8 files changed, 507 insertions, 5 deletions

diff --git a/engine/fragment.glsl b/engine/fragment.glsl
new file mode 100644
index 0000000..0c56a32
--- /dev/null
+++ b/engine/fragment.glsl
@@ -0,0 +1,7 @@
+#version 330 core
+out vec4 FragColor;
+
+void main()
+{
+    FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);
+}
diff --git a/engine/src/lib.rs b/engine/src/lib.rs
index ea74fd1..28cd2da 100644
--- a/engine/src/lib.rs
+++ b/engine/src/lib.rs
@@ -3,10 +3,13 @@
 use glfw::Window;
 pub use glfw::WindowSize;
 
+use crate::object::Object;
 use crate::vector::Vec2;
 
 mod renderer;
+mod shader;
 
+pub mod object;
 pub mod vector;
 
 pub struct Engine
@@ -42,12 +45,12 @@ impl Engine
     ///
     /// # Errors
     /// Will return `Err` if updating the window fails.
-    pub fn start(&self, mut func: impl FnMut()) -> Result<(), Error>
+    pub fn start(&self, objects: &[Object], mut func: impl FnMut()) -> Result<(), Error>
     {
         while !self.window.should_close() {
             func();
 
-            crate::renderer::render();
+            crate::renderer::render(objects.iter().map(Object::renderable));
 
             self.window
                 .swap_buffers()
diff --git a/engine/src/object.rs b/engine/src/object.rs
new file mode 100644
index 0000000..ff84127
--- /dev/null
+++ b/engine/src/object.rs
@@ -0,0 +1,69 @@
+use crate::renderer::Renderable;
+use crate::shader::{Kind as ShaderKind, Program as ShaderProgram, Shader};
+
+pub struct Object
+{
+    renderable: Renderable,
+}
+
+impl Object
+{
+    /// Returns a new `Object`.
+    ///
+    /// # Errors
+    /// Will return `Err` if shader creation fails or if shader program linking fails.
+    pub fn new(vertices: &[f32]) -> Result<Self, Error>
+    {
+        let vertex_shader = Shader::new(ShaderKind::Vertex);
+
+        vertex_shader
+            .set_source(include_str!("../vertex.glsl"))
+            .map_err(Error::CreateVertexShaderFailed)?;
+
+        vertex_shader
+            .compile()
+            .map_err(Error::CreateVertexShaderFailed)?;
+
+        let fragment_shader = Shader::new(ShaderKind::Fragment);
+
+        fragment_shader
+            .set_source(include_str!("../fragment.glsl"))
+            .map_err(Error::CreateFragmentShaderFailed)?;
+
+        fragment_shader
+            .compile()
+            .map_err(Error::CreateFragmentShaderFailed)?;
+
+        let shader_program = ShaderProgram::new();
+
+        shader_program.attach(&vertex_shader);
+        shader_program.attach(&fragment_shader);
+
+        shader_program
+            .link()
+            .map_err(Error::LinkShaderProgramFailed)?;
+
+        let renderable = Renderable::new(shader_program, vertices);
+
+        Ok(Self { renderable })
+    }
+
+    pub(crate) fn renderable(&self) -> &Renderable
+    {
+        &self.renderable
+    }
+}
+
+/// Object error
+#[derive(Debug, thiserror::Error)]
+pub enum Error
+{
+    #[error("Failed to create vertex shader")]
+    CreateVertexShaderFailed(#[source] crate::shader::Error),
+
+    #[error("Failed to create fragment shader")]
+    CreateFragmentShaderFailed(#[source] crate::shader::Error),
+
+    #[error("Failed to link shader program")]
+    LinkShaderProgramFailed(#[source] crate::shader::Error),
+}
diff --git a/engine/src/renderer/mod.rs b/engine/src/renderer/mod.rs
index 9cd379d..3c42f93 100644
--- a/engine/src/renderer/mod.rs
+++ b/engine/src/renderer/mod.rs
@@ -1,10 +1,17 @@
-use std::ffi::{c_void, CString};
+use std::ffi::{c_float, c_void, CString};
+use std::mem::size_of;
 use std::process::abort;
+use std::ptr::null;
 
 use glfw::WindowSize;
 
+use crate::renderer::vertex_array::{PrimitiveKind, VertexArray};
+use crate::renderer::vertex_buffers::{BufferUsage, VertexBuffers};
 use crate::vector::Vec2;
 
+mod vertex_array;
+mod vertex_buffers;
+
 pub fn initialize(window: &glfw::Window) -> Result<(), Error>
 {
     gl::load_with(|symbol| {
@@ -30,10 +37,51 @@ pub fn initialize(window: &glfw::Window) -> Result<(), Error>
     Ok(())
 }
 
-pub fn render()
+pub fn render<'renderable>(renderables: impl IntoIterator<Item = &'renderable Renderable>)
 {
     unsafe {
-        gl::Clear(gl::COLOR_BUFFER_BIT | gl::DEPTH_BUFFER_BIT);
+        gl::Clear(gl::COLOR_BUFFER_BIT);
+    }
+
+    for renderable in renderables {
+        renderable.shader_program.activate();
+
+        renderable.vertex_arr.draw(PrimitiveKind::Triangles, 0, 3);
+    }
+}
+
+pub struct Renderable
+{
+    shader_program: crate::shader::Program,
+    vertex_arr: VertexArray,
+}
+
+impl Renderable
+{
+    pub fn new(shader_program: crate::shader::Program, vertices: &[f32]) -> Self
+    {
+        let vertex_arr = VertexArray::new();
+
+        vertex_arr.bind();
+
+        let vertex_buffer = VertexBuffers::<1>::new();
+
+        vertex_buffer
+            .store(0, vertices, BufferUsage::Static)
+            .unwrap();
+
+        vertex_attrib_ptr(0);
+        enable_vertex_attrib_array(0);
+
+        unsafe {
+            gl::BindBuffer(gl::ARRAY_BUFFER, 0);
+            gl::BindVertexArray(0);
+        }
+
+        Self {
+            shader_program,
+            vertex_arr,
+        }
     }
 }
 
@@ -57,3 +105,28 @@ pub enum Error
     #[error("Failed to get window size")]
     GetWindowSizeFailed(#[source] glfw::Error),
 }
+
+fn vertex_attrib_ptr(index: usize)
+{
+    let stride = 3 * size_of::<c_float>();
+
+    unsafe {
+        #[allow(clippy::cast_possible_wrap, clippy::cast_possible_truncation)]
+        gl::VertexAttribPointer(
+            index as gl::types::GLuint,
+            3,
+            gl::FLOAT,
+            gl::FALSE,
+            stride as gl::types::GLsizei,
+            null(),
+        );
+    }
+}
+
+fn enable_vertex_attrib_array(index: usize)
+{
+    unsafe {
+        #[allow(clippy::cast_possible_truncation)]
+        gl::EnableVertexAttribArray(index as gl::types::GLuint);
+    }
+}
diff --git a/engine/src/renderer/vertex_array.rs b/engine/src/renderer/vertex_array.rs
new file mode 100644
index 0000000..e54f638
--- /dev/null
+++ b/engine/src/renderer/vertex_array.rs
@@ -0,0 +1,62 @@
+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 }
+    }
+
+    pub fn draw(&self, primitive_kind: PrimitiveKind, start_index: u32, index_cnt: u32)
+    {
+        self.bind();
+
+        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 bind(&self)
+    {
+        unsafe { gl::BindVertexArray(self.array) }
+    }
+}
+
+impl Drop for VertexArray
+{
+    fn drop(&mut self)
+    {
+        unsafe {
+            gl::DeleteVertexArrays(1, &self.array);
+        }
+    }
+}
+
+pub enum PrimitiveKind
+{
+    Triangles,
+}
+
+impl PrimitiveKind
+{
+    fn into_gl(self) -> gl::types::GLenum
+    {
+        match self {
+            Self::Triangles => gl::TRIANGLES,
+        }
+    }
+}
diff --git a/engine/src/renderer/vertex_buffers.rs b/engine/src/renderer/vertex_buffers.rs
new file mode 100644
index 0000000..a6d1a2c
--- /dev/null
+++ b/engine/src/renderer/vertex_buffers.rs
@@ -0,0 +1,83 @@
+use std::mem::size_of_val;
+
+pub struct VertexBuffers<const CNT: usize>
+{
+    buffers: [gl::types::GLuint; CNT],
+}
+
+impl<const CNT: usize> VertexBuffers<CNT>
+{
+    pub fn new() -> Self
+    {
+        let mut buffers = [gl::types::GLuint::default(); CNT];
+
+        unsafe {
+            #[allow(clippy::cast_possible_wrap, clippy::cast_possible_truncation)]
+            gl::GenBuffers(CNT as gl::types::GLsizei, buffers.as_mut_ptr());
+        };
+
+        Self { buffers }
+    }
+
+    pub fn store(
+        &self,
+        buffer_index: usize,
+        vertices: &[f32],
+        usage: BufferUsage,
+    ) -> Option<()>
+    {
+        let buffer = *self.buffers.get(buffer_index)?;
+
+        unsafe {
+            gl::BindBuffer(gl::ARRAY_BUFFER, buffer);
+        }
+
+        unsafe {
+            #[allow(clippy::cast_possible_wrap)]
+            gl::BufferData(
+                gl::ARRAY_BUFFER,
+                size_of_val(vertices) as gl::types::GLsizeiptr,
+                vertices.as_ptr().cast(),
+                usage.into_gl(),
+            );
+        }
+
+        Some(())
+    }
+}
+
+impl<const CNT: usize> Drop for VertexBuffers<CNT>
+{
+    fn drop(&mut self)
+    {
+        #[allow(clippy::cast_possible_wrap, clippy::cast_possible_truncation)]
+        unsafe {
+            gl::DeleteBuffers(CNT as gl::types::GLsizei, self.buffers.as_ptr());
+        }
+    }
+}
+
+#[allow(dead_code)]
+pub enum BufferUsage
+{
+    /// The buffer data is set only once and used by the GPU at most a few times.
+    Stream,
+
+    /// The buffer data is set only once and used many times.
+    Static,
+
+    /// The buffer data is changed a lot and used many times.
+    Dynamic,
+}
+
+impl BufferUsage
+{
+    fn into_gl(self) -> gl::types::GLenum
+    {
+        match self {
+            Self::Stream => gl::STREAM_DRAW,
+            Self::Static => gl::STATIC_DRAW,
+            Self::Dynamic => gl::DYNAMIC_DRAW,
+        }
+    }
+}
diff --git a/engine/src/shader.rs b/engine/src/shader.rs
new file mode 100644
index 0000000..0bbca77
--- /dev/null
+++ b/engine/src/shader.rs
@@ -0,0 +1,198 @@
+use std::ffi::CStr;
+use std::ptr::null_mut;
+
+#[derive(Debug)]
+pub struct Shader
+{
+    shader: gl::types::GLuint,
+}
+
+impl Shader
+{
+    pub fn new(kind: Kind) -> Self
+    {
+        let shader = unsafe { gl::CreateShader(kind.into_gl()) };
+
+        Self { shader }
+    }
+
+    pub fn set_source(&self, source: &str) -> Result<(), Error>
+    {
+        if !source.is_ascii() {
+            return Err(Error::SourceNotAscii);
+        }
+
+        unsafe {
+            #[allow(clippy::cast_possible_wrap, clippy::cast_possible_truncation)]
+            gl::ShaderSource(
+                self.shader,
+                1,
+                &source.as_ptr().cast(),
+                &(source.len() as gl::types::GLint),
+            );
+        }
+
+        Ok(())
+    }
+
+    pub fn compile(&self) -> Result<(), Error>
+    {
+        unsafe {
+            gl::CompileShader(self.shader);
+        }
+
+        let mut compile_success = gl::types::GLint::default();
+
+        unsafe {
+            gl::GetShaderiv(self.shader, gl::COMPILE_STATUS, &mut compile_success);
+        }
+
+        if compile_success == 0 {
+            let info_log = self.get_info_log();
+
+            return Err(Error::CompileFailed(info_log));
+        }
+
+        Ok(())
+    }
+
+    fn get_info_log(&self) -> String
+    {
+        let mut buf = vec![gl::types::GLchar::default(); 512];
+
+        unsafe {
+            #[allow(clippy::cast_possible_wrap, clippy::cast_possible_truncation)]
+            gl::GetShaderInfoLog(
+                self.shader,
+                buf.len() as gl::types::GLsizei,
+                null_mut(),
+                buf.as_mut_ptr(),
+            );
+        }
+
+        let info_log = unsafe { CStr::from_ptr(buf.as_ptr()) };
+
+        unsafe { String::from_utf8_unchecked(info_log.to_bytes().to_vec()) }
+    }
+}
+
+impl Drop for Shader
+{
+    fn drop(&mut self)
+    {
+        unsafe {
+            gl::DeleteShader(self.shader);
+        }
+    }
+}
+
+/// Shader kind.
+#[derive(Debug, Clone, Copy)]
+pub enum Kind
+{
+    Vertex,
+    Fragment,
+}
+
+impl Kind
+{
+    fn into_gl(self) -> gl::types::GLenum
+    {
+        match self {
+            Self::Vertex => gl::VERTEX_SHADER,
+            Self::Fragment => gl::FRAGMENT_SHADER,
+        }
+    }
+}
+
+/// Shader program
+#[derive(Debug)]
+pub struct Program
+{
+    program: gl::types::GLuint,
+}
+
+impl Program
+{
+    pub fn new() -> Self
+    {
+        let program = unsafe { gl::CreateProgram() };
+
+        Self { program }
+    }
+
+    pub fn attach(&self, shader: &Shader)
+    {
+        unsafe {
+            gl::AttachShader(self.program, shader.shader);
+        }
+    }
+
+    pub fn link(&self) -> Result<(), Error>
+    {
+        unsafe {
+            gl::LinkProgram(self.program);
+        }
+
+        let mut link_success = gl::types::GLint::default();
+
+        unsafe {
+            gl::GetProgramiv(self.program, gl::LINK_STATUS, &mut link_success);
+        }
+
+        if link_success == 0 {
+            let info_log = self.get_info_log();
+
+            return Err(Error::CompileFailed(info_log));
+        }
+
+        Ok(())
+    }
+
+    pub fn activate(&self)
+    {
+        unsafe {
+            gl::UseProgram(self.program);
+        }
+    }
+
+    fn get_info_log(&self) -> String
+    {
+        let mut buf = vec![gl::types::GLchar::default(); 512];
+
+        unsafe {
+            #[allow(clippy::cast_possible_wrap, clippy::cast_possible_truncation)]
+            gl::GetProgramInfoLog(
+                self.program,
+                buf.len() as gl::types::GLsizei,
+                null_mut(),
+                buf.as_mut_ptr(),
+            );
+        }
+
+        let info_log = unsafe { CStr::from_ptr(buf.as_ptr()) };
+
+        unsafe { String::from_utf8_unchecked(info_log.to_bytes().to_vec()) }
+    }
+}
+
+impl Drop for Program
+{
+    fn drop(&mut self)
+    {
+        unsafe {
+            gl::DeleteProgram(self.program);
+        }
+    }
+}
+
+/// Shader error.
+#[derive(Debug, thiserror::Error)]
+pub enum Error
+{
+    #[error("All characters in source are not within the ASCII range")]
+    SourceNotAscii,
+
+    #[error("Failed to compile: {0}")]
+    CompileFailed(String),
+}
diff --git a/engine/vertex.glsl b/engine/vertex.glsl
new file mode 100644
index 0000000..c74ea10
--- /dev/null
+++ b/engine/vertex.glsl
@@ -0,0 +1,7 @@
+#version 330 core
+layout (location = 0) in vec3 aPos;
+
+void main()
+{
+    gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);
+}