Declarative Markup Language
The Hydra Declarative Markup Language (HDML) is a XML based markup that is used for storing and initializing structured objects and values.
HDML only defines a structure.
HDML defines a set of layout management classes that are used to describe how widgets are laid out in an application's user interface. These layouts automatically position and resize widgets when the amount of space available for them changes, ensuring that they are consistently arranged and that the user interface as a whole remains usable.
The BoxLayout class lines up child widgets horizontally or vertically. BoxLayout takes the space it gets from its parent layout or from the parentWidget, divides it up into a row of boxes, and makes each managed widget fill one box.