Instead, inherit from GtkBox directly and set the orientation in
init(). Replace more gtk_container_add() by gtk_box_pack_start() in
the reparented classes.
Add "dialog-factory", "ui-manager" properties to GimpDockColumns and
let GimpDock look for these before trying to look for a dock window
which does not exist in single-window mode.
Add and use gimp_dock_columns_new() and add a GimpContext property to
GimpDockColumns. Also move the widget construction from _init() to
_constructor() in GimpDockWindow so we have a context object to pass
to gimp_dock_columns_new().
In order to make a GimpDock get hold of a GimpContext both in
single-window mode and in multi-window mode, don't make it look for a
GimpContext in a GimpDockWindow, put the context in GimpDockColumns
instead. GimpDockColumns exists both in s-w-m and m-w-m, contrary to
GimpDockWindow. Still use the GimpDockWindow as a backup though.
Martin Nordholts