internals.md

Owlkettle Internals

Every widget in owlkettle is either a renderable or a viewable widget. Renderable widgets provide declarative interfaces to GTK widgets. For example Button, Window and Entry are renderable widgets. Viewable widgets are abstractions over renderable widgets. Owlkettle applications are usually implemented as viewable widgets.

classDiagram
  class Widget {
    build() WidgetState
    update(state: WidgetState) WidgetState
  }
  class WidgetState {
    read()
  }
  class Viewable {
    view() WidgetState
  }
  class Renderable {
  }
  Viewable --> Widget: view
  WidgetState <|-- Viewable
  WidgetState <|-- Renderable
  Widget --> WidgetState: build/update

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Every widget has a state (WidgetState) and an updater object (Widget). The updater is used to update the internal widget state. It records which fields of the state the parent widget wants to set and which values these fields should be set to. This allows owlkettle to preserve the rest of widget's state.

Every viewable widget has a view method which returns the updaters for its child widget states. Viewable widgets are expanded using view until a renderable widget is reached.

flowchart LR
  subgraph updater
    direction BT
    Window .->|child| Label
  end
  App -->|build| AppState -->|view| updater
  updater -->|build/update| state
  subgraph state
    direction BT
    WindowState .->|child| LabelState
  end

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