Fix threading and stopping issues in Colors dream.

The colors dream could continue running indefinitely
if the system terminated it rather an it ending
voluntarily.

There were also problems with the GL finish actions being
performed on the wrong thread.

Refactored the dream to resolve both of these problems cleanly.

Bug: 7267653
Change-Id: Id58c473acebdc2eb3be342d792926c54185984a2

2 files changed, 494 insertions, 417 deletions

diff --git a/src/com/android/dreams/basic/Colors.java b/src/com/android/dreams/basic/Colors.java
index 021189f..5f16d2c 100644
--- a/src/com/android/dreams/basic/Colors.java
+++ b/src/com/android/dreams/basic/Colors.java
@@ -16,411 +16,36 @@
 
 package com.android.dreams.basic;
 
-import android.graphics.Color;
 import android.graphics.SurfaceTexture;
-import android.service.dreams.Dream;
+import android.service.dreams.DreamService;
 import android.util.Log;
-import android.view.Choreographer;
-import android.view.Choreographer.FrameCallback;
 import android.view.TextureView;
-import android.os.Looper;
-import android.os.SystemClock;
-
-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;
-import javax.microedition.khronos.opengles.GL;
-import android.opengl.GLUtils;
-
-import java.nio.ByteBuffer;
-import java.nio.ByteOrder;
-import java.nio.FloatBuffer;
-import java.nio.ShortBuffer;
-
-import static android.opengl.GLES20.*;
-
-public class Colors extends Dream implements TextureView.SurfaceTextureListener {
+import android.os.Handler;
+import android.os.HandlerThread;
+
+/**
+ * Plays a delightful show of colors.
+ * <p>
+ * This dream performs its rendering using OpenGL on a separate rendering thread.
+ * </p>
+ */
+public class Colors extends DreamService implements TextureView.SurfaceTextureListener {
     static final String TAG = Colors.class.getSimpleName();
-    static final boolean DEBUG = true;
+    static final boolean DEBUG = false;
+
     public static final void LOG(String fmt, Object... args) {
         if (!DEBUG) return;
         Log.v(TAG, String.format(fmt, args));
     }
 
-    // It's so easy to use OpenGLES 2.0!
-    private EGL10 mEgl;
-    private EGLDisplay mEglDisplay;
-    private EGLConfig mEglConfig;
-    private EGLContext mEglContext;
-    private EGLSurface mEglSurface;
-    private SurfaceTexture mSurface;
-    private GL mGL;
-
-    static final int EGL_CONTEXT_CLIENT_VERSION = 0x3098;
-    static final int EGL_OPENGL_ES2_BIT = 4;
-
-    volatile boolean mStop = false;
-
-    Square mSquare;
-    TextureView mTextureView;
-
-    private long mLastFrameTime;
-    private int mFrameNum = 0;
-
-    private FrameCallback mFrameCallback = new Choreographer.FrameCallback() {
-        @Override
-        public void doFrame(long frameTimeNanos) {
-            if (mStop) {
-                Looper.myLooper().quit();
-                return;
-            }
-
-            if (mSquare == null) {
-                initGL();
-
-                mSquare = new Square();
-                glClearColor(1f, 0f, 0f, 1.0f);
-
-                if (DEBUG) {
-                    mLastFrameTime = frameTimeNanos;
-                }
-            }
-
-            checkCurrent();
-
-            glViewport(0, 0, mWidth, mHeight);
-
-            if (DEBUG) {
-                mFrameNum ++;
-                final long t2 = frameTimeNanos;
-                final long dt = t2-mLastFrameTime;
-                final int fps = (int) (1e9f/dt);
-                if (0 == (mFrameNum % 10)) {
-                    LOG("frame %d fps=%d", mFrameNum, fps);
-                }
-                if (fps < 40) {
-                    LOG("JANK! (%d ms)", dt);
-                }
-                mLastFrameTime = t2;
-            }
-
-            glClear(GL_COLOR_BUFFER_BIT);
-            checkGlError();
-
-            mSquare.draw();
-
-            if (!mEgl.eglSwapBuffers(mEglDisplay, mEglSurface)) {
-                throw new RuntimeException("Cannot swap buffers");
-            }
-            checkEglError();
-
-            mChoreographer.postFrameCallback(mFrameCallback);
-        }
-    };
-
-    private int mHeight;
-
-    private int mWidth;
-    private Choreographer mChoreographer;
-
-    class Square {
-        // Straight from the API guide
-        private final String vertexShaderCode =
-            "attribute vec4 a_position;" +
-            "attribute vec4 a_color;" +
-            "varying vec4 v_color;" +
-            "void main() {" +
-            "  gl_Position = a_position;" +
-            "  v_color = a_color;" +
-            "}";
-
-        private final String fragmentShaderCode =
-            "precision mediump float;" +
-            "varying vec4 v_color;" +
-            "void main() {" +
-            "  gl_FragColor = v_color;" +
-            "}";
-
-        private final FloatBuffer vertexBuffer;
-        private final FloatBuffer colorBuffer;
-        private final int mProgram;
-        private int mPositionHandle;
-        private int mColorHandle;
-
-        private ShortBuffer drawListBuffer;
-
-
-        // number of coordinates per vertex in this array
-        final int COORDS_PER_VERTEX = 3;
-        float squareCoords[] = { -1f,  1f, 0f,   // top left
-                                 -1f, -1f, 0f,   // bottom left
-                                  1f, -1f, 0f,   // bottom right
-                                  1f,  1f, 0f }; // top right
-
-        private short drawOrder[] = { 0, 1, 2, 0, 2, 3 }; // order to draw vertices (CCW)
-
-        private final float HUES[] = { // reverse order due to CCW winding
-                60,  // yellow
-                120, // green
-                343, // red
-                200, // blue
-        };
-
-        private final int vertexCount = squareCoords.length / COORDS_PER_VERTEX;
-        private final int vertexStride = COORDS_PER_VERTEX * 4; // bytes per vertex
-
-        private float cornerFrequencies[] = new float[vertexCount];
-        private int cornerRotation;
-
-        final int COLOR_PLANES_PER_VERTEX = 4;
-        private final int colorStride = COLOR_PLANES_PER_VERTEX * 4; // bytes per vertex
-
-        // Set color with red, green, blue and alpha (opacity) values
-        float color[] = { 0.63671875f, 0.76953125f, 0.22265625f, 1.0f };
-
-        public Square() {
-            for (int i=0; i<vertexCount; i++) {
-                cornerFrequencies[i] = 1f + (float)(Math.random() * 5);
-            }
-            cornerRotation = (int)(Math.random() * vertexCount);
-            // initialize vertex byte buffer for shape coordinates
-            ByteBuffer bb = ByteBuffer.allocateDirect(
-            // (# of coordinate values * 4 bytes per float)
-                    squareCoords.length * 4);
-            bb.order(ByteOrder.nativeOrder());
-            vertexBuffer = bb.asFloatBuffer();
-            vertexBuffer.put(squareCoords);
-            vertexBuffer.position(0);
-
-            bb = ByteBuffer.allocateDirect(vertexCount * colorStride);
-            bb.order(ByteOrder.nativeOrder());
-            colorBuffer = bb.asFloatBuffer();
-
-            // initialize byte buffer for the draw list
-            ByteBuffer dlb = ByteBuffer.allocateDirect(
-            // (# of coordinate values * 2 bytes per short)
-                    drawOrder.length * 2);
-            dlb.order(ByteOrder.nativeOrder());
-            drawListBuffer = dlb.asShortBuffer();
-            drawListBuffer.put(drawOrder);
-            drawListBuffer.position(0);
-
-            mProgram = buildProgram(vertexShaderCode, fragmentShaderCode);
-
-            // Add program to OpenGL environment
-            glUseProgram(mProgram);
-            checkGlError("glUseProgram(" + mProgram + ")");
-
-            // get handle to vertex shader's a_position member
-            mPositionHandle = glGetAttribLocation(mProgram, "a_position");
-            checkGlError("glGetAttribLocation(a_position)");
-
-            // Enable a handle to the triangle vertices
-            glEnableVertexAttribArray(mPositionHandle);
-
-            // Prepare the triangle coordinate data
-            glVertexAttribPointer(mPositionHandle, COORDS_PER_VERTEX,
-                    GL_FLOAT, false,
-                    vertexStride, vertexBuffer);
-
-            mColorHandle = glGetAttribLocation(mProgram, "a_color");
-            checkGlError("glGetAttribLocation(a_color)");
-            glEnableVertexAttribArray(mColorHandle);
-            checkGlError("glEnableVertexAttribArray");
-        }
-
-        final float[] _tmphsv = new float[3];
-        public void draw() {
-            // same thing for colors
-            long now = SystemClock.uptimeMillis();
-            colorBuffer.clear();
-            final float t = now / 4000f; // set the base period to 4sec
-            for(int i=0; i<vertexCount; i++) {
-                final float freq = (float) Math.sin(2 * Math.PI * t / cornerFrequencies[i]);
-                _tmphsv[0] = HUES[(i + cornerRotation) % vertexCount];
-                _tmphsv[1] = 1f;
-                _tmphsv[2] = freq * 0.25f + 0.75f;
-                final int c = Color.HSVToColor(_tmphsv);
-                colorBuffer.put((float)((c & 0xFF0000) >> 16) / 0xFF);
-                colorBuffer.put((float)((c & 0x00FF00) >> 8) / 0xFF);
-                colorBuffer.put((float)(c & 0x0000FF) / 0xFF);
-                colorBuffer.put(/*a*/ 1f);
-            }
-            colorBuffer.position(0);
-            glVertexAttribPointer(mColorHandle, COLOR_PLANES_PER_VERTEX,
-                    GL_FLOAT, false,
-                    colorStride, colorBuffer);
-            checkGlError("glVertexAttribPointer");
-
-            // Draw the triangle
-            glDrawArrays(GL_TRIANGLE_FAN, 0, vertexCount);
-        }
-    }
-
-    private static 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();
+    private TextureView mTextureView;
 
-        glAttachShader(program, fragmentShader);
-        checkGlError();
+    // The handler thread and handler on which the GL renderer is running.
+    private HandlerThread mRendererHandlerThread;
+    private Handler mRendererHandler;
 
-        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(TAG, "Error while linking program:\n" + error);
-            glDeleteShader(vertexShader);
-            glDeleteShader(fragmentShader);
-            glDeleteProgram(program);
-            return 0;
-        }
-
-        return program;
-    }
-
-    private static 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(TAG, "Error while compiling shader:\n" + error);
-            glDeleteShader(shader);
-            return 0;
-        }
-
-        return shader;
-    }
-    @Override
-    public void onStart() {
-        super.onStart();
-    }
-
-    private void checkEglError() {
-        int error = mEgl.eglGetError();
-        if (error != EGL10.EGL_SUCCESS) {
-            Log.w(TAG, "EGL error = 0x" + Integer.toHexString(error));
-        }
-    }
-
-    private static void checkGlError() {
-        checkGlError("");
-    }
-
-    private static void checkGlError(String what) {
-        int error = glGetError();
-        if (error != GL_NO_ERROR) {
-            Log.w(TAG, "GL error: (" + what + ") = 0x" + Integer.toHexString(error));
-        }
-    }
-
-    private void finishGL() {
-        mEgl.eglDestroyContext(mEglDisplay, mEglContext);
-        mEgl.eglDestroySurface(mEglDisplay, mEglSurface);
-    }
-
-    private void checkCurrent() {
-        if (!mEglContext.equals(mEgl.eglGetCurrentContext()) ||
-                !mEglSurface.equals(mEgl.eglGetCurrentSurface(EGL10.EGL_DRAW))) {
-            if (!mEgl.eglMakeCurrent(mEglDisplay, mEglSurface, mEglSurface, mEglContext)) {
-                throw new RuntimeException("eglMakeCurrent failed "
-                        + GLUtils.getEGLErrorString(mEgl.eglGetError()));
-            }
-        }
-    }
-
-    private void initGL() {
-        mEgl = (EGL10) EGLContext.getEGL();
-
-        mEglDisplay = mEgl.eglGetDisplay(EGL10.EGL_DEFAULT_DISPLAY);
-        if (mEglDisplay == EGL10.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);
-
-        mEglSurface = mEgl.eglCreateWindowSurface(mEglDisplay, mEglConfig, mSurface, null);
-
-        if (mEglSurface == null || mEglSurface == EGL10.EGL_NO_SURFACE) {
-            int error = mEgl.eglGetError();
-            if (error == EGL10.EGL_BAD_NATIVE_WINDOW) {
-                Log.e(TAG, "createWindowSurface returned EGL_BAD_NATIVE_WINDOW.");
-                return;
-            }
-            throw new RuntimeException("createWindowSurface failed "
-                    + GLUtils.getEGLErrorString(error));
-        }
-
-        if (!mEgl.eglMakeCurrent(mEglDisplay, mEglSurface, mEglSurface, mEglContext)) {
-            throw new RuntimeException("eglMakeCurrent failed "
-                    + GLUtils.getEGLErrorString(mEgl.eglGetError()));
-        }
-
-        mGL = mEglContext.getGL();
-    }
-
-
-    EGLContext createContext(EGL10 egl, EGLDisplay eglDisplay, EGLConfig eglConfig) {
-        int[] attrib_list = { EGL_CONTEXT_CLIENT_VERSION, 2, EGL10.EGL_NONE };
-        return egl.eglCreateContext(eglDisplay, eglConfig, EGL10.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 static int[] getConfig() {
-        return new int[] {
-                EGL10.EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
-                EGL10.EGL_RED_SIZE, 8,
-                EGL10.EGL_GREEN_SIZE, 8,
-                EGL10.EGL_BLUE_SIZE, 8,
-                EGL10.EGL_ALPHA_SIZE, 8,
-                EGL10.EGL_DEPTH_SIZE, 0,
-                EGL10.EGL_STENCIL_SIZE, 0,
-                EGL10.EGL_NONE
-        };
-    }
+    // The current GL renderer, or null if the dream is not running.
+    private ColorsGLRenderer mRenderer;
 
     @Override
     public void onCreate() {
@@ -430,6 +55,12 @@ public class Colors extends Dream implements TextureView.SurfaceTextureListener
 
         mTextureView = new TextureView(this);
         mTextureView.setSurfaceTextureListener(this);
+
+        if (mRendererHandlerThread == null) {
+            mRendererHandlerThread = new HandlerThread(TAG);
+            mRendererHandlerThread.start();
+            mRendererHandler = new Handler(mRendererHandlerThread.getLooper());
+        }
     }
 
     @Override
@@ -441,36 +72,50 @@ public class Colors extends Dream implements TextureView.SurfaceTextureListener
     }
 
     @Override
-    public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
+    public void onSurfaceTextureAvailable(final SurfaceTexture surface,
+            final int width, final int height) {
         LOG("onSurfaceTextureAvailable(%s, %d, %d)", surface, width, height);
-        mSurface = surface;
 
-        mWidth = width;
-        mHeight = height;
-
-        new Thread() {
+        mRendererHandler.post(new Runnable() {
             @Override
             public void run() {
-                Looper.prepare();
-    
-                mChoreographer = Choreographer.getInstance();
-                mChoreographer.postFrameCallback(mFrameCallback);
-
-                Looper.loop();
+                if (mRenderer != null) {
+                    mRenderer.stop();
+                }
+                mRenderer = new ColorsGLRenderer(surface, width, height);
+                mRenderer.start();
             }
-        }.start();
+        });
     }
 
     @Override
-    public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {
+    public void onSurfaceTextureSizeChanged(SurfaceTexture surface,
+            final int width, final int height) {
         LOG("onSurfaceTextureSizeChanged(%s, %d, %d)", surface, width, height);
-        mWidth = width;
-        mHeight = height;
+
+        mRendererHandler.post(new Runnable() {
+            @Override
+            public void run() {
+                if (mRenderer != null) {
+                    mRenderer.setSize(width, height);
+                }
+            }
+        });
     }
 
     @Override
     public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
         LOG("onSurfaceTextureDestroyed(%s)", surface);
+
+        mRendererHandler.post(new Runnable() {
+            @Override
+            public void run() {
+                if (mRenderer != null) {
+                    mRenderer.stop();
+                    mRenderer = null;
+                }
+            }
+        });
         return false;
     }
 
@@ -478,11 +123,4 @@ public class Colors extends Dream implements TextureView.SurfaceTextureListener
     public void onSurfaceTextureUpdated(SurfaceTexture surface) {
         LOG("onSurfaceTextureUpdated(%s)", surface);
     }
-
-    @Override
-    public void finish() {
-        mStop = true;
-        finishGL();
-        super.finish();
-    }
 }
diff --git a/src/com/android/dreams/basic/ColorsGLRenderer.java b/src/com/android/dreams/basic/ColorsGLRenderer.java
new file mode 100644
index 0000000..3452261
--- /dev/null
+++ b/src/com/android/dreams/basic/ColorsGLRenderer.java
@@ -0,0 +1,439 @@
+/*
+ * Copyright (C) 2012 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.dreams.basic;
+
+import android.graphics.Color;
+import android.graphics.SurfaceTexture;
+import android.util.Log;
+import android.view.Choreographer;
+import android.os.SystemClock;
+
+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;
+import javax.microedition.khronos.opengles.GL;
+
+import android.opengl.EGL14;
+import android.opengl.GLUtils;
+
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.nio.FloatBuffer;
+import java.nio.ShortBuffer;
+
+import static android.opengl.GLES20.*;
+
+/**
+ * The OpenGL renderer for the {@link Colors} dream.
+ * <p>
+ * This class is single-threaded.  Its methods must only be called on the
+ * rendering thread.
+ * </p>
+ */
+final class ColorsGLRenderer implements Choreographer.FrameCallback {
+    static final String TAG = ColorsGLRenderer.class.getSimpleName();
+    static final boolean DEBUG = false;
+
+    private static final void LOG(String fmt, Object... args) {
+        if (!DEBUG) return;
+        Log.v(TAG, String.format(fmt, args));
+    }
+
+    private final SurfaceTexture mSurface;
+    private int mWidth;
+    private int mHeight;
+
+    private final Choreographer mChoreographer;
+
+    private Square mSquare;
+    private long mLastFrameTime;
+    private int mFrameNum = 0;
+
+    // It's so easy to use OpenGLES 2.0!
+    private EGL10 mEgl;
+    private EGLDisplay mEglDisplay;
+    private EGLConfig mEglConfig;
+    private EGLContext mEglContext;
+    private EGLSurface mEglSurface;
+    private GL mGL;
+
+    public ColorsGLRenderer(SurfaceTexture surface, int width, int height) {
+        mSurface = surface;
+        mWidth = width;
+        mHeight = height;
+
+        mChoreographer = Choreographer.getInstance();
+    }
+
+    public void start() {
+        initGL();
+        mSquare = new Square();
+
+        mFrameNum = 0;
+        mChoreographer.postFrameCallback(this);
+    }
+
+    public void stop() {
+        mChoreographer.removeFrameCallback(this);
+
+        mSquare = null;
+        finishGL();
+    }
+
+    public void setSize(int width, int height) {
+        mWidth = width;
+        mHeight = height;
+    }
+
+    @Override
+    public void doFrame(long frameTimeNanos) {
+        mFrameNum += 1;
+
+        // Clear on first frame.
+        if (mFrameNum == 1) {
+            glClearColor(1f, 0f, 0f, 1.0f);
+            if (DEBUG) {
+                mLastFrameTime = frameTimeNanos;
+            }
+        }
+
+        // Draw new frame.
+        checkCurrent();
+
+        glViewport(0, 0, mWidth, mHeight);
+
+        if (DEBUG) {
+            final long t2 = frameTimeNanos;
+            final long dt = t2 - mLastFrameTime;
+            final int fps = (int) (1e9f / dt);
+            if (0 == (mFrameNum % 10)) {
+                LOG("frame %d fps=%d", mFrameNum, fps);
+            }
+            if (fps < 40) {
+                LOG("JANK! (%d ms)", dt);
+            }
+            mLastFrameTime = t2;
+        }
+
+        glClear(GL_COLOR_BUFFER_BIT);
+        checkGlError();
+
+        mSquare.draw();
+
+        if (!mEgl.eglSwapBuffers(mEglDisplay, mEglSurface)) {
+            throw new RuntimeException("Cannot swap buffers");
+        }
+        checkEglError();
+
+        // Animate.  Post callback to run on next vsync.
+        mChoreographer.postFrameCallback(this);
+    }
+
+    private void checkCurrent() {
+        if (!mEglContext.equals(mEgl.eglGetCurrentContext()) ||
+                !mEglSurface.equals(mEgl.eglGetCurrentSurface(EGL10.EGL_DRAW))) {
+            if (!mEgl.eglMakeCurrent(mEglDisplay, mEglSurface, mEglSurface, mEglContext)) {
+                throw new RuntimeException("eglMakeCurrent failed "
+                        + GLUtils.getEGLErrorString(mEgl.eglGetError()));
+            }
+        }
+    }
+
+    private void initGL() {
+        mEgl = (EGL10) EGLContext.getEGL();
+
+        mEglDisplay = mEgl.eglGetDisplay(EGL10.EGL_DEFAULT_DISPLAY);
+        if (mEglDisplay == EGL10.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);
+
+        mEglSurface = mEgl.eglCreateWindowSurface(mEglDisplay, mEglConfig, mSurface, null);
+
+        if (mEglSurface == null || mEglSurface == EGL10.EGL_NO_SURFACE) {
+            int error = mEgl.eglGetError();
+            if (error == EGL10.EGL_BAD_NATIVE_WINDOW) {
+                Log.e(TAG, "createWindowSurface returned EGL_BAD_NATIVE_WINDOW.");
+                return;
+            }
+            throw new RuntimeException("createWindowSurface failed "
+                    + GLUtils.getEGLErrorString(error));
+        }
+
+        if (!mEgl.eglMakeCurrent(mEglDisplay, mEglSurface, mEglSurface, mEglContext)) {
+            throw new RuntimeException("eglMakeCurrent failed "
+                    + GLUtils.getEGLErrorString(mEgl.eglGetError()));
+        }
+
+        mGL = mEglContext.getGL();
+    }
+
+    private void finishGL() {
+        mEgl.eglDestroyContext(mEglDisplay, mEglContext);
+        mEgl.eglDestroySurface(mEglDisplay, mEglSurface);
+    }
+
+    private EGLContext createContext(EGL10 egl, EGLDisplay eglDisplay, EGLConfig eglConfig) {
+        int[] attrib_list = { EGL14.EGL_CONTEXT_CLIENT_VERSION, 2, EGL10.EGL_NONE };
+        return egl.eglCreateContext(eglDisplay, eglConfig, EGL10.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 static int[] getConfig() {
+        return new int[] {
+                EGL10.EGL_RENDERABLE_TYPE, EGL14.EGL_OPENGL_ES2_BIT,
+                EGL10.EGL_RED_SIZE, 8,
+                EGL10.EGL_GREEN_SIZE, 8,
+                EGL10.EGL_BLUE_SIZE, 8,
+                EGL10.EGL_ALPHA_SIZE, 8,
+                EGL10.EGL_DEPTH_SIZE, 0,
+                EGL10.EGL_STENCIL_SIZE, 0,
+                EGL10.EGL_NONE
+        };
+    }
+
+    private static 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(TAG, "Error while linking program:\n" + error);
+            glDeleteShader(vertexShader);
+            glDeleteShader(fragmentShader);
+            glDeleteProgram(program);
+            return 0;
+        }
+
+        return program;
+    }
+
+    private static 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(TAG, "Error while compiling shader:\n" + error);
+            glDeleteShader(shader);
+            return 0;
+        }
+
+        return shader;
+    }
+
+    private void checkEglError() {
+        int error = mEgl.eglGetError();
+        if (error != EGL10.EGL_SUCCESS) {
+            Log.w(TAG, "EGL error = 0x" + Integer.toHexString(error));
+        }
+    }
+
+    private static void checkGlError() {
+        checkGlError("");
+    }
+
+    private static void checkGlError(String what) {
+        int error = glGetError();
+        if (error != GL_NO_ERROR) {
+            Log.w(TAG, "GL error: (" + what + ") = 0x" + Integer.toHexString(error));
+        }
+    }
+
+    private final static class Square {
+        // Straight from the API guide
+        private final String vertexShaderCode =
+            "attribute vec4 a_position;" +
+            "attribute vec4 a_color;" +
+            "varying vec4 v_color;" +
+            "void main() {" +
+            "  gl_Position = a_position;" +
+            "  v_color = a_color;" +
+            "}";
+
+        private final String fragmentShaderCode =
+            "precision mediump float;" +
+            "varying vec4 v_color;" +
+            "void main() {" +
+            "  gl_FragColor = v_color;" +
+            "}";
+
+        private final FloatBuffer vertexBuffer;
+        private final FloatBuffer colorBuffer;
+        private final int mProgram;
+        private int mPositionHandle;
+        private int mColorHandle;
+
+        private ShortBuffer drawListBuffer;
+
+
+        // number of coordinates per vertex in this array
+        final int COORDS_PER_VERTEX = 3;
+        float squareCoords[] = { -1f,  1f, 0f,   // top left
+                                 -1f, -1f, 0f,   // bottom left
+                                  1f, -1f, 0f,   // bottom right
+                                  1f,  1f, 0f }; // top right
+
+        private short drawOrder[] = { 0, 1, 2, 0, 2, 3 }; // order to draw vertices (CCW)
+
+        private final float HUES[] = { // reverse order due to CCW winding
+                60,  // yellow
+                120, // green
+                343, // red
+                200, // blue
+        };
+
+        private final int vertexCount = squareCoords.length / COORDS_PER_VERTEX;
+        private final int vertexStride = COORDS_PER_VERTEX * 4; // bytes per vertex
+
+        private float cornerFrequencies[] = new float[vertexCount];
+        private int cornerRotation;
+
+        final int COLOR_PLANES_PER_VERTEX = 4;
+        private final int colorStride = COLOR_PLANES_PER_VERTEX * 4; // bytes per vertex
+
+        // Set color with red, green, blue and alpha (opacity) values
+        float color[] = { 0.63671875f, 0.76953125f, 0.22265625f, 1.0f };
+
+        public Square() {
+            for (int i=0; i<vertexCount; i++) {
+                cornerFrequencies[i] = 1f + (float)(Math.random() * 5);
+            }
+            cornerRotation = (int)(Math.random() * vertexCount);
+            // initialize vertex byte buffer for shape coordinates
+            ByteBuffer bb = ByteBuffer.allocateDirect(
+            // (# of coordinate values * 4 bytes per float)
+                    squareCoords.length * 4);
+            bb.order(ByteOrder.nativeOrder());
+            vertexBuffer = bb.asFloatBuffer();
+            vertexBuffer.put(squareCoords);
+            vertexBuffer.position(0);
+
+            bb = ByteBuffer.allocateDirect(vertexCount * colorStride);
+            bb.order(ByteOrder.nativeOrder());
+            colorBuffer = bb.asFloatBuffer();
+
+            // initialize byte buffer for the draw list
+            ByteBuffer dlb = ByteBuffer.allocateDirect(
+            // (# of coordinate values * 2 bytes per short)
+                    drawOrder.length * 2);
+            dlb.order(ByteOrder.nativeOrder());
+            drawListBuffer = dlb.asShortBuffer();
+            drawListBuffer.put(drawOrder);
+            drawListBuffer.position(0);
+
+            mProgram = buildProgram(vertexShaderCode, fragmentShaderCode);
+
+            // Add program to OpenGL environment
+            glUseProgram(mProgram);
+            checkGlError("glUseProgram(" + mProgram + ")");
+
+            // get handle to vertex shader's a_position member
+            mPositionHandle = glGetAttribLocation(mProgram, "a_position");
+            checkGlError("glGetAttribLocation(a_position)");
+
+            // Enable a handle to the triangle vertices
+            glEnableVertexAttribArray(mPositionHandle);
+
+            // Prepare the triangle coordinate data
+            glVertexAttribPointer(mPositionHandle, COORDS_PER_VERTEX,
+                    GL_FLOAT, false,
+                    vertexStride, vertexBuffer);
+
+            mColorHandle = glGetAttribLocation(mProgram, "a_color");
+            checkGlError("glGetAttribLocation(a_color)");
+            glEnableVertexAttribArray(mColorHandle);
+            checkGlError("glEnableVertexAttribArray");
+        }
+
+        final float[] _tmphsv = new float[3];
+        public void draw() {
+            // same thing for colors
+            long now = SystemClock.uptimeMillis();
+            colorBuffer.clear();
+            final float t = now / 4000f; // set the base period to 4sec
+            for(int i=0; i<vertexCount; i++) {
+                final float freq = (float) Math.sin(2 * Math.PI * t / cornerFrequencies[i]);
+                _tmphsv[0] = HUES[(i + cornerRotation) % vertexCount];
+                _tmphsv[1] = 1f;
+                _tmphsv[2] = freq * 0.25f + 0.75f;
+                final int c = Color.HSVToColor(_tmphsv);
+                colorBuffer.put((float)((c & 0xFF0000) >> 16) / 0xFF);
+                colorBuffer.put((float)((c & 0x00FF00) >> 8) / 0xFF);
+                colorBuffer.put((float)(c & 0x0000FF) / 0xFF);
+                colorBuffer.put(/*a*/ 1f);
+            }
+            colorBuffer.position(0);
+            glVertexAttribPointer(mColorHandle, COLOR_PLANES_PER_VERTEX,
+                    GL_FLOAT, false,
+                    colorStride, colorBuffer);
+            checkGlError("glVertexAttribPointer");
+
+            // Draw the triangle
+            glDrawArrays(GL_TRIANGLE_FAN, 0, vertexCount);
+        }
+    }
+}