The window-layouter component complements the window manager (wm) with the
policy of how windows are positioned on screen and how windows behave when the
user interacts with window elements like the maximize button or the window
title. Whereas the decorator defines how windows look, the layouter defines how
they behave.

By default, the window layouter presents each window as a floating window that
can be positioned by dragging the window title, or resized by dragging the
window border.


Configurable window placement
-----------------------------

The policy of the window layouter can be adjusted via its configuration. For
a given window label, the window's initial position and its maximized state
can be defined as follows:

! <config>
!   <policy label_prefix="mupdf" maximized="yes"/>
!   <policy label_prefix="nit_fb" xpos="50" ypos="50"/>
! </config>


Keyboard shortcuts
------------------

The window layouter is able to respond to key sequences. However, normally,
the layouter is not a regular nitpicker client but receives only those
input events that refer to the window decorations. It never owns the keyboard
focus. In order to propagate global key sequences to the layouter, nitpicker
must be explicitly configured to direct key sequences initiated with certain
keys to the decorator. For example, the following nitpicker configuration
routes key sequences starting with the left windows key to the decorator. The
window manager, in turn, forwards those events to the layouter.

! <start name="nitpicker">
!   ...
!   <config>
!     ...
!     <global-key name="KEY_LEFTMETA" label="wm -> decorator" />
!     ...
!   </config>
!   ...
! </start>

The response of the window layouter to key sequences can be expressed in the
layouter configuration as follows:

! <config>
!   <press key="KEY_LEFTMETA">
!     <press key="KEY_TAB"              action="next_window">
!       <release key="KEY_TAB">
!         <release key="KEY_LEFTMETA"   action="raise_window"/>
!       </release>
!     </press>
!     <press key="KEY_LEFTSHIFT">
!       <press key="KEY_TAB"            action="prev_window">
!         <release key="KEY_TAB">
!           <release key="KEY_LEFTMETA" action="raise_window"/>
!         </release>
!       </press>
!     </press>
!     <press key="KEY_ENTER"            action="toggle_fullscreen"/>
!   </press>
! </config>

Each '<press>' node defines the policy when the specified 'key' is pressed.
It can be equipped with an 'action' attribute that triggers a window action.
The supported window actions are:

:next_window:       Focus the next window in the focus history.
:prev_window:       Focus the previous window in the focus history.
:raise_window:      Bring the focused window to the front.
:toggle_fullscreen: Maximize/unmaximize the focused window.

By nesting '<press>' nodes, actions can be tied to key sequences. In the
example above, the 'next_window' action is executed only if TAB is pressed
while the left windows-key is kept pressed. Furthermore, key sequences can
contain specific release events. In the example above, the release of the left
windows key brings the focused window to front, but only if TAB was pressed
before.


