From 12f48046b2606fc77a1312a6d5e5fc7ff9feff88 Mon Sep 17 00:00:00 2001
From: HampusM <hampus@hampusmat.com>
Date: Fri, 13 Oct 2023 23:32:00 +0200
Subject: refactor(engine): move uses of OpenGL to OpenGL module

---
 engine/src/opengl/vertex_array.rs | 131 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 131 insertions(+)
 create mode 100644 engine/src/opengl/vertex_array.rs

(limited to 'engine/src/opengl/vertex_array.rs')

diff --git a/engine/src/opengl/vertex_array.rs b/engine/src/opengl/vertex_array.rs
new file mode 100644
index 0000000..f255b8a
--- /dev/null
+++ b/engine/src/opengl/vertex_array.rs
@@ -0,0 +1,131 @@
+use std::mem::size_of;
+
+use crate::opengl::currently_bound::CurrentlyBound;
+use crate::opengl::vertex_buffer::VertexBuffer;
+use crate::vertex::{Attribute, AttributeComponentType, Vertex};
+
+const VERTEX_STRIDE: usize = size_of::<Vertex>();
+
+#[derive(Debug)]
+pub struct VertexArray
+{
+    array: gl::types::GLuint,
+}
+
+impl VertexArray
+{
+    pub fn new() -> Self
+    {
+        let mut array = 0;
+
+        unsafe {
+            gl::GenVertexArrays(1, &mut array);
+        }
+
+        Self { array }
+    }
+
+    /// Draws the currently bound vertex array.
+    pub fn draw(
+        _currently_bound: &CurrentlyBound<Self>,
+        primitive_kind: PrimitiveKind,
+        start_index: u32,
+        index_cnt: u32,
+    )
+    {
+        unsafe {
+            #[allow(clippy::cast_possible_wrap)]
+            gl::DrawArrays(
+                primitive_kind.into_gl(),
+                start_index as gl::types::GLint,
+                index_cnt as gl::types::GLsizei,
+            );
+        }
+    }
+
+    pub fn configure_attrs(
+        _currently_bound: &CurrentlyBound<Self>,
+        _vert_buf_curr_bound: &CurrentlyBound<VertexBuffer>,
+    )
+    {
+        let mut offset = 0;
+
+        for attr in Vertex::attrs() {
+            Self::vertex_attrib_ptr(attr, offset);
+
+            Self::enable_vertex_attrib_array(attr.index);
+
+            offset += attr.component_size * attr.component_cnt as usize;
+        }
+    }
+
+    #[allow(clippy::inline_always)]
+    #[inline(always)]
+    pub fn bind(&self, cb: impl FnOnce(CurrentlyBound<'_, Self>))
+    {
+        unsafe { gl::BindVertexArray(self.array) }
+
+        // SAFETY: A vertex array object is currently bound
+        let currently_bound = unsafe { CurrentlyBound::new() };
+
+        cb(currently_bound);
+    }
+
+    fn vertex_attrib_ptr(vertex_attr: &Attribute, offset: usize)
+    {
+        unsafe {
+            #[allow(clippy::cast_possible_wrap, clippy::cast_possible_truncation)]
+            gl::VertexAttribPointer(
+                vertex_attr.index as gl::types::GLuint,
+                vertex_attr.component_cnt as i32,
+                Self::vertex_attr_type_to_gl(&vertex_attr.component_type),
+                gl::FALSE,
+                VERTEX_STRIDE as gl::types::GLsizei,
+                offset as *const _,
+            );
+        }
+    }
+
+    fn enable_vertex_attrib_array(index: usize)
+    {
+        unsafe {
+            #[allow(clippy::cast_possible_truncation)]
+            gl::EnableVertexAttribArray(index as gl::types::GLuint);
+        }
+    }
+
+    fn vertex_attr_type_to_gl(
+        vertex_attr_type: &AttributeComponentType,
+    ) -> gl::types::GLenum
+    {
+        match vertex_attr_type {
+            AttributeComponentType::Float => gl::FLOAT,
+        }
+    }
+}
+
+impl Drop for VertexArray
+{
+    fn drop(&mut self)
+    {
+        unsafe {
+            gl::DeleteVertexArrays(1, &self.array);
+        }
+    }
+}
+
+#[derive(Debug)]
+pub enum PrimitiveKind
+{
+    Triangles,
+}
+
+impl PrimitiveKind
+{
+    fn into_gl(self) -> gl::types::GLenum
+    {
+        match self {
+            Self::Triangles => gl::TRIANGLES,
+        }
+    }
+}
-- 
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