Hide Bookmark menu for new dynamically generated playlists

The bookmark menu with the option to create a bookmark
was inadvertently displayed for new dynamic playlists,
that had no associated folder or playlist file on disk.
(e.g. after selecting some track from the database for
playback), until the playlist was modified by the user.

Change-Id: I9d6809e4d03603c651459415327f28e38162ad53

apps/bookmark.c

@@ -1291,7 +1291,8 @@ bool bookmark_exists(void)
 
     char* name = playlist_get_name(NULL, global_temp_buffer,
                                    sizeof(global_temp_buffer));
-    if (generate_bookmark_file_name(bm_filename, sizeof(bm_filename), name, -1))
+    if (!playlist_dynamic_only() && 
+        generate_bookmark_file_name(bm_filename, sizeof(bm_filename), name, -1))
     {
         exist = file_exists(bm_filename);
     }
@@ -1311,8 +1312,10 @@ bool bookmark_is_bookmarkable_state(void)
         /* no track playing */
        (playlist_get_resume_info(&resume_index) == -1) ||
         /* invalid queue info */
-       (playlist_modified(NULL)))
+       (playlist_modified(NULL)) ||
-        /* can't bookmark while in the queue */
+        /* can't bookmark playlists modified by user */
+       (playlist_dynamic_only()))
+        /* can't bookmark playlists without associated folder or playlist file */
     {
         return false;
     }

apps/playlist.c

@@ -2698,6 +2698,22 @@ bool playlist_allow_dirplay(const struct playlist_info *playlist)
     return !!(playlist->flags & PLAYLIST_FLAG_DIRPLAY);
 }
 
+/*
+ * Returns true if the current playlist is neither
+ * associated  with a folder nor with an on-disk playlist.
+ */
+bool playlist_dynamic_only(void)
+{
+    /* NOTE: New dynamic playlists currently use root dir ("/")
+     *       as their placeholder filename – this could change.
+     */
+    if (!strcmp(current_playlist.filename, "/") &&
+        !(current_playlist.flags & PLAYLIST_FLAG_DIRPLAY))
+        return true;
+
+    return false;
+}
+
 /*
  * Move track at index to new_index.  Tracks between the two are shifted
  * appropriately.  Returns 0 on success and -1 on failure.

apps/playlist.h

@@ -133,6 +133,7 @@ int playlist_get_display_index(void);
 int playlist_amount(void);
 void playlist_set_last_shuffled_start(void);
 struct playlist_info *playlist_get_current(void);
+bool playlist_dynamic_only(void);
 
 /* Exported functions for all playlists.  Pass NULL for playlist_info
    structure to work with current playlist. */