From 42d9e8826384ea89d9eeb48e192859deecf95e17 Mon Sep 17 00:00:00 2001
From: Ben Loftis <ben@harrisonconsoles.com>
Date: Fri, 25 Jun 2021 16:18:20 -0500
Subject: [PATCH] Playlist UI Tweaks:  assign pgroup_id's on Import (libardour
 part)

---
 libs/ardour/ardour/playlist.h | 22 ++++++++++++++++++++--
 libs/ardour/playlist.cc       | 13 +++++++++++++
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/libs/ardour/ardour/playlist.h b/libs/ardour/ardour/playlist.h
index dc301132d6..b08ecb42a6 100644
--- a/libs/ardour/ardour/playlist.h
+++ b/libs/ardour/ardour/playlist.h
@@ -110,8 +110,26 @@ public:
 	bool set_name (const std::string& str);
 	void set_region_ownership ();
 
-	std::string pgroup_id()                 { return _pgroup_id; }
-	void set_pgroup_id(std::string pgid)    { _pgroup_id = pgid; PropertyChanged (Properties::name); }
+	/*playlist group IDs (pgroup_id) is a group identifier that is implicitly
+	 * or explicitly assigned to playlists so they can be associated with each other.
+	 *
+	 * For example, when you switch a track's playlist, you can choose to
+	 *  switch other tracks to the same pgroup_id
+	 *
+	 * pgroup_id's should be unique; currently we use a timestamp to avoid duplicates.
+	 * pgroup_id's are human-readable strings; use string comparison to find matches.
+	 *
+	 * To be useful, we want every playlist to be assigned a sensible pgroup_id
+	 * Some examples of pgroup_id's getting assigned *explicitly* include:
+	 *  when the user makes a new playlist for a track or Track Group
+	 *  when the user triggers an action like "new playlist for rec-armed tracks"
+	 * Some examples of pgroup_id's getting assigned *implicitly* include:
+	 *  the user makes the first recording pass ("take") in an empty playlist
+	 *  the user imports tracks.
+	 */
+	static std::string    generate_pgroup_id();
+	std::string           pgroup_id()                     { return _pgroup_id; }
+	void                  set_pgroup_id(std::string pgid) { _pgroup_id = pgid; PropertyChanged (Properties::name); }
 
 	virtual void clear (bool with_signals = true);
 	virtual void dump () const;
diff --git a/libs/ardour/playlist.cc b/libs/ardour/playlist.cc
index 49d5f2c619..39c1bbdf29 100644
--- a/libs/ardour/playlist.cc
+++ b/libs/ardour/playlist.cc
@@ -30,6 +30,8 @@
 #include <stdint.h>
 #include <string>
 
+#include <glibmm/datetime.h>
+
 #include "pbd/stateful_diff_command.h"
 #include "pbd/strsplit.h"
 #include "pbd/types_convert.h"
@@ -2240,6 +2242,17 @@ Playlist::clear_owned_changes ()
 	Stateful::clear_owned_changes ();
 }
 
+string
+Playlist::generate_pgroup_id ()
+{
+	time_t now;
+	time (&now);
+	Glib::DateTime tm (Glib::DateTime::create_now_local (now));
+	string gid;
+	gid = (tm.format ("%F %H.%M.%S"));
+	return gid;
+}
+
 void
 Playlist::update (const RegionListProperty::ChangeRecord& change)
 {