WIP "Vertex buffers: Vertex input description"

TODO: "Vertex buffer creation"
https://vulkan-tutorial.com/Vertex_buffers/Vertex_buffer_creation

Note that triangle drawing doesn't work at this stage.

shaders/shader.vert

@@ -1,20 +1,11 @@
 #version 450
 
+layout(location = 0) in vec2 inPosition;
+layout(location = 1) in vec3 inColor;
+
 layout(location = 0) out vec3 fragColor;
 
-vec2 positions[3] = vec2[](
-    vec2( 0.0, -0.5),
-    vec2( 0.5,  0.5),
-    vec2(-0.5,  0.5)
-);
-
-vec3 colors[3] = vec3[](
-    vec3(1.0, 0.0, 0.0),
-    vec3(0.0, 1.0, 0.0),
-    vec3(0.0, 0.0, 1.0)
-);
-
 void main() {
-    gl_Position = vec4(positions[gl_VertexIndex], 0.0, 1.0);
+    gl_Position = vec4(inPosition, 0.0, 1.0);
-    fragColor = colors[gl_VertexIndex];
+    fragColor = inColor;
 }

src/main.rs

@@ -1,8 +1,11 @@
 mod ffi;
+mod math3d;
 
 use std::collections::HashSet;
 use std::ffi::{c_void, CStr, CString};
 
+use math3d::Vertex;
+
 const WINDOW_WIDTH: i32 = 800;
 const WINDOW_HEIGHT: i32 = 600;
 
@@ -926,7 +929,19 @@ impl VulkanApp {
         let shader_stages: [ffi::VkPipelineShaderStageCreateInfo; 2] =
             [vert_shader_stage_info, frag_shader_stage_info];
 
-        let vertex_input_info = Self::create_vertex_input_state_info_struct();
+        let mut vertex_input_info: ffi::VkPipelineVertexInputStateCreateInfo =
+            unsafe { std::mem::zeroed() };
+        vertex_input_info.sType =
+            ffi::VkStructureType_VK_STRUCTURE_TYPE_PIPELINE_VERTEX_INPUT_STATE_CREATE_INFO;
+
+        let bind_desc = Vertex::get_binding_description();
+        let attr_descs = Vertex::get_attribute_descriptions();
+
+        vertex_input_info.vertexBindingDescriptionCount = 1;
+        vertex_input_info.vertexAttributeDescriptionCount = attr_descs.len() as u32;
+
+        vertex_input_info.pVertexBindingDescriptions = std::ptr::addr_of!(bind_desc);
+        vertex_input_info.pVertexAttributeDescriptions = attr_descs.as_ptr();
 
         let mut input_assembly: ffi::VkPipelineInputAssemblyStateCreateInfo =
             unsafe { std::mem::zeroed() };
@@ -1074,19 +1089,6 @@ impl VulkanApp {
         dynamic_state
     }
 
-    fn create_vertex_input_state_info_struct() -> ffi::VkPipelineVertexInputStateCreateInfo {
-        let mut vertex_input_info: ffi::VkPipelineVertexInputStateCreateInfo =
-            unsafe { std::mem::zeroed() };
-        vertex_input_info.sType =
-            ffi::VkStructureType_VK_STRUCTURE_TYPE_PIPELINE_VERTEX_INPUT_STATE_CREATE_INFO;
-        vertex_input_info.vertexBindingDescriptionCount = 0;
-        vertex_input_info.pVertexBindingDescriptions = std::ptr::null();
-        vertex_input_info.vertexAttributeDescriptionCount = 0;
-        vertex_input_info.pVertexBindingDescriptions = std::ptr::null();
-
-        vertex_input_info
-    }
-
     fn create_viewport(&self) -> ffi::VkViewport {
         let mut viewport: ffi::VkViewport = unsafe { std::mem::zeroed() };
         viewport.x = 0.0;

src/math3d.rs

@@ -0,0 +1,111 @@
+use crate::ffi;
+
+#[repr(C)]
+#[derive(Copy, Clone, PartialEq, Debug)]
+pub struct Vertex {
+    pos: [f32; 2],
+    color: [f32; 3],
+}
+
+impl Default for Vertex {
+    fn default() -> Self {
+        Self {
+            pos: [0.0, 0.0],
+            color: [0.0, 0.0, 0.0],
+        }
+    }
+}
+
+impl Vertex {
+    pub fn pos_offset() -> usize {
+        0
+    }
+
+    pub fn color_offset() -> usize {
+        let mut offset = std::mem::size_of::<[f32; 2]>();
+        let alignment = std::mem::align_of::<[f32; 3]>();
+        while offset % alignment != 0 {
+            offset += 1;
+        }
+
+        offset
+    }
+
+    pub fn get_binding_description() -> ffi::VkVertexInputBindingDescription {
+        let mut bind_desc: ffi::VkVertexInputBindingDescription = unsafe { std::mem::zeroed() };
+
+        bind_desc.binding = 0;
+        bind_desc.stride = std::mem::size_of::<Self>() as u32;
+        bind_desc.inputRate = ffi::VkVertexInputRate_VK_VERTEX_INPUT_RATE_VERTEX;
+
+        bind_desc
+    }
+
+    pub fn get_attribute_descriptions() -> [ffi::VkVertexInputAttributeDescription; 2] {
+        let mut attr_descs: [ffi::VkVertexInputAttributeDescription; 2] =
+            unsafe { std::mem::zeroed() };
+
+        attr_descs[0].binding = 0;
+        attr_descs[0].location = 0;
+        attr_descs[0].format = ffi::VkFormat_VK_FORMAT_R32G32_SFLOAT;
+        attr_descs[0].offset = Self::pos_offset() as u32;
+
+        attr_descs[1].binding = 0;
+        attr_descs[1].location = 1;
+        attr_descs[1].format = ffi::VkFormat_VK_FORMAT_R32G32B32_SFLOAT;
+        attr_descs[1].offset = Self::color_offset() as u32;
+
+        attr_descs
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn offsets() {
+        let mut vertex = Vertex {
+            pos: [1.0, 2.0],
+            color: [3.0, 4.0, 5.0],
+        };
+
+        let root_ptr: *const f32 = &vertex as *const Vertex as *const f32;
+
+        let pos_offset = Vertex::pos_offset();
+        assert!(pos_offset + 4 <= std::mem::size_of::<Vertex>());
+
+        let pos_0_ptr = unsafe { root_ptr.byte_add(pos_offset) };
+        assert_eq!(unsafe { *pos_0_ptr }, vertex.pos[0]);
+
+        assert!(pos_offset + 8 <= std::mem::size_of::<Vertex>());
+        let pos_1_ptr = unsafe { root_ptr.byte_add(pos_offset + 4) };
+        assert_eq!(unsafe { *pos_1_ptr }, vertex.pos[1]);
+
+        let color_offset = Vertex::color_offset();
+        assert!(color_offset + 4 <= std::mem::size_of::<Vertex>());
+
+        let col_0_ptr = unsafe { root_ptr.byte_add(color_offset) };
+        assert_eq!(unsafe { *col_0_ptr }, vertex.color[0]);
+
+        assert!(color_offset + 8 <= std::mem::size_of::<Vertex>());
+        let col_1_ptr = unsafe { root_ptr.byte_add(color_offset + 4) };
+        assert_eq!(unsafe { *col_1_ptr }, vertex.color[1]);
+
+        assert!(color_offset + 12 <= std::mem::size_of::<Vertex>());
+        let col_2_ptr = unsafe { root_ptr.byte_add(color_offset + 8) };
+        assert_eq!(unsafe { *col_2_ptr }, vertex.color[2]);
+
+        vertex.pos[0] = 0.123;
+        vertex.pos[1] = 0.456;
+        vertex.color[0] = 0.789;
+        vertex.color[1] = 1.234;
+        vertex.color[2] = 1.567;
+
+        assert_eq!(unsafe { *pos_0_ptr }, vertex.pos[0]);
+        assert_eq!(unsafe { *pos_1_ptr }, vertex.pos[1]);
+        assert_eq!(unsafe { *col_0_ptr }, vertex.color[0]);
+        assert_eq!(unsafe { *col_1_ptr }, vertex.color[1]);
+        assert_eq!(unsafe { *col_2_ptr }, vertex.color[2]);
+    }
+}