Trait CompositeEncoder 

pub trait CompositeEncoder {
    type Rec;
    type Args;

    // Required methods
    fn begin_composite(&self, rec: &Self::Rec, args: &Self::Args);
    fn composite_draw(&self, rec: &Self::Rec, args: &Self::Args);
    fn begin_text(&self, rec: &Self::Rec, args: &Self::Args) -> bool;
    fn text_draw(
        &self,
        rec: &Self::Rec,
        args: &Self::Args,
        call: &TextDrawCall,
    ) -> Result<(), String>;
    fn end_composite(&self, rec: &Self::Rec, args: &Self::Args);
}

The composite pass: tonemap (+ optional LUT grade) the post-stack scene onto the swapchain image, then layer the text overlay on top in the same pass. Its begin -> composite-draw -> text-loop -> end shape is identical on every backend; the swapchain target lifecycle, the descriptor binding, and the text-geometry uploads stay backend-specific behind the trait. Args carries the per-frame binding context each backend needs (DX: the swapchain back-buffer + its RTV, the scene SRV, the window size, the frame slot; VK: the acquired image index + the frame slot).

Every backend uploads a frame’s text geometry into one persistent buffer per frame-in-flight slot, reserved up front with text_upload_bytes and appended to per call, and binds sub-ranges of it: no GPU buffer is created per label per frame anywhere. DX and VK append inside text_draw; Metal (which drives its own composite loop rather than this trait) writes the whole frame’s geometry into its slot before the render graph runs.

Required Associated Types

type Rec

Per-backend command recorder (DX ID3D12GraphicsCommandList, VK vk::CommandBuffer).

type Args

Per-invocation binding context (see the trait doc).

Required Methods

fn begin_composite(&self, rec: &Self::Rec, args: &Self::Args)

Begin the pass: target the swapchain image (DX transitions it to RENDER_TARGET + binds the RTV; VK begins the composite render pass) and set the full-window viewport / scissor.

fn composite_draw(&self, rec: &Self::Rec, args: &Self::Args)

The fullscreen tonemap draw: bind the composite pipeline + its inputs (scene, bloom, LUT) + push constants, draw the fullscreen triangle.

fn begin_text(&self, rec: &Self::Rec, args: &Self::Args) -> bool

Bind the text pipeline + any one-time text state. Returns false when text is inert (no pipeline or no atlases), so the driver skips the call loop.

fn text_draw( &self, rec: &Self::Rec, args: &Self::Args, call: &TextDrawCall, ) -> Result<(), String>

Encode one text draw call: append its vertex/index geometry to this frame slot’s persistent upload buffer, bind the atlas plus the two sub-ranges, and draw.

fn end_composite(&self, rec: &Self::Rec, args: &Self::Args)

End the pass: DX transitions the back-buffer back to PRESENT; VK ends the render pass.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors