Make triangle asymmetric to properly test shakiness

Cargo.toml

@@ -19,6 +19,7 @@ block2 = "0.5.1"
 objc2 = "0.5.2"
 objc2-foundation = { version = "0.2.2", features = ["all", "block2"] }
 objc2-quartz-core = { version = "0.2.2", features = ["all"] }
+bytemuck = "1.16.1"
 
 [target.'cfg(target_os = "macos")'.dependencies]
 objc2-app-kit = { version = "0.2.2", features = ["all"] }

src/shader.wgsl

@@ -1,9 +1,16 @@
-// Copied verbatim from `wgpu/examples/src/hello_triangle/shader.wgsl`
+// Adapted from `wgpu/examples/src/hello_triangle/shader.wgsl`
+@group(0)
+@binding(0)
+var<uniform> canvas_width: f32;
+
 @vertex
 fn vs_main(@builtin(vertex_index) in_vertex_index: u32) -> @builtin(position) vec4<f32> {
-    let x = f32(i32(in_vertex_index) - 1);
-    let y = f32(i32(in_vertex_index & 1u) * 2 - 1);
-    return vec4<f32>(x, y, 0.0, 1.0);
+    var positions = array<vec4<f32>, 3>(
+        vec4<f32>(1.0 - 200.0 / canvas_width, 1.0, 0.0, 1.0),   // Top vertex
+        vec4<f32>(-1.0, -1.0, 0.0, 1.0), // Bottom left vertex
+        vec4<f32>(1.0, -1.0, 0.0, 1.0)   // Bottom right vertex
+    );
+    return positions[in_vertex_index];
 }
 
 @fragment

src/wgpu_triangle.rs

@@ -1,5 +1,6 @@
 //! Adapted from `wgpu/examples/src/hello_triangle`.
 use std::cell::RefCell;
+use wgpu::util::DeviceExt;
 
 use crate::frame_counter::FrameCounter;
 
@@ -13,6 +14,8 @@ pub struct Triangle<'window> {
     queue: wgpu::Queue,
     shader: wgpu::ShaderModule,
     pipeline_layout: wgpu::PipelineLayout,
+    bind_group: wgpu::BindGroup,
+    uniform_buf: wgpu::Buffer,
     render_pipeline: wgpu::RenderPipeline,
     config: RefCell<wgpu::SurfaceConfiguration>,
     frame_counter: FrameCounter,
@@ -58,12 +61,40 @@ impl<'window> Triangle<'window> {
             source: wgpu::ShaderSource::Wgsl(include_str!("shader.wgsl").into()),
         });
 
+        let bind_group_layout = device.create_bind_group_layout(&wgpu::BindGroupLayoutDescriptor {
+            label: None,
+            entries: &[wgpu::BindGroupLayoutEntry {
+                binding: 0,
+                visibility: wgpu::ShaderStages::VERTEX,
+                ty: wgpu::BindingType::Buffer {
+                    ty: wgpu::BufferBindingType::Uniform,
+                    has_dynamic_offset: false,
+                    min_binding_size: wgpu::BufferSize::new(4),
+                },
+                count: None,
+            }],
+        });
         let pipeline_layout = device.create_pipeline_layout(&wgpu::PipelineLayoutDescriptor {
             label: None,
-            bind_group_layouts: &[],
+            bind_group_layouts: &[&bind_group_layout],
             push_constant_ranges: &[],
         });
 
+        let uniform_buf = device.create_buffer_init(&wgpu::util::BufferInitDescriptor {
+            label: Some("Uniform Buffer"),
+            contents: bytemuck::cast_slice(&[width as f32]),
+            usage: wgpu::BufferUsages::UNIFORM | wgpu::BufferUsages::COPY_DST,
+        });
+
+        let bind_group = device.create_bind_group(&wgpu::BindGroupDescriptor {
+            layout: &bind_group_layout,
+            entries: &[wgpu::BindGroupEntry {
+                binding: 0,
+                resource: uniform_buf.as_entire_binding(),
+            }],
+            label: None,
+        });
+
         let swapchain_capabilities = surface.get_capabilities(&adapter);
         let swapchain_format = swapchain_capabilities.formats[0];
 
@@ -106,13 +137,18 @@ impl<'window> Triangle<'window> {
             queue,
             shader,
             pipeline_layout,
+            uniform_buf,
+            bind_group,
             render_pipeline,
             config: RefCell::new(config),
             frame_counter: FrameCounter::new(),
         }
     }
 
     pub fn resize(&self, width: u32, height: u32) {
+        self.queue
+            .write_buffer(&self.uniform_buf, 0, bytemuck::cast_slice(&[width as f32]));
+
         let mut config = self.config.borrow_mut();
         config.width = width;
         config.height = height;
@@ -146,6 +182,7 @@ impl<'window> Triangle<'window> {
                 occlusion_query_set: None,
             });
             rpass.set_pipeline(&self.render_pipeline);
+            rpass.set_bind_group(0, &self.bind_group, &[]);
             rpass.draw(0..3, 0..1);
         }