Loads a specified shader from "/minecraft/shaders/"

ShaderHelper.java

package net.minecraft.src;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.nio.IntBuffer;

import static org.lwjgl.opengl.GL11.*;
import static org.lwjgl.opengl.GL20.*;
import org.lwjgl.opengl.ContextCapabilities;
import org.lwjgl.BufferUtils;

public class ShaderHelper {

	private int vertex_shader = 0;
	private int fragment_shader = 0;
	private int program = 0;

	public ShaderHelper() {
		program = glCreateProgram();
	}

	public ShaderHelper addShader(String shader, int type) {
		String line = "";
		String source  = "";
		String filepath = ModLoader.getMinecraftInstance().getMinecraftDir().getAbsolutePath() + "/shaders/" + shader;

		BufferedReader reader;
		try {
			reader = new BufferedReader(new FileReader(filepath));
			while((line = reader.readLine()) != null) {
				source += line + "\n";
			}
		} catch(Exception e) {
			throw new RuntimeException("Unable to load shader from: " + filepath);
		}

		if(type == GL_VERTEX_SHADER) {
			vertex_shader = compile(GL_VERTEX_SHADER, source);
			if (this.vertex_shader == 0) System.out.println("Error Vertex Shader!");
			link(filepath, vertex_shader);
		} else if(type == GL_FRAGMENT_SHADER) {
			fragment_shader = compile(GL_FRAGMENT_SHADER, source);
			if (this.fragment_shader == 0) System.out.println("Error Fragment Shader!");
			link(filepath, fragment_shader);
		} else {
			System.out.println("Shader type \"" + type + "\" cannot be resolved.");
		}
		return this;
	}

	private int compile(int type, String shader_source) {
		System.out.println("Compiling: " + type);
		int shader =  glCreateShader(type);
		if (shader == 0) {
			System.out.println("Cannot create shader.");
			return 0;
		}
		glShaderSource(shader, shader_source);
		glCompileShader(shader);
		System.out.println(shader);
		return shader;
	}

	private void link(String source, int sort) {
		System.out.println("linking: " + sort);
		glAttachShader(this.program, sort);
		glLinkProgram(this.program);
		IntBuffer result = BufferUtils.createIntBuffer(1);
		System.out.println(result);
		glGetProgram(this.program, GL_LINK_STATUS, result);
		if (result.get(0) != 1) {
			throw new RuntimeException("Error while compiling shader. \n\nin: " + source + "\n\n" +  glGetProgramInfoLog(this.program, 5000));
		}
		System.out.println(glGetProgramInfoLog(this.program, 5000));
	}

	public void bind() {
		glUseProgram(this.program);
	}

	public void unbind() {
		glUseProgram(0);
	}	
}