ShaderCreator.java

package com.javamarcher.shader;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import org.lwjgl.opengl.GL20;

public class ShaderCreator {
	private static final String INCLUDE_KEYWORD = "#include";
	private final int vertexShaderId;
	private final int fragmentShaderId;
	private int programId = 0;
	
	public ShaderCreator(String vertexFileName, String fragmentFileName) {
		vertexShaderId = loadShader(vertexFileName, GL20.GL_VERTEX_SHADER);
		fragmentShaderId = loadShader(fragmentFileName, GL20.GL_FRAGMENT_SHADER);
	}
	
	/**
	 * Binds the shader ids to a shader program
	 * and returns the program id. 
	 */
	public int createShader() {
		programId = GL20.glCreateProgram();
		GL20.glAttachShader(programId, vertexShaderId);
		GL20.glAttachShader(programId, fragmentShaderId);
		return programId;
	}
	
	public void cleanup() {
		GL20.glUseProgram(0);
		GL20.glDetachShader(getProgramId(), vertexShaderId);
		GL20.glDetachShader(getProgramId(), fragmentShaderId);
		
		GL20.glDeleteShader(vertexShaderId);
		GL20.glDeleteShader(fragmentShaderId);
		GL20.glDeleteProgram(getProgramId());
	}
	
	/**
	 * Loads the shader based on the given path and returns the shader id. 
	 */
	private int loadShader(String filename, int type) {
		final StringBuilder shaderSource = new StringBuilder();
		int shaderId = 0;
		
		try {
			final BufferedReader reader = new BufferedReader(new FileReader(filename));
			String sourceLine;
			while((sourceLine = reader.readLine()) != null) {
				// Only append if no include pragma was found
				if(!parseIncludePragma(shaderSource, sourceLine)) {
					shaderSource.append(sourceLine).append("\n");
				}
			}
			reader.close();
		} catch (IOException e) {
			e.printStackTrace();
			System.exit(-1);
		}
		
		shaderId = GL20.glCreateShader(type);
		GL20.glShaderSource(shaderId, shaderSource);
		GL20.glCompileShader(shaderId);
		
		if(GL20.glGetShaderi(shaderId, GL20.GL_COMPILE_STATUS) == 0) {
			System.err.println("Shader compilation failed!");
			System.err.println(GL20.glGetShaderInfoLog(shaderId));
			System.exit(1);
		}
		
		return shaderId;
	}
	
	private boolean parseIncludePragma(StringBuilder shaderSource, String currentLine) throws IOException {
		if(currentLine.startsWith(INCLUDE_KEYWORD)) {
			final String includeFilename = currentLine.substring(currentLine.indexOf("[") + 1, currentLine.indexOf("]"));
			
			final BufferedReader reader = new BufferedReader(new FileReader(includeFilename));
			String line;
			while((line = reader.readLine()) != null) {
				shaderSource.append(line).append("\n");
			}
			reader.close();
			return true;
		}
		return false;
	}

	public int getVertexShaderId() {
		return vertexShaderId;
	}

	public int getFragmentShaderId() {
		return fragmentShaderId;
	}

	public int getProgramId() {
		return programId;
	}
}