if an xfade involves only 2 regions, clamp its length to the overlap between them

git-svn-id: svn://localhost/ardour2/branches/3.0@12238 d708f5d6-7413-0410-9779-e7cbd77b26cf

gtk2_ardour/editor_drag.cc

@@ -4559,12 +4559,6 @@ CrossfadeEdgeDrag::CrossfadeEdgeDrag (Editor* e, AudioRegionView* rv, ArdourCanv
 	, arv (rv)
 	, start (start_yn)
 {
-	cerr << "new xfade drag\n";
-}
-
-CrossfadeEdgeDrag::~CrossfadeEdgeDrag ()
-{
-	cerr << "destory xfade drag\n";
 }
 
 void
@@ -4590,8 +4584,14 @@ CrossfadeEdgeDrag::motion (GdkEvent*, bool)
 		len = ar->fade_out()->back()->when;
 	}
 
+	/* how long should it be ? */
+
 	new_length = len + _editor->unit_to_frame (distance);
 
+	/* now check with the region that this is legal */
+
+	new_length = ar->verify_xfade_bounds (new_length, start);
+
 	if (start) {
 		arv->redraw_start_xfade_to (ar, new_length);
 	} else {
@@ -4616,7 +4616,7 @@ CrossfadeEdgeDrag::finished (GdkEvent*, bool)
 		len = ar->fade_out()->back()->when;
 	}
 
-	new_length = len + _editor->unit_to_frame (distance);
+	new_length = ar->verify_xfade_bounds (len + _editor->unit_to_frame (distance), start);
 	
 	if (start) {
 		ar->set_fade_in_length (new_length);

gtk2_ardour/editor_drag.h

@@ -978,7 +978,6 @@ class CrossfadeEdgeDrag : public Drag
 {
   public:
 	CrossfadeEdgeDrag (Editor*, AudioRegionView*, ArdourCanvas::Item*, bool start);
-	~CrossfadeEdgeDrag ();
 
 	void start_grab (GdkEvent*, Gdk::Cursor* c = 0);
 	void motion (GdkEvent*, bool);

libs/ardour/ardour/audioregion.h

@@ -143,6 +143,8 @@ class AudioRegion : public Region
 	void set_default_fade_in ();
 	void set_default_fade_out ();
 
+	framecnt_t verify_xfade_bounds (framecnt_t, bool start);
+	
 	void set_envelope_active (bool yn);
 	void set_default_envelope ();
 

libs/ardour/audioregion.cc

@@ -1801,6 +1801,59 @@ AudioRegion::set_fade_out_is_xfade (bool yn)
 	_fade_out_is_xfade = yn;
 }
 
+framecnt_t
+AudioRegion::verify_xfade_bounds (framecnt_t len, bool start)
+{
+	boost::shared_ptr<Playlist> pl (playlist());
+
+	if (!pl) {
+		/* not currently in a playlist - xfade length is unbounded
+		   (and irrelevant)
+		*/
+		return len;
+	}
+
+	boost::shared_ptr<RegionList> rl;
+	framecnt_t maxlen;
+
+	if (start) {
+		rl = pl->regions_at (position());
+	} else {
+		rl = pl->regions_at (last_frame());
+	}
+	
+	RegionList::iterator i;
+	boost::shared_ptr<Region> other;
+	uint32_t n = 0;
+
+	/* count and find the other region in a single pass through the list */
+
+	for (i = rl->begin(); i != rl->end(); ++i) {
+		if ((*i).get() != this) {
+			other = *i;
+		}
+		++n;
+	}
+
+	if (n != 2) {
+		/* zero or multiple regions stacked here - don't care about xfades */
+		return len;
+	}
+
+	/* we overlap a single region. clamp the length of an xfade to
+	   the duration of the overlap.
+	*/
+
+	if (start) {
+		maxlen = other->last_frame() - position();
+	} else {
+		maxlen = last_frame() - other->position();
+	}
+
+	return min (maxlen, len);
+		
+}
+
 extern "C" {
 
 	int region_read_peaks_from_c (void *arg, uint32_t npeaks, uint32_t start, uint32_t cnt, intptr_t data, uint32_t n_chan, double samples_per_unit)