lumen-engine 0.2.2

Core composition model and rendering orchestration for Lumen.
Documentation 
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use crate::node::{NodeId, NodeParamEvalContext, NodeParams, PortRef};

use crate::gpu::{
    BoundFrame, CompiledOutput, FrameBindContext, GpuCompileNode, GpuCompiledNode, RasterHandle,
    compiler,
};

pub(crate) const SHADER: &str = include_str!("blur.wgsl");

#[derive(Debug, Clone, lumen_macros::Delegate)]
pub struct BlurParams {
    /// Blur radius in pixels.
    #[meta(min = 0, step = 0.5)]
    pub radius: f64,
}

impl Default for BlurParams {
    fn default() -> Self {
        Self { radius: 4.0 }
    }
}

/// Applies a simple box blur to a raster.
#[derive(Debug, Clone, lumen_macros::Node)]
#[node(kind = "blur", name = "Blur", category = "processing")]
pub struct Blur {
    pub id: NodeId,
    #[params]
    pub params: BlurParamsDelegate,
    #[input()]
    pub source: PortRef,
}

impl Default for Blur {
    fn default() -> Self {
        Self {
            id: NodeId::new(0),
            params: BlurParamsDelegate::default(),
            source: PortRef::empty(),
        }
    }
}

#[derive(Debug, Clone)]
struct CompiledBlur {
    node_id: NodeId,
    params: BlurParamsDelegate,
    buffer: lumen_gpu::BufferId,
}

impl GpuCompiledNode for CompiledBlur {
    fn node_id(&self) -> NodeId {
        self.node_id
    }

    fn bind(&self, ctx: &FrameBindContext<'_>, bound: &mut BoundFrame) -> crate::Result<()> {
        let params = self.params.eval(&NodeParamEvalContext {
            node_id: self.node_id,
            expr: &ctx.expr_context(self.node_id, "params"),
        })?;
        let radius = params.radius.round().clamp(0.0, 32.0) as u32;
        let params = compiler::BlurParams {
            values: [radius, 0, 0, 0],
        };
        bound.write_buffer(self.buffer, 0, bytemuck::bytes_of(&params));
        Ok(())
    }
}

impl GpuCompileNode for Blur {
    fn compile_gpu(
        &self,
        ctx: &mut crate::gpu::CompileContext<'_>,
        port: &PortRef,
    ) -> crate::Result<CompiledOutput> {
        let (source, texture, params) = ctx.compile_unary_filter(
            self.id,
            &self.source,
            port,
            "blur",
            SHADER,
            std::mem::size_of::<compiler::BlurParams>() as u64,
        )?;
        ctx.register_compiled_node(CompiledBlur {
            node_id: self.id,
            params: self.params.clone(),
            buffer: params,
        });
        Ok(CompiledOutput::Raster(RasterHandle {
            texture,
            domain: source.domain,
            metadata: source.metadata,
        }))
    }
}