Trait gui::Renderer

pub trait Renderer {
    fn renderable_area(&self) -> BBox;
    fn render(&self, object: &dyn Widget, bbox: BBox, cap: &dyn Cap) -> BBox;

    fn pre_render(&self) { ... }
    fn post_render(&self) { ... }
}

An abstraction for objects used for rendering widgets.

Required Methods

fn renderable_area(&self) -> BBox

Retrieve the bounding box of the renderable area (typically the screen). Note that the units to be used are not specified. That is, the result could be in pixels, characters (in case of a terminal), or just arbitrary numbers (if virtual coordinates are being used), as long as this Renderer knows how to interpret them.

fn render(&self, object: &dyn Widget, bbox: BBox, cap: &dyn Cap) -> BBox

Render an object.

Objects are represented as Widget and need to be cast into the actual widget type to render by the Renderer itself, should that be necessary. A simplified implementation could look as follows:

fn render(&self, widget: &dyn Widget, bbox: BBox, cap: &dyn Cap) -> BBox {
  if let Some(widget1) = widget.downcast_ref::<ConcreteWidget1>() {
    self.render_concrete_widget1(widget1, bbox)
  } else if let Some(widget2) = widget.downcast_ref::<ConcreteWidget1>() {
    self.render_concrete_widget2(widget2, bbox)
  } else {
    panic!("Widget {:?} is unknown to the renderer", widget)
  }
}

Provided Methods

fn pre_render(&self)

Perform some pre-render step.

fn post_render(&self)

Perform some post-render step.

Implementors