Decouple Mesh primitives from main Primitive type

graphics/src/mesh.rs

@@ -0,0 +1,75 @@
+use crate::color;
+use crate::core::{Rectangle, Size};
+use crate::gradient;
+use crate::Damage;
+
+use bytemuck::{Pod, Zeroable};
+
+/// A low-level primitive to render a mesh of triangles.
+#[derive(Debug, Clone, PartialEq)]
+pub enum Mesh {
+    /// A mesh with a solid color.
+    Solid {
+        /// The vertices and indices of the mesh.
+        buffers: Indexed<SolidVertex2D>,
+
+        /// The size of the drawable region of the mesh.
+        ///
+        /// Any geometry that falls out of this region will be clipped.
+        size: Size,
+    },
+    /// A mesh with a gradient.
+    Gradient {
+        /// The vertices and indices of the mesh.
+        buffers: Indexed<GradientVertex2D>,
+
+        /// The size of the drawable region of the mesh.
+        ///
+        /// Any geometry that falls out of this region will be clipped.
+        size: Size,
+    },
+}
+
+impl Damage for Mesh {
+    fn bounds(&self) -> Rectangle {
+        match self {
+            Self::Solid { size, .. } | Self::Gradient { size, .. } => {
+                Rectangle::with_size(*size)
+            }
+        }
+    }
+}
+
+/// A set of [`Vertex2D`] and indices representing a list of triangles.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Indexed<T> {
+    /// The vertices of the mesh
+    pub vertices: Vec<T>,
+
+    /// The list of vertex indices that defines the triangles of the mesh.
+    ///
+    /// Therefore, this list should always have a length that is a multiple of 3.
+    pub indices: Vec<u32>,
+}
+
+/// A two-dimensional vertex with a color.
+#[derive(Copy, Clone, Debug, PartialEq, Zeroable, Pod)]
+#[repr(C)]
+pub struct SolidVertex2D {
+    /// The vertex position in 2D space.
+    pub position: [f32; 2],
+
+    /// The color of the vertex in __linear__ RGBA.
+    pub color: color::Packed,
+}
+
+/// A vertex which contains 2D position & packed gradient data.
+#[derive(Copy, Clone, Debug, PartialEq, Zeroable, Pod)]
+#[repr(C)]
+pub struct GradientVertex2D {
+    /// The vertex position in 2D space.
+    pub position: [f32; 2],
+
+    /// The packed vertex data of the gradient.
+    pub gradient: gradient::Packed,
+}