# tile_pipeline.rs - source
Source of the Rust file `maplibre/src/render/resource/tile_pipeline.rs`.

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    //! Utility for declaring pipelines.

    use std::borrow::Cow;

    use crate::render::{
        resource::{FragmentState, RenderPipeline, RenderPipelineDescriptor, VertexState},
        settings::RendererSettings,
    };

    pub struct TilePipeline {
        name: Cow<'static, str>,
        /// Is the depth stencil used?
        depth_stencil_enabled: bool,
        /// This pipeline updates the stenctil
        update_stencil: bool,
        /// Force a write and ignore stencil
        debug_stencil: bool,
        wireframe: bool,
        msaa: bool,
        raster: bool,
        settings: RendererSettings,

        vertex_state: VertexState,
        fragment_state: FragmentState,
    }

    impl TilePipeline {
        pub fn new(
            name: Cow<'static, str>,
            settings: RendererSettings,
            vertex_state: VertexState,
            fragment_state: FragmentState,
            depth_stencil_enabled: bool,
            update_stencil: bool,
            debug_stencil: bool,
            wireframe: bool,
            multisampling: bool,
            raster: bool,
        ) -> Self {
            TilePipeline {
                name,
                depth_stencil_enabled,
                update_stencil,
                debug_stencil,
                wireframe,
                msaa: multisampling,
                raster,
                settings,
                vertex_state,
                fragment_state,
            }
        }
    }

    impl RenderPipeline for TilePipeline {
        fn describe_render_pipeline(self) -> RenderPipelineDescriptor {
            let stencil_state = if self.update_stencil {
                wgpu::StencilFaceState {
                    compare: wgpu::CompareFunction::Always, // Allow ALL values to update the stencil
                    fail_op: wgpu::StencilOperation::Keep,
                    depth_fail_op: wgpu::StencilOperation::Keep, // This is used when the depth test already failed
                    pass_op: wgpu::StencilOperation::Replace,
                }
            } else {
                wgpu::StencilFaceState {
                    compare: if self.debug_stencil {
                        wgpu::CompareFunction::Always
                    } else {
                        wgpu::CompareFunction::Equal
                    },
                    fail_op: wgpu::StencilOperation::Keep,
                    depth_fail_op: wgpu::StencilOperation::Keep,
                    pass_op: wgpu::StencilOperation::Keep,
                }
            };

            RenderPipelineDescriptor {
                label: Some(self.name),
                layout: if self.raster {
                    Some(vec![vec![
                        wgpu::BindGroupLayoutEntry {
                            binding: 0,
                            visibility: wgpu::ShaderStages::FRAGMENT,
                            ty: wgpu::BindingType::Texture {
                                multisampled: false,
                                view_dimension: wgpu::TextureViewDimension::D2,
                                sample_type: wgpu::TextureSampleType::Float { filterable: true },
                            },
                            count: None,
                        },
                        wgpu::BindGroupLayoutEntry {
                            binding: 1,
                            visibility: wgpu::ShaderStages::FRAGMENT,
                            ty: wgpu::BindingType::Sampler(wgpu::SamplerBindingType::Filtering),
                            count: None,
                        },
                    ]])
                } else {
                    None
                },
                vertex: self.vertex_state,
                fragment: self.fragment_state,
                primitive: wgpu::PrimitiveState {
                    topology: wgpu::PrimitiveTopology::TriangleList,
                    polygon_mode: if self.update_stencil {
                        wgpu::PolygonMode::Fill
                    } else if self.wireframe {
                        wgpu::PolygonMode::Line
                    } else {
                        wgpu::PolygonMode::Fill
                    },
                    front_face: wgpu::FrontFace::Ccw,
                    strip_index_format: None,
                    cull_mode: None, // Maps look the same from he bottom and above -> No culling needed
                    conservative: false,
                    unclipped_depth: false,
                },
                depth_stencil: if !self.depth_stencil_enabled {
                    None
                } else {
                    Some(wgpu::DepthStencilState {
                        format: self.settings.depth_texture_format,
                        depth_write_enabled: !self.update_stencil,
                        depth_compare: wgpu::CompareFunction::Greater,
                        stencil: wgpu::StencilState {
                            front: stencil_state,
                            back: stencil_state,
                            read_mask: 0xff, // Applied to stencil values being read from the stencil buffer
                            write_mask: 0xff, // Applied to fragment stencil values before being written to  the stencil buffer
                        },
                        bias: wgpu::DepthBiasState::default(),
                    })
                },
                multisample: wgpu::MultisampleState {
                    count: if self.msaa {
                        self.settings.msaa.samples
                    } else {
                        1
                    },
                    mask: !0,
                    alpha_to_coverage_enabled: false,
                },
            }
        }
    }