+/**
+Positions Widgets inside a Container.
+
+A layout operates on constraints, which are used to form a linear program that
+is then solved to obtain positions and dimensions that fulfill the constraints.
+There are three kinds of constraints available: ordering, alignment and
+dimension matching.
+
+Ordering constraints specify that the widgets should be placed next to other
+along X or Y axis. These operate on one axis at a time, so a widget could be
+"right of" another even if they are separated by hundreds of pixels vertically.
+The widgets will be separated by a spacing value, which is settable on a per-
+layout basis.
+
+Alignment constraints make the corresponding edges of two widgets be on the
+same line. These are incompatible with ordering constraints, so only one or
+the other should be used between any pair of widgets for the same axis.
+
+Dimension matching constraints force the two widgets to have the same dimension
+along the relevant axis.
+
+In addition to constraints, there are some other properties that can be set on
+widgets to determine how they are laid out. Gravity affects which edge of the
+container the widget should be placed at. This is a relatively weak hint and
+will be overridden by many other things. Margins can also be specified to
+prevent widgets from getting too close to the container's edges.
+
+Usually widgets are made as small as their content allows. Setting the expand
+flag for a widget causes it to use as much space as possible. If multiple co-
+dependent widgets have the expand flag set, the results are currently
+undefined.
+
+Since specifiyng constraints manually can be quite tedious, there are some
+derived Layout classes that implement common positioning patterns. See
+MixedRows and Grid.
+*/