Just changing the preference for hiding or showing a dock window does
not actually trigger a state change. To enable that, the preferences
pack manager must manually instruct the DockWindowManager to save its
state into the preferences before storing a preference pack, and must
instruct the DockWindowManager to load its new state from the
preferences after loading a pack.
Preference Packs are collections of preferences that can be applied en
mass to the user's current setup. Any preference that can be stored in
user.cfg can be stored in a preference pack, and they are designed to be
easy to distribute.
Support is also added for saving a subset of current preferences into a
new preference pack in order to facilitate easy creation of new
"themes", etc.
