Re-organize custom module as pipeline module

... and move `Shader` widget to `iced_widget` crate

wgpu/src/primitive.rs

@@ -1,10 +1,12 @@
 //! Draw using different graphical primitives.
+pub mod pipeline;
+
+pub use pipeline::Pipeline;
+
 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>;
@@ -14,44 +16,15 @@ 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),
-        })
-    }
+    /// A custom pipeline primitive.
+    Pipeline(Pipeline),
 }
 
 impl Damage for Custom {
     fn bounds(&self) -> Rectangle {
         match self {
             Self::Mesh(mesh) => mesh.bounds(),
-            Self::Shader(shader) => shader.bounds,
+            Self::Pipeline(pipeline) => pipeline.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()
-    }
-}