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Minimal OpenGL example ported from https://www.lwjgl.org/guide
(ns lwjgl-demo.core
(:gen-class)
(:import (org.lwjgl Version)
(org.lwjgl.glfw GLFWErrorCallback GLFW GLFWKeyCallbackI Callbacks)
(org.lwjgl.opengl GL GL33)
(org.lwjgl.system MemoryStack)))
; embedded nREPL
(require '[nrepl.server :refer [start-server stop-server]])
(defonce server (start-server :port 7888))
; The window handle
(declare window)
; forward references
(declare init main-loop draw)
(defn -main [& args]
(println (str "Hello LWJGL " (Version/getVersion) "!"))
(init)
(main-loop)
; Free the window callbacks and destroy the window
(Callbacks/glfwFreeCallbacks window)
(GLFW/glfwDestroyWindow window)
; Terminate GLFW and free the error callback
(GLFW/glfwTerminate)
(-> (GLFW/glfwSetErrorCallback nil) (.free)))
(defn init []
; Setup an error callback. The default implementation
; will print the error message in System.err.
(-> (GLFWErrorCallback/createPrint System/err) (.set))
; Initialize GLFW. Most GLFW functions will not work before doing this.
(when (not (GLFW/glfwInit))
(throw (IllegalStateException. "Unable to initialize GLFW")))
; Configure GLFW
(GLFW/glfwDefaultWindowHints) ; optional, the current window hints are already the default
(GLFW/glfwWindowHint GLFW/GLFW_VISIBLE GLFW/GLFW_FALSE) ; the window will stay hidden after creation
(GLFW/glfwWindowHint GLFW/GLFW_RESIZABLE GLFW/GLFW_TRUE) ; the window will be resizable
; Create the window
(def window (GLFW/glfwCreateWindow 300 300 "Hello, World!" 0 0))
(when (zero? window)
(throw (RuntimeException. "Failed to create the GLFW window")))
; Setup a key callback. It will be called every time a key is pressed, repeated or released.
(GLFW/glfwSetKeyCallback window (reify GLFWKeyCallbackI
(invoke [this window key scancode action mods]
(when (and (= key GLFW/GLFW_KEY_ESCAPE)
(= action GLFW/GLFW_RELEASE))
; We will detect this in the rendering loop
(GLFW/glfwSetWindowShouldClose window true)))))
; Get the thread stack and push a new frame
(let [stack (MemoryStack/stackPush)
p-width (.mallocInt stack 1)
p-height (.mallocInt stack 1)]
; Get the window size passed to glfwCreateWindow
(GLFW/glfwGetWindowSize ^long window p-width p-height)
(let [vidmode (-> (GLFW/glfwGetPrimaryMonitor) ; Get the resolution of the primary monitor
(GLFW/glfwGetVideoMode))
xpos (/ (- (.width vidmode)
(.get p-width 0))
2)
ypos (/ (- (.height vidmode)
(.get p-height 0))
2)]
(GLFW/glfwSetWindowPos window xpos ypos)) ; Center the window
(MemoryStack/stackPop) ; pop stack frame
)
(GLFW/glfwMakeContextCurrent window) ; Make the OpenGL context current
(GLFW/glfwSwapInterval 1) ; Enable v-sync
(GLFW/glfwShowWindow window)) ; Make the window visible
(defn main-loop []
; This line is critical for LWJGL's interoperation with GLFW's
; OpenGL context, or any context that is managed externally.
; LWJGL detects the context that is current in the current thread,
; creates the GLCapabilities instance and makes the OpenGL
; bindings available for use.
(GL/createCapabilities)
; Set the clear color
(GL33/glClearColor 1.0 0.0 0.0 0.0)
; Run the rendering loop until the user has attempted to close
; the window or has pressed the ESCAPE key.
(while (not (GLFW/glfwWindowShouldClose window))
(draw)))
(defn draw []
(GL33/glClearColor 1.0 0.0 0.0 0.0)
; clear the framebuffer
(GL33/glClear (bit-or GL33/GL_COLOR_BUFFER_BIT GL33/GL_DEPTH_BUFFER_BIT))
; swap the color buffers
(GLFW/glfwSwapBuffers window)
; Poll for window events. The key callback above will only be
; invoked during this call.
(GLFW/glfwPollEvents))
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