Module pugl_ui::ui

The UI struct and widget management facilities

Principles

Widgets are kept in a Vec<dyn Box<Widget>. To address an individual widget unambiguously the widgets ID is used which directly corresponds to the index of the widget in the Vec.

Moreover widgets are kept in a hierarchical tree. So each widget, except for the root widget with the ID 0 has exactly one parent widget. As of now a widget's geometry is a subset of the parent's geometry. This limitation implicates that for widgets that need to overlay other widgets, like drop down widgets, a new mechanism needs to be implemented, like floating widgets.

The widget hierachy tree is used to perform two things.

• Perform the widget layouting. Each widget is responsible to layout its children.

• Event propagation. The UI finds the widget that recieves the event, if the widget does not process the event, the event is propagated to its parent.

Structs

UI	The central interface between application, widgets and the windowing system
WidgetNode	A node in the widget tree (internal use only)

Enums

EventState

Used to indicate if an event has been processed