Window-owning +controls and non-window-owning controls

Controls are similar to windows in the Window Server in that they are both +bounded areas of the screen and both user interface elements. They are not +synonymous, however, as a control may take up the whole of a window’s area +or only part of it. For this reason controls are divided into two types: window-owning +controls and non-window-owning controls.

Window-owning controls

A window-owning control +has the same size and position as a window in the Window Server. Window-owning +controls may overlap each other and may be moved around the screen within +the bounds of their parent window. Dialogs, menus, toolbars and top-level +controls are typically window-owning controls.

Non-window-owning controls (lodger controls)

The +majority of controls are non-window-owning. A non-window-owning control’s extent typically +covers only part of a window on the screen: usually it is one of a number +of controls within a larger compound control which acts +as a container.

Examples of non-window-owning controls include command +buttons, text boxes and labels.

Non-window-owning controls give greater +efficiency as they require fewer resources in the Window Server and fewer +process switches. They can also result in faster intialisation and redrawing +because a compound control and all its non-window-owning components can be +drawn with a single flush to the window server.

Associated windows

All controls have an associated +window, whether they are window-owning or not. For a window-owning +control the associated window is the window it owns. For a non-window-owning +control the associated window is the window owned by the nearest window-owning +control above it in the control hierarchy.