Allow trim of midi regions to before the start of the source. Fixes #3156.

git-svn-id: svn://localhost/ardour2/branches/3.0@8212 d708f5d6-7413-0410-9779-e7cbd77b26cf

4 files changed, 36 insertions, 21 deletions

diff --git a/libs/ardour/ardour/midi_region.h b/libs/ardour/ardour/midi_region.h
index 853272d349..dae984c331 100644
--- a/libs/ardour/ardour/midi_region.h
+++ b/libs/ardour/ardour/midi_region.h
@@ -107,13 +107,20 @@ class MidiRegion : public Region
 	boost::shared_ptr<MidiModel> model()             { return midi_source()->model(); }
 	boost::shared_ptr<const MidiModel> model() const { return midi_source()->model(); }
 
+	void fix_negative_start ();
+
+  protected:
+	
+	virtual bool can_trim_start_before_source_start () const {
+		return true;
+	}
+
   private:
 	friend class RegionFactory;
 
 	MidiRegion (const SourceList&);
 	MidiRegion (boost::shared_ptr<const MidiRegion>, frameoffset_t offset = 0, bool offset_relative = true);
 
-  private:
 	framecnt_t _read_at (const SourceList&, Evoral::EventSink<framepos_t>& dst,
 			     framepos_t position,
 			     framecnt_t dur,
diff --git a/libs/ardour/ardour/region.h b/libs/ardour/ardour/region.h
index 3ad61919b1..ed4923bc40 100644
--- a/libs/ardour/ardour/region.h
+++ b/libs/ardour/ardour/region.h
@@ -315,6 +315,10 @@ class Region
 	/** Constructor for derived types only */
 	Region (Session& s, framepos_t start, framecnt_t length, const std::string& name, DataType);
 
+	virtual bool can_trim_start_before_source_start () const {
+		return false;
+	}
+
   protected:
 	void send_change (const PBD::PropertyChange&);
         void mid_thaw (const PBD::PropertyChange&);
diff --git a/libs/ardour/midi_region.cc b/libs/ardour/midi_region.cc
index f9fb791bad..74276ff5b6 100644
--- a/libs/ardour/midi_region.cc
+++ b/libs/ardour/midi_region.cc
@@ -121,7 +121,7 @@ MidiRegion::set_position_internal (framepos_t pos, bool allow_bbt_recompute)
 	BeatsFramesConverter old_converter(_session.tempo_map(), _position - _start);
 	double length_beats = old_converter.from(_length);
 
-	Region::set_position_internal(pos, allow_bbt_recompute);
+	Region::set_position_internal (pos, allow_bbt_recompute);
 
 	BeatsFramesConverter new_converter(_session.tempo_map(), pos - _start);
 
@@ -306,9 +306,22 @@ MidiRegion::model_automation_state_changed (Evoral::Parameter const & p)
 	}
 
 	/* the source will have an iterator into the model, and that iterator will have been set up
-	   for a given set of filtered_paramters, so now that we've changed that list we must invalidate
+	   for a given set of filtered_parameters, so now that we've changed that list we must invalidate
 	   the iterator.
 	*/
 	Glib::Mutex::Lock lm (midi_source(0)->mutex());
 	midi_source(0)->invalidate ();
 }
+
+/** This is called when a trim drag has resulted in a -ve _start time for this region.
+ *  Fix it up by adding some empty space to the source.
+ */
+void
+MidiRegion::fix_negative_start ()
+{
+        BeatsFramesConverter c (_session.tempo_map(), _position);
+
+	MidiModel::WriteLock lock (model()->edit_lock ());
+	model()->insert_silence_at_start (c.from (-_start));
+	_start = 0;
+}
diff --git a/libs/ardour/region.cc b/libs/ardour/region.cc
index 5c25d34c60..585689a656 100644
--- a/libs/ardour/region.cc
+++ b/libs/ardour/region.cc
@@ -732,13 +732,7 @@ Region::trim_start (framepos_t new_position, void */*src*/)
 		return;
 	}
 	framepos_t new_start;
-	frameoffset_t start_shift;
-
-	if (new_position > _position) {
-		start_shift = new_position - _position;
-	} else {
-		start_shift = -(_position - new_position);
-	}
+	frameoffset_t const start_shift = new_position - _position;
 
 	if (start_shift > 0) {
 
@@ -759,6 +753,7 @@ Region::trim_start (framepos_t new_position, void */*src*/)
 		} else {
 			new_start = _start + start_shift;
 		}
+		
 	} else {
 		return;
 	}
@@ -813,9 +808,10 @@ Region::modify_front (framepos_t new_position, bool reset_fade, void *src)
 		framecnt_t newlen = 0;
 		framepos_t delta = 0;
 
-		/* can't trim it back passed where source position zero is located */
-		
-		new_position = max (new_position, source_zero);
+		if (!can_trim_start_before_source_start ()) {
+			/* can't trim it back past where source position zero is located */
+			new_position = max (new_position, source_zero);
+		}
 		
 		if (new_position > _position) {
 			newlen = _length - (new_position - _position);
@@ -887,18 +883,13 @@ Region::trim_to (framepos_t position, framecnt_t length, void *src)
 void
 Region::trim_to_internal (framepos_t position, framecnt_t length, void */*src*/)
 {
-	frameoffset_t start_shift;
 	framepos_t new_start;
 
 	if (locked()) {
 		return;
 	}
 
-	if (position > _position) {
-		start_shift = position - _position;
-	} else {
-		start_shift = -(_position - position);
-	}
+	frameoffset_t const start_shift = position - _position;
 
 	if (start_shift > 0) {
 
@@ -910,7 +901,7 @@ Region::trim_to_internal (framepos_t position, framecnt_t length, void */*src*/)
 
 	} else if (start_shift < 0) {
 
-		if (_start < -start_shift) {
+		if (_start < -start_shift && !can_trim_start_before_source_start ()) {
 			new_start = 0;
 		} else {
 			new_start = _start + start_shift;
@@ -1609,7 +1600,7 @@ Region::can_trim () const
 
         ct = CanTrim (ct | FrontTrimLater | EndTrimEarlier);
 
-        if (start() != 0) {
+        if (start() != 0 || can_trim_start_before_source_start ()) {
                 ct = CanTrim (ct | FrontTrimEarlier);
         }