1 files changed, 107 insertions, 2 deletions

diff --git a/stockton-skeleton/src/draw_passes/mod.rs b/stockton-skeleton/src/draw_passes/mod.rs
index a0dbba5..5a92a45 100644
--- a/stockton-skeleton/src/draw_passes/mod.rs
+++ b/stockton-skeleton/src/draw_passes/mod.rs
@@ -1,6 +1,12 @@
 //! Traits and common draw passes.
+use std::ops::Range;
+
 use super::{queue_negotiator::QueueNegotiator, RenderingContext};
 use crate::types::*;
+use hal::{
+    image::Layout,
+    pass::{AttachmentLoadOp, AttachmentOps, AttachmentStoreOp},
+};
 use stockton_types::Session;
 
 use anyhow::Result;
@@ -11,7 +17,7 @@ pub mod util;
 pub use cons::ConsDrawPass;
 
 /// One of several 'passes' that draw on each frame.
-pub trait DrawPass {
+pub trait DrawPass<P: PassPosition> {
     /// Queue any necessary draw commands to cmd_buffer
     /// This should assume the command buffer isn't in the middle of a renderpass, and should leave it as such.
     fn queue_draw(
@@ -34,7 +40,7 @@ pub trait DrawPass {
 
 /// A type that can be made into a specific draw pass type.
 /// This allows extra data to be used in initialisation without the Renderer needing to worry about it.
-pub trait IntoDrawPass<T: DrawPass> {
+pub trait IntoDrawPass<T: DrawPass<P>, P: PassPosition> {
     fn init(self, session: &mut Session, context: &mut RenderingContext) -> Result<T>;
 
     /// This function should ask the queue negotatior to find families for any auxilary operations this draw pass needs to perform
@@ -45,3 +51,102 @@ pub trait IntoDrawPass<T: DrawPass> {
         queue_negotiator: &mut QueueNegotiator,
     ) -> Result<Vec<(&'a QueueFamilyT, Vec<f32>)>>;
 }
+
+/// Used so that draw passes can determine what state shared resources are in and how they should be left.
+pub trait PassPosition: private::Sealed {
+    /// The layout the image is in going in.
+    fn layout_in() -> Layout;
+
+    /// The layout the image should be once this drawpass is completed
+    fn layout_out() -> Layout;
+
+    /// Has the layout already been cleared this frame
+    fn is_cleared() -> bool;
+
+    /// Convenience function to get a range from layout_in() to layout_out()
+    fn layout_as_range() -> Range<Layout> {
+        Self::layout_in()..Self::layout_out()
+    }
+
+    /// Convenience function to get the attachment ops that should be used when loading the image attachment.
+    fn attachment_ops() -> AttachmentOps {
+        match Self::is_cleared() {
+            true => AttachmentOps::new(AttachmentLoadOp::Load, AttachmentStoreOp::Store),
+            false => AttachmentOps::new(AttachmentLoadOp::Clear, AttachmentStoreOp::Store),
+        }
+    }
+}
+
+/// Pass is at the beginning of the list
+pub struct Beginning;
+impl PassPosition for Beginning {
+    fn layout_in() -> Layout {
+        Layout::Undefined
+    }
+
+    fn layout_out() -> Layout {
+        Layout::ColorAttachmentOptimal
+    }
+
+    fn is_cleared() -> bool {
+        false
+    }
+}
+
+/// Pass is in the middle of the list
+pub struct Middle;
+impl PassPosition for Middle {
+    fn layout_in() -> Layout {
+        Layout::ColorAttachmentOptimal
+    }
+
+    fn layout_out() -> Layout {
+        Layout::ColorAttachmentOptimal
+    }
+
+    fn is_cleared() -> bool {
+        true
+    }
+}
+
+/// Pass is at the end of the list
+pub struct End;
+impl PassPosition for End {
+    fn layout_in() -> Layout {
+        Layout::ColorAttachmentOptimal
+    }
+
+    fn layout_out() -> Layout {
+        Layout::Present
+    }
+
+    fn is_cleared() -> bool {
+        true
+    }
+}
+
+/// Pass is the only draw pass being used
+pub struct Singular;
+impl PassPosition for Singular {
+    fn layout_in() -> Layout {
+        Layout::Undefined
+    }
+
+    fn layout_out() -> Layout {
+        Layout::Present
+    }
+
+    fn is_cleared() -> bool {
+        false
+    }
+}
+
+mod private {
+    use super::{Beginning, End, Middle, Singular};
+
+    pub trait Sealed {}
+    impl Sealed for Beginning {}
+    impl Sealed for Middle {}
+    impl Sealed for End {}
+    impl Sealed for Singular {}
+}