From 2c11bc7d05bd2bebb40b52cb473d5a2335f007e4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Manuel=20Tom=C3=A1s?= <jtomas1815@gmail.com>
Date: Sun, 17 Jan 2021 09:34:40 -0300
Subject: Render using opengl

---
 src/main.rs | 123 ++++++++++++++++++++++++++++++++++++++++++++++--------------
 1 file changed, 95 insertions(+), 28 deletions(-)

(limited to 'src')

diff --git a/src/main.rs b/src/main.rs
index 7424f7a..aa149e3 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -7,12 +7,32 @@ use number::Number;
 
 use std::thread;
 use std::time::Duration;
+use std::os::raw::c_void;
+use std::ffi::{CString, CStr};
 
 use sdl2::event::Event;
 use sdl2::keyboard::Keycode;
 use sdl2::pixels::Color;
 use sdl2::rect::Rect;
 
+use gl::types::*;
+
+fn shader_from_source(source: &CStr, shader_type: GLenum) -> GLuint {
+    unsafe {
+        let shader: GLuint = gl::CreateShader(shader_type);
+        gl::ShaderSource(shader, 1, &source.as_ptr(), std::ptr::null());
+        gl::CompileShader(shader);
+        let mut success: gl::types::GLint = 1;
+        unsafe {
+                gl::GetShaderiv(shader, gl::COMPILE_STATUS, &mut success);
+        }
+        if success == 0 {
+            println!("Compilation error: {}", source.to_str().unwrap());
+        }
+        shader
+    }
+}
+
 fn main() {
     let a = Lerp::new(vec![2.0, -2.0, 2.0]);
     let b = Lerp::new(vec![-1.0, 1.0, 2.0]);
@@ -23,18 +43,84 @@ fn main() {
     let sdl_context = sdl2::init().unwrap();
     let video_subsystem = sdl_context.video().unwrap();
 
+    let gl_attr = video_subsystem.gl_attr();
+
+    gl_attr.set_context_profile(sdl2::video::GLProfile::Core);
+    gl_attr.set_context_version(4, 1);
+
+    let window_w: u32 = 800;
+    let window_h: u32 = 600;
+
     let window = video_subsystem
-        .window("rust-sdl2 demo", 800, 600)
+        .window("bezier", window_w, window_h)
         .position_centered()
+        .opengl()
         .build()
         .unwrap();
 
-    let mut canvas = window.into_canvas().build().unwrap();
+    let gl_context = window.gl_create_context().unwrap();
+
+    gl::load_with(|s| video_subsystem.gl_get_proc_address(s) as *const std::os::raw::c_void);
+
+    unsafe {
+        gl::Viewport(0, 0, window_w as i32, window_h as i32);
+    }
+
+    let vertices: [f32; 18] = [
+        // first triangle
+        1.0, 1.0, 0.0,
+        1.0, -1.0, 0.0,
+        -1.0, 1.0, 0.0,
+        // // second triangle
+        1.0, -1.0, 0.0,
+        -1.0, -1.0, 0.0,
+        -1.0, 1.0, 0.0
+    ];
+
+    let vertex_shader_source = b"
+    #version 410 core
+    layout (location = 0) in vec3 aPos;
+
+    void main() {
+        gl_Position = vec4(aPos.xyz, 1.0);
+    }
+    ".to_vec();
+
+    let fragment_shader_source = b"
+    #version 410 core
+    out vec4 FragColor;
+
+    void main() {
+        FragColor = vec4(0.4, 0.8, 0.2, 1.0);
+    }
+    ".to_vec();
+
+    let mut vbo: GLuint = 0;
+    let mut vao: GLuint = 0;
+    unsafe {
+        gl::GenVertexArrays(1, &mut vao);
+        gl::BindVertexArray(vao);
+        gl::GenBuffers(1, &mut vbo);
+        gl::BindBuffer(gl::ARRAY_BUFFER, vbo);
+        gl::BufferData(gl::ARRAY_BUFFER, (vertices.len() * std::mem::size_of::<f32>()) as GLsizeiptr, vertices.as_ptr() as *const GLvoid, gl::STATIC_DRAW);
+        gl::VertexAttribPointer(0, 3, gl::FLOAT, gl::FALSE, (3 * std::mem::size_of::<f32>()) as GLint, std::ptr::null());
+        gl::EnableVertexAttribArray(0);
+    }
+
+    let mut shader_program: GLuint = 0;
+    unsafe {
+        let vertex_shader = shader_from_source(&CString::from_vec_unchecked(vertex_shader_source), gl::VERTEX_SHADER);
+        let fragment_shader = shader_from_source(&CString::from_vec_unchecked(fragment_shader_source), gl::FRAGMENT_SHADER);
+        shader_program = gl::CreateProgram();
+        gl::AttachShader(shader_program, vertex_shader);
+        gl::AttachShader(shader_program, fragment_shader);
+        gl::LinkProgram(shader_program);
+        gl::DeleteShader(vertex_shader);
+        gl::DeleteShader(fragment_shader);
+    }
 
     let mut event_pump = sdl_context.event_pump().unwrap();
     'running: loop {
-        canvas.set_draw_color(Color::RGB(20, 20, 20));
-        canvas.clear();
         for event in event_pump.poll_iter() {
             match event {
                 Event::Quit { .. }
@@ -46,31 +132,12 @@ fn main() {
             }
         }
 
-        let s = -600.0 / 10.0;
-        let k = 600.0 / 2.0;
-        for t in -800..800 {
-            let x = k + s * pa.eval(t as Number / 100.0);
-            let y = k + s * pb.eval(t as Number / 100.0);
-            let z = k + s * p.eval(t as Number / 100.0);
-            canvas.set_draw_color(Color::RGB(180, 20, 20));
-            canvas
-                .fill_rect(Rect::new(400 + t, x as i32, 5, 5))
-                .unwrap();
-            canvas.set_draw_color(Color::RGB(20, 180, 20));
-            canvas
-                .fill_rect(Rect::new(400 + t, y as i32, 5, 5))
-                .unwrap();
-            canvas.set_draw_color(Color::RGB(20, 20, 180));
-            canvas
-                .fill_rect(Rect::new(400 + t, z as i32, 2, 2))
-                .unwrap();
-            canvas.set_draw_color(Color::RGB(255, 0, 0));
-            canvas
-                .fill_rect(Rect::new(400 + t, k as i32, 2, 2))
-                .unwrap();
+        unsafe {
+            gl::Clear(gl::COLOR_BUFFER_BIT);
+            gl::UseProgram(shader_program);
+            gl::DrawArrays(gl::TRIANGLES, 0, 6);
         }
 
-        canvas.present();
-        thread::sleep(Duration::new(0, 1_000_000_000u32 / 60));
+        window.gl_swap_window();
     }
 }
-- 
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