Refactor `triangle::Pipeline` into `prepare` and `render` architecture

And get rid of the staging belt! :tada:

1 files changed, 338 insertions, 223 deletions

diff --git a/wgpu/src/triangle.rs b/wgpu/src/triangle.rs
index efdd214b..572af1e8 100644
--- a/wgpu/src/triangle.rs
+++ b/wgpu/src/triangle.rs
@@ -14,50 +14,56 @@ use tracing::info_span;
 #[derive(Debug)]
 pub struct Pipeline {
     blit: Option<msaa::Blit>,
-    index_buffer: Buffer<u32>,
-    index_strides: Vec<u32>,
     solid: solid::Pipeline,
 
     /// Gradients are currently not supported on WASM targets due to their need of storage buffers.
     #[cfg(not(target_arch = "wasm32"))]
     gradient: gradient::Pipeline,
+
+    layers: Vec<Layer>,
+    prepare_layer: usize,
+    render_layer: usize,
 }
 
-impl Pipeline {
-    pub fn new(
+#[derive(Debug)]
+struct Layer {
+    index_buffer: Buffer<u32>,
+    index_strides: Vec<u32>,
+    solid: solid::Layer,
+
+    #[cfg(not(target_arch = "wasm32"))]
+    gradient: gradient::Layer,
+}
+
+impl Layer {
+    fn new(
         device: &wgpu::Device,
-        format: wgpu::TextureFormat,
-        antialiasing: Option<settings::Antialiasing>,
-    ) -> Pipeline {
-        Pipeline {
-            blit: antialiasing.map(|a| msaa::Blit::new(device, format, a)),
+        solid: &solid::Pipeline,
+        #[cfg(not(target_arch = "wasm32"))] gradient: &gradient::Pipeline,
+    ) -> Self {
+        Self {
             index_buffer: Buffer::new(
                 device,
                 "iced_wgpu::triangle vertex buffer",
                 wgpu::BufferUsages::INDEX | wgpu::BufferUsages::COPY_DST,
             ),
             index_strides: Vec::new(),
-            solid: solid::Pipeline::new(device, format, antialiasing),
+            solid: solid::Layer::new(device, &solid.constants_layout),
 
             #[cfg(not(target_arch = "wasm32"))]
-            gradient: gradient::Pipeline::new(device, format, antialiasing),
+            gradient: gradient::Layer::new(device, &gradient.constants_layout),
         }
     }
 
-    pub fn draw(
+    fn prepare(
         &mut self,
         device: &wgpu::Device,
-        staging_belt: &mut wgpu::util::StagingBelt,
-        encoder: &mut wgpu::CommandEncoder,
-        target: &wgpu::TextureView,
-        target_size: Size<u32>,
-        transformation: Transformation,
-        scale_factor: f32,
+        queue: &wgpu::Queue,
+        solid: &solid::Pipeline,
+        #[cfg(not(target_arch = "wasm32"))] gradient: &gradient::Pipeline,
         meshes: &[Mesh<'_>],
+        transformation: Transformation,
     ) {
-        #[cfg(feature = "tracing")]
-        let _ = info_span!("Wgpu::Triangle", "DRAW").entered();
-
         // Count the total amount of vertices & indices we need to handle
         let count = mesh::attribute_count_of(meshes);
 
@@ -75,6 +81,7 @@ impl Pipeline {
             .resize(device, count.gradient_vertices);
 
         // Prepare dynamic buffers & data store for writing
+        self.index_buffer.clear();
         self.index_strides.clear();
         self.solid.vertices.clear();
         self.solid.uniforms.clear();
@@ -99,13 +106,8 @@ impl Pipeline {
             let transform =
                 transformation * Transformation::translate(origin.x, origin.y);
 
-            let new_index_offset = self.index_buffer.write(
-                device,
-                staging_belt,
-                encoder,
-                index_offset,
-                indices,
-            );
+            let new_index_offset =
+                self.index_buffer.write(queue, index_offset, indices);
 
             index_offset += new_index_offset;
             self.index_strides.push(indices.len() as u32);
@@ -116,9 +118,7 @@ impl Pipeline {
                     self.solid.uniforms.push(&solid::Uniforms::new(transform));
 
                     let written_bytes = self.solid.vertices.write(
-                        device,
-                        staging_belt,
-                        encoder,
+                        queue,
                         solid_vertex_offset,
                         &buffers.vertices,
                     );
@@ -130,9 +130,7 @@ impl Pipeline {
                     buffers, gradient, ..
                 } => {
                     let written_bytes = self.gradient.vertices.write(
-                        device,
-                        staging_belt,
-                        encoder,
+                        queue,
                         gradient_vertex_offset,
                         &buffers.vertices,
                     );
@@ -196,14 +194,14 @@ impl Pipeline {
             let uniforms_resized = self.solid.uniforms.resize(device);
 
             if uniforms_resized {
-                self.solid.bind_group = solid::Pipeline::bind_group(
+                self.solid.constants = solid::Layer::bind_group(
                     device,
                     self.solid.uniforms.raw(),
-                    &self.solid.bind_group_layout,
+                    &solid.constants_layout,
                 )
             }
 
-            self.solid.uniforms.write(device, staging_belt, encoder);
+            self.solid.uniforms.write(queue);
         }
 
         #[cfg(not(target_arch = "wasm32"))]
@@ -218,22 +216,169 @@ impl Pipeline {
             let storage_resized = self.gradient.storage.resize(device);
 
             if uniforms_resized || storage_resized {
-                self.gradient.bind_group = gradient::Pipeline::bind_group(
+                self.gradient.constants = gradient::Layer::bind_group(
                     device,
                     self.gradient.uniforms.raw(),
                     self.gradient.storage.raw(),
-                    &self.gradient.bind_group_layout,
+                    &gradient.constants_layout,
                 );
             }
 
             // Write to GPU
-            self.gradient.uniforms.write(device, staging_belt, encoder);
-            self.gradient.storage.write(device, staging_belt, encoder);
+            self.gradient.uniforms.write(queue);
+            self.gradient.storage.write(queue);
 
             // Cleanup
             self.gradient.color_stop_offset = 0;
             self.gradient.color_stops_pending_write.color_stops.clear();
         }
+    }
+
+    fn render<'a>(
+        &'a mut self,
+        solid: &'a solid::Pipeline,
+        #[cfg(not(target_arch = "wasm32"))] gradient: &'a gradient::Pipeline,
+        meshes: &[Mesh<'_>],
+        scale_factor: f32,
+        render_pass: &mut wgpu::RenderPass<'a>,
+    ) {
+        let mut num_solids = 0;
+        #[cfg(not(target_arch = "wasm32"))]
+        let mut num_gradients = 0;
+        let mut last_is_solid = None;
+
+        for (index, mesh) in meshes.iter().enumerate() {
+            let clip_bounds = (mesh.clip_bounds() * scale_factor).snap();
+
+            render_pass.set_scissor_rect(
+                clip_bounds.x,
+                clip_bounds.y,
+                clip_bounds.width,
+                clip_bounds.height,
+            );
+
+            match mesh {
+                Mesh::Solid { .. } => {
+                    if !last_is_solid.unwrap_or(false) {
+                        render_pass.set_pipeline(&solid.pipeline);
+
+                        last_is_solid = Some(true);
+                    }
+
+                    render_pass.set_bind_group(
+                        0,
+                        &self.solid.constants,
+                        &[self.solid.uniforms.offset_at_index(num_solids)],
+                    );
+
+                    render_pass.set_vertex_buffer(
+                        0,
+                        self.solid.vertices.slice_from_index(num_solids),
+                    );
+
+                    num_solids += 1;
+                }
+                #[cfg(not(target_arch = "wasm32"))]
+                Mesh::Gradient { .. } => {
+                    if last_is_solid.unwrap_or(true) {
+                        render_pass.set_pipeline(&gradient.pipeline);
+
+                        last_is_solid = Some(false);
+                    }
+
+                    render_pass.set_bind_group(
+                        0,
+                        &self.gradient.constants,
+                        &[self
+                            .gradient
+                            .uniforms
+                            .offset_at_index(num_gradients)],
+                    );
+
+                    render_pass.set_vertex_buffer(
+                        0,
+                        self.gradient.vertices.slice_from_index(num_gradients),
+                    );
+
+                    num_gradients += 1;
+                }
+                #[cfg(target_arch = "wasm32")]
+                Mesh::Gradient { .. } => {}
+            };
+
+            render_pass.set_index_buffer(
+                self.index_buffer.slice_from_index(index),
+                wgpu::IndexFormat::Uint32,
+            );
+
+            render_pass.draw_indexed(0..self.index_strides[index], 0, 0..1);
+        }
+    }
+}
+
+impl Pipeline {
+    pub fn new(
+        device: &wgpu::Device,
+        format: wgpu::TextureFormat,
+        antialiasing: Option<settings::Antialiasing>,
+    ) -> Pipeline {
+        Pipeline {
+            blit: antialiasing.map(|a| msaa::Blit::new(device, format, a)),
+            solid: solid::Pipeline::new(device, format, antialiasing),
+
+            #[cfg(not(target_arch = "wasm32"))]
+            gradient: gradient::Pipeline::new(device, format, antialiasing),
+
+            layers: Vec::new(),
+            prepare_layer: 0,
+            render_layer: 0,
+        }
+    }
+
+    pub fn prepare(
+        &mut self,
+        device: &wgpu::Device,
+        queue: &wgpu::Queue,
+        meshes: &[Mesh<'_>],
+        transformation: Transformation,
+    ) {
+        #[cfg(feature = "tracing")]
+        let _ = info_span!("Wgpu::Triangle", "PREPARE").entered();
+
+        if self.layers.len() <= self.prepare_layer {
+            self.layers.push(Layer::new(
+                device,
+                &self.solid,
+                #[cfg(not(target_arch = "wasm32"))]
+                &self.gradient,
+            ));
+        }
+
+        let layer = &mut self.layers[self.prepare_layer];
+        layer.prepare(
+            device,
+            queue,
+            &self.solid,
+            #[cfg(not(target_arch = "wasm32"))]
+            &self.gradient,
+            meshes,
+            transformation,
+        );
+
+        self.prepare_layer += 1;
+    }
+
+    pub fn render(
+        &mut self,
+        device: &wgpu::Device,
+        encoder: &mut wgpu::CommandEncoder,
+        target: &wgpu::TextureView,
+        target_size: Size<u32>,
+        meshes: &[Mesh<'_>],
+        scale_factor: f32,
+    ) {
+        #[cfg(feature = "tracing")]
+        let _ = info_span!("Wgpu::Triangle", "DRAW").entered();
 
         // Configure render pass
         {
@@ -268,87 +413,29 @@ impl Pipeline {
                     depth_stencil_attachment: None,
                 });
 
-            let mut num_solids = 0;
-            #[cfg(not(target_arch = "wasm32"))]
-            let mut num_gradients = 0;
-            let mut last_is_solid = None;
-
-            for (index, mesh) in meshes.iter().enumerate() {
-                let clip_bounds = (mesh.clip_bounds() * scale_factor).snap();
-
-                render_pass.set_scissor_rect(
-                    clip_bounds.x,
-                    clip_bounds.y,
-                    clip_bounds.width,
-                    clip_bounds.height,
-                );
-
-                match mesh {
-                    Mesh::Solid { .. } => {
-                        if !last_is_solid.unwrap_or(false) {
-                            render_pass.set_pipeline(&self.solid.pipeline);
-
-                            last_is_solid = Some(true);
-                        }
-
-                        render_pass.set_bind_group(
-                            0,
-                            &self.solid.bind_group,
-                            &[self.solid.uniforms.offset_at_index(num_solids)],
-                        );
-
-                        render_pass.set_vertex_buffer(
-                            0,
-                            self.solid.vertices.slice_from_index(num_solids),
-                        );
-
-                        num_solids += 1;
-                    }
-                    #[cfg(not(target_arch = "wasm32"))]
-                    Mesh::Gradient { .. } => {
-                        if last_is_solid.unwrap_or(true) {
-                            render_pass.set_pipeline(&self.gradient.pipeline);
-
-                            last_is_solid = Some(false);
-                        }
-
-                        render_pass.set_bind_group(
-                            0,
-                            &self.gradient.bind_group,
-                            &[self
-                                .gradient
-                                .uniforms
-                                .offset_at_index(num_gradients)],
-                        );
-
-                        render_pass.set_vertex_buffer(
-                            0,
-                            self.gradient
-                                .vertices
-                                .slice_from_index(num_gradients),
-                        );
-
-                        num_gradients += 1;
-                    }
-                    #[cfg(target_arch = "wasm32")]
-                    Mesh::Gradient { .. } => {}
-                };
-
-                render_pass.set_index_buffer(
-                    self.index_buffer.slice_from_index(index),
-                    wgpu::IndexFormat::Uint32,
-                );
+            let layer = &mut self.layers[self.render_layer];
 
-                render_pass.draw_indexed(0..self.index_strides[index], 0, 0..1);
-            }
+            layer.render(
+                &self.solid,
+                #[cfg(not(target_arch = "wasm32"))]
+                &self.gradient,
+                meshes,
+                scale_factor,
+                &mut render_pass,
+            );
         }
 
-        self.index_buffer.clear();
+        self.render_layer += 1;
 
         if let Some(blit) = &mut self.blit {
             blit.draw(encoder, target);
         }
     }
+
+    pub fn end_frame(&mut self) {
+        self.prepare_layer = 0;
+        self.render_layer = 0;
+    }
 }
 
 fn fragment_target(
@@ -390,10 +477,62 @@ mod solid {
     #[derive(Debug)]
     pub struct Pipeline {
         pub pipeline: wgpu::RenderPipeline,
+        pub constants_layout: wgpu::BindGroupLayout,
+    }
+
+    #[derive(Debug)]
+    pub struct Layer {
         pub vertices: Buffer<triangle::ColoredVertex2D>,
         pub uniforms: dynamic::Buffer<Uniforms>,
-        pub bind_group_layout: wgpu::BindGroupLayout,
-        pub bind_group: wgpu::BindGroup,
+        pub constants: wgpu::BindGroup,
+    }
+
+    impl Layer {
+        pub fn new(
+            device: &wgpu::Device,
+            constants_layout: &wgpu::BindGroupLayout,
+        ) -> Self {
+            let vertices = Buffer::new(
+                device,
+                "iced_wgpu::triangle::solid vertex buffer",
+                wgpu::BufferUsages::VERTEX | wgpu::BufferUsages::COPY_DST,
+            );
+
+            let uniforms = dynamic::Buffer::uniform(
+                device,
+                "iced_wgpu::triangle::solid uniforms",
+            );
+
+            let constants =
+                Self::bind_group(device, uniforms.raw(), constants_layout);
+
+            Self {
+                vertices,
+                uniforms,
+                constants,
+            }
+        }
+
+        pub fn bind_group(
+            device: &wgpu::Device,
+            buffer: &wgpu::Buffer,
+            layout: &wgpu::BindGroupLayout,
+        ) -> wgpu::BindGroup {
+            device.create_bind_group(&wgpu::BindGroupDescriptor {
+                label: Some("iced_wgpu::triangle::solid bind group"),
+                layout,
+                entries: &[wgpu::BindGroupEntry {
+                    binding: 0,
+                    resource: wgpu::BindingResource::Buffer(
+                        wgpu::BufferBinding {
+                            buffer,
+                            offset: 0,
+                            size: Some(Uniforms::min_size()),
+                        },
+                    ),
+                }],
+            })
+        }
     }
 
     #[derive(Debug, Clone, Copy, ShaderType)]
@@ -416,18 +555,7 @@ mod solid {
             format: wgpu::TextureFormat,
             antialiasing: Option<settings::Antialiasing>,
         ) -> Self {
-            let vertices = Buffer::new(
-                device,
-                "iced_wgpu::triangle::solid vertex buffer",
-                wgpu::BufferUsages::VERTEX | wgpu::BufferUsages::COPY_DST,
-            );
-
-            let uniforms = dynamic::Buffer::uniform(
-                device,
-                "iced_wgpu::triangle::solid uniforms",
-            );
-
-            let bind_group_layout = device.create_bind_group_layout(
+            let constants_layout = device.create_bind_group_layout(
                 &wgpu::BindGroupLayoutDescriptor {
                     label: Some("iced_wgpu::triangle::solid bind group layout"),
                     entries: &[wgpu::BindGroupLayoutEntry {
@@ -443,13 +571,10 @@ mod solid {
                 },
             );
 
-            let bind_group =
-                Self::bind_group(device, uniforms.raw(), &bind_group_layout);
-
             let layout = device.create_pipeline_layout(
                 &wgpu::PipelineLayoutDescriptor {
                     label: Some("iced_wgpu::triangle::solid pipeline layout"),
-                    bind_group_layouts: &[&bind_group_layout],
+                    bind_group_layouts: &[&constants_layout],
                     push_constant_ranges: &[],
                 },
             );
@@ -501,33 +626,9 @@ mod solid {
 
             Self {
                 pipeline,
-                vertices,
-                uniforms,
-                bind_group_layout,
-                bind_group,
+                constants_layout,
             }
         }
-
-        pub fn bind_group(
-            device: &wgpu::Device,
-            buffer: &wgpu::Buffer,
-            layout: &wgpu::BindGroupLayout,
-        ) -> wgpu::BindGroup {
-            device.create_bind_group(&wgpu::BindGroupDescriptor {
-                label: Some("iced_wgpu::triangle::solid bind group"),
-                layout,
-                entries: &[wgpu::BindGroupEntry {
-                    binding: 0,
-                    resource: wgpu::BindingResource::Buffer(
-                        wgpu::BufferBinding {
-                            buffer,
-                            offset: 0,
-                            size: Some(Uniforms::min_size()),
-                        },
-                    ),
-                }],
-            })
-        }
     }
 }
 
@@ -545,15 +646,90 @@ mod gradient {
     #[derive(Debug)]
     pub struct Pipeline {
         pub pipeline: wgpu::RenderPipeline,
+        pub constants_layout: wgpu::BindGroupLayout,
+    }
+
+    #[derive(Debug)]
+    pub struct Layer {
         pub vertices: Buffer<Vertex2D>,
         pub uniforms: dynamic::Buffer<Uniforms>,
         pub storage: dynamic::Buffer<Storage>,
+        pub constants: wgpu::BindGroup,
         pub color_stop_offset: i32,
         //Need to store these and then write them all at once
         //or else they will be padded to 256 and cause gaps in the storage buffer
         pub color_stops_pending_write: Storage,
-        pub bind_group_layout: wgpu::BindGroupLayout,
-        pub bind_group: wgpu::BindGroup,
+    }
+
+    impl Layer {
+        pub fn new(
+            device: &wgpu::Device,
+            constants_layout: &wgpu::BindGroupLayout,
+        ) -> Self {
+            let vertices = Buffer::new(
+                device,
+                "iced_wgpu::triangle::gradient vertex buffer",
+                wgpu::BufferUsages::VERTEX | wgpu::BufferUsages::COPY_DST,
+            );
+
+            let uniforms = dynamic::Buffer::uniform(
+                device,
+                "iced_wgpu::triangle::gradient uniforms",
+            );
+
+            // Note: with a WASM target storage buffers are not supported. Will need to use UBOs & static
+            // sized array (eg like the 32-sized array on OpenGL side right now) to make gradients work
+            let storage = dynamic::Buffer::storage(
+                device,
+                "iced_wgpu::triangle::gradient storage",
+            );
+
+            let constants = Self::bind_group(
+                device,
+                uniforms.raw(),
+                storage.raw(),
+                constants_layout,
+            );
+
+            Self {
+                vertices,
+                uniforms,
+                storage,
+                constants,
+                color_stop_offset: 0,
+                color_stops_pending_write: Storage {
+                    color_stops: vec![],
+                },
+            }
+        }
+
+        pub fn bind_group(
+            device: &wgpu::Device,
+            uniform_buffer: &wgpu::Buffer,
+            storage_buffer: &wgpu::Buffer,
+            layout: &wgpu::BindGroupLayout,
+        ) -> wgpu::BindGroup {
+            device.create_bind_group(&wgpu::BindGroupDescriptor {
+                label: Some("iced_wgpu::triangle::gradient bind group"),
+                layout,
+                entries: &[
+                    wgpu::BindGroupEntry {
+                        binding: 0,
+                        resource: wgpu::BindingResource::Buffer(
+                            wgpu::BufferBinding {
+                                buffer: uniform_buffer,
+                                offset: 0,
+                                size: Some(Uniforms::min_size()),
+                            },
+                        ),
+                    },
+                    wgpu::BindGroupEntry {
+                        binding: 1,
+                        resource: storage_buffer.as_entire_binding(),
+                    },
+                ],
+            })
+        }
     }
 
     #[derive(Debug, ShaderType)]
@@ -584,25 +760,7 @@ mod gradient {
             format: wgpu::TextureFormat,
             antialiasing: Option<settings::Antialiasing>,
         ) -> Self {
-            let vertices = Buffer::new(
-                device,
-                "iced_wgpu::triangle::gradient vertex buffer",
-                wgpu::BufferUsages::VERTEX | wgpu::BufferUsages::COPY_DST,
-            );
-
-            let uniforms = dynamic::Buffer::uniform(
-                device,
-                "iced_wgpu::triangle::gradient uniforms",
-            );
-
-            //Note: with a WASM target storage buffers are not supported. Will need to use UBOs & static
-            // sized array (eg like the 32-sized array on OpenGL side right now) to make gradients work
-            let storage = dynamic::Buffer::storage(
-                device,
-                "iced_wgpu::triangle::gradient storage",
-            );
-
-            let bind_group_layout = device.create_bind_group_layout(
+            let constants_layout = device.create_bind_group_layout(
                 &wgpu::BindGroupLayoutDescriptor {
                     label: Some(
                         "iced_wgpu::triangle::gradient bind group layout",
@@ -634,19 +792,12 @@ mod gradient {
                 },
             );
 
-            let bind_group = Pipeline::bind_group(
-                device,
-                uniforms.raw(),
-                storage.raw(),
-                &bind_group_layout,
-            );
-
             let layout = device.create_pipeline_layout(
                 &wgpu::PipelineLayoutDescriptor {
                     label: Some(
                         "iced_wgpu::triangle::gradient pipeline layout",
                     ),
-                    bind_group_layouts: &[&bind_group_layout],
+                    bind_group_layouts: &[&constants_layout],
                     push_constant_ranges: &[],
                 },
             );
@@ -694,44 +845,8 @@ mod gradient {
 
             Self {
                 pipeline,
-                vertices,
-                uniforms,
-                storage,
-                color_stop_offset: 0,
-                color_stops_pending_write: Storage {
-                    color_stops: vec![],
-                },
-                bind_group_layout,
-                bind_group,
+                constants_layout,
             }
         }
-
-        pub fn bind_group(
-            device: &wgpu::Device,
-            uniform_buffer: &wgpu::Buffer,
-            storage_buffer: &wgpu::Buffer,
-            layout: &wgpu::BindGroupLayout,
-        ) -> wgpu::BindGroup {
-            device.create_bind_group(&wgpu::BindGroupDescriptor {
-                label: Some("iced_wgpu::triangle::gradient bind group"),
-                layout,
-                entries: &[
-                    wgpu::BindGroupEntry {
-                        binding: 0,
-                        resource: wgpu::BindingResource::Buffer(
-                            wgpu::BufferBinding {
-                                buffer: uniform_buffer,
-                                offset: 0,
-                                size: Some(Uniforms::min_size()),
-                            },
-                        ),
-                    },
-                    wgpu::BindGroupEntry {
-                        binding: 1,
-                        resource: storage_buffer.as_entire_binding(),
-                    },
-                ],
-            })
-        }
     }
 }