/*
 * Copyright (C) 2009 The Android Open Source Project
 *
 * 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.android.systemui;

import static android.opengl.GLES20.*;
import static javax.microedition.khronos.egl.EGL10.*;

import android.app.ActivityManager;
import android.app.WallpaperManager;
import android.content.BroadcastReceiver;
import android.content.ComponentCallbacks2;
import android.content.Context;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Point;
import android.graphics.Rect;
import android.graphics.RectF;
import android.graphics.Region.Op;
import android.opengl.GLUtils;
import android.os.SystemProperties;
import android.renderscript.Matrix4f;
import android.service.wallpaper.WallpaperService;
import android.util.Log;
import android.view.Display;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.WindowManager;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;

import javax.microedition.khronos.egl.EGL10;
import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.egl.EGLContext;
import javax.microedition.khronos.egl.EGLDisplay;
import javax.microedition.khronos.egl.EGLSurface;

/**
 * Default built-in wallpaper that simply shows a static image.
 */
@SuppressWarnings({"UnusedDeclaration"})
public class ImageWallpaper extends WallpaperService {
    private static final String TAG = "ImageWallpaper";
    private static final String GL_LOG_TAG = "ImageWallpaperGL";
    private static final boolean DEBUG = false;
    private static final String PROPERTY_KERNEL_QEMU = "ro.kernel.qemu";

    static final boolean FIXED_SIZED_SURFACE = true;
    static final boolean USE_OPENGL = true;

    WallpaperManager mWallpaperManager;

    DrawableEngine mEngine;

    boolean mIsHwAccelerated;

    @Override
    public void onCreate() {
        super.onCreate();
        mWallpaperManager = (WallpaperManager) getSystemService(WALLPAPER_SERVICE);

        //noinspection PointlessBooleanExpression,ConstantConditions
        if (FIXED_SIZED_SURFACE && USE_OPENGL) {
            if (!isEmulator()) {
                mIsHwAccelerated = ActivityManager.isHighEndGfx();
            }
        }
    }

    @Override
    public void onTrimMemory(int level) {
        if (mEngine != null) {
            mEngine.trimMemory(level);
        }
    }

    private static boolean isEmulator() {
        return "1".equals(SystemProperties.get(PROPERTY_KERNEL_QEMU, "0"));
    }

    @Override
    public Engine onCreateEngine() {
        mEngine = new DrawableEngine();
        return mEngine;
    }

    class DrawableEngine extends Engine {
        static final int EGL_CONTEXT_CLIENT_VERSION = 0x3098;
        static final int EGL_OPENGL_ES2_BIT = 4;

        // TODO: Not currently used, keeping around until we know we don't need it
        @SuppressWarnings({"UnusedDeclaration"})
        private WallpaperObserver mReceiver;

        Bitmap mBackground;
        int mBackgroundWidth = -1, mBackgroundHeight = -1;
        int mLastSurfaceWidth = -1, mLastSurfaceHeight = -1;
        int mLastRotation = -1;
        float mXOffset = 0.5f;
        float mYOffset = 0.5f;
        float mScale = 1f;

        boolean mVisible = true;
        boolean mRedrawNeeded;
        boolean mOffsetsChanged;
        int mLastXTranslation;
        int mLastYTranslation;

        private EGL10 mEgl;
        private EGLDisplay mEglDisplay;
        private EGLConfig mEglConfig;
        private EGLContext mEglContext;
        private EGLSurface mEglSurface;

        private static final String sSimpleVS =
                "attribute vec4 position;\n" +
                "attribute vec2 texCoords;\n" +
                "varying vec2 outTexCoords;\n" +
                "uniform mat4 projection;\n" +
                "\nvoid main(void) {\n" +
                "    outTexCoords = texCoords;\n" +
                "    gl_Position = projection * position;\n" +
                "}\n\n";
        private static final String sSimpleFS =
                "precision mediump float;\n\n" +
                "varying vec2 outTexCoords;\n" +
                "uniform sampler2D texture;\n" +
                "\nvoid main(void) {\n" +
                "    gl_FragColor = texture2D(texture, outTexCoords);\n" +
                "}\n\n";

        private static final int FLOAT_SIZE_BYTES = 4;
        private static final int TRIANGLE_VERTICES_DATA_STRIDE_BYTES = 5 * FLOAT_SIZE_BYTES;
        private static final int TRIANGLE_VERTICES_DATA_POS_OFFSET = 0;
        private static final int TRIANGLE_VERTICES_DATA_UV_OFFSET = 3;

        class WallpaperObserver extends BroadcastReceiver {
            @Override
            public void onReceive(Context context, Intent intent) {
                if (DEBUG) {
                    Log.d(TAG, "onReceive");
                }

                mLastSurfaceWidth = mLastSurfaceHeight = -1;
                mBackground = null;
                mBackgroundWidth = -1;
                mBackgroundHeight = -1;
                mRedrawNeeded = true;
                drawFrame();
            }
        }

        public DrawableEngine() {
            super();
            setFixedSizeAllowed(true);
        }

        public void trimMemory(int level) {
            if (level >= ComponentCallbacks2.TRIM_MEMORY_RUNNING_LOW &&
                    mBackground != null) {
                if (DEBUG) {
                    Log.d(TAG, "trimMemory");
                }
                mBackground.recycle();
                mBackground = null;
                mBackgroundWidth = -1;
                mBackgroundHeight = -1;
                mWallpaperManager.forgetLoadedWallpaper();
            }
        }

        @Override
        public void onCreate(SurfaceHolder surfaceHolder) {
            if (DEBUG) {
                Log.d(TAG, "onCreate");
            }

            super.onCreate(surfaceHolder);

            // TODO: Don't need this currently because the wallpaper service
            // will restart the image wallpaper whenever the image changes.
            //IntentFilter filter = new IntentFilter(Intent.ACTION_WALLPAPER_CHANGED);
            //mReceiver = new WallpaperObserver();
            //registerReceiver(mReceiver, filter, null, mHandler);

            updateSurfaceSize(surfaceHolder);

            setOffsetNotificationsEnabled(false);
        }

        @Override
        public void onDestroy() {
            super.onDestroy();
            if (mReceiver != null) {
                unregisterReceiver(mReceiver);
            }
            mBackground = null;
            mWallpaperManager.forgetLoadedWallpaper();
        }

        void updateSurfaceSize(SurfaceHolder surfaceHolder) {
            Point p = getDefaultDisplaySize();

            // Load background image dimensions, if we haven't saved them yet
            if (mBackgroundWidth <= 0 || mBackgroundHeight <= 0) {
                // Need to load the image to get dimensions
                mWallpaperManager.forgetLoadedWallpaper();
                updateWallpaperLocked();
                if (mBackgroundWidth <= 0 || mBackgroundHeight <= 0) {
                    // Default to the display size if we can't find the dimensions
                    mBackgroundWidth = p.x;
                    mBackgroundHeight = p.y;
                }
            }

            // Force the wallpaper to cover the screen in both dimensions
            int surfaceWidth = Math.max(p.x, mBackgroundWidth);
            int surfaceHeight = Math.max(p.y, mBackgroundHeight);

            // If the surface dimensions haven't changed, then just return
            final Rect frame = surfaceHolder.getSurfaceFrame();
            if (frame != null) {
                final int dw = frame.width();
                final int dh = frame.height();
                if (surfaceWidth == dw && surfaceHeight == dh) {
                    return;
                }
            }

            if (FIXED_SIZED_SURFACE) {
                // Used a fixed size surface, because we are special.  We can do
                // this because we know the current design of window animations doesn't
                // cause this to break.
                surfaceHolder.setFixedSize(surfaceWidth, surfaceHeight);
            } else {
                surfaceHolder.setSizeFromLayout();
            }
        }

        @Override
        public void onVisibilityChanged(boolean visible) {
            if (DEBUG) {
                Log.d(TAG, "onVisibilityChanged: mVisible, visible=" + mVisible + ", " + visible);
            }

            if (mVisible != visible) {
                if (DEBUG) {
                    Log.d(TAG, "Visibility changed to visible=" + visible);
                }
                mVisible = visible;
                drawFrame();
            }
        }

        @Override
        public void onTouchEvent(MotionEvent event) {
            super.onTouchEvent(event);
        }

        @Override
        public void onOffsetsChanged(float xOffset, float yOffset,
                float xOffsetStep, float yOffsetStep,
                int xPixels, int yPixels) {
            if (DEBUG) {
                Log.d(TAG, "onOffsetsChanged: xOffset=" + xOffset + ", yOffset=" + yOffset
                        + ", xOffsetStep=" + xOffsetStep + ", yOffsetStep=" + yOffsetStep
                        + ", xPixels=" + xPixels + ", yPixels=" + yPixels);
            }

            if (mXOffset != xOffset || mYOffset != yOffset) {
                if (DEBUG) {
                    Log.d(TAG, "Offsets changed to (" + xOffset + "," + yOffset + ").");
                }
                mXOffset = xOffset;
                mYOffset = yOffset;
                mOffsetsChanged = true;
            }
            drawFrame();
        }

        @Override
        public void onSurfaceChanged(SurfaceHolder holder, int format, int width, int height) {
            if (DEBUG) {
                Log.d(TAG, "onSurfaceChanged: width=" + width + ", height=" + height);
            }

            super.onSurfaceChanged(holder, format, width, height);

            drawFrame();
        }

        @Override
        public void onSurfaceDestroyed(SurfaceHolder holder) {
            super.onSurfaceDestroyed(holder);
            mLastSurfaceWidth = mLastSurfaceHeight = -1;
        }

        @Override
        public void onSurfaceCreated(SurfaceHolder holder) {
            super.onSurfaceCreated(holder);
            mLastSurfaceWidth = mLastSurfaceHeight = -1;
        }

        @Override
        public void onSurfaceRedrawNeeded(SurfaceHolder holder) {
            if (DEBUG) {
                Log.d(TAG, "onSurfaceRedrawNeeded");
            }
            super.onSurfaceRedrawNeeded(holder);

            drawFrame();
        }

        private Point getDefaultDisplaySize() {
            Point p = new Point();
            Context c = ImageWallpaper.this.getApplicationContext();
            WindowManager wm = (WindowManager)c.getSystemService(Context.WINDOW_SERVICE);
            Display d = wm.getDefaultDisplay();
            d.getRealSize(p);
            return p;
        }

        void drawFrame() {
            try {
                int newRotation = ((WindowManager) getSystemService(WINDOW_SERVICE)).
                        getDefaultDisplay().getRotation();

                // Sometimes a wallpaper is not large enough to cover the screen in one dimension.
                // Call updateSurfaceSize -- it will only actually do the update if the dimensions
                // should change
                if (newRotation != mLastRotation) {
                    // Update surface size (if necessary)
                    updateSurfaceSize(getSurfaceHolder());
                }
                SurfaceHolder sh = getSurfaceHolder();
                final Rect frame = sh.getSurfaceFrame();
                final int dw = frame.width();
                final int dh = frame.height();
                boolean surfaceDimensionsChanged = dw != mLastSurfaceWidth
                        || dh != mLastSurfaceHeight;

                boolean redrawNeeded = surfaceDimensionsChanged || newRotation != mLastRotation;
                if (!redrawNeeded && !mOffsetsChanged) {
                    if (DEBUG) {
                        Log.d(TAG, "Suppressed drawFrame since redraw is not needed "
                                + "and offsets have not changed.");
                    }
                    return;
                }
                mLastRotation = newRotation;

                // Load bitmap if it is not yet loaded or if it was loaded at a different size
                if (mBackground == null || surfaceDimensionsChanged) {
                    if (DEBUG) {
                        Log.d(TAG, "Reloading bitmap: mBackground, bgw, bgh, dw, dh = " +
                                mBackground + ", " +
                                ((mBackground == null) ? 0 : mBackground.getWidth()) + ", " +
                                ((mBackground == null) ? 0 : mBackground.getHeight()) + ", " +
                                dw + ", " + dh);
                    }
                    mWallpaperManager.forgetLoadedWallpaper();
                    updateWallpaperLocked();
                    if (mBackground == null) {
                        if (DEBUG) {
                            Log.d(TAG, "Unable to load bitmap");
                        }
                        return;
                    }
                    if (DEBUG) {
                        if (dw != mBackground.getWidth() || dh != mBackground.getHeight()) {
                            Log.d(TAG, "Surface != bitmap dimensions: surface w/h, bitmap w/h: " +
                                    dw + ", " + dh + ", " + mBackground.getWidth() + ", " +
                                    mBackground.getHeight());
                        }
                    }
                }

                // Center the scaled image
                mScale = Math.max(1f, Math.max(dw / (float) mBackground.getWidth(),
                        dh / (float) mBackground.getHeight()));
                final int availw = dw - (int) (mBackground.getWidth() * mScale);
                final int availh = dh - (int) (mBackground.getHeight() * mScale);
                int xPixels = availw / 2;
                int yPixels = availh / 2;

                // Adjust the image for xOffset/yOffset values. If window manager is handling offsets,
                // mXOffset and mYOffset are set to 0.5f by default and therefore xPixels and yPixels
                // will remain unchanged
                final int availwUnscaled = dw - mBackground.getWidth();
                final int availhUnscaled = dh - mBackground.getHeight();
                if (availwUnscaled < 0)
                    xPixels += (int) (availwUnscaled * (mXOffset - .5f) + .5f);
                if (availhUnscaled < 0)
                    yPixels += (int) (availhUnscaled * (mYOffset - .5f) + .5f);

                mOffsetsChanged = false;
                mRedrawNeeded = false;
                if (surfaceDimensionsChanged) {
                    mLastSurfaceWidth = dw;
                    mLastSurfaceHeight = dh;
                }
                if (!redrawNeeded && xPixels == mLastXTranslation && yPixels == mLastYTranslation) {
                    if (DEBUG) {
                        Log.d(TAG, "Suppressed drawFrame since the image has not "
                                + "actually moved an integral number of pixels.");
                    }
                    return;
                }
                mLastXTranslation = xPixels;
                mLastYTranslation = yPixels;

                if (DEBUG) {
                    Log.d(TAG, "Redrawing wallpaper");
                }

                if (mIsHwAccelerated) {
                    if (!drawWallpaperWithOpenGL(sh, availw, availh, xPixels, yPixels)) {
                        drawWallpaperWithCanvas(sh, availw, availh, xPixels, yPixels);
                    }
                } else {
                    drawWallpaperWithCanvas(sh, availw, availh, xPixels, yPixels);
                }
            } finally {
                if (FIXED_SIZED_SURFACE && !mIsHwAccelerated) {
                    // If the surface is fixed-size, we should only need to
                    // draw it once and then we'll let the window manager
                    // position it appropriately.  As such, we no longer needed
                    // the loaded bitmap.  Yay!
                    // hw-accelerated renderer retains bitmap for faster rotation
                    mBackground = null;
                    mWallpaperManager.forgetLoadedWallpaper();
                }
            }
        }

        private void updateWallpaperLocked() {
            Throwable exception = null;
            try {
                mBackground = null;
                mBackgroundWidth = -1;
                mBackgroundHeight = -1;
                mBackground = mWallpaperManager.getBitmap();
                mBackgroundWidth = mBackground.getWidth();
                mBackgroundHeight = mBackground.getHeight();
            } catch (RuntimeException e) {
                exception = e;
            } catch (OutOfMemoryError e) {
                exception = e;
            }

            if (exception != null) {
                mBackground = null;
                mBackgroundWidth = -1;
                mBackgroundHeight = -1;
                // Note that if we do fail at this, and the default wallpaper can't
                // be loaded, we will go into a cycle.  Don't do a build where the
                // default wallpaper can't be loaded.
                Log.w(TAG, "Unable to load wallpaper!", exception);
                try {
                    mWallpaperManager.clear();
                } catch (IOException ex) {
                    // now we're really screwed.
                    Log.w(TAG, "Unable reset to default wallpaper!", ex);
                }
            }
        }

        private void drawWallpaperWithCanvas(SurfaceHolder sh, int w, int h, int left, int top) {
            Canvas c = sh.lockCanvas();
            if (c != null) {
                try {
                    if (DEBUG) {
                        Log.d(TAG, "Redrawing: left=" + left + ", top=" + top);
                    }

                    final float right = left + mBackground.getWidth() * mScale;
                    final float bottom = top + mBackground.getHeight() * mScale;
                    if (w < 0 || h < 0) {
                        c.save(Canvas.CLIP_SAVE_FLAG);
                        c.clipRect(left, top, right, bottom,
                                Op.DIFFERENCE);
                        c.drawColor(0xff000000);
                        c.restore();
                    }
                    if (mBackground != null) {
                        RectF dest = new RectF(left, top, right, bottom);
                        // add a filter bitmap?
                        c.drawBitmap(mBackground, null, dest, null);
                    }
                } finally {
                    sh.unlockCanvasAndPost(c);
                }
            }
        }

        private boolean drawWallpaperWithOpenGL(SurfaceHolder sh, int w, int h, int left, int top) {
            if (!initGL(sh)) return false;

            final float right = left + mBackground.getWidth() * mScale;
            final float bottom = top + mBackground.getHeight() * mScale;

            final Rect frame = sh.getSurfaceFrame();
            final Matrix4f ortho = new Matrix4f();
            ortho.loadOrtho(0.0f, frame.width(), frame.height(), 0.0f, -1.0f, 1.0f);

            final FloatBuffer triangleVertices = createMesh(left, top, right, bottom);

            final int texture = loadTexture(mBackground);
            final int program = buildProgram(sSimpleVS, sSimpleFS);

            final int attribPosition = glGetAttribLocation(program, "position");
            final int attribTexCoords = glGetAttribLocation(program, "texCoords");
            final int uniformTexture = glGetUniformLocation(program, "texture");
            final int uniformProjection = glGetUniformLocation(program, "projection");

            checkGlError();

            glViewport(0, 0, frame.width(), frame.height());
            glBindTexture(GL_TEXTURE_2D, texture);

            glUseProgram(program);
            glEnableVertexAttribArray(attribPosition);
            glEnableVertexAttribArray(attribTexCoords);
            glUniform1i(uniformTexture, 0);
            glUniformMatrix4fv(uniformProjection, 1, false, ortho.getArray(), 0);

            checkGlError();

            if (w > 0 || h > 0) {
                glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
                glClear(GL_COLOR_BUFFER_BIT);
            }

            // drawQuad
            triangleVertices.position(TRIANGLE_VERTICES_DATA_POS_OFFSET);
            glVertexAttribPointer(attribPosition, 3, GL_FLOAT, false,
                    TRIANGLE_VERTICES_DATA_STRIDE_BYTES, triangleVertices);

            triangleVertices.position(TRIANGLE_VERTICES_DATA_UV_OFFSET);
            glVertexAttribPointer(attribTexCoords, 3, GL_FLOAT, false,
                    TRIANGLE_VERTICES_DATA_STRIDE_BYTES, triangleVertices);

            glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

            boolean status = mEgl.eglSwapBuffers(mEglDisplay, mEglSurface);
            checkEglError();

            finishGL();

            return status;
        }

        private FloatBuffer createMesh(int left, int top, float right, float bottom) {
            final float[] verticesData = {
                    // X, Y, Z, U, V
                     left,  bottom, 0.0f, 0.0f, 1.0f,
                     right, bottom, 0.0f, 1.0f, 1.0f,
                     left,  top,    0.0f, 0.0f, 0.0f,
                     right, top,    0.0f, 1.0f, 0.0f,
            };

            final int bytes = verticesData.length * FLOAT_SIZE_BYTES;
            final FloatBuffer triangleVertices = ByteBuffer.allocateDirect(bytes).order(
                    ByteOrder.nativeOrder()).asFloatBuffer();
            triangleVertices.put(verticesData).position(0);
            return triangleVertices;
        }

        private int loadTexture(Bitmap bitmap) {
            int[] textures = new int[1];

            glActiveTexture(GL_TEXTURE0);
            glGenTextures(1, textures, 0);
            checkGlError();

            int texture = textures[0];
            glBindTexture(GL_TEXTURE_2D, texture);
            checkGlError();

            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
            glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

            GLUtils.texImage2D(GL_TEXTURE_2D, 0, GL_RGBA, bitmap, GL_UNSIGNED_BYTE, 0);
            checkGlError();

            return texture;
        }

        private int buildProgram(String vertex, String fragment) {
            int vertexShader = buildShader(vertex, GL_VERTEX_SHADER);
            if (vertexShader == 0) return 0;

            int fragmentShader = buildShader(fragment, GL_FRAGMENT_SHADER);
            if (fragmentShader == 0) return 0;

            int program = glCreateProgram();
            glAttachShader(program, vertexShader);
            checkGlError();

            glAttachShader(program, fragmentShader);
            checkGlError();

            glLinkProgram(program);
            checkGlError();

            int[] status = new int[1];
            glGetProgramiv(program, GL_LINK_STATUS, status, 0);
            if (status[0] != GL_TRUE) {
                String error = glGetProgramInfoLog(program);
                Log.d(GL_LOG_TAG, "Error while linking program:\n" + error);
                glDeleteShader(vertexShader);
                glDeleteShader(fragmentShader);
                glDeleteProgram(program);
                return 0;
            }

            return program;
        }

        private int buildShader(String source, int type) {
            int shader = glCreateShader(type);

            glShaderSource(shader, source);
            checkGlError();

            glCompileShader(shader);
            checkGlError();

            int[] status = new int[1];
            glGetShaderiv(shader, GL_COMPILE_STATUS, status, 0);
            if (status[0] != GL_TRUE) {
                String error = glGetShaderInfoLog(shader);
                Log.d(GL_LOG_TAG, "Error while compiling shader:\n" + error);
                glDeleteShader(shader);
                return 0;
            }

            return shader;
        }

        private void checkEglError() {
            int error = mEgl.eglGetError();
            if (error != EGL_SUCCESS) {
                Log.w(GL_LOG_TAG, "EGL error = " + GLUtils.getEGLErrorString(error));
            }
        }

        private void checkGlError() {
            int error = glGetError();
            if (error != GL_NO_ERROR) {
                Log.w(GL_LOG_TAG, "GL error = 0x" + Integer.toHexString(error), new Throwable());
            }
        }

        private void finishGL() {
            mEgl.eglMakeCurrent(mEglDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
            mEgl.eglDestroySurface(mEglDisplay, mEglSurface);
            mEgl.eglDestroyContext(mEglDisplay, mEglContext);
            mEgl.eglTerminate(mEglDisplay);
        }

        private boolean initGL(SurfaceHolder surfaceHolder) {
            mEgl = (EGL10) EGLContext.getEGL();

            mEglDisplay = mEgl.eglGetDisplay(EGL_DEFAULT_DISPLAY);
            if (mEglDisplay == EGL_NO_DISPLAY) {
                throw new RuntimeException("eglGetDisplay failed " +
                        GLUtils.getEGLErrorString(mEgl.eglGetError()));
            }

            int[] version = new int[2];
            if (!mEgl.eglInitialize(mEglDisplay, version)) {
                throw new RuntimeException("eglInitialize failed " +
                        GLUtils.getEGLErrorString(mEgl.eglGetError()));
            }

            mEglConfig = chooseEglConfig();
            if (mEglConfig == null) {
                throw new RuntimeException("eglConfig not initialized");
            }

            mEglContext = createContext(mEgl, mEglDisplay, mEglConfig);
            if (mEglContext == EGL_NO_CONTEXT) {
                throw new RuntimeException("createContext failed " +
                        GLUtils.getEGLErrorString(mEgl.eglGetError()));
            }

            int attribs[] = {
                EGL_WIDTH, 1,
                EGL_HEIGHT, 1,
                EGL_NONE
            };
            EGLSurface tmpSurface = mEgl.eglCreatePbufferSurface(mEglDisplay, mEglConfig, attribs);
            mEgl.eglMakeCurrent(mEglDisplay, tmpSurface, tmpSurface, mEglContext);

            int[] maxSize = new int[1];
            Rect frame = surfaceHolder.getSurfaceFrame();
            glGetIntegerv(GL_MAX_TEXTURE_SIZE, maxSize, 0);

            mEgl.eglMakeCurrent(mEglDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
            mEgl.eglDestroySurface(mEglDisplay, tmpSurface);

            if(frame.width() > maxSize[0] || frame.height() > maxSize[0]) {
                mEgl.eglDestroyContext(mEglDisplay, mEglContext);
                mEgl.eglTerminate(mEglDisplay);
                Log.e(GL_LOG_TAG, "requested  texture size " +
                    frame.width() + "x" + frame.height() + " exceeds the support maximum of " +
                    maxSize[0] + "x" + maxSize[0]);
                return false;
            }

            mEglSurface = mEgl.eglCreateWindowSurface(mEglDisplay, mEglConfig, surfaceHolder, null);
            if (mEglSurface == null || mEglSurface == EGL_NO_SURFACE) {
                int error = mEgl.eglGetError();
                if (error == EGL_BAD_NATIVE_WINDOW || error == EGL_BAD_ALLOC) {
                    Log.e(GL_LOG_TAG, "createWindowSurface returned " +
                                         GLUtils.getEGLErrorString(error) + ".");
                    return false;
                }
                throw new RuntimeException("createWindowSurface failed " +
                        GLUtils.getEGLErrorString(error));
            }

            if (!mEgl.eglMakeCurrent(mEglDisplay, mEglSurface, mEglSurface, mEglContext)) {
                throw new RuntimeException("eglMakeCurrent failed " +
                        GLUtils.getEGLErrorString(mEgl.eglGetError()));
            }

            return true;
        }


        EGLContext createContext(EGL10 egl, EGLDisplay eglDisplay, EGLConfig eglConfig) {
            int[] attrib_list = { EGL_CONTEXT_CLIENT_VERSION, 2, EGL_NONE };
            return egl.eglCreateContext(eglDisplay, eglConfig, EGL_NO_CONTEXT, attrib_list);
        }

        private EGLConfig chooseEglConfig() {
            int[] configsCount = new int[1];
            EGLConfig[] configs = new EGLConfig[1];
            int[] configSpec = getConfig();
            if (!mEgl.eglChooseConfig(mEglDisplay, configSpec, configs, 1, configsCount)) {
                throw new IllegalArgumentException("eglChooseConfig failed " +
                        GLUtils.getEGLErrorString(mEgl.eglGetError()));
            } else if (configsCount[0] > 0) {
                return configs[0];
            }
            return null;
        }

        private int[] getConfig() {
            return new int[] {
                    EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
                    EGL_RED_SIZE, 8,
                    EGL_GREEN_SIZE, 8,
                    EGL_BLUE_SIZE, 8,
                    EGL_ALPHA_SIZE, 0,
                    EGL_DEPTH_SIZE, 0,
                    EGL_STENCIL_SIZE, 0,
                    EGL_CONFIG_CAVEAT, EGL_NONE,
                    EGL_NONE
            };
        }
    }
}