puwei/library-vlc/src/main/java/com/yinuo/library/vlc/ShaderHelper.java

package com.yinuo.library.vlc;

import android.util.Log;

import static android.opengl.GLES20.GL_COMPILE_STATUS;
import static android.opengl.GLES20.GL_FRAGMENT_SHADER;
import static android.opengl.GLES20.GL_LINK_STATUS;
import static android.opengl.GLES20.GL_VALIDATE_STATUS;
import static android.opengl.GLES20.GL_VERTEX_SHADER;
import static android.opengl.GLES20.glAttachShader;
import static android.opengl.GLES20.glCompileShader;
import static android.opengl.GLES20.glCreateProgram;
import static android.opengl.GLES20.glCreateShader;
import static android.opengl.GLES20.glDeleteProgram;
import static android.opengl.GLES20.glDeleteShader;
import static android.opengl.GLES20.glGetProgramiv;
import static android.opengl.GLES20.glGetShaderiv;
import static android.opengl.GLES20.glLinkProgram;
import static android.opengl.GLES20.glShaderSource;
import static android.opengl.GLES20.glValidateProgram;

/**
 * Created by liwentian on 17/6/22.
 */

public class ShaderHelper {

    private static final String TAG = "ShaderHelper";

    /**
     * Loads and compiles a vertex shader, returning the OpenGL object ID.
     */
    public static int compileVertexShader(String shaderCode) {
        return compileShader(GL_VERTEX_SHADER, shaderCode);
    }

    /**
     * Loads and compiles a fragment shader, returning the OpenGL object ID.
     */
    public static int compileFragmentShader(String shaderCode) {
        return compileShader(GL_FRAGMENT_SHADER, shaderCode);
    }

    /**
     * Compiles a shader, returning the OpenGL object ID.
     */
    private static int compileShader(int type, String shaderCode) {
        // Create a new shader object.
        final int shaderObjectId = glCreateShader(type);

        if (shaderObjectId == 0) {
            Log.w(TAG, "Could not create new shader.");
            return 0;
        }

        // Pass in the shader source.
        glShaderSource(shaderObjectId, shaderCode);

        // Compile the shader.
        glCompileShader(shaderObjectId);

        // Get the compilation status.
        final int[] compileStatus = new int[1];
        glGetShaderiv(shaderObjectId, GL_COMPILE_STATUS,
                compileStatus, 0);

        // Print the shader info log to the Android log output.
//        Log.v(TAG, "Results of compiling source:" + "\n" + shaderCode
//                + "\n:" + glGetShaderInfoLog(shaderObjectId));

        // Verify the compile status.
        if (compileStatus[0] == 0) {
            // If it failed, delete the shader object.
            glDeleteShader(shaderObjectId);

            Log.w(TAG, "Compilation of shader failed.");

            return 0;
        }

        // Return the shader object ID.
        return shaderObjectId;
    }

    /**
     * Links a vertex shader and a fragment shader together into an OpenGL
     * program. Returns the OpenGL program object ID, or 0 if linking failed.
     */
    public static int linkProgram(int vertexShaderId, int fragmentShaderId) {

        // Create a new program object.
        final int programObjectId = glCreateProgram();

        if (programObjectId == 0) {
            Log.w(TAG, "Could not create new program");

            return 0;
        }

        // Attach the vertex shader to the program.
        glAttachShader(programObjectId, vertexShaderId);

        // Attach the fragment shader to the program.
        glAttachShader(programObjectId, fragmentShaderId);

        // Link the two shaders together into a program.
        glLinkProgram(programObjectId);

        // Get the link status.
        final int[] linkStatus = new int[1];
        glGetProgramiv(programObjectId, GL_LINK_STATUS,
                linkStatus, 0);

        // Print the program info log to the Android log output.
//        Log.v(
//                TAG,
//                "Results of linking program:\n"
//                        + glGetProgramInfoLog(programObjectId));

        // Verify the link status.
        if (linkStatus[0] == 0) {
            // If it failed, delete the program object.
            glDeleteProgram(programObjectId);

            Log.w(TAG, "Linking of program failed.");

            return 0;
        }

        // Return the program object ID.
        return programObjectId;
    }

    /**
     * Validates an OpenGL program. Should only be called when developing the
     * application.
     */
    public static boolean validateProgram(int programObjectId) {
        glValidateProgram(programObjectId);
        final int[] validateStatus = new int[1];
        glGetProgramiv(programObjectId, GL_VALIDATE_STATUS,
                validateStatus, 0);
//        Log.v(TAG, "Results of validating program: " + validateStatus[0]
//                + "\nLog:" + glGetProgramInfoLog(programObjectId));

        return validateStatus[0] != 0;
    }

    /**
     * Helper function that compiles the shaders, links and validates the
     * program, returning the program ID.
     */
    public static int buildProgram(String vertexShaderSource,
                                   String fragmentShaderSource) {
        int program;

        // Compile the shaders.
        int vertexShader = compileVertexShader(vertexShaderSource);
        int fragmentShader = compileFragmentShader(fragmentShaderSource);

        // Link them into a shader program.
        program = linkProgram(vertexShader, fragmentShader);

        validateProgram(program);

        return program;
    }
}