path: root/core/src/renderer.rs

//! Write your own renderer.
#[cfg(debug_assertions)]
mod null;

#[cfg(debug_assertions)]
pub use null::Null;

use crate::layout;
use crate::{Background, BorderRadius, Color, Element, Rectangle, Vector};

/// A component that can be used by widgets to draw themselves on a screen.
pub trait Renderer: Sized {
    /// The supported theme of the [`Renderer`].
    type Theme;

    /// Lays out the elements of a user interface.
    ///
    /// You should override this if you need to perform any operations before or
    /// after layouting. For instance, trimming the measurements cache.
    fn layout<Message>(
        &mut self,
        element: &Element<'_, Message, Self>,
        limits: &layout::Limits,
    ) -> layout::Node {
        element.as_widget().layout(self, limits)
    }

    /// Draws the primitives recorded in the given closure in a new layer.
    ///
    /// The layer will clip its contents to the provided `bounds`.
    fn with_layer(&mut self, bounds: Rectangle, f: impl FnOnce(&mut Self));

    /// Applies a `translation` to the primitives recorded in the given closure.
    fn with_translation(
        &mut self,
        translation: Vector,
        f: impl FnOnce(&mut Self),
    );

    /// Fills a [`Quad`] with the provided [`Background`].
    fn fill_quad(&mut self, quad: Quad, background: impl Into<Background>);

    /// Clears all of the recorded primitives in the [`Renderer`].
    fn clear(&mut self);
}

/// A polygon with four sides.
#[derive(Debug, Clone, Copy, PartialEq)]
pub struct Quad {
    /// The bounds of the [`Quad`].
    pub bounds: Rectangle,

    /// The border radius of the [`Quad`].
    pub border_radius: BorderRadius,

    /// The border width of the [`Quad`].
    pub border_width: f32,

    /// The border color of the [`Quad`].
    pub border_color: Color,
}

/// The styling attributes of a [`Renderer`].
#[derive(Debug, Clone, Copy, PartialEq)]
pub struct Style {
    /// The text color
    pub text_color: Color,
}

impl Default for Style {
    fn default() -> Self {
        Style {
            text_color: Color::BLACK,
        }
    }
}