Add new ManagedEGLContext class to help apps participate in memory trimming.

This class provides an API for an application to know when it is time to
destroy its EGL context when memory is being trimmed.  By having this in
the framework, we can still detect whether it will be useful to destroy
any EGL contexts (because we know if doing so will destroy all of them).

Change-Id: I1eac8d640052778052926b875c7928008f752182

1 files changed, 136 insertions, 0 deletions

diff --git a/opengl/java/android/opengl/ManagedEGLContext.java b/opengl/java/android/opengl/ManagedEGLContext.java
new file mode 100644
index 0000000..d3a3662
--- /dev/null
+++ b/opengl/java/android/opengl/ManagedEGLContext.java
@@ -0,0 +1,136 @@
+/*
+ * Copyright (C) 2010 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 android.opengl;
+
+import static javax.microedition.khronos.egl.EGL10.EGL_DEFAULT_DISPLAY;
+import static javax.microedition.khronos.egl.EGL10.EGL_NO_DISPLAY;
+
+import java.util.ArrayList;
+
+import javax.microedition.khronos.egl.EGL10;
+import javax.microedition.khronos.egl.EGLContext;
+import javax.microedition.khronos.egl.EGLDisplay;
+
+import android.os.Looper;
+import android.util.Log;
+
+import com.google.android.gles_jni.EGLImpl;
+
+/**
+ * The per-process memory overhead of hardware accelerated graphics can
+ * be quite large on some devices.  For small memory devices, being able to
+ * terminate all EGL contexts so that this graphics driver memory can be
+ * reclaimed can significant improve the overall behavior of the device.  This
+ * class helps app developers participate in releasing their EGL context
+ * when appropriate and possible.
+ * 
+ * <p>To use, simple instantiate this class with the EGLContext you create.
+ * When you have done this, if the device is getting low on memory and all
+ * of the currently created EGL contexts in the process are being managed
+ * through this class, then they will all be asked to terminate through the
+ * call to {@link #onTerminate}.
+ */
+public abstract class ManagedEGLContext {
+    static final String TAG = "ManagedEGLContext";
+
+    static final ArrayList<ManagedEGLContext> sActive
+            = new ArrayList<ManagedEGLContext>();
+
+    final EGLContext mContext;
+
+    /**
+     * Instantiate to manage the given EGLContext.
+     */
+    public ManagedEGLContext(EGLContext context) {
+        mContext = context;
+        synchronized (sActive) {
+            sActive.add(this);
+        }
+    }
+
+    /**
+     * Retrieve the EGLContext being managed by the class.
+     */
+    public EGLContext getContext() {
+        return mContext;
+    }
+
+    /**
+     * Force-terminate the ManagedEGLContext.  This will cause
+     * {@link #onTerminate(EGLContext)} to be called.  You <em>must</em>
+     * call this when destroying the EGLContext, so that the framework
+     * knows to stop managing it.
+     */
+    public void terminate() {
+        execTerminate();
+    }
+
+    void execTerminate() {
+        onTerminate(mContext);
+    }
+
+    /**
+     * Override this method to destroy the EGLContext when appropriate.
+     * <em>Note that this method is always called on the main thread
+     * of the process.</em>  If your EGLContext was created on a different
+     * thread, you will need to implement this method to hand off the work
+     * of destroying the context to that thread.
+     */
+    public abstract void onTerminate(EGLContext context);
+
+    /** @hide */
+    public static boolean doTerminate() {
+        ArrayList<ManagedEGLContext> active;
+
+        if (Looper.getMainLooper() != Looper.myLooper()) {
+            throw new IllegalStateException("Called on wrong thread");
+        }
+
+        synchronized (sActive) {
+            // If there are no active managed contexts, we will not even
+            // try to terminate.
+            if (sActive.size() <= 0) {
+                return false;
+            }
+
+            // Need to check how many EGL contexts are actually running,
+            // to compare with how many we are managing.
+            EGL10 egl = (EGL10) EGLContext.getEGL();
+            EGLDisplay display = egl.eglGetDisplay(EGL_DEFAULT_DISPLAY);
+
+            if (display == EGL_NO_DISPLAY) {
+                Log.w(TAG, "doTerminate failed: no display");
+                return false;
+            }
+
+            if (EGLImpl.getInitCount(display) != sActive.size()) {
+                Log.w(TAG, "doTerminate failed: EGL count is " + EGLImpl.getInitCount(display)
+                        + " but managed count is " + sActive.size());
+                return false;
+            }
+
+            active = new ArrayList<ManagedEGLContext>(sActive);
+            sActive.clear();
+        }
+
+        for (int i=0; i<active.size(); i++) {
+            active.get(i).execTerminate();
+        }
+
+        return true;
+    }
+}