input: add insert-next support for drag-and-drop

This commit adds a DND_INSERT_NEXT action option for drag-and-drop,
allows for selecting it through the --drag-and-drop=insert-next option,
and adds the necessary plumbing to make that happen when something is
dragged onto the player.

1 files changed, 8 insertions, 7 deletions

diff --git a/DOCS/man/options.rst b/DOCS/man/options.rst
index 39a075e74c..3dcdc4eba4 100644
--- a/DOCS/man/options.rst
+++ b/DOCS/man/options.rst
@@ -3197,13 +3197,14 @@ Window
 ``--snap-window``
     (Windows only) Snap the player window to screen edges.
 
-``--drag-and-drop=<no|auto|replace|append>``
-    Controls the default behavior of drag and drop on platforms that support this.
-    ``auto`` will obey what the underlying os/platform gives mpv. Typically, holding
-    shift during the drag and drop will append the item to the playlist. Otherwise,
-    it will completely replace it. ``replace`` and ``append`` always force replacing
-    and appending to the playlist respectively. ``no`` disables all drag and drop
-    behavior.
+``--drag-and-drop=<no|auto|replace|append|insert-next>``
+    Controls the default behavior of drag and drop on platforms that support
+    this. ``auto`` will obey what the underlying os/platform gives mpv.
+    Typically, holding shift during the drag and drop will append the item to
+    the playlist. Otherwise, it will completely replace it. ``replace``,
+    ``append``, and ``insert-next`` always force replacing, appending to, and
+    inserting next into the playlist respectively. ``no`` disables all drag and
+    drop behavior.
 
 ``--ontop``
     Makes the player window stay on top of other windows.