Function render_shadows 

pub fn render_shadows(
    gpu: &ShadowGpuState<'_>,
    pipelines: &ShadowPipelines<'_>,
    descs: &[ShadowDesc],
) -> Result<ShadowRenderStats, UiError>

Render all descs shadows, compositing each onto gpu.target_view.

Ping-pong textures are allocated once for the entire batch. Each shadow issues separate command-encoder submissions so wgpu’s internal ordering guarantees sequential execution.

The caller must ensure the main frame encoder has NOT yet been submitted — shadows are composited onto the target before the solid/gradient/textured passes so content renders on top.

Errors

Propagates any UiError from sub-passes.