Don't restore wildly wrong sized wallpapers

If the dimensions of the original are sufficiently different from the
device's preferred dimensions, just don't restore the image.  This
avoids bad letterboxing / clipping on e.g. phone <-> tablet data
migration.

The expansion/shrinkage ratios used here allow restores of saved
wallpaper images among HVGA devices, among WVGA variants, and
among tablets; but skip restoring wallpapers across those
categories (where severe clipping or letterboxing would occur).

Bug 3261863

Change-Id: I75e75d6401d18f1df10d75796ee04e21d2302cfa

2 files changed, 126 insertions, 1 deletions

diff --git a/core/java/android/app/backup/FileBackupHelperBase.java b/core/java/android/app/backup/FileBackupHelperBase.java
index 1e3158f..887a2e6 100644
--- a/core/java/android/app/backup/FileBackupHelperBase.java
+++ b/core/java/android/app/backup/FileBackupHelperBase.java
@@ -81,7 +81,7 @@ class FileBackupHelperBase {
         }
     }
 
-    void writeFile(File f, BackupDataInputStream in) {
+    boolean writeFile(File f, BackupDataInputStream in) {
         int result = -1;
 
         // Create the enclosing directory.
@@ -98,6 +98,7 @@ class FileBackupHelperBase {
                 mExceptionLogged = true;
             }
         }
+        return (result == 0);
     }
 
     public void writeNewStateDescription(ParcelFileDescriptor fd) {
diff --git a/core/java/android/app/backup/WallpaperBackupHelper.java b/core/java/android/app/backup/WallpaperBackupHelper.java
new file mode 100644
index 0000000..9808200
--- /dev/null
+++ b/core/java/android/app/backup/WallpaperBackupHelper.java
@@ -0,0 +1,124 @@
+/*
+ * 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.app.backup;
+
+import android.app.WallpaperManager;
+import android.content.Context;
+import android.graphics.BitmapFactory;
+import android.os.ParcelFileDescriptor;
+import android.util.Slog;
+
+import java.io.File;
+
+/**
+ * Helper for backing up / restoring wallpapers.  Basically an AbsoluteFileBackupHelper,
+ * but with logic for deciding what to do with restored wallpaper images.
+ *
+ * @hide
+ */
+public class WallpaperBackupHelper extends FileBackupHelperBase implements BackupHelper {
+    private static final String TAG = "WallpaperBackupHelper";
+    private static final boolean DEBUG = false;
+
+    // This path must match what the WallpaperManagerService uses
+    private static final String WALLPAPER_IMAGE = "/data/data/com.android.settings/files/wallpaper";
+
+    // Stage file - should be adjacent to the WALLPAPER_IMAGE location.  The wallpapers
+    // will be saved to this file from the restore stream, then renamed to the proper
+    // location if it's deemed suitable.
+    private static final String STAGE_FILE = "/data/data/com.android.settings/files/wallpaper-tmp";
+
+    Context mContext;
+    String[] mFiles;
+    double mDesiredMinWidth;
+    double mDesiredMinHeight;
+
+    /**
+     * Construct a helper for backing up / restoring the files at the given absolute locations
+     * within the file system.
+     *
+     * @param context
+     * @param files
+     */
+    public WallpaperBackupHelper(Context context, String... files) {
+        super(context);
+
+        mContext = context;
+        mFiles = files;
+
+        WallpaperManager wpm;
+        wpm = (WallpaperManager) context.getSystemService(Context.WALLPAPER_SERVICE);
+        mDesiredMinWidth = (double) wpm.getDesiredMinimumWidth();
+        mDesiredMinHeight = (double) wpm.getDesiredMinimumHeight();
+    }
+
+    /**
+     * Based on oldState, determine which of the files from the application's data directory
+     * need to be backed up, write them to the data stream, and fill in newState with the
+     * state as it exists now.
+     */
+    public void performBackup(ParcelFileDescriptor oldState, BackupDataOutput data,
+            ParcelFileDescriptor newState) {
+        performBackup_checked(oldState, data, newState, mFiles, mFiles);
+    }
+
+    /**
+     * Restore one absolute file entity from the restore stream.  If we're restoring the
+     * magic wallpaper file, take specific action to determine whether it is suitable for
+     * the current device.
+     */
+    public void restoreEntity(BackupDataInputStream data) {
+        final String key = data.getKey();
+        if (isKeyInList(key, mFiles)) {
+            if (key.equals(WALLPAPER_IMAGE)) {
+                // restore the file to the stage for inspection
+                File f = new File(STAGE_FILE);
+                if (writeFile(f, data)) {
+
+                    // Preflight the restored image's dimensions without loading it
+                    BitmapFactory.Options options = new BitmapFactory.Options();
+                    options.inJustDecodeBounds = true;
+                    BitmapFactory.decodeFile(STAGE_FILE, options);
+
+                    if (DEBUG) Slog.v(TAG, "Restoring wallpaper image w=" + options.outWidth
+                            + " h=" + options.outHeight);
+
+                    // how much does the image differ from our preference?
+                    double widthRatio = mDesiredMinWidth / options.outWidth;
+                    double heightRatio = mDesiredMinHeight / options.outHeight;
+                    if (widthRatio > 0.8 && widthRatio < 1.25
+                            && heightRatio > 0.8 && heightRatio < 1.25) {
+                        // sufficiently close to our resolution; go ahead and use it
+                        if (DEBUG) Slog.v(TAG, "wallpaper dimension match; using");
+                        f.renameTo(new File(WALLPAPER_IMAGE));
+                        // TODO: spin a service to copy the restored image to sd/usb storage,
+                        // since it does not exist anywhere other than the private wallpaper
+                        // file.
+                    } else {
+                        if (DEBUG) Slog.v(TAG, "dimensions too far off: wr=" + widthRatio
+                                + " hr=" + heightRatio);
+                        f.delete();
+                    }
+                }
+            } else {
+                // Some other normal file; just decode it to its destination
+                File f = new File(key);
+                writeFile(f, data);
+            }
+        }
+    }
+}