **argv )
 //    Fl_Group *pack = new Fl_Group( 0, 0, 5000, 600 );
 
     {
-        Track *tempo_track = new Track( 0, 0, 800, 24 );
+        Track *tempo_track = new Track( 100, 0, 800, 24 );
 
         tempo_track->label( "tempo map" );
         tempo_track->add( new Tempo_Point( 0, 120 ) );