Added support for custom shader widget for iced_wgpu backend.

wgpu/src/primitive.rs

@@ -1,6 +1,10 @@
 //! Draw using different graphical primitives.
 use crate::core::Rectangle;
+use crate::custom;
 use crate::graphics::{Damage, Mesh};
+use std::any::Any;
+use std::fmt::Debug;
+use std::sync::Arc;
 
 /// The graphical primitives supported by `iced_wgpu`.
 pub type Primitive = crate::graphics::Primitive<Custom>;
@@ -10,12 +14,44 @@ pub type Primitive = crate::graphics::Primitive<Custom>;
 pub enum Custom {
     /// A mesh primitive.
     Mesh(Mesh),
+    /// A custom shader primitive
+    Shader(Shader),
+}
+
+impl Custom {
+    /// Create a custom [`Shader`] primitive.
+    pub fn shader<P: custom::Primitive>(
+        bounds: Rectangle,
+        primitive: P,
+    ) -> Self {
+        Self::Shader(Shader {
+            bounds,
+            primitive: Arc::new(primitive),
+        })
+    }
 }
 
 impl Damage for Custom {
     fn bounds(&self) -> Rectangle {
         match self {
             Self::Mesh(mesh) => mesh.bounds(),
+            Self::Shader(shader) => shader.bounds,
         }
     }
 }
+
+#[derive(Clone, Debug)]
+/// A custom primitive which can be used to render primitives associated with a custom pipeline.
+pub struct Shader {
+    /// The bounds of the [`Shader`].
+    pub bounds: Rectangle,
+
+    /// The [`custom::Primitive`] to render.
+    pub primitive: Arc<dyn custom::Primitive>,
+}
+
+impl PartialEq for Shader {
+    fn eq(&self, other: &Self) -> bool {
+        self.primitive.type_id() == other.primitive.type_id()
+    }
+}