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/*
* Copyright 2018 Google LLC All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.skar.examples.helloskar.rendering;
import android.content.Context;
import android.opengl.GLES20;
import android.util.Log;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
/**
* Shader helper functions.
*/
public class ShaderUtil {
/**
* Converts a raw text file, saved as a resource, into an OpenGL ES shader.
*
* @param type The type of shader we will be creating.
* @param filename The filename of the asset file about to be turned into a shader.
* @return The shader object handler.
*/
public static int loadGLShader(String tag, Context context, int type, String filename)
throws IOException {
String code = readRawTextFileFromAssets(context, filename);
int shader = GLES20.glCreateShader(type);
GLES20.glShaderSource(shader, code);
GLES20.glCompileShader(shader);
// Get the compilation status.
final int[] compileStatus = new int[1];
GLES20.glGetShaderiv(shader, GLES20.GL_COMPILE_STATUS, compileStatus, 0);
// If the compilation failed, delete the shader.
if (compileStatus[0] == 0) {
Log.e(tag, "Error compiling shader: " + GLES20.glGetShaderInfoLog(shader));
GLES20.glDeleteShader(shader);
shader = 0;
}
if (shader == 0) {
throw new RuntimeException("Error creating shader.");
}
return shader;
}
/**
* Checks if we've had an error inside of OpenGL ES, and if so what that error is.
*
* @param label Label to report in case of error.
* @throws RuntimeException If an OpenGL error is detected.
*/
public static void checkGLError(String tag, String label) {
int lastError = GLES20.GL_NO_ERROR;
// Drain the queue of all errors.
int error;
while ((error = GLES20.glGetError()) != GLES20.GL_NO_ERROR) {
Log.e(tag, label + ": glError " + error);
lastError = error;
}
if (lastError != GLES20.GL_NO_ERROR) {
throw new RuntimeException(label + ": glError " + lastError);
}
}
/**
* Converts a raw text file into a string.
*
* @param filename The filename of the asset file about to be turned into a shader.
* @return The context of the text file, or null in case of error.
*/
private static String readRawTextFileFromAssets(Context context, String filename)
throws IOException {
try (InputStream inputStream = context.getAssets().open(filename);
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream))) {
StringBuilder sb = new StringBuilder();
String line;
while ((line = reader.readLine()) != null) {
sb.append(line).append("\n");
}
return sb.toString();
}
}
}
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