15 files changed, 539 insertions, 73 deletions

diff --git a/examples/bezier_tool/src/main.rs b/examples/bezier_tool/src/main.rs
index efdb3924..023eb0f7 100644
--- a/examples/bezier_tool/src/main.rs
+++ b/examples/bezier_tool/src/main.rs
@@ -286,7 +286,10 @@ use iced::{
 };
 
 pub fn main() {
-    Example::run(Settings::default())
+    Example::run(Settings {
+        antialiasing: true,
+        ..Settings::default()
+    });
 }
 
 #[derive(Default)]
diff --git a/examples/clock/src/main.rs b/examples/clock/src/main.rs
index 0a70709f..f7fb6f2d 100644
--- a/examples/clock/src/main.rs
+++ b/examples/clock/src/main.rs
@@ -4,7 +4,10 @@ use iced::{
 };
 
 pub fn main() {
-    Clock::run(Settings::default())
+    Clock::run(Settings {
+        antialiasing: true,
+        ..Settings::default()
+    })
 }
 
 struct Clock {
diff --git a/examples/solar_system/src/main.rs b/examples/solar_system/src/main.rs
index d05acf84..9e7dba2f 100644
--- a/examples/solar_system/src/main.rs
+++ b/examples/solar_system/src/main.rs
@@ -14,7 +14,10 @@ use iced::{
 use std::time::Instant;
 
 pub fn main() {
-    SolarSystem::run(Settings::default())
+    SolarSystem::run(Settings {
+        antialiasing: true,
+        ..Settings::default()
+    })
 }
 
 struct SolarSystem {
diff --git a/src/application.rs b/src/application.rs
index 0a4b6d9e..1b73101a 100644
--- a/src/application.rs
+++ b/src/application.rs
@@ -178,6 +178,11 @@ pub trait Application: Sized {
             _settings.into(),
             iced_wgpu::Settings {
                 default_font: _settings.default_font,
+                antialiasing: if _settings.antialiasing {
+                    Some(iced_wgpu::settings::MSAA::X4)
+                } else {
+                    None
+                },
             },
         );
 
diff --git a/src/settings.rs b/src/settings.rs
index 77c7e0b9..f70e577f 100644
--- a/src/settings.rs
+++ b/src/settings.rs
@@ -16,6 +16,15 @@ pub struct Settings {
     /// If `None` is provided, a default system font will be chosen.
     // TODO: Add `name` for web compatibility
     pub default_font: Option<&'static [u8]>,
+
+    /// If set to true, the renderer will try to use antialiasing for some
+    /// primitives.
+    ///
+    /// Enabling it can produce a smoother result in some widgets, like the
+    /// `Canvas`, at a performance cost.
+    ///
+    /// By default, it is disabled.
+    pub antialiasing: bool,
 }
 
 #[cfg(not(target_arch = "wasm32"))]
diff --git a/wgpu/src/lib.rs b/wgpu/src/lib.rs
index d38e2a31..90d28353 100644
--- a/wgpu/src/lib.rs
+++ b/wgpu/src/lib.rs
@@ -25,6 +25,7 @@
 #![forbid(unsafe_code)]
 #![forbid(rust_2018_idioms)]
 pub mod defaults;
+pub mod settings;
 pub mod triangle;
 pub mod widget;
 pub mod window;
@@ -33,7 +34,6 @@ mod image;
 mod primitive;
 mod quad;
 mod renderer;
-mod settings;
 mod target;
 mod text;
 mod transformation;
diff --git a/wgpu/src/renderer.rs b/wgpu/src/renderer.rs
index 25b2e99a..29adcfb6 100644
--- a/wgpu/src/renderer.rs
+++ b/wgpu/src/renderer.rs
@@ -51,7 +51,8 @@ impl Renderer {
         let text_pipeline = text::Pipeline::new(device, settings.default_font);
         let quad_pipeline = quad::Pipeline::new(device);
         let image_pipeline = crate::image::Pipeline::new(device);
-        let triangle_pipeline = triangle::Pipeline::new(device);
+        let triangle_pipeline =
+            triangle::Pipeline::new(device, settings.antialiasing);
 
         Self {
             quad_pipeline,
@@ -105,6 +106,8 @@ impl Renderer {
                 &layer,
                 encoder,
                 target.texture,
+                width,
+                height,
             );
         }
 
@@ -308,6 +311,8 @@ impl Renderer {
         layer: &Layer<'_>,
         encoder: &mut wgpu::CommandEncoder,
         target: &wgpu::TextureView,
+        target_width: u32,
+        target_height: u32,
     ) {
         let bounds = layer.bounds * scale_factor;
 
@@ -323,6 +328,8 @@ impl Renderer {
                 device,
                 encoder,
                 target,
+                target_width,
+                target_height,
                 translated,
                 &layer.meshes,
                 bounds,
diff --git a/wgpu/src/settings.rs b/wgpu/src/settings.rs
index dbe81830..c8a0cadf 100644
--- a/wgpu/src/settings.rs
+++ b/wgpu/src/settings.rs
@@ -7,4 +7,26 @@ pub struct Settings {
     ///
     /// If `None` is provided, a default system font will be chosen.
     pub default_font: Option<&'static [u8]>,
+
+    /// The antialiasing strategy that will be used for triangle primitives.
+    pub antialiasing: Option<MSAA>,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum MSAA {
+    X2,
+    X4,
+    X8,
+    X16,
+}
+
+impl MSAA {
+    pub(crate) fn sample_count(&self) -> u32 {
+        match self {
+            MSAA::X2 => 2,
+            MSAA::X4 => 4,
+            MSAA::X8 => 8,
+            MSAA::X16 => 16,
+        }
+    }
 }
diff --git a/wgpu/src/shader/blit.frag b/wgpu/src/shader/blit.frag
new file mode 100644
index 00000000..dfed960f
--- /dev/null
+++ b/wgpu/src/shader/blit.frag
@@ -0,0 +1,12 @@
+#version 450
+
+layout(location = 0) in vec2 v_Uv;
+
+layout(set = 0, binding = 0) uniform sampler u_Sampler;
+layout(set = 1, binding = 0) uniform texture2D u_Texture;
+
+layout(location = 0) out vec4 o_Color;
+
+void main() {
+    o_Color = texture(sampler2D(u_Texture, u_Sampler), v_Uv);
+}
diff --git a/wgpu/src/shader/blit.frag.spv b/wgpu/src/shader/blit.frag.spv
new file mode 100644
index 00000000..2c5638b5
--- /dev/null
+++ b/wgpu/src/shader/blit.frag.spv
diff --git a/wgpu/src/shader/blit.vert b/wgpu/src/shader/blit.vert
new file mode 100644
index 00000000..1c081b9e
--- /dev/null
+++ b/wgpu/src/shader/blit.vert
@@ -0,0 +1,26 @@
+#version 450
+
+layout(location = 0) out vec2 o_Uv;
+
+const vec2 positions[6] = vec2[6](
+    vec2(-1.0, -1.0),
+    vec2(-1.0, 1.0),
+    vec2(1.0, 1.0),
+    vec2(-1.0, -1.0),
+    vec2(1.0, -1.0),
+    vec2(1.0, 1.0)
+);
+
+const vec2 uvs[6] = vec2[6](
+    vec2(0.0, 0.0),
+    vec2(0.0, 1.0),
+    vec2(1.0, 1.0),
+    vec2(0.0, 0.0),
+    vec2(1.0, 0.0),
+    vec2(1.0, 1.0)
+);
+
+void main() {
+    o_Uv = uvs[gl_VertexIndex];
+    gl_Position = vec4(positions[gl_VertexIndex], 0.0, 1.0);
+}
diff --git a/wgpu/src/shader/blit.vert.spv b/wgpu/src/shader/blit.vert.spv
new file mode 100644
index 00000000..ad697d48
--- /dev/null
+++ b/wgpu/src/shader/blit.vert.spv
diff --git a/wgpu/src/shader/image.vert b/wgpu/src/shader/image.vert
deleted file mode 100644
index 688c2311..00000000
--- a/wgpu/src/shader/image.vert
+++ /dev/null
@@ -1,24 +0,0 @@
-#version 450
-
-layout(location = 0) in vec2 v_Pos;
-layout(location = 1) in vec2 i_Pos;
-layout(location = 2) in vec2 i_Scale;
-
-layout (set = 0, binding = 0) uniform Globals {
-    mat4 u_Transform;
-};
-
-layout(location = 0) out vec2 o_Uv;
-
-void main() {
-    o_Uv = v_Pos;
-
-    mat4 i_Transform = mat4(
-        vec4(i_Scale.x, 0.0, 0.0, 0.0),
-        vec4(0.0, i_Scale.y, 0.0, 0.0),
-        vec4(0.0, 0.0, 1.0, 0.0),
-        vec4(i_Pos, 0.0, 1.0)
-    );
-
-    gl_Position = u_Transform * i_Transform * vec4(v_Pos, 0.0, 1.0);
-}
diff --git a/wgpu/src/triangle.rs b/wgpu/src/triangle.rs
index 3cc1d3fb..9159b0a2 100644
--- a/wgpu/src/triangle.rs
+++ b/wgpu/src/triangle.rs
@@ -1,32 +1,82 @@
 //! Draw meshes of triangles.
-use crate::Transformation;
+use crate::{settings, Transformation};
 use iced_native::{Point, Rectangle};
 use std::{mem, sync::Arc};
 
+mod msaa;
+
+const UNIFORM_BUFFER_SIZE: usize = 100;
+const VERTEX_BUFFER_SIZE: usize = 100_000;
+const INDEX_BUFFER_SIZE: usize = 100_000;
+
 #[derive(Debug)]
 pub(crate) struct Pipeline {
     pipeline: wgpu::RenderPipeline,
+    blit: Option<msaa::Blit>,
     constants: wgpu::BindGroup,
-    constants_buffer: wgpu::Buffer,
+    uniforms_buffer: Buffer<Uniforms>,
+    vertex_buffer: Buffer<Vertex2D>,
+    index_buffer: Buffer<u32>,
+}
+
+#[derive(Debug)]
+struct Buffer<T> {
+    raw: wgpu::Buffer,
+    size: usize,
+    usage: wgpu::BufferUsage,
+    _type: std::marker::PhantomData<T>,
+}
+
+impl<T> Buffer<T> {
+    pub fn new(
+        device: &wgpu::Device,
+        size: usize,
+        usage: wgpu::BufferUsage,
+    ) -> Self {
+        let raw = device.create_buffer(&wgpu::BufferDescriptor {
+            size: (std::mem::size_of::<T>() * size) as u64,
+            usage,
+        });
+
+        Buffer {
+            raw,
+            size,
+            usage,
+            _type: std::marker::PhantomData,
+        }
+    }
+
+    pub fn ensure_capacity(&mut self, device: &wgpu::Device, size: usize) {
+        if self.size < size {
+            self.raw = device.create_buffer(&wgpu::BufferDescriptor {
+                size: (std::mem::size_of::<T>() * size) as u64,
+                usage: self.usage,
+            });
+
+            self.size = size;
+        }
+    }
 }
 
 impl Pipeline {
-    pub fn new(device: &mut wgpu::Device) -> Pipeline {
+    pub fn new(
+        device: &mut wgpu::Device,
+        antialiasing: Option<settings::MSAA>,
+    ) -> Pipeline {
         let constant_layout =
             device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
                 bindings: &[wgpu::BindGroupLayoutBinding {
                     binding: 0,
                     visibility: wgpu::ShaderStage::VERTEX,
-                    ty: wgpu::BindingType::UniformBuffer { dynamic: false },
+                    ty: wgpu::BindingType::UniformBuffer { dynamic: true },
                 }],
             });
 
-        let constants_buffer = device
-            .create_buffer_mapped(
-                1,
-                wgpu::BufferUsage::UNIFORM | wgpu::BufferUsage::COPY_DST,
-            )
-            .fill_from_slice(&[Uniforms::default()]);
+        let constants_buffer = Buffer::new(
+            device,
+            UNIFORM_BUFFER_SIZE,
+            wgpu::BufferUsage::UNIFORM | wgpu::BufferUsage::COPY_DST,
+        );
 
         let constant_bind_group =
             device.create_bind_group(&wgpu::BindGroupDescriptor {
@@ -34,7 +84,7 @@ impl Pipeline {
                 bindings: &[wgpu::Binding {
                     binding: 0,
                     resource: wgpu::BindingResource::Buffer {
-                        buffer: &constants_buffer,
+                        buffer: &constants_buffer.raw,
                         range: 0..std::mem::size_of::<Uniforms>() as u64,
                     },
                 }],
@@ -110,15 +160,28 @@ impl Pipeline {
                         },
                     ],
                 }],
-                sample_count: 1,
+                sample_count: antialiasing
+                    .map(|a| a.sample_count())
+                    .unwrap_or(1),
                 sample_mask: !0,
                 alpha_to_coverage_enabled: false,
             });
 
         Pipeline {
             pipeline,
+            blit: antialiasing.map(|a| msaa::Blit::new(device, a)),
             constants: constant_bind_group,
-            constants_buffer,
+            uniforms_buffer: constants_buffer,
+            vertex_buffer: Buffer::new(
+                device,
+                VERTEX_BUFFER_SIZE,
+                wgpu::BufferUsage::VERTEX | wgpu::BufferUsage::COPY_DST,
+            ),
+            index_buffer: Buffer::new(
+                device,
+                INDEX_BUFFER_SIZE,
+                wgpu::BufferUsage::INDEX | wgpu::BufferUsage::COPY_DST,
+            ),
         }
     }
 
@@ -127,50 +190,116 @@ impl Pipeline {
         device: &mut wgpu::Device,
         encoder: &mut wgpu::CommandEncoder,
         target: &wgpu::TextureView,
+        target_width: u32,
+        target_height: u32,
         transformation: Transformation,
         meshes: &Vec<(Point, Arc<Mesh2D>)>,
         bounds: Rectangle<u32>,
     ) {
+        // This looks a bit crazy, but we are just counting how many vertices
+        // and indices we will need to handle.
+        // TODO: Improve readability
+        let (total_vertices, total_indices) = meshes
+            .iter()
+            .map(|(_, mesh)| (mesh.vertices.len(), mesh.indices.len()))
+            .fold((0, 0), |(total_v, total_i), (v, i)| {
+                (total_v + v, total_i + i)
+            });
+
+        // Then we ensure the current buffers are big enough, resizing if
+        // necessary
+        self.uniforms_buffer.ensure_capacity(device, meshes.len());
+        self.vertex_buffer.ensure_capacity(device, total_vertices);
+        self.index_buffer.ensure_capacity(device, total_indices);
+
+        let mut uniforms: Vec<Uniforms> = Vec::with_capacity(meshes.len());
+        let mut offsets: Vec<(
+            wgpu::BufferAddress,
+            wgpu::BufferAddress,
+            usize,
+        )> = Vec::with_capacity(meshes.len());
+        let mut last_vertex = 0;
+        let mut last_index = 0;
+
+        // We upload everything upfront
         for (origin, mesh) in meshes {
-            let uniforms = Uniforms {
+            let transform = Uniforms {
                 transform: (transformation
                     * Transformation::translate(origin.x, origin.y))
                 .into(),
             };
 
-            let constants_buffer = device
-                .create_buffer_mapped(1, wgpu::BufferUsage::COPY_SRC)
-                .fill_from_slice(&[uniforms]);
-
-            encoder.copy_buffer_to_buffer(
-                &constants_buffer,
-                0,
-                &self.constants_buffer,
-                0,
-                std::mem::size_of::<Uniforms>() as u64,
-            );
-
-            let vertices_buffer = device
+            let vertex_buffer = device
                 .create_buffer_mapped(
                     mesh.vertices.len(),
-                    wgpu::BufferUsage::VERTEX,
+                    wgpu::BufferUsage::COPY_SRC,
                 )
                 .fill_from_slice(&mesh.vertices);
 
-            let indices_buffer = device
+            let index_buffer = device
                 .create_buffer_mapped(
                     mesh.indices.len(),
-                    wgpu::BufferUsage::INDEX,
+                    wgpu::BufferUsage::COPY_SRC,
                 )
                 .fill_from_slice(&mesh.indices);
 
+            encoder.copy_buffer_to_buffer(
+                &vertex_buffer,
+                0,
+                &self.vertex_buffer.raw,
+                last_vertex as u64,
+                (std::mem::size_of::<Vertex2D>() * mesh.vertices.len()) as u64,
+            );
+
+            encoder.copy_buffer_to_buffer(
+                &index_buffer,
+                0,
+                &self.index_buffer.raw,
+                last_index as u64,
+                (std::mem::size_of::<u32>() * mesh.indices.len()) as u64,
+            );
+
+            uniforms.push(transform);
+            offsets.push((
+                last_vertex as u64,
+                last_index as u64,
+                mesh.indices.len(),
+            ));
+
+            last_vertex += mesh.vertices.len();
+            last_index += mesh.indices.len();
+        }
+
+        let uniforms_buffer = device
+            .create_buffer_mapped(uniforms.len(), wgpu::BufferUsage::COPY_SRC)
+            .fill_from_slice(&uniforms);
+
+        encoder.copy_buffer_to_buffer(
+            &uniforms_buffer,
+            0,
+            &self.uniforms_buffer.raw,
+            0,
+            (std::mem::size_of::<Uniforms>() * uniforms.len()) as u64,
+        );
+
+        {
+            let (attachment, resolve_target, load_op) =
+                if let Some(blit) = &mut self.blit {
+                    let (attachment, resolve_target) =
+                        blit.targets(device, target_width, target_height);
+
+                    (attachment, Some(resolve_target), wgpu::LoadOp::Clear)
+                } else {
+                    (target, None, wgpu::LoadOp::Load)
+                };
+
             let mut render_pass =
                 encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
                     color_attachments: &[
                         wgpu::RenderPassColorAttachmentDescriptor {
-                            attachment: target,
-                            resolve_target: None,
-                            load_op: wgpu::LoadOp::Load,
+                            attachment,
+                            resolve_target,
+                            load_op,
                             store_op: wgpu::StoreOp::Store,
                             clear_color: wgpu::Color {
                                 r: 0.0,
@@ -183,18 +312,34 @@ impl Pipeline {
                     depth_stencil_attachment: None,
                 });
 
-            render_pass.set_pipeline(&self.pipeline);
-            render_pass.set_bind_group(0, &self.constants, &[]);
-            render_pass.set_index_buffer(&indices_buffer, 0);
-            render_pass.set_vertex_buffers(0, &[(&vertices_buffer, 0)]);
-            render_pass.set_scissor_rect(
-                bounds.x,
-                bounds.y,
-                bounds.width,
-                bounds.height,
-            );
+            for (i, (vertex_offset, index_offset, indices)) in
+                offsets.drain(..).enumerate()
+            {
+                render_pass.set_pipeline(&self.pipeline);
+                render_pass.set_bind_group(
+                    0,
+                    &self.constants,
+                    &[(std::mem::size_of::<Uniforms>() * i) as u64],
+                );
+                render_pass
+                    .set_index_buffer(&self.index_buffer.raw, index_offset);
+                render_pass.set_vertex_buffers(
+                    0,
+                    &[(&self.vertex_buffer.raw, vertex_offset)],
+                );
+                render_pass.set_scissor_rect(
+                    bounds.x,
+                    bounds.y,
+                    bounds.width,
+                    bounds.height,
+                );
+
+                render_pass.draw_indexed(0..indices as u32, 0, 0..1);
+            }
+        }
 
-            render_pass.draw_indexed(0..mesh.indices.len() as u32, 0, 0..1);
+        if let Some(blit) = &mut self.blit {
+            blit.draw(encoder, target);
         }
     }
 }
diff --git a/wgpu/src/triangle/msaa.rs b/wgpu/src/triangle/msaa.rs
new file mode 100644
index 00000000..93fbe49b
--- /dev/null
+++ b/wgpu/src/triangle/msaa.rs
@@ -0,0 +1,255 @@
+use crate::settings;
+
+#[derive(Debug)]
+pub struct Blit {
+    pipeline: wgpu::RenderPipeline,
+    constants: wgpu::BindGroup,
+    texture_layout: wgpu::BindGroupLayout,
+    sample_count: u32,
+    targets: Option<Targets>,
+}
+
+impl Blit {
+    pub fn new(device: &wgpu::Device, antialiasing: settings::MSAA) -> Blit {
+        let sampler = device.create_sampler(&wgpu::SamplerDescriptor {
+            address_mode_u: wgpu::AddressMode::ClampToEdge,
+            address_mode_v: wgpu::AddressMode::ClampToEdge,
+            address_mode_w: wgpu::AddressMode::ClampToEdge,
+            mag_filter: wgpu::FilterMode::Linear,
+            min_filter: wgpu::FilterMode::Linear,
+            mipmap_filter: wgpu::FilterMode::Linear,
+            lod_min_clamp: -100.0,
+            lod_max_clamp: 100.0,
+            compare_function: wgpu::CompareFunction::Always,
+        });
+
+        let constant_layout =
+            device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
+                bindings: &[wgpu::BindGroupLayoutBinding {
+                    binding: 0,
+                    visibility: wgpu::ShaderStage::FRAGMENT,
+                    ty: wgpu::BindingType::Sampler,
+                }],
+            });
+
+        let constant_bind_group =
+            device.create_bind_group(&wgpu::BindGroupDescriptor {
+                layout: &constant_layout,
+                bindings: &[wgpu::Binding {
+                    binding: 0,
+                    resource: wgpu::BindingResource::Sampler(&sampler),
+                }],
+            });
+
+        let texture_layout =
+            device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
+                bindings: &[wgpu::BindGroupLayoutBinding {
+                    binding: 0,
+                    visibility: wgpu::ShaderStage::FRAGMENT,
+                    ty: wgpu::BindingType::SampledTexture {
+                        multisampled: false,
+                        dimension: wgpu::TextureViewDimension::D2,
+                    },
+                }],
+            });
+
+        let layout =
+            device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
+                bind_group_layouts: &[&constant_layout, &texture_layout],
+            });
+
+        let vs = include_bytes!("../shader/blit.vert.spv");
+        let vs_module = device.create_shader_module(
+            &wgpu::read_spirv(std::io::Cursor::new(&vs[..]))
+                .expect("Read blit vertex shader as SPIR-V"),
+        );
+
+        let fs = include_bytes!("../shader/blit.frag.spv");
+        let fs_module = device.create_shader_module(
+            &wgpu::read_spirv(std::io::Cursor::new(&fs[..]))
+                .expect("Read blit fragment shader as SPIR-V"),
+        );
+
+        let pipeline =
+            device.create_render_pipeline(&wgpu::RenderPipelineDescriptor {
+                layout: &layout,
+                vertex_stage: wgpu::ProgrammableStageDescriptor {
+                    module: &vs_module,
+                    entry_point: "main",
+                },
+                fragment_stage: Some(wgpu::ProgrammableStageDescriptor {
+                    module: &fs_module,
+                    entry_point: "main",
+                }),
+                rasterization_state: Some(wgpu::RasterizationStateDescriptor {
+                    front_face: wgpu::FrontFace::Cw,
+                    cull_mode: wgpu::CullMode::None,
+                    depth_bias: 0,
+                    depth_bias_slope_scale: 0.0,
+                    depth_bias_clamp: 0.0,
+                }),
+                primitive_topology: wgpu::PrimitiveTopology::TriangleList,
+                color_states: &[wgpu::ColorStateDescriptor {
+                    format: wgpu::TextureFormat::Bgra8UnormSrgb,
+                    color_blend: wgpu::BlendDescriptor {
+                        src_factor: wgpu::BlendFactor::SrcAlpha,
+                        dst_factor: wgpu::BlendFactor::OneMinusSrcAlpha,
+                        operation: wgpu::BlendOperation::Add,
+                    },
+                    alpha_blend: wgpu::BlendDescriptor {
+                        src_factor: wgpu::BlendFactor::One,
+                        dst_factor: wgpu::BlendFactor::OneMinusSrcAlpha,
+                        operation: wgpu::BlendOperation::Add,
+                    },
+                    write_mask: wgpu::ColorWrite::ALL,
+                }],
+                depth_stencil_state: None,
+                index_format: wgpu::IndexFormat::Uint16,
+                vertex_buffers: &[],
+                sample_count: 1,
+                sample_mask: !0,
+                alpha_to_coverage_enabled: false,
+            });
+
+        Blit {
+            pipeline,
+            constants: constant_bind_group,
+            texture_layout: texture_layout,
+            sample_count: antialiasing.sample_count(),
+            targets: None,
+        }
+    }
+
+    pub fn targets(
+        &mut self,
+        device: &wgpu::Device,
+        width: u32,
+        height: u32,
+    ) -> (&wgpu::TextureView, &wgpu::TextureView) {
+        match &mut self.targets {
+            None => {
+                self.targets = Some(Targets::new(
+                    &device,
+                    &self.texture_layout,
+                    self.sample_count,
+                    width,
+                    height,
+                ));
+            }
+            Some(targets) => {
+                if targets.width != width || targets.height != height {
+                    self.targets = Some(Targets::new(
+                        &device,
+                        &self.texture_layout,
+                        self.sample_count,
+                        width,
+                        height,
+                    ));
+                }
+            }
+        }
+
+        let targets = self.targets.as_ref().unwrap();
+
+        (&targets.attachment, &targets.resolve)
+    }
+
+    pub fn draw(
+        &self,
+        encoder: &mut wgpu::CommandEncoder,
+        target: &wgpu::TextureView,
+    ) {
+        let mut render_pass =
+            encoder.begin_render_pass(&wgpu::RenderPassDescriptor {
+                color_attachments: &[
+                    wgpu::RenderPassColorAttachmentDescriptor {
+                        attachment: target,
+                        resolve_target: None,
+                        load_op: wgpu::LoadOp::Load,
+                        store_op: wgpu::StoreOp::Store,
+                        clear_color: wgpu::Color {
+                            r: 0.0,
+                            g: 0.0,
+                            b: 0.0,
+                            a: 0.0,
+                        },
+                    },
+                ],
+                depth_stencil_attachment: None,
+            });
+
+        render_pass.set_pipeline(&self.pipeline);
+        render_pass.set_bind_group(0, &self.constants, &[]);
+        render_pass.set_bind_group(
+            1,
+            &self.targets.as_ref().unwrap().bind_group,
+            &[],
+        );
+        render_pass.draw(0..6, 0..1);
+    }
+}
+
+#[derive(Debug)]
+struct Targets {
+    attachment: wgpu::TextureView,
+    resolve: wgpu::TextureView,
+    bind_group: wgpu::BindGroup,
+    width: u32,
+    height: u32,
+}
+
+impl Targets {
+    pub fn new(
+        device: &wgpu::Device,
+        texture_layout: &wgpu::BindGroupLayout,
+        sample_count: u32,
+        width: u32,
+        height: u32,
+    ) -> Targets {
+        let extent = wgpu::Extent3d {
+            width,
+            height,
+            depth: 1,
+        };
+
+        let attachment = device.create_texture(&wgpu::TextureDescriptor {
+            size: extent,
+            array_layer_count: 1,
+            mip_level_count: 1,
+            sample_count,
+            dimension: wgpu::TextureDimension::D2,
+            format: wgpu::TextureFormat::Bgra8UnormSrgb,
+            usage: wgpu::TextureUsage::OUTPUT_ATTACHMENT,
+        });
+
+        let resolve = device.create_texture(&wgpu::TextureDescriptor {
+            size: extent,
+            array_layer_count: 1,
+            mip_level_count: 1,
+            sample_count: 1,
+            dimension: wgpu::TextureDimension::D2,
+            format: wgpu::TextureFormat::Bgra8UnormSrgb,
+            usage: wgpu::TextureUsage::OUTPUT_ATTACHMENT
+                | wgpu::TextureUsage::SAMPLED,
+        });
+
+        let attachment = attachment.create_default_view();
+        let resolve = resolve.create_default_view();
+
+        let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
+            layout: texture_layout,
+            bindings: &[wgpu::Binding {
+                binding: 0,
+                resource: wgpu::BindingResource::TextureView(&resolve),
+            }],
+        });
+
+        Targets {
+            attachment,
+            resolve,
+            bind_group,
+            width,
+            height,
+        }
+    }
+}