Timeline: Improve drag scrolling behavior.

timeline/src/Sequence_Widget.C

@@ -442,7 +442,7 @@ Sequence_Widget::handle ( int m )
 
             if ( ! _drag )
             {
-                begin_drag ( Drag(  Y, x_to_offset( X ) ) );
+                begin_drag ( Drag( X, Y, x_to_offset( X ), start() ) );
                 _log.hold();
             }
 
@@ -463,7 +463,7 @@ Sequence_Widget::handle ( int m )
                 const nframes_t of = timeline->x_to_offset( X );
 
                 int64_t s = (int64_t)of - _drag->offset;
-                
+                             
                 if ( s < 0 )
                     s = 0;
 
@@ -473,29 +473,25 @@ Sequence_Widget::handle ( int m )
                     sequence()->snap( this );
 
                 if ( X >= sequence()->x() + sequence()->w() ||
-                     X <= sequence()->x() )
+                     X <= sequence()->drawable_x() )
                 {
                     /* this drag needs to scroll */
 
-                    nframes_t pos = timeline->xoffset;
-
-                    nframes_t d = timeline->x_to_ts( 100 );
+                    int64_t pos = s - ( _drag->mouse_offset - _drag->offset );
+                    
 
-                    if ( X <= sequence()->x() )
-                    {
-
-                        if ( pos > d )
-                            pos -= d;
-                        else
-                            pos = 0;
-                    }
-                    else
-                        pos += d;
+                    if ( X > sequence()->x() + sequence()->w() )
+                        pos -= timeline->x_to_ts( sequence()->drawable_w() );
 
-                    timeline->xposition( timeline->ts_to_x(  pos ) );
+                    if ( s == 0 )
+                        pos = 0;
 
-//                    timeline->update_length( start() + length() );
+                    if ( pos < 0 )
+                        pos = 0;
 
+                    timeline->xposition(timeline->ts_to_x(pos));
+                    
+                    /* timeline->redraw();  */
                     sequence()->damage( FL_DAMAGE_USER1 );
                 }
 

timeline/src/Sequence_Widget.H

@@ -39,8 +39,9 @@ struct Drag
 
 //    nframes_t start;
     int64_t offset;
+    int64_t mouse_offset;
 
-    Drag( int X, int Y, uint64_t offset=0 ) : x( X ), y( Y ), offset( offset ) { state = 0; }
+    Drag( int X, int Y, uint64_t offset=0, uint64_t mouse_offset = 0 ) : x( X ), y( Y ), offset( offset ), mouse_offset( mouse_offset ) { state = 0; }
 };
 
 /* most common position description. /offset/ is only used by Regions,

timeline/src/Timeline.C

@@ -938,7 +938,21 @@ Timeline::prev_line ( nframes_t *frame, bool bar ) const
 nframes_t
 Timeline::x_to_offset ( int x ) const
 {
-    return x_to_ts( max( 0, x - Track::width() ) ) + xoffset;
+    int d = x - Track::width();
+
+    int64_t r;
+    
+    if ( d < 0 )
+        r = (int64_t)xoffset - x_to_ts( 0 - d );
+    else
+        r = (int64_t)xoffset + x_to_ts( d );
+
+    if ( r > JACK_MAX_FRAMES )
+        return JACK_MAX_FRAMES;
+    else if ( r < 0 )
+            return 0;
+    else
+        return r;
 }
 
 int
@@ -1837,7 +1851,7 @@ Timeline::xposition ( int X )
 {
     xoffset = x_to_ts( X );
 
-    int dx = ts_to_x( _old_xposition ) - ts_to_x( xoffset );
+    long dx = ts_to_x( _old_xposition ) - ts_to_x( xoffset );
 
     if ( dx )
         damage( FL_DAMAGE_SCROLL );