1 files changed, 120 insertions, 0 deletions
diff --git a/vgcodec/src/paint.rs b/vgcodec/src/paint.rs
new file mode 100644
index 0000000..3da0647
--- /dev/null
+++ b/vgcodec/src/paint.rs
@@ -0,0 +1,120 @@
+use std::{borrow::Cow, sync::Arc};
+use wgpu::{util::DeviceExt, BindGroup, Buffer, ComputePipeline, Extent3d, Texture};
+
+use crate::app::App;
+
+pub struct Painter {
+    app: Arc<App>,
+    size: Extent3d,
+
+    pipeline: ComputePipeline,
+    bind_group: BindGroup,
+
+    uniform_buffer_size: u64,
+    uniform_buffer: Buffer,
+    uniform_staging_buffer: Buffer,
+}
+
+impl Painter {
+    pub fn new(app: &Arc<App>, extent: Extent3d, tex_a: &Texture, tex_b: &Texture) -> Self {
+        let App { device, .. } = app.as_ref();
+        let cs_module = device.create_shader_module(wgpu::ShaderModuleDescriptor {
+            label: None,
+            source: wgpu::ShaderSource::Wgsl(Cow::Borrowed(include_str!("paint.wgsl"))),
+        });
+
+        let uniform_buffer_size = std::mem::size_of::<u32>() as wgpu::BufferAddress;
+        let uniform_staging_buffer = device.create_buffer(&wgpu::BufferDescriptor {
+            label: None,
+            size: uniform_buffer_size,
+            usage: wgpu::BufferUsages::MAP_READ | wgpu::BufferUsages::COPY_DST,
+            mapped_at_creation: false,
+        });
+        let uniform_buffer = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
+            label: None,
+            contents: bytemuck::cast_slice(&[0u32]),
+            usage: wgpu::BufferUsages::STORAGE
+                | wgpu::BufferUsages::COPY_DST
+                | wgpu::BufferUsages::COPY_SRC,
+        });
+
+        let pipeline = device.create_compute_pipeline(&wgpu::ComputePipelineDescriptor {
+            label: None,
+            layout: None,
+            module: &cs_module,
+            entry_point: "main",
+        });
+
+        let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
+            label: None,
+            layout: &pipeline.get_bind_group_layout(0),
+            entries: &[
+                wgpu::BindGroupEntry {
+                    binding: 0,
+                    resource: wgpu::BindingResource::TextureView(
+                        &tex_a.create_view(&wgpu::TextureViewDescriptor::default()),
+                    ),
+                },
+                wgpu::BindGroupEntry {
+                    binding: 1,
+                    resource: wgpu::BindingResource::TextureView(
+                        &tex_b.create_view(&wgpu::TextureViewDescriptor::default()),
+                    ),
+                },
+                wgpu::BindGroupEntry {
+                    binding: 2,
+                    resource: uniform_buffer.as_entire_binding(),
+                },
+            ],
+        });
+        Self {
+            app: app.clone(),
+            size: extent,
+            pipeline,
+            uniform_buffer_size,
+            uniform_buffer,
+            bind_group,
+            uniform_staging_buffer,
+        }
+    }
+
+    pub async fn run(&mut self) -> u32 {
+        let App { device, queue, .. } = self.app.as_ref();
+
+        let mut encoder =
+            device.create_command_encoder(&wgpu::CommandEncoderDescriptor { label: None });
+        {
+            let mut cpass =
+                encoder.begin_compute_pass(&wgpu::ComputePassDescriptor { label: None });
+            cpass.set_pipeline(&self.pipeline);
+            cpass.set_bind_group(0, &self.bind_group, &[]);
+            cpass.dispatch_workgroups(self.size.width, self.size.height, 1);
+        }
+
+        encoder.copy_buffer_to_buffer(
+            &self.uniform_buffer,
+            0,
+            &self.uniform_staging_buffer,
+            0,
+            self.uniform_buffer_size,
+        );
+
+        queue.submit(Some(encoder.finish()));
+
+        let buffer_slice = self.uniform_staging_buffer.slice(..);
+        let (sender, receiver) = futures_intrusive::channel::shared::oneshot_channel();
+        buffer_slice.map_async(wgpu::MapMode::Read, move |v| {
+            sender.send(v.unwrap()).unwrap()
+        });
+        device.poll(wgpu::Maintain::Wait);
+        receiver.receive().await;
+
+        let data = buffer_slice.get_mapped_range();
+        let result: u32 = bytemuck::cast_slice(&data).to_vec()[0];
+
+        drop(data);
+        self.uniform_staging_buffer.unmap();
+
+        result
+    }
+}