When the user starts a drag-and-drop operation and the sidebar needs
to ask the application for which drag action to perform, then the
sidebar will emit this signal.
The application can evaluate the context for customary actions, or
it can check the type of the files indicated by source_file_list against the
possible actions for the destination dest_file.
The drag action to use must be the return value of the signal handler.
The drag action to use, for example, GDK_ACTION_COPY
or GDK_ACTION_MOVE, or 0 if no action is allowed here (i.e. drops
are not allowed in the specified dest_file).
When the user starts a drag-and-drop operation and the sidebar needs to ask the application for which drag action to perform, then the sidebar will emit this signal.
The application can evaluate the context for customary actions, or it can check the type of the files indicated by source_file_list against the possible actions for the destination dest_file.
The drag action to use must be the return value of the signal handler.