PlaylistEdit: postpone UpdateQueuedSong() when adding multiple songs

Implement a "bulk" edit mode that postpones both UpdateQueuedSong()
and OnModified().  This way, the playlist version gets incremented
only once.  More importantly: when adding multiple songs to a queue
that consists of only one song, the first song that got added will
always be played next.  By postponing this choice, all newly added
songs get a chance to become the next song.  Fixes the second (and
last) part of Mantis ticket 0004005.

1 files changed, 35 insertions, 0 deletions

diff --git a/src/PlaylistEdit.cxx b/src/PlaylistEdit.cxx
index 3eea2491e..0dffd3d80 100644
--- a/src/PlaylistEdit.cxx
+++ b/src/PlaylistEdit.cxx
@@ -40,6 +40,12 @@
 void
 playlist::OnModified()
 {
+	if (bulk_edit) {
+		/* postponed to CommitBulk() */
+		bulk_modified = true;
+		return;
+	}
+
 	queue.IncrementVersion();
 
 	idle_add(IDLE_PLAYLIST);
@@ -56,6 +62,35 @@ playlist::Clear(PlayerControl &pc)
 	OnModified();
 }
 
+void
+playlist::BeginBulk()
+{
+	assert(!bulk_edit);
+
+	bulk_edit = true;
+	bulk_modified = false;
+}
+
+void
+playlist::CommitBulk(PlayerControl &pc)
+{
+	assert(bulk_edit);
+
+	bulk_edit = false;
+	if (!bulk_modified)
+		return;
+
+	if (queued < 0)
+		/* if no song was queued, UpdateQueuedSong() is being
+		   ignored in "bulk" edit mode; now that we have
+		   shuffled all new songs, we can pick a random one
+		   (instead of always picking the first one that was
+		   added) */
+		UpdateQueuedSong(pc, nullptr);
+
+	OnModified();
+}
+
 PlaylistResult
 playlist::AppendFile(PlayerControl &pc,
 		     const char *path_utf8, unsigned *added_id)