Introduce custom backend-specific primitives

7 files changed, 129 insertions, 152 deletions

diff --git a/graphics/Cargo.toml b/graphics/Cargo.toml
index 02621695..7a9e6aee 100644
--- a/graphics/Cargo.toml
+++ b/graphics/Cargo.toml
@@ -32,10 +32,6 @@ features = ["derive"]
 version = "0.9"
 path = "../core"
 
-[dependencies.tiny-skia]
-version = "0.9"
-optional = true
-
 [dependencies.image]
 version = "0.24"
 optional = true
diff --git a/graphics/src/backend.rs b/graphics/src/backend.rs
index 70ccc664..3ff24335 100644
--- a/graphics/src/backend.rs
+++ b/graphics/src/backend.rs
@@ -6,6 +6,13 @@ use iced_core::{Font, Point, Size};
 
 use std::borrow::Cow;
 
+/// The graphics backend of a [`Renderer`].
+///
+/// [`Renderer`]: crate::Renderer
+pub trait Backend {
+    type Primitive;
+}
+
 /// A graphics backend that supports text rendering.
 pub trait Text {
     /// The icon font of the backend.
diff --git a/graphics/src/damage.rs b/graphics/src/damage.rs
index c6b0f759..1add6707 100644
--- a/graphics/src/damage.rs
+++ b/graphics/src/damage.rs
@@ -1,11 +1,68 @@
 //! Track and compute the damage of graphical primitives.
+use crate::core::alignment;
 use crate::core::{Rectangle, Size};
 use crate::Primitive;
 
 use std::sync::Arc;
 
-/// Computes the damage regions between the two given primitives.
-pub fn regions(a: &Primitive, b: &Primitive) -> Vec<Rectangle> {
+pub trait Damage: PartialEq {
+    /// Returns the bounds of the [`Damage`].
+    fn bounds(&self) -> Rectangle;
+}
+
+impl<T: Damage> Damage for Primitive<T> {
+    fn bounds(&self) -> Rectangle {
+        match self {
+            Self::Text {
+                bounds,
+                horizontal_alignment,
+                vertical_alignment,
+                ..
+            } => {
+                let mut bounds = *bounds;
+
+                bounds.x = match horizontal_alignment {
+                    alignment::Horizontal::Left => bounds.x,
+                    alignment::Horizontal::Center => {
+                        bounds.x - bounds.width / 2.0
+                    }
+                    alignment::Horizontal::Right => bounds.x - bounds.width,
+                };
+
+                bounds.y = match vertical_alignment {
+                    alignment::Vertical::Top => bounds.y,
+                    alignment::Vertical::Center => {
+                        bounds.y - bounds.height / 2.0
+                    }
+                    alignment::Vertical::Bottom => bounds.y - bounds.height,
+                };
+
+                bounds.expand(1.5)
+            }
+            Self::Quad { bounds, .. }
+            | Self::Image { bounds, .. }
+            | Self::Svg { bounds, .. } => bounds.expand(1.0),
+            Self::Clip { bounds, .. } => bounds.expand(1.0),
+            Self::SolidMesh { size, .. } | Self::GradientMesh { size, .. } => {
+                Rectangle::with_size(*size)
+            }
+            Self::Group { primitives } => primitives
+                .iter()
+                .map(Self::bounds)
+                .fold(Rectangle::with_size(Size::ZERO), |a, b| {
+                    Rectangle::union(&a, &b)
+                }),
+            Self::Translate {
+                translation,
+                content,
+            } => content.bounds() + *translation,
+            Self::Cache { content } => content.bounds(),
+            Self::Custom(custom) => custom.bounds(),
+        }
+    }
+}
+
+fn regions<T: Damage>(a: &Primitive<T>, b: &Primitive<T>) -> Vec<Rectangle> {
     match (a, b) {
         (
             Primitive::Group {
@@ -76,7 +133,10 @@ pub fn regions(a: &Primitive, b: &Primitive) -> Vec<Rectangle> {
 }
 
 /// Computes the damage regions between the two given lists of primitives.
-pub fn list(previous: &[Primitive], current: &[Primitive]) -> Vec<Rectangle> {
+pub fn list<T: Damage>(
+    previous: &[Primitive<T>],
+    current: &[Primitive<T>],
+) -> Vec<Rectangle> {
     let damage = previous
         .iter()
         .zip(current)
@@ -93,7 +153,7 @@ pub fn list(previous: &[Primitive], current: &[Primitive]) -> Vec<Rectangle> {
 
         // Extend damage by the added/removed primitives
         damage
-            .chain(bigger[smaller.len()..].iter().map(Primitive::bounds))
+            .chain(bigger[smaller.len()..].iter().map(Damage::bounds))
             .collect()
     }
 }
diff --git a/graphics/src/geometry.rs b/graphics/src/geometry.rs
index 729c3d44..5e547bae 100644
--- a/graphics/src/geometry.rs
+++ b/graphics/src/geometry.rs
@@ -14,20 +14,10 @@ pub use text::Text;
 
 pub use crate::gradient::{self, Gradient};
 
-use crate::Primitive;
-
-/// A bunch of shapes that can be drawn.
-#[derive(Debug, Clone)]
-pub struct Geometry(pub Primitive);
-
-impl From<Geometry> for Primitive {
-    fn from(geometry: Geometry) -> Self {
-        geometry.0
-    }
-}
-
 /// A renderer capable of drawing some [`Geometry`].
 pub trait Renderer: crate::core::Renderer {
+    type Geometry;
+
     /// Draws the given layers of [`Geometry`].
-    fn draw(&mut self, layers: Vec<Geometry>);
+    fn draw(&mut self, layers: Vec<Self::Geometry>);
 }
diff --git a/graphics/src/lib.rs b/graphics/src/lib.rs
index 226b245b..055a9216 100644
--- a/graphics/src/lib.rs
+++ b/graphics/src/lib.rs
@@ -8,8 +8,8 @@
     html_logo_url = "https://raw.githubusercontent.com/iced-rs/iced/9ab6923e943f784985e9ef9ca28b10278297225d/docs/logo.svg"
 )]
 #![deny(
-    missing_debug_implementations,
-    missing_docs,
+    //missing_debug_implementations,
+    //missing_docs,
     unsafe_code,
     unused_results,
     clippy::extra_unused_lifetimes,
@@ -41,7 +41,9 @@ pub mod geometry;
 pub mod image;
 
 pub use antialiasing::Antialiasing;
+pub use backend::Backend;
 pub use compositor::Compositor;
+pub use damage::Damage;
 pub use error::Error;
 pub use gradient::Gradient;
 pub use primitive::Primitive;
@@ -49,7 +51,4 @@ pub use renderer::Renderer;
 pub use transformation::Transformation;
 pub use viewport::Viewport;
 
-#[cfg(feature = "geometry")]
-pub use geometry::Geometry;
-
 pub use iced_core as core;
diff --git a/graphics/src/primitive.rs b/graphics/src/primitive.rs
index 187c6c6c..f8b005ad 100644
--- a/graphics/src/primitive.rs
+++ b/graphics/src/primitive.rs
@@ -12,8 +12,7 @@ use std::sync::Arc;
 
 /// A rendering primitive.
 #[derive(Debug, Clone, PartialEq)]
-#[non_exhaustive]
-pub enum Primitive {
+pub enum Primitive<T> {
     /// A text primitive
     Text {
         /// The contents of the text
@@ -90,41 +89,17 @@ pub enum Primitive {
         /// Any geometry that falls out of this region will be clipped.
         size: Size,
     },
-    /// A [`tiny_skia`] path filled with some paint.
-    #[cfg(feature = "tiny-skia")]
-    Fill {
-        /// The path to fill.
-        path: tiny_skia::Path,
-        /// The paint to use.
-        paint: tiny_skia::Paint<'static>,
-        /// The fill rule to follow.
-        rule: tiny_skia::FillRule,
-        /// The transform to apply to the path.
-        transform: tiny_skia::Transform,
-    },
-    /// A [`tiny_skia`] path stroked with some paint.
-    #[cfg(feature = "tiny-skia")]
-    Stroke {
-        /// The path to stroke.
-        path: tiny_skia::Path,
-        /// The paint to use.
-        paint: tiny_skia::Paint<'static>,
-        /// The stroke settings.
-        stroke: tiny_skia::Stroke,
-        /// The transform to apply to the path.
-        transform: tiny_skia::Transform,
-    },
     /// A group of primitives
     Group {
         /// The primitives of the group
-        primitives: Vec<Primitive>,
+        primitives: Vec<Primitive<T>>,
     },
     /// A clip primitive
     Clip {
         /// The bounds of the clip
         bounds: Rectangle,
         /// The content of the clip
-        content: Box<Primitive>,
+        content: Box<Primitive<T>>,
     },
     /// A primitive that applies a translation
     Translate {
@@ -132,7 +107,7 @@ pub enum Primitive {
         translation: Vector,
 
         /// The primitive to translate
-        content: Box<Primitive>,
+        content: Box<Primitive<T>>,
     },
     /// A cached primitive.
     ///
@@ -140,11 +115,13 @@ pub enum Primitive {
     /// generation is expensive.
     Cache {
         /// The cached primitive
-        content: Arc<Primitive>,
+        content: Arc<Primitive<T>>,
     },
+    /// A backend-specific primitive.
+    Custom(T),
 }
 
-impl Primitive {
+impl<T> Primitive<T> {
     /// Creates a [`Primitive::Group`].
     pub fn group(primitives: Vec<Self>) -> Self {
         Self::Group { primitives }
@@ -165,68 +142,6 @@ impl Primitive {
             content: Box::new(self),
         }
     }
-
-    /// Returns the bounds of the [`Primitive`].
-    pub fn bounds(&self) -> Rectangle {
-        match self {
-            Self::Text {
-                bounds,
-                horizontal_alignment,
-                vertical_alignment,
-                ..
-            } => {
-                let mut bounds = *bounds;
-
-                bounds.x = match horizontal_alignment {
-                    alignment::Horizontal::Left => bounds.x,
-                    alignment::Horizontal::Center => {
-                        bounds.x - bounds.width / 2.0
-                    }
-                    alignment::Horizontal::Right => bounds.x - bounds.width,
-                };
-
-                bounds.y = match vertical_alignment {
-                    alignment::Vertical::Top => bounds.y,
-                    alignment::Vertical::Center => {
-                        bounds.y - bounds.height / 2.0
-                    }
-                    alignment::Vertical::Bottom => bounds.y - bounds.height,
-                };
-
-                bounds.expand(1.5)
-            }
-            Self::Quad { bounds, .. }
-            | Self::Image { bounds, .. }
-            | Self::Svg { bounds, .. } => bounds.expand(1.0),
-            Self::Clip { bounds, .. } => bounds.expand(1.0),
-            Self::SolidMesh { size, .. } | Self::GradientMesh { size, .. } => {
-                Rectangle::with_size(*size)
-            }
-            #[cfg(feature = "tiny-skia")]
-            Self::Fill { path, .. } | Self::Stroke { path, .. } => {
-                let bounds = path.bounds();
-
-                Rectangle {
-                    x: bounds.x(),
-                    y: bounds.y(),
-                    width: bounds.width(),
-                    height: bounds.height(),
-                }
-                .expand(1.0)
-            }
-            Self::Group { primitives } => primitives
-                .iter()
-                .map(Self::bounds)
-                .fold(Rectangle::with_size(Size::ZERO), |a, b| {
-                    Rectangle::union(&a, &b)
-                }),
-            Self::Translate {
-                translation,
-                content,
-            } => content.bounds() + *translation,
-            Self::Cache { content } => content.bounds(),
-        }
-    }
 }
 
 /// A set of [`Vertex2D`] and indices representing a list of triangles.
@@ -268,9 +183,3 @@ unsafe impl Zeroable for GradientVertex2D {}
 
 #[allow(unsafe_code)]
 unsafe impl Pod for GradientVertex2D {}
-
-impl From<()> for Primitive {
-    fn from(_: ()) -> Self {
-        Self::Group { primitives: vec![] }
-    }
-}
diff --git a/graphics/src/renderer.rs b/graphics/src/renderer.rs
index 7e70a766..9acfc2b7 100644
--- a/graphics/src/renderer.rs
+++ b/graphics/src/renderer.rs
@@ -1,5 +1,5 @@
 //! Create a renderer from a [`Backend`].
-use crate::backend;
+use crate::backend::{self, Backend};
 use crate::Primitive;
 
 use iced_core::image;
@@ -16,13 +16,13 @@ use std::marker::PhantomData;
 
 /// A backend-agnostic renderer that supports all the built-in widgets.
 #[derive(Debug)]
-pub struct Renderer<B, Theme> {
+pub struct Renderer<B: Backend, Theme> {
     backend: B,
-    primitives: Vec<Primitive>,
+    primitives: Vec<Primitive<B::Primitive>>,
     theme: PhantomData<Theme>,
 }
 
-impl<B, T> Renderer<B, T> {
+impl<B: Backend, T> Renderer<B, T> {
     /// Creates a new [`Renderer`] from the given [`Backend`].
     pub fn new(backend: B) -> Self {
         Self {
@@ -38,7 +38,7 @@ impl<B, T> Renderer<B, T> {
     }
 
     /// Enqueues the given [`Primitive`] in the [`Renderer`] for drawing.
-    pub fn draw_primitive(&mut self, primitive: Primitive) {
+    pub fn draw_primitive(&mut self, primitive: Primitive<B::Primitive>) {
         self.primitives.push(primitive);
     }
 
@@ -46,13 +46,42 @@ impl<B, T> Renderer<B, T> {
     /// of the [`Renderer`].
     pub fn with_primitives<O>(
         &mut self,
-        f: impl FnOnce(&mut B, &[Primitive]) -> O,
+        f: impl FnOnce(&mut B, &[Primitive<B::Primitive>]) -> O,
     ) -> O {
         f(&mut self.backend, &self.primitives)
     }
+
+    pub fn start_layer(&mut self) -> Vec<Primitive<B::Primitive>> {
+        std::mem::take(&mut self.primitives)
+    }
+
+    pub fn end_layer(
+        &mut self,
+        primitives: Vec<Primitive<B::Primitive>>,
+        bounds: Rectangle,
+    ) {
+        let layer = std::mem::replace(&mut self.primitives, primitives);
+
+        self.primitives.push(Primitive::group(layer).clip(bounds));
+    }
+
+    pub fn start_translation(&mut self) -> Vec<Primitive<B::Primitive>> {
+        std::mem::take(&mut self.primitives)
+    }
+
+    pub fn end_translation(
+        &mut self,
+        primitives: Vec<Primitive<B::Primitive>>,
+        translation: Vector,
+    ) {
+        let layer = std::mem::replace(&mut self.primitives, primitives);
+
+        self.primitives
+            .push(Primitive::group(layer).translate(translation));
+    }
 }
 
-impl<B, T> iced_core::Renderer for Renderer<B, T> {
+impl<B: Backend, T> iced_core::Renderer for Renderer<B, T> {
     type Theme = T;
 
     fn layout<Message>(
@@ -64,13 +93,11 @@ impl<B, T> iced_core::Renderer for Renderer<B, T> {
     }
 
     fn with_layer(&mut self, bounds: Rectangle, f: impl FnOnce(&mut Self)) {
-        let current = std::mem::take(&mut self.primitives);
+        let current = self.start_layer();
 
         f(self);
 
-        let layer = std::mem::replace(&mut self.primitives, current);
-
-        self.primitives.push(Primitive::group(layer).clip(bounds));
+        self.end_layer(current, bounds);
     }
 
     fn with_translation(
@@ -78,14 +105,11 @@ impl<B, T> iced_core::Renderer for Renderer<B, T> {
         translation: Vector,
         f: impl FnOnce(&mut Self),
     ) {
-        let current = std::mem::take(&mut self.primitives);
+        let current = self.start_translation();
 
         f(self);
 
-        let layer = std::mem::replace(&mut self.primitives, current);
-
-        self.primitives
-            .push(Primitive::group(layer).translate(translation));
+        self.end_translation(current, translation);
     }
 
     fn fill_quad(
@@ -109,7 +133,7 @@ impl<B, T> iced_core::Renderer for Renderer<B, T> {
 
 impl<B, T> text::Renderer for Renderer<B, T>
 where
-    B: backend::Text,
+    B: Backend + backend::Text,
 {
     type Font = Font;
 
@@ -188,7 +212,7 @@ where
 
 impl<B, T> image::Renderer for Renderer<B, T>
 where
-    B: backend::Image,
+    B: Backend + backend::Image,
 {
     type Handle = image::Handle;
 
@@ -203,7 +227,7 @@ where
 
 impl<B, T> svg::Renderer for Renderer<B, T>
 where
-    B: backend::Svg,
+    B: Backend + backend::Svg,
 {
     fn dimensions(&self, handle: &svg::Handle) -> Size<u32> {
         self.backend().viewport_dimensions(handle)
@@ -222,11 +246,3 @@ where
         })
     }
 }
-
-#[cfg(feature = "geometry")]
-impl<B, T> crate::geometry::Renderer for Renderer<B, T> {
-    fn draw(&mut self, layers: Vec<crate::Geometry>) {
-        self.primitives
-            .extend(layers.into_iter().map(crate::Geometry::into));
-    }
-}