Share `msaa::Blit` texture between multiple windows

4 files changed, 112 insertions, 69 deletions

diff --git a/wgpu/src/lib.rs b/wgpu/src/lib.rs
index ccad08d5..030bcade 100644
--- a/wgpu/src/lib.rs
+++ b/wgpu/src/lib.rs
@@ -117,7 +117,7 @@ impl Renderer {
     ) {
         self.draw_overlay(overlay, viewport);
         self.prepare(engine, device, queue, format, encoder, viewport);
-        self.render(engine, device, encoder, frame, clear_color, viewport);
+        self.render(engine, encoder, frame, clear_color, viewport);
 
         self.triangle_storage.trim();
         self.text_storage.trim();
@@ -153,7 +153,8 @@ impl Renderer {
                     &mut engine.staging_belt,
                     &mut self.triangle_storage,
                     &layer.triangles,
-                    viewport.projection() * Transformation::scale(scale_factor),
+                    Transformation::scale(scale_factor),
+                    viewport.physical_size(),
                 );
             }
 
@@ -187,7 +188,6 @@ impl Renderer {
     fn render(
         &mut self,
         engine: &mut Engine,
-        device: &wgpu::Device,
         encoder: &mut wgpu::CommandEncoder,
         frame: &wgpu::TextureView,
         clear_color: Option<Color>,
@@ -264,13 +264,11 @@ impl Renderer {
                 let _ = ManuallyDrop::into_inner(render_pass);
 
                 mesh_layer += engine.triangle_pipeline.render(
-                    device,
                     encoder,
                     frame,
                     &self.triangle_storage,
                     mesh_layer,
                     &layer.triangles,
-                    viewport.physical_size(),
                     physical_bounds,
                     scale,
                 );
diff --git a/wgpu/src/shader/blit.wgsl b/wgpu/src/shader/blit.wgsl
index c2ea223f..d7633808 100644
--- a/wgpu/src/shader/blit.wgsl
+++ b/wgpu/src/shader/blit.wgsl
@@ -1,22 +1,14 @@
-var<private> positions: array<vec2<f32>, 6> = array<vec2<f32>, 6>(
-    vec2<f32>(-1.0, 1.0),
-    vec2<f32>(-1.0, -1.0),
-    vec2<f32>(1.0, -1.0),
-    vec2<f32>(-1.0, 1.0),
-    vec2<f32>(1.0, 1.0),
-    vec2<f32>(1.0, -1.0)
-);
-
 var<private> uvs: array<vec2<f32>, 6> = array<vec2<f32>, 6>(
     vec2<f32>(0.0, 0.0),
-    vec2<f32>(0.0, 1.0),
+    vec2<f32>(1.0, 0.0),
     vec2<f32>(1.0, 1.0),
     vec2<f32>(0.0, 0.0),
-    vec2<f32>(1.0, 0.0),
+    vec2<f32>(0.0, 1.0),
     vec2<f32>(1.0, 1.0)
 );
 
 @group(0) @binding(0) var u_sampler: sampler;
+@group(0) @binding(1) var<uniform> u_ratio: vec2<f32>;
 @group(1) @binding(0) var u_texture: texture_2d<f32>;
 
 struct VertexInput {
@@ -30,9 +22,11 @@ struct VertexOutput {
 
 @vertex
 fn vs_main(input: VertexInput) -> VertexOutput {
+    let uv = uvs[input.vertex_index];
+
     var out: VertexOutput;
-    out.uv = uvs[input.vertex_index];
-    out.position = vec4<f32>(positions[input.vertex_index], 0.0, 1.0);
+    out.uv = uv * u_ratio;
+    out.position = vec4<f32>(uv * vec2(2.0, -2.0) + vec2(-1.0, 1.0), 0.0, 1.0);
 
     return out;
 }
diff --git a/wgpu/src/triangle.rs b/wgpu/src/triangle.rs
index 06c0ef02..98ba41b3 100644
--- a/wgpu/src/triangle.rs
+++ b/wgpu/src/triangle.rs
@@ -184,8 +184,16 @@ impl Pipeline {
         belt: &mut wgpu::util::StagingBelt,
         storage: &mut Storage,
         items: &[Item],
-        projection: Transformation,
+        scale: Transformation,
+        target_size: Size<u32>,
     ) {
+        let projection = if let Some(blit) = &mut self.blit {
+            blit.prepare(device, encoder, belt, target_size) * scale
+        } else {
+            Transformation::orthographic(target_size.width, target_size.height)
+                * scale
+        };
+
         for item in items {
             match item {
                 Item::Group {
@@ -233,13 +241,11 @@ impl Pipeline {
 
     pub fn render(
         &mut self,
-        device: &wgpu::Device,
         encoder: &mut wgpu::CommandEncoder,
         target: &wgpu::TextureView,
         storage: &Storage,
         start: usize,
         batch: &Batch,
-        target_size: Size<u32>,
         bounds: Rectangle,
         screen_transformation: Transformation,
     ) -> usize {
@@ -274,13 +280,11 @@ impl Pipeline {
         });
 
         render(
-            device,
             encoder,
             target,
             self.blit.as_mut(),
             &self.solid,
             &self.gradient,
-            target_size,
             bounds,
             items,
         );
@@ -294,20 +298,17 @@ impl Pipeline {
 }
 
 fn render<'a>(
-    device: &wgpu::Device,
     encoder: &mut wgpu::CommandEncoder,
     target: &wgpu::TextureView,
     mut blit: Option<&mut msaa::Blit>,
     solid: &solid::Pipeline,
     gradient: &gradient::Pipeline,
-    target_size: Size<u32>,
     bounds: Rectangle,
     group: impl Iterator<Item = (&'a Layer, &'a [Mesh], Transformation)>,
 ) {
     {
         let (attachment, resolve_target, load) = if let Some(blit) = &mut blit {
-            let (attachment, resolve_target) =
-                blit.targets(device, target_size.width, target_size.height);
+            let (attachment, resolve_target) = blit.targets();
 
             (
                 attachment,
diff --git a/wgpu/src/triangle/msaa.rs b/wgpu/src/triangle/msaa.rs
index 14abd20b..fcee6b3e 100644
--- a/wgpu/src/triangle/msaa.rs
+++ b/wgpu/src/triangle/msaa.rs
@@ -1,13 +1,18 @@
+use crate::core::{Size, Transformation};
 use crate::graphics;
 
+use std::num::NonZeroU64;
+
 #[derive(Debug)]
 pub struct Blit {
     format: wgpu::TextureFormat,
     pipeline: wgpu::RenderPipeline,
     constants: wgpu::BindGroup,
+    ratio: wgpu::Buffer,
     texture_layout: wgpu::BindGroupLayout,
     sample_count: u32,
     targets: Option<Targets>,
+    last_region: Option<Size<u32>>,
 }
 
 impl Blit {
@@ -19,27 +24,52 @@ impl Blit {
         let sampler =
             device.create_sampler(&wgpu::SamplerDescriptor::default());
 
+        let ratio = device.create_buffer(&wgpu::BufferDescriptor {
+            label: Some("iced-wgpu::triangle::msaa ratio"),
+            size: std::mem::size_of::<Ratio>() as u64,
+            usage: wgpu::BufferUsages::COPY_DST | wgpu::BufferUsages::UNIFORM,
+            mapped_at_creation: false,
+        });
+
         let constant_layout =
             device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
                 label: Some("iced_wgpu::triangle:msaa uniforms layout"),
-                entries: &[wgpu::BindGroupLayoutEntry {
-                    binding: 0,
-                    visibility: wgpu::ShaderStages::FRAGMENT,
-                    ty: wgpu::BindingType::Sampler(
-                        wgpu::SamplerBindingType::NonFiltering,
-                    ),
-                    count: None,
-                }],
+                entries: &[
+                    wgpu::BindGroupLayoutEntry {
+                        binding: 0,
+                        visibility: wgpu::ShaderStages::FRAGMENT,
+                        ty: wgpu::BindingType::Sampler(
+                            wgpu::SamplerBindingType::NonFiltering,
+                        ),
+                        count: None,
+                    },
+                    wgpu::BindGroupLayoutEntry {
+                        binding: 1,
+                        visibility: wgpu::ShaderStages::VERTEX,
+                        ty: wgpu::BindingType::Buffer {
+                            ty: wgpu::BufferBindingType::Uniform,
+                            has_dynamic_offset: false,
+                            min_binding_size: None,
+                        },
+                        count: None,
+                    },
+                ],
             });
 
         let constant_bind_group =
             device.create_bind_group(&wgpu::BindGroupDescriptor {
                 label: Some("iced_wgpu::triangle::msaa uniforms bind group"),
                 layout: &constant_layout,
-                entries: &[wgpu::BindGroupEntry {
-                    binding: 0,
-                    resource: wgpu::BindingResource::Sampler(&sampler),
-                }],
+                entries: &[
+                    wgpu::BindGroupEntry {
+                        binding: 0,
+                        resource: wgpu::BindingResource::Sampler(&sampler),
+                    },
+                    wgpu::BindGroupEntry {
+                        binding: 1,
+                        resource: ratio.as_entire_binding(),
+                    },
+                ],
             });
 
         let texture_layout =
@@ -88,9 +118,7 @@ impl Blit {
                     entry_point: "fs_main",
                     targets: &[Some(wgpu::ColorTargetState {
                         format,
-                        blend: Some(
-                            wgpu::BlendState::PREMULTIPLIED_ALPHA_BLENDING,
-                        ),
+                        blend: Some(wgpu::BlendState::ALPHA_BLENDING),
                         write_mask: wgpu::ColorWrites::ALL,
                     })],
                 }),
@@ -112,43 +140,61 @@ impl Blit {
             format,
             pipeline,
             constants: constant_bind_group,
+            ratio,
             texture_layout,
             sample_count: antialiasing.sample_count(),
             targets: None,
+            last_region: None,
         }
     }
 
-    pub fn targets(
+    pub fn prepare(
         &mut self,
         device: &wgpu::Device,
-        width: u32,
-        height: u32,
-    ) -> (&wgpu::TextureView, &wgpu::TextureView) {
+        encoder: &mut wgpu::CommandEncoder,
+        belt: &mut wgpu::util::StagingBelt,
+        region_size: Size<u32>,
+    ) -> Transformation {
         match &mut self.targets {
-            None => {
+            Some(targets)
+                if region_size.width <= targets.size.width
+                    && region_size.height <= targets.size.height => {}
+            _ => {
                 self.targets = Some(Targets::new(
                     device,
                     self.format,
                     &self.texture_layout,
                     self.sample_count,
-                    width,
-                    height,
+                    region_size,
                 ));
             }
-            Some(targets) => {
-                if targets.width != width || targets.height != height {
-                    self.targets = Some(Targets::new(
-                        device,
-                        self.format,
-                        &self.texture_layout,
-                        self.sample_count,
-                        width,
-                        height,
-                    ));
-                }
-            }
         }
 
+        let targets = self.targets.as_mut().unwrap();
+
+        if Some(region_size) != self.last_region {
+            let ratio = Ratio {
+                u: region_size.width as f32 / targets.size.width as f32,
+                v: region_size.height as f32 / targets.size.height as f32,
+            };
+
+            belt.write_buffer(
+                encoder,
+                &self.ratio,
+                0,
+                NonZeroU64::new(std::mem::size_of::<Ratio>() as u64)
+                    .expect("non-empty ratio"),
+                device,
+            )
+            .copy_from_slice(bytemuck::bytes_of(&ratio));
+
+            self.last_region = Some(region_size);
+        }
+
+        Transformation::orthographic(targets.size.width, targets.size.height)
+    }
+
+    pub fn targets(&self) -> (&wgpu::TextureView, &wgpu::TextureView) {
         let targets = self.targets.as_ref().unwrap();
 
         (&targets.attachment, &targets.resolve)
@@ -191,8 +237,7 @@ struct Targets {
     attachment: wgpu::TextureView,
     resolve: wgpu::TextureView,
     bind_group: wgpu::BindGroup,
-    width: u32,
-    height: u32,
+    size: Size<u32>,
 }
 
 impl Targets {
@@ -201,12 +246,11 @@ impl Targets {
         format: wgpu::TextureFormat,
         texture_layout: &wgpu::BindGroupLayout,
         sample_count: u32,
-        width: u32,
-        height: u32,
+        size: Size<u32>,
     ) -> Targets {
         let extent = wgpu::Extent3d {
-            width,
-            height,
+            width: size.width,
+            height: size.height,
             depth_or_array_layers: 1,
         };
 
@@ -252,8 +296,14 @@ impl Targets {
             attachment,
             resolve,
             bind_group,
-            width,
-            height,
+            size,
         }
     }
 }
+
+#[derive(Debug, Clone, Copy, bytemuck::Pod, bytemuck::Zeroable)]
+#[repr(C)]
+struct Ratio {
+    u: f32,
+    v: f32,
+}