But, since the Parent property of a control is a Control, the Parent property will be Nil-since a Window is not subclassed from the Control class. If a control is not enclosed by another control, then its “parent” is its window. If you attempt to get the parent of a control whose parent is in another window, you will get an InvalidParentException error. Obviously, the parent control must be in the same window as its child controls. To make this work automatically, you must create them in the order that respects the hierarchy: first create the TabPanel, then the GroupBox, and then the RadioButtons. In this case, the GroupBox is the parent of the RadioButtons and the TabPanel is the parent of the GroupBox. For example, you can place a GroupBox within a TabPanel and then place several RadioButtons within the GroupBox. You can create more than one level of nesting.

When you copy a parent control, you copy all its child controls as well. If you move it completely inside another control, it becomes the child of that control. If you move a child outside its parent, it is no longer a child of that control. If a control is not completely enclosed by another control then it doesn't automatically become a child it simply overlaps the other control. If you create a child control before its parent, you can set its parent using its Parent property. You can use the Parent property of the RectControl class to either get or set the parent of an existing control. That is, create the control that encloses the others first, then create the child controls or duplicate existing child controls and keep them inside the parent control. This works automatically if you create the controls in the order of: parent-child. The control that encloses the others is known as the parent control and the controls that are entirely within its borders are the child controls.

The TabPanel and PagePanel controls also designed to enclose other controls. For example, you use the GroupBox control to organize other controls, usually RadioButtons or possibly Checkboxes. In some cases you build portions of your interface by placing some controls within another control. The following class constants of the DragItem class can be used to specify the value of the Action parameter with the DragEnter, DragExit, and DragOver events. Instead, you create and modify the RectControl subclasses like PushButtons, TextFields, ListBoxes, etc. A RectControl cannot be created or modified directly. This means that all controls inherit the properties of the RectControl.

RectControl is the base class for most other control classes.

Xojo controls