gtk2_ardour: implement "Unlink from unselected" for MIDI regions

An attempt to satisfy #8848.

Add a new action, "fork-regions-from-unselected", which unlinks all
selected MIDI regions from any unselected regions, but maintains links
within the selection, and add the new action to the region MIDI context
menu as "Unlink from unselected". Rename the existing "fork-region" action
to "fork-selected-regions", and amend the existing "Unlink from other
copies" menu item to "Unlink all selected regions" to (try to) clarify the
difference.

Attach the <Tertiary>U default key-binding to the new action: I personally
think it's generally slightly more useful (otherwise I wouldn't have
implemented it), though I'm not that fussed.

In the case that there's only one MIDI region selected, or that none of
the selected regions are mutually linked, both actions will have exactly
the same result. Ideally, we'd only show a single menu item in this case,
but that would require (a) implementing a function to check whether the
selection contains any linked regions, and (b) making the region MIDI
context sub-menu dynamically generated, so that it can change based on the
result of that function, neither of which I've tried to do yet.

gtk2_ardour/ardour.keys.in

@@ -175,7 +175,7 @@ This mode provides many different operations on both regions and control points,
 @edit|Editor/alternate-redo|                                <@PRIMARY@>y|redo
 @select|Editor/select-all-between-cursors|                  <@PRIMARY@>u|select all regions enclosed by Range
 @select|Editor/select-all-within-cursors|                              u|select all regions touched by Range
-@rop|Region/fork-region|                                   <@TERTIARY@>u|unlink midi from other regions
+@rop|Region/fork-regions-from-unselected|                  <@TERTIARY@>u|unlink midi from unselected regions
 @eep|Region/insert-region-from-source-list|                            i|insert from region list
 @sess|Common/addExistingAudioFiles|                         <@PRIMARY@>i|import audio files
 @gselect|Common/invert-selection|               <@PRIMARY@><@TERTIARY@>i|invert selection

gtk2_ardour/ardour.menus.in

@@ -357,7 +357,8 @@
         <menuitem action='legatize-region'/>
         <menuitem action='remove-overlap'/>
         <menuitem action='transform-region'/>
-        <menuitem action='fork-region'/>
+        <menuitem action='fork-selected-regions'/>
+        <menuitem action='fork-regions-from-unselected'/>
         <menuitem action='deinterlace-midi'/>
         <menuitem action='show-region-list-editor'/>
       </menu>
@@ -857,7 +858,8 @@
       <menuitem action='legatize-region'/>
       <menuitem action='remove-overlap'/>
       <menuitem action='transform-region'/>
-      <menuitem action='fork-region'/>
+      <menuitem action='fork-selected-regions'/>
+      <menuitem action='fork-regions-from-unselected'/>
       <menuitem action='deinterlace-midi'/>
       <menuitem action='show-region-list-editor'/>
     </menu>

gtk2_ardour/editor.h

@@ -1368,7 +1368,8 @@ private:
 	void transpose_region ();
 	void transpose_regions (const RegionSelection& rs);
 	void insert_patch_change (bool from_context);
-	void fork_region ();
+	void fork_selected_regions ();
+	void fork_regions_from_unselected ();
 
 	void do_insert_time ();
 	void insert_time (Temporal::timepos_t const &, Temporal::timecnt_t const &, Editing::InsertTimeOption, bool, bool, bool, bool, bool, bool);

gtk2_ardour/editor_actions.cc

@@ -1910,7 +1910,8 @@ Editor::register_region_actions ()
 	register_region_action (_region_actions, RegionActionTarget (SelectedRegions|EnteredRegions), "remove-overlap", _("Remove Overlap"), sigc::bind(sigc::mem_fun (*this, &Editor::legatize_region), true));
 	register_region_action (_region_actions, RegionActionTarget (SelectedRegions|EnteredRegions), "insert-patch-change", _("Insert Patch Change..."), sigc::bind (sigc::mem_fun (*this, &Editor::insert_patch_change), false));
 	register_region_action (_region_actions, RegionActionTarget (SelectedRegions|EnteredRegions), "insert-patch-change-context", _("Insert Patch Change..."), sigc::bind (sigc::mem_fun (*this, &Editor::insert_patch_change), true));
-	register_region_action (_region_actions, RegionActionTarget (SelectedRegions|EnteredRegions), "fork-region", _("Unlink from other copies"), sigc::mem_fun (*this, &Editor::fork_region));
+	register_region_action (_region_actions, RegionActionTarget (SelectedRegions|EnteredRegions), "fork-selected-regions", _("Unlink all selected regions"), sigc::mem_fun (*this, &Editor::fork_selected_regions));
+	register_region_action (_region_actions, RegionActionTarget (SelectedRegions|EnteredRegions), "fork-regions-from-unselected", _("Unlink from unselected"), sigc::mem_fun (*this, &Editor::fork_regions_from_unselected));
 	register_region_action (_region_actions, RegionActionTarget (SelectedRegions|EnteredRegions), "strip-region-silence", _("Strip Silence..."), sigc::mem_fun (*this, &Editor::strip_region_silence));
 	register_region_action (_region_actions, RegionActionTarget (SelectedRegions), "set-selection-from-region", _("Set Range Selection"), sigc::mem_fun (*this, &Editor::set_selection_from_region));
 

gtk2_ardour/editor_ops.cc

@@ -5871,8 +5871,91 @@ Editor::apply_midi_note_edit_op (MidiOperator& op, const RegionSelection& rs)
 	}
 }
 
+#include "ardour/midi_source.h" // MidiSource::name()
+
 void
-Editor::fork_region ()
+Editor::fork_regions_from_unselected ()
+{
+	/* keep linkage between regions in the selection, but unlink from unselected regions */
+	RegionSelection rs = get_regions_from_selection_and_entered ();
+
+	if (rs.empty()) {
+		return;
+	}
+
+	CursorContext::Handle cursor_ctx = CursorContext::create(*this, _cursors->wait);
+	bool in_command = false;
+
+	gdk_flush ();
+
+	/* find the set of all MidiSources associated with the selected regions */
+	std::set<boost::shared_ptr<MidiSource> > sources_list;
+	for (const auto& r : rs) {
+		const MidiRegionView* const mrv = dynamic_cast<const MidiRegionView*>(r);
+		if (!mrv)
+			continue; // not a MIDI region
+
+		sources_list.insert(mrv->midi_region()->midi_source());
+	}
+
+	std::set<boost::shared_ptr<Playlist> > affected_playlists;
+	for (auto r : rs) {
+		const MidiRegionView* const mrv = dynamic_cast<const MidiRegionView*>(r);
+		if (mrv && sources_list.find(mrv->midi_region()->midi_source()) != sources_list.end()) {
+			affected_playlists.insert(mrv->region()->playlist());
+		}
+	}
+	for (auto p : affected_playlists) {
+		p->clear_changes ();
+		p->freeze ();
+	}
+
+	/* iterate over sources that need to be duplicated */
+	for (const auto& ms : sources_list) {
+		/* duplicate source */
+		boost::shared_ptr<MidiSource> new_source = _session->create_midi_source_for_session (ms->name());
+		for (RegionSelection::iterator r = rs.begin(); r != rs.end(); ) {
+			RegionSelection::iterator tmp = r;
+			++tmp;
+
+			const MidiRegionView* const mrv = dynamic_cast<const MidiRegionView*>(*r);
+
+			if (!mrv) {
+				r = tmp;
+				continue;
+			}
+			if (mrv->midi_region()->midi_source() != ms) {
+				r = tmp;
+				continue;
+			}
+
+			try {
+				if (!in_command) {
+					begin_reversible_command (_("Unlink from unselected"));
+					in_command = true;
+				}
+				boost::shared_ptr<Playlist> playlist = mrv->region()->playlist();
+				boost::shared_ptr<Region> new_region = mrv->midi_region()->clone (new_source);
+				new_region->set_name (mrv->region()->name() + "-unlinked-region");
+				playlist->replace_region (mrv->region(), new_region, mrv->region()->position());
+			} catch (...) {
+				error << string_compose (_("Could not unlink %1"), mrv->region()->name()) << endmsg;
+			}
+			r = tmp;
+		}
+	}
+	if (in_command) {
+		for (auto p : affected_playlists) {
+			p->thaw ();
+			_session->add_command(new StatefulDiffCommand (p));
+		}
+
+		commit_reversible_command ();
+	}
+}
+
+void
+Editor::fork_selected_regions ()
 {
 	RegionSelection rs = get_regions_from_selection_and_entered ();
 

gtk2_ardour/editor_selection.cc

@@ -1539,7 +1539,8 @@ Editor::sensitize_the_right_region_actions (bool because_canvas_crossing)
 		_region_actions->get_action("legatize-region")->set_sensitive (false);
 		_region_actions->get_action("remove-overlap")->set_sensitive (false);
 		_region_actions->get_action("transform-region")->set_sensitive (false);
-		_region_actions->get_action("fork-region")->set_sensitive (false);
+		_region_actions->get_action("fork-selected-regions")->set_sensitive (false);
+		_region_actions->get_action("fork-regions-from-unselected")->set_sensitive (false);
 		_region_actions->get_action("insert-patch-change-context")->set_sensitive (false);
 		_region_actions->get_action("insert-patch-change")->set_sensitive (false);
 		_region_actions->get_action("transpose-region")->set_sensitive (false);