Bug 791263 - Disable screenshotting under low-memory conditions. r=blassey

mobile/android/base/MemoryMonitor.java

@@ -148,17 +148,27 @@ class MemoryMonitor extends BroadcastReceiver {
             if (GeckoApp.checkLaunchState(GeckoApp.LaunchState.GeckoRunning)) {
                 GeckoAppShell.onLowMemory();
             }
+            ScreenshotHandler.disableScreenshot();
             GeckoAppShell.geckoEventSync();
         }
     }
 
-    private synchronized boolean decreaseMemoryPressure() {
-        if (mMemoryPressure > 0) {
-            mMemoryPressure--;
-            Log.d(LOGTAG, "Decreased memory pressure to " + mMemoryPressure);
-            return true;
+    private boolean decreaseMemoryPressure() {
+        int newLevel;
+        synchronized (this) {
+            if (mMemoryPressure <= 0) {
+                return false;
+            }
+
+            newLevel = --mMemoryPressure;
         }
-        return false;
+        Log.d(LOGTAG, "Decreased memory pressure to " + newLevel);
+
+        if (newLevel == MEMORY_PRESSURE_NONE) {
+            ScreenshotHandler.enableScreenshot();
+        }
+
+        return true;
     }
 
     class PressureDecrementer implements Runnable {

mobile/android/base/ScreenshotHandler.java

@@ -17,6 +17,7 @@ import android.graphics.Rect;
 import android.graphics.RectF;
 import android.opengl.GLES20;
 import android.util.FloatMath;
+import android.util.Log;
 
 import java.nio.ByteBuffer;
 import java.util.Iterator;
@@ -39,7 +40,7 @@ public final class ScreenshotHandler implements Runnable {
     private final int mMaxPixels;
 
     private final Queue<PendingScreenshot> mPendingScreenshots;
-    private final ByteBuffer mBuffer;
+    private ByteBuffer mBuffer;
     private int mBufferWidth;
     private int mBufferHeight;
     private RectF mPageRect;
@@ -51,11 +52,16 @@ public final class ScreenshotHandler implements Runnable {
     private boolean mIsRepaintRunnablePosted;
 
     private static synchronized ScreenshotHandler getInstance() {
+        if (sDisableScreenshot) {
+            return null;
+        }
         if (sInstance == null) {
             try {
                 sInstance = new ScreenshotHandler();
             } catch (UnsupportedOperationException e) {
-                // initialization failed, fall through and return null
+                // initialization failed, fall through and return null.
+                // also set the disable flag so we don't try again.
+                sDisableScreenshot = true;
             }
         }
         return sInstance;
@@ -76,13 +82,34 @@ public final class ScreenshotHandler implements Runnable {
         clearDirtyRect();
     }
 
+    private void cleanup() {
+        discardPendingScreenshots();
+        mBuffer = DirectBufferAllocator.free(mBuffer);
+    }
+
     // Invoked via reflection from robocop test
-    public static void disableScreenshot() {
+    public static synchronized void disableScreenshot() {
+        if (sDisableScreenshot) {
+            return;
+        }
         sDisableScreenshot = true;
+        if (sInstance != null) {
+            sInstance.cleanup();
+            sInstance = null;
+        }
+        Log.i(LOGTAG, "Screenshotting disabled");
+    }
+
+    public static synchronized void enableScreenshot() {
+        if (!sDisableScreenshot) {
+            return;
+        }
+        sDisableScreenshot = false;
+        Log.i(LOGTAG, "Screenshotting enabled");
     }
 
     public static void screenshotWholePage(Tab tab) {
-        if (sDisableScreenshot || GeckoApp.mAppContext.isApplicationInBackground()) {
+        if (GeckoApp.mAppContext.isApplicationInBackground()) {
             return;
         }
         ScreenshotHandler handler = getInstance();
@@ -93,6 +120,14 @@ public final class ScreenshotHandler implements Runnable {
         handler.screenshotWholePage(tab.getId());
     }
 
+    private void discardPendingScreenshots() {
+        synchronized (mPendingScreenshots) {
+            for (Iterator<PendingScreenshot> i = mPendingScreenshots.iterator(); i.hasNext(); ) {
+                i.next().discard();
+            }
+        }
+    }
+
     private void screenshotWholePage(int tabId) {
         LayerView layerView = GeckoApp.mAppContext.getLayerView();
         if (layerView == null) {
@@ -111,11 +146,7 @@ public final class ScreenshotHandler implements Runnable {
             mTabId = tabId;
             clearDirtyRect();
         }
-        synchronized (mPendingScreenshots) {
-            for (Iterator<PendingScreenshot> i = mPendingScreenshots.iterator(); i.hasNext(); ) {
-                i.next().discard();
-            }
-        }
+        discardPendingScreenshots();
 
         int dstx = 0;
         int dsty = 0;
@@ -140,9 +171,6 @@ public final class ScreenshotHandler implements Runnable {
 
     // Called from native code by JNI
     public static void notifyPaintedRect(float top, float left, float bottom, float right) {
-        if (sDisableScreenshot) {
-            return;
-        }
         ScreenshotHandler handler = getInstance();
         if (handler == null) {
             return;

widget/android/AndroidBridge.cpp

@@ -2480,6 +2480,9 @@ nsresult AndroidBridge::TakeScreenshot(nsIDOMWindow *window, int32_t srcX, int32
     uint32_t stride = bufW * 2 /* 16 bpp */;
 
     void* data = env->GetDirectBufferAddress(buffer);
+    if (!data)
+        return NS_ERROR_FAILURE;
+
     nsRefPtr<gfxImageSurface> surf = new gfxImageSurface(static_cast<unsigned char*>(data), nsIntSize(bufW, bufH), stride, gfxASurface::ImageFormatRGB16_565);
     if (surf->CairoStatus() != 0) {
         ALOG_BRIDGE("Error creating gfxImageSurface");