lemur/src/window/game_screen.rs

use std::sync::Arc;

use egui::Widget;
use wgpu::{util::DeviceExt as _, BindGroup, BindGroupLayout, RenderPipeline};

use crate::graphics::TextureSink;

pub struct GameScreen {
    bind_group: Arc<BindGroup>,
}

impl GameScreen {
    fn init_pipeline(render_state: &egui_wgpu::RenderState) {
        let device = &render_state.device;

        let bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
            label: Some("texture bind group layout"),
            entries: &[
                wgpu::BindGroupLayoutEntry {
                    binding: 0,
                    visibility: wgpu::ShaderStages::FRAGMENT,
                    ty: wgpu::BindingType::Texture {
                        sample_type: wgpu::TextureSampleType::Float { filterable: true },
                        view_dimension: wgpu::TextureViewDimension::D2,
                        multisampled: false,
                    },
                    count: None,
                },
                wgpu::BindGroupLayoutEntry {
                    binding: 1,
                    visibility: wgpu::ShaderStages::FRAGMENT,
                    ty: wgpu::BindingType::Sampler(wgpu::SamplerBindingType::Filtering),
                    count: None,
                },
                wgpu::BindGroupLayoutEntry {
                    binding: 2,
                    visibility: wgpu::ShaderStages::FRAGMENT,
                    ty: wgpu::BindingType::Buffer {
                        ty: wgpu::BufferBindingType::Uniform,
                        has_dynamic_offset: false,
                        min_binding_size: None,
                    },
                    count: None,
                },
            ],
        });

        let shader = device.create_shader_module(wgpu::include_wgsl!("../anaglyph.wgsl"));
        let render_pipeline_layout =
            device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
                label: Some("render pipeline layout"),
                bind_group_layouts: &[&bind_group_layout],
                push_constant_ranges: &[],
            });
        let render_pipeline = device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
            label: Some("render pipeline"),
            layout: Some(&render_pipeline_layout),
            vertex: wgpu::VertexState {
                module: &shader,
                entry_point: "vs_main",
                buffers: &[],
                compilation_options: wgpu::PipelineCompilationOptions::default(),
            },
            fragment: Some(wgpu::FragmentState {
                module: &shader,
                entry_point: "fs_main",
                targets: &[Some(wgpu::ColorTargetState {
                    format: wgpu::TextureFormat::Bgra8Unorm,
                    blend: Some(wgpu::BlendState::REPLACE),
                    write_mask: wgpu::ColorWrites::ALL,
                })],
                compilation_options: wgpu::PipelineCompilationOptions::default(),
            }),
            primitive: wgpu::PrimitiveState {
                topology: wgpu::PrimitiveTopology::TriangleList,
                strip_index_format: None,
                front_face: wgpu::FrontFace::Ccw,
                cull_mode: Some(wgpu::Face::Back),
                polygon_mode: wgpu::PolygonMode::Fill,
                unclipped_depth: false,
                conservative: false,
            },
            depth_stencil: None,
            multisample: wgpu::MultisampleState {
                count: 1,
                mask: !0,
                alpha_to_coverage_enabled: false,
            },
            multiview: None,
            cache: None,
        });

        render_state
            .renderer
            .write()
            .callback_resources
            .insert(SharedGameScreenResources {
                pipeline: render_pipeline,
                bind_group_layout,
            });
    }

    pub fn init(render_state: &egui_wgpu::RenderState) -> (Self, TextureSink) {
        Self::init_pipeline(render_state);

        let device = &render_state.device;
        let queue = &render_state.queue;

        let (sink, texture_view) = TextureSink::new(device, queue.clone());
        let sampler = device.create_sampler(&wgpu::SamplerDescriptor::default());
        let colors = Colors {
            left: [1.0, 0.0, 0.0, 1.0],
            right: [0.0, 0.7734375, 0.9375, 1.0],
        };

        let color_buf = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
            label: Some("colors"),
            contents: bytemuck::bytes_of(&colors),
            usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
        });

        let renderer = render_state.renderer.read();
        let resources: &SharedGameScreenResources = renderer.callback_resources.get().unwrap();

        let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
            label: Some("bind group"),
            layout: &resources.bind_group_layout,
            entries: &[
                wgpu::BindGroupEntry {
                    binding: 0,
                    resource: wgpu::BindingResource::TextureView(&texture_view),
                },
                wgpu::BindGroupEntry {
                    binding: 1,
                    resource: wgpu::BindingResource::Sampler(&sampler),
                },
                wgpu::BindGroupEntry {
                    binding: 2,
                    resource: color_buf.as_entire_binding(),
                },
            ],
        });

        (
            Self {
                bind_group: Arc::new(bind_group),
            },
            sink,
        )
    }
}

impl Widget for &GameScreen {
    fn ui(self, ui: &mut egui::Ui) -> egui::Response {
        let response = ui.allocate_rect(ui.clip_rect(), egui::Sense::hover());
        let callback = egui_wgpu::Callback::new_paint_callback(
            response.rect,
            GameScreenCallback {
                bind_group: self.bind_group.clone(),
            },
        );
        ui.painter().add(callback);
        response
    }
}

struct GameScreenCallback {
    bind_group: Arc<BindGroup>,
}

impl egui_wgpu::CallbackTrait for GameScreenCallback {
    fn paint(
        &self,
        info: egui::PaintCallbackInfo,
        render_pass: &mut wgpu::RenderPass<'static>,
        callback_resources: &egui_wgpu::CallbackResources,
    ) {
        let resources: &SharedGameScreenResources = callback_resources.get().unwrap();
        let viewport = info.viewport_in_pixels();
        let left = viewport.left_px as f32;
        let top = viewport.top_px as f32;
        let width = viewport.width_px as f32;
        let height = viewport.height_px as f32;
        let aspect_ratio = 384.0 / 224.0;
        let w = width.min(height * aspect_ratio);
        let h = height.min(width / aspect_ratio);
        let x = left + (width - w) / 2.0;
        let y = top + (height - h) / 2.0;
        render_pass.set_pipeline(&resources.pipeline);
        render_pass.set_bind_group(0, &self.bind_group, &[]);
        render_pass.set_viewport(x, y, w, h, 0.0, 1.0);
        render_pass.draw(0..6, 0..1);
    }
}

struct SharedGameScreenResources {
    pipeline: RenderPipeline,
    bind_group_layout: BindGroupLayout,
}

#[derive(Clone, Copy, bytemuck::Pod, bytemuck::Zeroable)]
#[repr(C)]
struct Colors {
    left: [f32; 4],
    right: [f32; 4],
}