Hacked together rainbow square

src/main/java/org/hirw/game/Scene.java

@@ -1,6 +1,5 @@
 package org.hirw.game;
 
-
 public abstract class Scene {
   public Scene() {}
 

src/main/java/org/hirw/game/Shader.java

@@ -1,8 +1,12 @@
 package org.hirw.game;
 
+import static org.lwjgl.opengl.ARBVertexArrayObject.glBindVertexArray;
+import static org.lwjgl.opengl.ARBVertexArrayObject.glGenVertexArrays;
 import static org.lwjgl.opengl.GL20.*;
 
 import java.io.IOException;
+import java.nio.FloatBuffer;
+import java.nio.IntBuffer;
 import java.nio.file.Files;
 import java.nio.file.InvalidPathException;
 import java.nio.file.NoSuchFileException;
@@ -13,6 +17,7 @@ import java.util.Map;
 import lombok.Getter;
 import lombok.Setter;
 import org.hirw.game.util.Log;
+import org.lwjgl.BufferUtils;
 
 public class Shader {
   private enum ShaderType {
@@ -35,6 +40,20 @@ public class Shader {
   @Getter @Setter private int fragmentID;
   @Getter @Setter private int shaderProgramID;
 
+  private float[] vertexArray = {
+    0.5f, -0.5f, 0.0f, /*          */ 1.0f, 0.0f, 0.0f, 1.0f, //
+    -0.5f, 0.5f, 0.0f, /*          */ 0.0f, 1.0f, 0.0f, 1.0f, //
+    0.5f, 0.5f, 0.0f, /*          */ 0.0f, 0.0f, 1.0f, 1.0f, //
+    -0.5f, -0.5f, 0.0f, /*          */ 1.0f, 1.0f, 0.0f, 1.0f, //
+  };
+
+  private int[] elementArray = {
+    2, 1, 0, //
+    0, 1, 3
+  };
+
+  @Getter private int vaoID, vboID, eboID;
+
   public Shader(String fragPath, String vertPath) {
     this.fragmentSource = readFromFile(fragPath);
     this.vertexSource = readFromFile(vertPath);
@@ -48,6 +67,7 @@ public class Shader {
     compileShader(ShaderType.FRAG);
     compileShader(ShaderType.VERT);
     createProgram();
+    thingy();
   }
 
   private void compileShader(ShaderType shaderType) {
@@ -112,4 +132,46 @@ public class Shader {
 
     return source;
   }
+
+  private void thingy() {
+    this.vaoID = glGenVertexArrays();
+    glBindVertexArray(this.vaoID);
+
+    FloatBuffer vertexBuffer = BufferUtils.createFloatBuffer(this.vertexArray.length);
+    vertexBuffer.put(this.vertexArray).flip();
+
+    this.vboID = glGenBuffers();
+    glBindBuffer(GL_ARRAY_BUFFER, this.vboID);
+    glBufferData(GL_ARRAY_BUFFER, vertexBuffer, GL_STATIC_DRAW);
+
+    IntBuffer elementBuffer = BufferUtils.createIntBuffer(this.elementArray.length);
+    elementBuffer.put(this.elementArray).flip();
+
+    this.eboID = glGenBuffers();
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, this.eboID);
+    glBufferData(GL_ELEMENT_ARRAY_BUFFER, elementBuffer, GL_STATIC_DRAW);
+
+    int positionsSize = 3;
+    int colourSize = 4;
+    int floatSizeBytes = 4;
+    int vertexSizeBytes = (positionsSize + colourSize) * floatSizeBytes;
+    glVertexAttribPointer(0, positionsSize, GL_FLOAT, false, vertexSizeBytes, 0);
+    glEnableVertexAttribArray(0);
+
+    glVertexAttribPointer(
+        1, colourSize, GL_FLOAT, false, vertexSizeBytes, positionsSize * floatSizeBytes);
+    glEnableVertexAttribArray(1);
+  }
+
+  public void update() {
+    glUseProgram(this.shaderProgramID);
+    glBindVertexArray(this.vaoID);
+    glEnableVertexAttribArray(0);
+    glEnableVertexAttribArray(1);
+    glDrawElements(GL_TRIANGLES, this.elementArray.length, GL_UNSIGNED_INT, 0);
+    glDisableVertexAttribArray(0);
+    glDisableVertexAttribArray(1);
+    glBindVertexArray(0);
+    glUseProgram(0);
+  }
 }

src/main/java/org/hirw/game/Window.java

@@ -18,6 +18,8 @@ public class Window {
 
   private static Window window = null;
 
+  private Shader shader;
+
   private Window() {
     this.width = 1280;
     this.height = 720;
@@ -81,6 +83,7 @@ public class Window {
     GL.createCapabilities();
     glClearColor(0.0f, 0.0f, 2.0f, 0.0f);
     Shader someShader = new Shader();
+    this.shader = someShader;
     someShader.init();
   }
 
@@ -89,6 +92,7 @@ public class Window {
       Time.update();
       SceneManager.getScene().update();
       glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+      this.shader.update();
       glfwSwapBuffers(glfwWindow);
       glfwPollEvents();
     }