Share `msaa::Blit` texture between multiple windows

1 files changed, 92 insertions, 42 deletions

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,
+}