Add static meta-data for x-ardour/region.pbdid DnD

During drag-motion callbacks the data to be dragged is n/a.
However we like to discriminate if drop is possible.

When dragging regions, the data-type of the region to be dragged
is unknown, so different `x-ardour/region` targets are not an
option, either.

Until a better option is presented, a static global is used
to set the data-type for region.pbdid drags.

gtk2_ardour/editor_canvas_events.cc

@@ -1211,26 +1211,18 @@ Editor::track_canvas_drag_motion (Glib::RefPtr<Gdk::DragContext> const& context,
 	if (can_drop) {
 
 		if (target == "x-ardour/region.pbdid") {
-#if 0
-			// TODO check drag_source::drag_data_get() -> SelectionData& region
-
-			if (tv.first == 0 && region) {
+			if (tv.first == 0 && pbdid_dragged_dt != DataType::NIL) {
 				/* drop to drop-zone */
-				context->drag_status (context->get_suggested_action(), time);
+				context->drag_status (Gdk::ACTION_COPY, time);
 				return true;
 			}
 
-			if ((boost::dynamic_pointer_cast<AudioRegion> (region) != 0 && dynamic_cast<AudioTimeAxisView*> (tv.first) != 0) ||
-			    (boost::dynamic_pointer_cast<MidiRegion> (region) != 0 && dynamic_cast<MidiTimeAxisView*> (tv.first) != 0)) {
+			if ((pbdid_dragged_dt == DataType::AUDIO && dynamic_cast<AudioTimeAxisView*> (tv.first) != 0) ||
+			    (pbdid_dragged_dt == DataType::MIDI  && dynamic_cast<MidiTimeAxisView*> (tv.first) != 0)) {
 				/* audio to audio OR MIDI to MIDI */
-				context->drag_status (context->get_suggested_action(), time);
+				context->drag_status (Gdk::ACTION_COPY, time);
 				return true;
 			}
-#else
-			/* region drop always works */
-			context->drag_status (context->get_suggested_action(), time);
-#endif
-			return true;
 		} else {
 			/* DND originating from outside ardour
 			 *

gtk2_ardour/public_editor.cc

@@ -31,6 +31,8 @@ const int PublicEditor::horizontal_spacing = 6;
 
 sigc::signal<void> PublicEditor::DropDownKeys;
 
+ARDOUR::DataType PublicEditor::pbdid_dragged_dt = ARDOUR::DataType::NIL;
+
 PublicEditor::PublicEditor (Gtk::Widget& content)
 	: Tabbable (content, _("Editor"), X_("editor"))
 {

gtk2_ardour/public_editor.h

@@ -425,6 +425,9 @@ public:
 			: action (a), target (tgt) {}
 	};
 
+	/* data-type of [region] object currently dragged with x-ardour/region.pbdid */
+	static ARDOUR::DataType pbdid_dragged_dt;
+
 	std::map<std::string,RegionAction> region_action_map;
 
 	Glib::RefPtr<Gtk::ActionGroup> editor_actions;

gtk2_ardour/region_list_base.cc

@@ -48,6 +48,7 @@
 #include "gui_thread.h"
 #include "keyboard.h"
 #include "main_clock.h"
+#include "public_editor.h"
 #include "region_list_base.h"
 #include "ui_config.h"
 #include "utils.h"
@@ -82,8 +83,10 @@ RegionListBase::RegionListBase ()
 	_model = TreeStore::create (_columns);
 	_model->set_sort_column (0, SORT_ASCENDING);
 
-	_display.add_object_drag (_columns.region.index (), "x-ardour/region.pbdid", Gtk::TARGET_SAME_APP);
+	_display.add_object_drag (-1, "x-ardour/region.pbdid", Gtk::TARGET_SAME_APP);
 	_display.set_drag_column (_columns.name.index ());
+	_display.signal_drag_begin ().connect (sigc::mem_fun (*this, &RegionListBase::drag_begin));
+	_display.signal_drag_end ().connect (sigc::mem_fun (*this, &RegionListBase::drag_end));
 	_display.signal_drag_data_get ().connect (sigc::mem_fun (*this, &RegionListBase::drag_data_get));
 
 	_display.set_model (_model);
@@ -226,19 +229,37 @@ RegionListBase::leave_notify (GdkEventCrossing*)
 	return false;
 }
 
+void
+RegionListBase::drag_begin (Glib::RefPtr<Gdk::DragContext> const&)
+{
+	if (_display.get_selection ()->count_selected_rows () == 0) {
+		PublicEditor::instance ().pbdid_dragged_dt = DataType::NIL;
+	}
+	TreeView::Selection::ListHandle_Path rows = _display.get_selection ()->get_selected_rows ();
+	for (TreeView::Selection::ListHandle_Path::iterator i = rows.begin (); i != rows.end (); ++i) {
+		boost::shared_ptr<Region> region           = (*_model->get_iter (*i))[_columns.region];
+		PublicEditor::instance ().pbdid_dragged_dt = region->data_type ();
+		break;
+	}
+}
+
+void
+RegionListBase::drag_end (Glib::RefPtr<Gdk::DragContext> const&)
+{
+	PublicEditor::instance ().pbdid_dragged_dt = DataType::NIL;
+}
+
 void
 RegionListBase::drag_data_get (Glib::RefPtr<Gdk::DragContext> const&, Gtk::SelectionData& data, guint, guint)
 {
 	if (data.get_target () != "x-ardour/region.pbdid") {
 		return;
 	}
-
-	list<boost::shared_ptr<ARDOUR::Region>> regions;
-	TreeView*                               source;
-	_display.get_object_drag_data (regions, &source);
-
-	if (!regions.empty ()) {
-		data.set (data.get_target (), regions.front ()->id ().to_s ());
+	TreeView::Selection::ListHandle_Path rows = _display.get_selection ()->get_selected_rows ();
+	for (TreeView::Selection::ListHandle_Path::iterator i = rows.begin (); i != rows.end (); ++i) {
+		boost::shared_ptr<Region> region = (*_model->get_iter (*i))[_columns.region];
+		data.set (data.get_target (), region->id ().to_s ());
+		break;
 	}
 }
 

gtk2_ardour/region_list_base.h

@@ -214,6 +214,8 @@ protected:
 
 	void clock_format_changed ();
 
+	void drag_begin (Glib::RefPtr<Gdk::DragContext> const&);
+	void drag_end (Glib::RefPtr<Gdk::DragContext> const&);
 	void drag_data_get (Glib::RefPtr<Gdk::DragContext> const&, Gtk::SelectionData&, guint, guint);
 
 	virtual bool list_region (boost::shared_ptr<ARDOUR::Region>) const;

gtk2_ardour/triggerbox_ui.cc

@@ -801,12 +801,21 @@ TriggerEntry::drag_begin (Glib::RefPtr<Gdk::DragContext> const& context)
 		/* ctx leaves scope, cr is destroyed, and pixmap surface is flush()ed */
 	}
 
+	boost::shared_ptr<Region> region = trigger ()->region ();
+	if (region) {
+		PublicEditor::instance ().pbdid_dragged_dt = region->data_type ();
+	} else {
+		PublicEditor::instance ().pbdid_dragged_dt = DataType::NIL;
+	}
 	context->set_icon (pixmap->get_colormap (), pixmap, Glib::RefPtr<Gdk::Bitmap> (NULL), width / 2, height / 2);
 }
 
 void
 TriggerEntry::drag_end (Glib::RefPtr<Gdk::DragContext> const&)
 {
+	if (_drag_active) {
+		PublicEditor::instance ().pbdid_dragged_dt = DataType::NIL;
+	}
 	_drag_active = false;
 }
 
@@ -942,8 +951,9 @@ TriggerBoxUI::slot_at_y (int y) const
 bool
 TriggerBoxUI::drag_motion (Glib::RefPtr<Gdk::DragContext> const& context, int, int y, guint time)
 {
-	bool     can_drop = true;
-	uint64_t n        = slot_at_y (y);
+	bool can_drop = PublicEditor::instance ().pbdid_dragged_dt == _triggerbox.data_type ();
+
+	uint64_t n = slot_at_y (y);
 	if (n >= _slots.size ()) {
 		assert (0);
 		can_drop = false;