core.clj

(ns game.core
  (:import
    (org.lwjgl.glfw GLFW GLFWKeyCallbackI GLFWWindowSizeCallbackI)
    (org.lwjgl.opengl GL GL11 GL15 GL20 GL30)
    (org.lwjgl.system MemoryUtil MemoryStack)))

(def width 300)
(def height 300)

(defn set-uniform [x y & {:keys [shader name :as opts]}]
  (GL20/glUniform2fv (GL20/glGetUniformLocation (shader :pid) name), (float-array [x y])))

(defn init-window [] 
  (GLFW/glfwInit)
  (GLFW/glfwWindowHint GLFW/GLFW_VISIBLE GLFW/GLFW_FALSE)
  (GLFW/glfwWindowHint GLFW/GLFW_RESIZABLE GLFW/GLFW_TRUE)
  (def window (GLFW/glfwCreateWindow width height "Hello World" MemoryUtil/NULL MemoryUtil/NULL))
  (GLFW/glfwMakeContextCurrent window)
  (GLFW/glfwSwapInterval 1)
  (GLFW/glfwShowWindow window)
  (GL/createCapabilities)
  (GL11/glClearColor 0.0 1.0 1.0 1.0)
  (GLFW/glfwSetKeyCallback 
    window
    (reify GLFWKeyCallbackI
      (invoke [this window key scancode action mods]
        (when (and (= key GLFW/GLFW_KEY_ESCAPE) (= action GLFW/GLFW_RELEASE))
          (GLFW/glfwSetWindowShouldClose window true)))))
  (GLFW/glfwSetWindowSizeCallback 
    window
    (reify GLFWWindowSizeCallbackI
      (invoke [this window width height]
        (GL11/glViewport 0 0 width height)
        (def width width)
        (def height height)))))

(defn init-mesh [buf]
  (def vao (GL30/glGenVertexArrays))
  (GL30/glBindVertexArray vao)
  (def vbo (GL15/glGenBuffers))
  (GL15/glBindBuffer GL15/GL_ARRAY_BUFFER vbo)
  (GL15/glBufferData GL15/GL_ARRAY_BUFFER (float-array buf) GL15/GL_STATIC_DRAW)
  (GL30/glVertexAttribPointer 0 3 GL11/GL_FLOAT false 0 0)
  (GL15/glBindBuffer GL15/GL_ARRAY_BUFFER 0)
  (GL30/glEnableVertexAttribArray 0)
  (GL30/glBindVertexArray 0)
  {:vao vao :vbo vbo})

(defn init-shader [vf ff]
  (let [pid (GL20/glCreateProgram)
        vid (GL20/glCreateShader GL20/GL_VERTEX_SHADER)
        fid (GL20/glCreateShader GL20/GL_FRAGMENT_SHADER)]
  (GL20/glShaderSource vid (slurp vf))
  (GL20/glCompileShader vid)
  (GL20/glShaderSource fid (slurp ff))
  (GL20/glCompileShader fid)
  (GL20/glAttachShader pid vid)
  (GL20/glAttachShader pid fid)
  (GL20/glLinkProgram pid)
  (GL20/glValidateProgram pid)
  {:pid pid}))

(defn make-trig []
  [-1 +1 +0  +1 +1 +0  +1 -1 +0
   -1 +1 +0  -1 -1 +0  +1 -1 +0])

(defn init [] 
  (init-window)
  (def shader (init-shader "shaders/vert.glsl" "shaders/frag.glsl"))
  (def mesh (init-mesh (make-trig))))

(defn render [mesh]
  (GL30/glBindVertexArray (mesh :vao))
  (GL20/glUseProgram (shader :pid))
  (set-uniform width height :shader shader :name "res")
  (GL11/glDrawArrays GL11/GL_TRIANGLES 0 (count (make-trig)))
  (GLFW/glfwSwapBuffers window)
  (GL30/glBindVertexArray 0)
  (GL20/glUseProgram 0))

(defn run []
  (loop []
    (when (not (GLFW/glfwWindowShouldClose window))
      (GL11/glClear (bit-or GL11/GL_COLOR_BUFFER_BIT GL11/GL_DEPTH_BUFFER_BIT))
      (render mesh)
      (GLFW/glfwPollEvents)
      (recur))))

(defn -main []
  (init)
  (run))