Reduce unnecessary OOM from screen captures.

WebContents.getContentBitmapAsync was unnecessarily passing the bitmap
to java before compressing it and saving to disk.

Instead, changes the API so that the caller provides a directory in which to
grab screenshots, and then WebContents seemlessly creates a new temp
file, compresses to jpeg and saves to that directory, requiring 0 java heap
allocation. As part of this async screen capture, also get a public Uri
for exporting via ContentProvider because all clients do this anyway.
BUG=651348

Change-Id: I6be01348f225adfa370c6a5e08ebd57f15e8fe93
Reviewed-on: https://chromium-review.googlesource.com/935670Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Commit-Queue: Yaron Friedman <yfriedman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550240}

base/android/callback_android.cc

@@ -5,6 +5,7 @@
 #include "base/android/callback_android.h"
 
 #include "base/android/jni_array.h"
+#include "base/android/jni_string.h"
 #include "base/android/scoped_java_ref.h"
 #include "jni/Callback_jni.h"
 
@@ -13,25 +14,29 @@ namespace android {
 
 void RunCallbackAndroid(const JavaRef<jobject>& callback,
                         const JavaRef<jobject>& arg) {
-  Java_Helper_onObjectResultFromNative(base::android::AttachCurrentThread(),
-                                       callback, arg);
+  Java_Helper_onObjectResultFromNative(AttachCurrentThread(), callback, arg);
 }
 
 void RunCallbackAndroid(const JavaRef<jobject>& callback, bool arg) {
-  Java_Helper_onBooleanResultFromNative(base::android::AttachCurrentThread(),
-                                        callback, static_cast<jboolean>(arg));
+  Java_Helper_onBooleanResultFromNative(AttachCurrentThread(), callback,
+                                        static_cast<jboolean>(arg));
 }
 
 void RunCallbackAndroid(const JavaRef<jobject>& callback, int arg) {
-  Java_Helper_onIntResultFromNative(base::android::AttachCurrentThread(),
-                                    callback, arg);
+  Java_Helper_onIntResultFromNative(AttachCurrentThread(), callback, arg);
+}
+
+void RunStringCallbackAndroid(const JavaRef<jobject>& callback,
+                              const std::string& arg) {
+  JNIEnv* env = AttachCurrentThread();
+  ScopedJavaLocalRef<jstring> java_string = ConvertUTF8ToJavaString(env, arg);
+  Java_Helper_onObjectResultFromNative(env, callback, java_string);
 }
 
 void RunCallbackAndroid(const JavaRef<jobject>& callback,
                         const std::vector<uint8_t>& arg) {
-  JNIEnv* env = base::android::AttachCurrentThread();
-  base::android::ScopedJavaLocalRef<jbyteArray> j_bytes =
-      base::android::ToJavaByteArray(env, arg);
+  JNIEnv* env = AttachCurrentThread();
+  ScopedJavaLocalRef<jbyteArray> j_bytes = ToJavaByteArray(env, arg);
   Java_Helper_onObjectResultFromNative(env, callback, j_bytes);
 }
 

base/android/callback_android.h

@@ -24,6 +24,9 @@ void BASE_EXPORT RunCallbackAndroid(const JavaRef<jobject>& callback,
 
 void BASE_EXPORT RunCallbackAndroid(const JavaRef<jobject>& callback, int arg);
 
+void BASE_EXPORT RunStringCallbackAndroid(const JavaRef<jobject>& callback,
+                                          const std::string& arg);
+
 void BASE_EXPORT RunCallbackAndroid(const JavaRef<jobject>& callback,
                                     const std::vector<uint8_t>& arg);
 

chrome/android/java/src/org/chromium/chrome/browser/customtabs/CustomTabObserver.java

@@ -5,8 +5,8 @@
 package org.chromium.chrome.browser.customtabs;
 
 import android.app.Application;
-import android.graphics.Bitmap;
 import android.graphics.Rect;
+import android.net.Uri;
 import android.os.SystemClock;
 import android.support.customtabs.CustomTabsSessionToken;
 import android.text.TextUtils;
@@ -14,6 +14,7 @@ import android.text.TextUtils;
 import org.chromium.base.metrics.RecordHistogram;
 import org.chromium.chrome.R;
 import org.chromium.chrome.browser.prerender.ExternalPrerenderHandler;
+import org.chromium.chrome.browser.share.ShareHelper;
 import org.chromium.chrome.browser.tab.EmptyTabObserver;
 import org.chromium.chrome.browser.tab.Tab;
 import org.chromium.chrome.browser.tab.TabObserver;
@@ -103,7 +104,7 @@ class CustomTabObserver extends EmptyTabObserver {
         } else if (mCurrentState == STATE_WAITING_LOAD_FINISH) {
             if (mCustomTabsConnection != null) {
                 mCustomTabsConnection.sendNavigationInfo(
-                        mSession, tab.getUrl(), tab.getTitle(), null);
+                        mSession, tab.getUrl(), tab.getTitle(), (Uri) null);
             }
             mPageLoadStartedTimestamp = SystemClock.elapsedRealtime();
         }
@@ -198,11 +199,11 @@ class CustomTabObserver extends EmptyTabObserver {
         if (!mCustomTabsConnection.shouldSendNavigationInfoForSession(mSession)) return;
         if (tab.getWebContents() == null) return;
 
-        tab.getWebContents().getContentBitmapAsync(
-                mContentBitmapWidth, mContentBitmapHeight, (Bitmap bitmap) -> {
-                    if (TextUtils.isEmpty(tab.getTitle()) && bitmap == null) return;
+        ShareHelper.captureScreenshotForContents(tab.getWebContents(), mContentBitmapWidth,
+                mContentBitmapHeight, (Uri snapshotPath) -> {
+                    if (TextUtils.isEmpty(tab.getTitle()) && snapshotPath == null) return;
                     mCustomTabsConnection.sendNavigationInfo(
-                            mSession, tab.getUrl(), tab.getTitle(), bitmap);
+                            mSession, tab.getUrl(), tab.getTitle(), snapshotPath);
                 });
     }
 }

chrome/android/java/src/org/chromium/chrome/browser/customtabs/CustomTabsConnection.java

@@ -1012,10 +1012,15 @@ public class CustomTabsConnection {
      * @param session The session to use for getting client callback.
      * @param url The current url for the tab.
      * @param title The current title for the tab.
-     * @param screenshot A screenshot of the tab contents.
+     * @param snapshotPath Uri location for screenshot of the tab contents which is publicly
+     *         available for sharing.
      */
     public void sendNavigationInfo(
-            CustomTabsSessionToken session, String url, String title, Bitmap screenshot) { }
+            CustomTabsSessionToken session, String url, String title, Uri snapshotPath) {}
+
+    // TODO(yfriedman): Remove when internal code is deleted.
+    public void sendNavigationInfo(
+            CustomTabsSessionToken session, String url, String title, Bitmap snapshotPath) {}
 
     /**
      * Called when the bottom bar for the custom tab has been hidden or shown completely by user

chrome/android/java/src/org/chromium/chrome/browser/share/ShareHelper.java

@@ -45,6 +45,7 @@ import org.chromium.base.StreamUtil;
 import org.chromium.base.VisibleForTesting;
 import org.chromium.base.metrics.CachedMetrics;
 import org.chromium.chrome.R;
+import org.chromium.content_public.browser.WebContents;
 import org.chromium.ui.UiUtils;
 
 import java.io.File;
@@ -366,54 +367,60 @@ public class ShareHelper {
         }.execute();
     }
 
-    /**
-     * Persists the screenshot file and notifies the file provider that the file is ready to be
-     * accessed by the client.
-     *
-     * The bitmap is compressed to JPEG before being written to the file.
-     *
-     * @param screenshot  The screenshot bitmap to be written to file.
-     * @param callback    The callback that will be called once the bitmap is saved.
-     */
-    public static void saveScreenshotToDisk(final Bitmap screenshot, final Context context,
-            final Callback<Uri> callback) {
-        if (screenshot == null) {
-            callback.onResult(null);
-            return;
+    private static class ExternallyVisibleUriCallback implements Callback<String> {
+        private Callback<Uri> mComposedCallback;
+        ExternallyVisibleUriCallback(Callback<Uri> cb) {
+            mComposedCallback = cb;
         }
 
-        new AsyncTask<Void, Void, Uri>() {
-            @Override
-            protected Uri doInBackground(Void... params) {
-                FileOutputStream fOut = null;
-                try {
-                    File path = new File(UiUtils.getDirectoryForImageCapture(context) + "/"
-                            + SHARE_IMAGES_DIRECTORY_NAME);
-                    if (path.exists() || path.mkdir()) {
-                        String fileName = String.valueOf(System.currentTimeMillis());
-                        File saveFile = File.createTempFile(fileName, JPEG_EXTENSION, path);
-                        fOut = new FileOutputStream(saveFile);
-                        screenshot.compress(Bitmap.CompressFormat.JPEG, 85, fOut);
-                        return ApiCompatibilityUtils.getUriForImageCaptureFile(saveFile);
-                    }
-                } catch (IOException ie) {
-                    Log.w(TAG, "Ignoring IOException when saving screenshot.", ie);
-                } finally {
-                    StreamUtil.closeQuietly(fOut);
+        @Override
+        public void onResult(final String path) {
+            if (TextUtils.isEmpty(path)) {
+                mComposedCallback.onResult(null);
+                return;
+            }
+
+            new AsyncTask<Void, Void, Uri>() {
+                @Override
+                protected Uri doInBackground(Void... v) {
+                    return ApiCompatibilityUtils.getUriForImageCaptureFile(new File(path));
                 }
 
-                return null;
+                @Override
+                protected void onPostExecute(Uri uri) {
+                    mComposedCallback.onResult(uri);
+                }
             }
+                    .executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
+        }
+    }
 
-            @Override
-            protected void onPostExecute(Uri fileUri) {
-                fileUri = ApplicationStatus.getStateForApplication()
-                                != ApplicationState.HAS_DESTROYED_ACTIVITIES
-                        ? fileUri
-                        : null;
-                callback.onResult(fileUri);
-            }
-        }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
+    // TODO(yfriedman): Remove after internal tree is updated.
+    public static void saveScreenshotToDisk(
+            Bitmap screenshot, Context context, Callback<Uri> callback) {}
+
+    /**
+     * Captures a screenshot for the provided web contents, persists it and notifies the file
+     * provider that the file is ready to be accessed by the client.
+     *
+     * The screenshot is compressed to JPEG before being written to the file.
+     *
+     * @param contents The WebContents instance for which to capture a screenshot.
+     * @param width    The desired width of the resulting screenshot, or 0 for "auto."
+     * @param height   The desired height of the resulting screenshot, or 0 for "auto."
+     * @param callback The callback that will be called once the screenshot is saved.
+     */
+    public static void captureScreenshotForContents(
+            WebContents contents, int width, int height, Callback<Uri> callback) {
+        try {
+            String path = UiUtils.getDirectoryForImageCapture(ContextUtils.getApplicationContext())
+                    + File.separator + SHARE_IMAGES_DIRECTORY_NAME;
+            contents.getContentBitmapAsync(
+                    width, height, path, new ExternallyVisibleUriCallback(callback));
+        } catch (IOException e) {
+            Log.e(TAG, "Error getting content bitmap: ", e);
+            callback.onResult(null);
+        }
     }
 
     /**

chrome/android/java/src/org/chromium/chrome/browser/share/ShareMenuActionHandler.java

@@ -18,7 +18,6 @@ import org.chromium.chrome.browser.printing.PrintShareActivity;
 import org.chromium.chrome.browser.tab.Tab;
 import org.chromium.chrome.browser.util.ChromeFileProvider;
 import org.chromium.components.ui_metrics.CanonicalURLResult;
-import org.chromium.content_public.browser.ContentBitmapCallback;
 import org.chromium.content_public.browser.WebContents;
 import org.chromium.net.GURLUtils;
 
@@ -196,15 +195,14 @@ public class ShareMenuActionHandler {
         if (blockingUri == null) return;
 
         // Start screenshot capture and notify the provider when it is ready.
-        ContentBitmapCallback callback =
-                (bitmap) -> ShareHelper.saveScreenshotToDisk(bitmap, mainActivity, result -> {
+        Callback<Uri> callback = (saveFile) -> {
             // Unblock the file once it is saved to disk.
-            ChromeFileProvider.notifyFileReady(blockingUri, result);
-        });
+            ChromeFileProvider.notifyFileReady(blockingUri, saveFile);
+        };
         if (sScreenshotCaptureSkippedForTesting) {
-            callback.onFinishGetBitmap(null);
+            callback.onResult(null);
         } else {
-            webContents.getContentBitmapAsync(0, 0, callback);
+            ShareHelper.captureScreenshotForContents(webContents, 0, 0, callback);
         }
     }
 

content/browser/web_contents/web_contents_android.cc

@@ -8,6 +8,7 @@
 #include <string>
 #include <vector>
 
+#include "base/android/callback_android.h"
 #include "base/android/jni_android.h"
 #include "base/android/jni_array.h"
 #include "base/android/jni_string.h"
@@ -16,6 +17,7 @@
 #include "base/json/json_writer.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
+#include "base/task_scheduler/post_task.h"
 #include "content/browser/accessibility/browser_accessibility_android.h"
 #include "content/browser/accessibility/browser_accessibility_manager_android.h"
 #include "content/browser/android/content_view_core.h"
@@ -44,6 +46,7 @@
 #include "ui/android/overscroll_refresh_handler.h"
 #include "ui/android/window_android.h"
 #include "ui/gfx/android/java_bitmap.h"
+#include "ui/gfx/codec/jpeg_codec.h"
 #include "ui/gfx/geometry/point.h"
 #include "ui/gfx/geometry/rect.h"
 
@@ -131,6 +134,34 @@ void AXTreeSnapshotCallback(const ScopedJavaGlobalRef<jobject>& callback,
   Java_WebContentsImpl_onAccessibilitySnapshot(env, j_root, callback);
 }
 
+std::string CompressAndSaveBitmap(const std::string& dir,
+                                  const SkBitmap& bitmap) {
+  base::AssertBlockingAllowed();
+
+  std::vector<unsigned char> data;
+  if (!gfx::JPEGCodec::Encode(bitmap, 85, &data))
+    return std::string();
+
+  base::FilePath screenshot_dir(dir);
+  if (!base::DirectoryExists(screenshot_dir)) {
+    base::CreateDirectory(screenshot_dir);
+  }
+
+  base::FilePath screenshot_path;
+  base::ScopedFILE out_file(
+      base::CreateAndOpenTemporaryFileInDir(screenshot_dir, &screenshot_path));
+  unsigned int bytes_written =
+      fwrite(reinterpret_cast<const char*>(data.data()), 1, data.size(),
+             out_file.get());
+
+  // If there were errors, don't leave a partial file around.
+  if (bytes_written != data.size()) {
+    base::DeleteFile(screenshot_path, false);
+    return std::string();
+  }
+  return screenshot_path.value();
+}
+
 }  // namespace
 
 // static
@@ -589,12 +620,14 @@ void WebContentsAndroid::GetContentBitmap(
     const JavaParamRef<jobject>& obj,
     jint width,
     jint height,
+    const JavaParamRef<jstring>& jpath,
     const JavaParamRef<jobject>& jcallback) {
-  RenderWidgetHostViewAndroid* view = GetRenderWidgetHostViewAndroid();
   base::OnceCallback<void(const SkBitmap&)> result_callback = base::BindOnce(
       &WebContentsAndroid::OnFinishGetContentBitmap, weak_factory_.GetWeakPtr(),
       ScopedJavaGlobalRef<jobject>(env, obj),
-      ScopedJavaGlobalRef<jobject>(env, jcallback));
+      ScopedJavaGlobalRef<jobject>(env, jcallback),
+      ConvertJavaStringToUTF8(env, jpath));
+  RenderWidgetHostViewAndroid* view = GetRenderWidgetHostViewAndroid();
   if (!view) {
     std::move(result_callback).Run(SkBitmap());
     return;
@@ -704,13 +737,22 @@ ScopedJavaLocalRef<jobject> WebContentsAndroid::GetOrCreateEventForwarder(
 void WebContentsAndroid::OnFinishGetContentBitmap(
     const JavaRef<jobject>& obj,
     const JavaRef<jobject>& callback,
+    const std::string& path,
     const SkBitmap& bitmap) {
   JNIEnv* env = base::android::AttachCurrentThread();
   ScopedJavaLocalRef<jobject> java_bitmap;
-  if (!bitmap.drawsNothing())
-    java_bitmap = gfx::ConvertToJavaBitmap(&bitmap);
-  Java_WebContentsImpl_onGetContentBitmapFinished(env, obj, callback,
-                                                  java_bitmap);
+  if (!bitmap.drawsNothing()) {
+    auto task_runner = base::CreateSequencedTaskRunnerWithTraits(
+        {base::MayBlock(), base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN});
+    base::PostTaskAndReplyWithResult(
+        task_runner.get(), FROM_HERE,
+        base::BindOnce(&CompressAndSaveBitmap, path, bitmap),
+        base::BindOnce(&base::android::RunStringCallbackAndroid,
+                       ScopedJavaGlobalRef<jobject>(env, callback.obj())));
+    return;
+  }
+  // If readback failed, call empty callback
+  base::android::RunStringCallbackAndroid(callback, std::string());
 }
 
 void WebContentsAndroid::OnFinishDownloadImage(

content/browser/web_contents/web_contents_android.h

@@ -178,6 +178,7 @@ class CONTENT_EXPORT WebContentsAndroid
                         const base::android::JavaParamRef<jobject>& obj,
                         jint width,
                         jint height,
+                        const base::android::JavaParamRef<jstring>& jpath,
                         const base::android::JavaParamRef<jobject>& jcallback);
 
   void ReloadLoFiImages(JNIEnv* env,
@@ -206,6 +207,7 @@ class CONTENT_EXPORT WebContentsAndroid
   bool IsPictureInPictureAllowedForFullscreenVideo(
       JNIEnv* env,
       const base::android::JavaParamRef<jobject>& obj);
+
   base::android::ScopedJavaLocalRef<jobject> GetFullscreenVideoSize(
       JNIEnv* env,
       const base::android::JavaParamRef<jobject>& obj);
@@ -228,6 +230,7 @@ class CONTENT_EXPORT WebContentsAndroid
 
   void OnFinishGetContentBitmap(const base::android::JavaRef<jobject>& obj,
                                 const base::android::JavaRef<jobject>& callback,
+                                const std::string& path,
                                 const SkBitmap& bitmap);
 
   void OnFinishDownloadImage(const base::android::JavaRef<jobject>& obj,

content/public/android/BUILD.gn

@@ -232,7 +232,6 @@ android_library("content_java") {
     "java/src/org/chromium/content_public/browser/ActionModeCallbackHelper.java",
     "java/src/org/chromium/content_public/browser/ChildProcessUtils.java",
     "java/src/org/chromium/content_public/browser/InputMethodManagerWrapper.java",
-    "java/src/org/chromium/content_public/browser/ContentBitmapCallback.java",
     "java/src/org/chromium/content_public/browser/ContentViewCore.java",
     "java/src/org/chromium/content_public/browser/GestureListenerManager.java",
     "java/src/org/chromium/content_public/browser/GestureStateListener.java",

content/public/android/java/src/org/chromium/content/browser/webcontents/WebContentsImpl.java

@@ -15,6 +15,7 @@ import android.os.ParcelUuid;
 import android.os.Parcelable;
 import android.support.annotation.Nullable;
 
+import org.chromium.base.Callback;
 import org.chromium.base.Log;
 import org.chromium.base.ThreadUtils;
 import org.chromium.base.VisibleForTesting;
@@ -30,7 +31,6 @@ import org.chromium.content.browser.selection.SelectionPopupControllerImpl;
 import org.chromium.content_public.browser.AccessibilitySnapshotCallback;
 import org.chromium.content_public.browser.AccessibilitySnapshotNode;
 import org.chromium.content_public.browser.ChildProcessImportance;
-import org.chromium.content_public.browser.ContentBitmapCallback;
 import org.chromium.content_public.browser.ImageDownloadCallback;
 import org.chromium.content_public.browser.JavaScriptCallback;
 import org.chromium.content_public.browser.MessagePort;
@@ -622,13 +622,9 @@ public class WebContentsImpl implements WebContents, RenderFrameHostDelegate {
     }
 
     @Override
-    public void getContentBitmapAsync(int width, int height, ContentBitmapCallback callback) {
-        nativeGetContentBitmap(mNativeWebContentsAndroid, width, height, callback);
-    }
-
-    @CalledByNative
-    private void onGetContentBitmapFinished(ContentBitmapCallback callback, Bitmap bitmap) {
-        callback.onFinishGetBitmap(bitmap);
+    public void getContentBitmapAsync(
+            int width, int height, String path, Callback<String> callback) {
+        nativeGetContentBitmap(mNativeWebContentsAndroid, width, height, path, callback);
     }
 
     @Override
@@ -827,8 +823,8 @@ public class WebContentsImpl implements WebContents, RenderFrameHostDelegate {
             long nativeWebContentsAndroid, AccessibilitySnapshotCallback callback);
     private native void nativeSetOverscrollRefreshHandler(
             long nativeWebContentsAndroid, OverscrollRefreshHandler nativeOverscrollRefreshHandler);
-    private native void nativeGetContentBitmap(
-            long nativeWebContentsAndroid, int width, int height, ContentBitmapCallback callback);
+    private native void nativeGetContentBitmap(long nativeWebContentsAndroid, int width, int height,
+            String path, Callback<String> callback);
     private native void nativeReloadLoFiImages(long nativeWebContentsAndroid);
     private native int nativeDownloadImage(long nativeWebContentsAndroid,
             String url, boolean isFavicon, int maxBitmapSize,

content/public/android/java/src/org/chromium/content_public/browser/ContentBitmapCallback.java

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-package org.chromium.content_public.browser;
-
-import android.graphics.Bitmap;
-
-/**
-* An interface used to get notified of the completion of content bitmap acquisition.
-*/
-public interface ContentBitmapCallback {
-    /**
-     * Called when bitmap version of the content is acquired.
-     *
-     * @param bitmap content snapshot in the format of {@link Bitmap}, or null
-     *        if the operation failed.
-     */
-    void onFinishGetBitmap(Bitmap bitmap);
-}

content/public/android/java/src/org/chromium/content_public/browser/WebContents.java

@@ -9,6 +9,7 @@ import android.os.Handler;
 import android.os.Parcelable;
 import android.support.annotation.Nullable;
 
+import org.chromium.base.Callback;
 import org.chromium.base.VisibleForTesting;
 import org.chromium.ui.OverscrollRefreshHandler;
 import org.chromium.ui.base.EventForwarder;
@@ -393,10 +394,11 @@ public interface WebContents extends Parcelable {
      *
      * @param width The width of the resulting bitmap, or 0 for "auto."
      * @param height The height of the resulting bitmap, or 0 for "auto."
+     * @param path The folder in which to store the screenshot.
      * @param callback May be called synchronously, or at a later point, to deliver the bitmap
      *                 result (or a failure code).
      */
-    void getContentBitmapAsync(int width, int height, ContentBitmapCallback callback);
+    void getContentBitmapAsync(int width, int height, String path, Callback<String> callback);
 
     /**
      * Reloads all the Lo-Fi images in this WebContents.

content/public/test/android/javatests/src/org/chromium/content/browser/test/mock/MockWebContents.java

@@ -9,8 +9,8 @@ import android.graphics.Rect;
 import android.os.Handler;
 import android.os.Parcel;
 
+import org.chromium.base.Callback;
 import org.chromium.content_public.browser.AccessibilitySnapshotCallback;
-import org.chromium.content_public.browser.ContentBitmapCallback;
 import org.chromium.content_public.browser.ImageDownloadCallback;
 import org.chromium.content_public.browser.JavaScriptCallback;
 import org.chromium.content_public.browser.MessagePort;
@@ -213,7 +213,8 @@ public class MockWebContents implements WebContents {
     public void setOverscrollRefreshHandler(OverscrollRefreshHandler handler) {}
 
     @Override
-    public void getContentBitmapAsync(int width, int height, ContentBitmapCallback callback) {}
+    public void getContentBitmapAsync(
+            int width, int height, String path, Callback<String> callback) {}
 
     @Override
     public void reloadLoFiImages() {}