Layout
All components are extrinsically sized, that is they have a property called position that can be set to define where the component is drawn. This position specifies a bounding box for the component to draw in. How the component fills the bounding box depends on the used component.
Some components are intrinsically sized, that is they have a width and height attribute.
A component that can contain other components is called a container and has a property layout. The layout property specifies which algorithm is used to layout the components in the container.
Guiml comes with a few predefined layout algorithms that can be combined to create a wide variety of layouts. If that is not sufficient for your needs you can write your own layout algorithm.