93 lines
2.8 KiB
Rust
93 lines
2.8 KiB
Rust
//! Write your own renderer.
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//!
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//! You will need to implement the `Renderer` trait first. It simply contains
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//! an `Output` associated type.
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//!
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//! There is no common trait to draw all the widgets. Instead, every [`Widget`]
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//! constrains its generic `Renderer` type as necessary.
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//!
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//! This approach is flexible and composable. For instance, the
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//! [`Text`] widget only needs a [`text::Renderer`] while a [`Checkbox`] widget
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//! needs both a [`text::Renderer`] and a [`checkbox::Renderer`], reusing logic.
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//!
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//! In the end, a __renderer__ satisfying all the constraints is
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//! needed to build a [`UserInterface`].
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//!
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//! [`Widget`]: crate::Widget
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//! [`UserInterface`]: crate::UserInterface
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//! [`Text`]: crate::widget::Text
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//! [`text::Renderer`]: crate::widget::text::Renderer
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//! [`Checkbox`]: crate::widget::Checkbox
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//! [`checkbox::Renderer`]: crate::widget::checkbox::Renderer
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#[cfg(debug_assertions)]
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mod null;
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#[cfg(debug_assertions)]
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pub use null::Null;
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use crate::layout;
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use crate::{Background, Color, Element, Rectangle, Vector};
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/// A component that can take the state of a user interface and produce an
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/// output for its users.
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pub trait Renderer: Sized {
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/// Lays out the elements of a user interface.
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///
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/// You should override this if you need to perform any operations before or
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/// after layouting. For instance, trimming the measurements cache.
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fn layout<'a, Message>(
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&mut self,
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element: &Element<'a, Message, Self>,
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limits: &layout::Limits,
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) -> layout::Node {
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element.layout(self, limits)
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}
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/// Draws the primitives recorded in the given closure in a new layer.
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///
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/// The layer will clip its contents to the provided `bounds`.
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fn with_layer(&mut self, bounds: Rectangle, f: impl FnOnce(&mut Self));
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/// Applies a `translation` to the primitives recorded in the given closure.
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fn with_translation(
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&mut self,
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translation: Vector,
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f: impl FnOnce(&mut Self),
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);
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/// Clears all of the recorded primitives in the [`Renderer`].
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fn clear(&mut self);
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/// Fills a [`Quad`] with the provided [`Background`].
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fn fill_quad(&mut self, quad: Quad, background: impl Into<Background>);
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}
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/// A polygon with four sides.
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#[derive(Debug, Clone, Copy, PartialEq)]
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pub struct Quad {
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/// The bounds of the [`Quad`].
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pub bounds: Rectangle,
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/// The border radius of the [`Quad`].
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pub border_radius: f32,
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/// The border width of the [`Quad`].
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pub border_width: f32,
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/// The border color of the [`Quad`].
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pub border_color: Color,
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}
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/// The styling attributes of a [`Renderer`].
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#[derive(Debug, Clone, Copy, PartialEq)]
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pub struct Style {
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/// The text color
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pub text_color: Color,
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}
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impl Default for Style {
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fn default() -> Self {
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Style {
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text_color: Color::BLACK,
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}
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}
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}
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