Added a way to fix struct offsets automatically

example/src/main.rs

@@ -1,4 +1,4 @@
-use std::iter;
+use std::{iter, mem::MaybeUninit};
 
 use crate::shader::ENTRY_FS_MAIN;
 use futures::executor::block_on;
@@ -143,6 +143,7 @@ impl<'a> State<'a> {
             label: Some("uniforms"),
             contents: bytemuck::cast_slice(&[shader::Uniforms {
                 color_rgb: [1.0, 1.0, 1.0, 1.0],
+                _pad_color_rgb: []
             }]),
             usage: wgpu::BufferUsages::UNIFORM,
         });

example/src/shader.rs

@@ -1,14 +1,15 @@
 // File automatically generated by build.rs.
 // Changes made to this file will not be saved.
-#[repr(C)]
+#[repr(C, packed)]
 #[derive(Debug, Copy, Clone, PartialEq, bytemuck::Pod, bytemuck::Zeroable)]
 pub struct VertexInput {
     pub position: [f32; 3],
 }
-#[repr(C)]
+#[repr(C, packed)]
 #[derive(Debug, Copy, Clone, PartialEq, bytemuck::Pod, bytemuck::Zeroable)]
 pub struct Uniforms {
     pub color_rgb: [f32; 4],
+    pub _pad_color_rgb: [u8; 16 - 0 - core::mem::size_of::<[f32; 4]>()],
 }
 const _: () = assert!(
     std::mem::size_of:: < Uniforms > () == 16, "size of Uniforms does not match WGSL"

wgsl_to_wgpu/src/structs.rs

@@ -94,8 +94,16 @@ fn rust_struct(
         const _: () = assert!(std::mem::size_of::<#struct_name>() == #struct_size, #assert_size_text);
     };
 
+    // Assume types used in global variables are host shareable and require validation.
+    // This includes storage, uniform, and workgroup variables.
+    // This also means types that are never used will not be validated.
+    // Structs used only for vertex inputs do not require validation on desktop platforms.
+    // Vertex input layout is handled already by setting the attribute offsets and types.
+    // This allows vertex input field types without padding like vec3 for positions.
+    let is_host_shareable = global_variable_types.contains(&t_handle);
+
     let has_rts_array = struct_has_rts_array_member(members, module);
-    let members = struct_members(members, module, options);
+    let members = struct_members(members, module, options, layout.size as usize, is_host_shareable);
     let mut derives = Vec::new();
 
     derives.push(quote!(Debug));
@@ -122,14 +130,6 @@ fn rust_struct(
         derives.push(quote!(serde::Deserialize));
     }
 
-    // Assume types used in global variables are host shareable and require validation.
-    // This includes storage, uniform, and workgroup variables.
-    // This also means types that are never used will not be validated.
-    // Structs used only for vertex inputs do not require validation on desktop platforms.
-    // Vertex input layout is handled already by setting the attribute offsets and types.
-    // This allows vertex input field types without padding like vec3 for positions.
-    let is_host_shareable = global_variable_types.contains(&t_handle);
-
     let assert_layout = if options.derive_bytemuck && is_host_shareable {
         // Assert that the Rust layout matches the WGSL layout.
         // Enable for bytemuck since it uses the Rust struct's memory layout.
@@ -142,7 +142,7 @@ fn rust_struct(
     };
 
     let repr_c = if !has_rts_array {
-        quote!(#[repr(C)])
+        quote!(#[repr(C, packed)])
     } else {
         quote!()
     };
@@ -180,6 +180,8 @@ fn struct_members(
     members: &[naga::StructMember],
     module: &naga::Module,
     options: WriteOptions,
+    struct_size: usize, 
+    enable_padding: bool,
 ) -> Vec<TokenStream> {
     members
         .iter()
@@ -204,8 +206,25 @@ fn struct_members(
                     pub #member_name: Vec<#element_type>
                 )
             } else {
-                let member_type = rust_type(module, ty, options.matrix_vector_types);
+              let member_type = rust_type(module, ty, options.matrix_vector_types);
+              if !enable_padding {
                 quote!(pub #member_name: #member_type)
+              } else {
+                let current_offset = Index::from(member.offset as usize);
+
+                let next_offset = if index == members.len() - 1 {
+                  Index::from(struct_size)
+                } else {
+                  Index::from(members[index + 1].offset as usize)
+                };
+
+                let pad_member_name = Ident::new(&format!("_pad_{}", member_name), Span::call_site());
+
+                quote!(
+                  pub #member_name: #member_type,
+                  pub #pad_member_name: [u8; #next_offset - #current_offset - core::mem::size_of::<#member_type>()]
+                )
+              }
             }
         })
         .collect()