alpha2-render 0.2.0

use crate::{RenderError, RenderSize, RenderedTexture, Renderer, pipeline::CachedPipeline};
use alpha2_shaders::FULLSCREEN_TEXTURE_QUAD_WGSL;

impl Renderer {
    /// Draws one premultiplied RGBA texel over an opaque clear target.
    ///
    /// # Errors
    /// Returns [`RenderError::Gpu`] when the GPU rejected the draw.
    #[allow(clippy::too_many_lines)]
    pub fn render_quad(
        &self,
        size: RenderSize,
        source: [u8; 4],
    ) -> Result<RenderedTexture, RenderError> {
        let format = self.intermediate_format();
        let mut encoder = self.command_encoder("alpha2 quad encoder");
        let target = self
            .textures
            .acquire(self.gpu.device(), size, format, "alpha2 quad target");
        let input = self.gpu.device().create_texture(&wgpu::TextureDescriptor {
            label: None,
            size: wgpu::Extent3d {
                width: 1,
                height: 1,
                depth_or_array_layers: 1,
            },
            mip_level_count: 1,
            sample_count: 1,
            dimension: wgpu::TextureDimension::D2,
            format: wgpu::TextureFormat::Rgba8Unorm,
            usage: wgpu::TextureUsages::TEXTURE_BINDING | wgpu::TextureUsages::COPY_DST,
            view_formats: &[],
        });
        self.gpu.queue().write_texture(
            wgpu::TexelCopyTextureInfo {
                texture: &input,
                mip_level: 0,
                origin: wgpu::Origin3d::ZERO,
                aspect: wgpu::TextureAspect::All,
            },
            &source,
            wgpu::TexelCopyBufferLayout {
                offset: 0,
                bytes_per_row: Some(4),
                rows_per_image: Some(1),
            },
            wgpu::Extent3d {
                width: 1,
                height: 1,
                depth_or_array_layers: 1,
            },
        );
        let cached = self.quad_pipeline();
        let input_view = crate::pool::default_view(&input);
        let group = self
            .gpu
            .device()
            .create_bind_group(&wgpu::BindGroupDescriptor {
                label: None,
                layout: &cached.bind_group_layout,
                entries: &[wgpu::BindGroupEntry {
                    binding: 0,
                    resource: wgpu::BindingResource::TextureView(&input_view),
                }],
            });
        {
            let mut pass = encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                label: None,
                color_attachments: &[Some(wgpu::RenderPassColorAttachment {
                    view: target.view(),
                    depth_slice: None,
                    resolve_target: None,
                    ops: wgpu::Operations {
                        load: wgpu::LoadOp::Clear(wgpu::Color::BLACK),
                        store: wgpu::StoreOp::Store,
                    },
                })],
                depth_stencil_attachment: None,
                timestamp_writes: None,
                occlusion_query_set: None,
                multiview_mask: None,
            });
            pass.set_pipeline(&cached.pipeline);
            pass.set_bind_group(0, &group, &[]);
            pass.draw(0..3, 0..1);
        }
        self.submit([encoder.finish()])?;
        Ok(RenderedTexture::pooled(size, format, target))
    }

    pub(crate) fn quad_pipeline(&self) -> &CachedPipeline {
        self.pipelines.quad.get_or_init(|| {
            let bind_group_layout =
                self.gpu
                    .device()
                    .create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
                        label: Some("alpha2 quad layout"),
                        entries: &[wgpu::BindGroupLayoutEntry {
                            binding: 0,
                            visibility: wgpu::ShaderStages::FRAGMENT,
                            ty: wgpu::BindingType::Texture {
                                sample_type: wgpu::TextureSampleType::Float { filterable: false },
                                view_dimension: wgpu::TextureViewDimension::D2,
                                multisampled: false,
                            },
                            count: None,
                        }],
                    });
            let shader = self
                .gpu
                .device()
                .create_shader_module(wgpu::ShaderModuleDescriptor {
                    label: Some("alpha2 quad shader"),
                    source: wgpu::ShaderSource::Wgsl(FULLSCREEN_TEXTURE_QUAD_WGSL.into()),
                });
            let pipeline_layout =
                self.gpu
                    .device()
                    .create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
                        label: Some("alpha2 quad pipeline layout"),
                        bind_group_layouts: &[Some(&bind_group_layout)],
                        immediate_size: 0,
                    });
            let pipeline =
                self.gpu
                    .device()
                    .create_render_pipeline(&wgpu::RenderPipelineDescriptor {
                        label: Some("alpha2 quad pipeline"),
                        layout: Some(&pipeline_layout),
                        vertex: wgpu::VertexState {
                            module: &shader,
                            entry_point: Some("vs"),
                            buffers: &[],
                            compilation_options: wgpu::PipelineCompilationOptions::default(),
                        },
                        fragment: Some(wgpu::FragmentState {
                            module: &shader,
                            entry_point: Some("fs"),
                            targets: &[Some(wgpu::ColorTargetState {
                                format: self.intermediate_format(),
                                blend: Some(wgpu::BlendState::PREMULTIPLIED_ALPHA_BLENDING),
                                write_mask: wgpu::ColorWrites::ALL,
                            })],
                            compilation_options: wgpu::PipelineCompilationOptions::default(),
                        }),
                        primitive: wgpu::PrimitiveState::default(),
                        depth_stencil: None,
                        multisample: wgpu::MultisampleState::default(),
                        multiview_mask: None,
                        cache: None,
                    });
            CachedPipeline {
                bind_group_layout,
                pipeline,
            }
        })
    }
}