Trait RenderObjectWithLayoutCallbackMixin

Source

pub trait RenderObjectWithLayoutCallbackMixin: RenderBox {
    // Required methods
    fn layout_callback_data(
        self: RenderHandle<Self>,
        app: &App,
    ) -> &RenderObjectWithLayoutCallbackData;
    fn layout_callback_data_mut(
        self: RenderHandle<Self>,
        app: &mut App,
    ) -> &mut RenderObjectWithLayoutCallbackData;
    fn layout_callback(self: RenderHandle<Self>, app: &mut App);

    // Provided methods
    fn run_layout_callback(self: RenderHandle<Self>, app: &mut App) { ... }
    fn schedule_layout_callback(self: RenderHandle<Self>, app: &mut App) { ... }
}

Expand description

A mixin for RenderObjects that run a layout callback (typically one that builds a widget subtree) during perform_layout, as LayoutBuilder’s render object does.

Implementers keep the bag under a field named layout_callback, implement layout_callback, and call run_layout_callback in their perform_layout. The mixin is on the box protocol here because scheduling needs the tree methods.