Add Wallpaper scale methods to be used by WallpaperPicker

Bug: 151868130
Test: manual
Change-Id: I13fe94ca8c1f1feb733bfc0d189ff18c9036c4a3

packages/SystemUI/shared/src/com/android/systemui/shared/system/WallpaperEngineCompat.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2020 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.systemui.shared.system;
+
+import android.graphics.Rect;
+import android.os.RemoteException;
+import android.service.wallpaper.IWallpaperEngine;
+import android.util.Log;
+
+/**
+ * @see IWallpaperEngine
+ */
+public class WallpaperEngineCompat {
+
+    private static final String TAG = "WallpaperEngineCompat";
+
+    private final IWallpaperEngine mWrappedEngine;
+
+    public WallpaperEngineCompat(IWallpaperEngine wrappedEngine) {
+        mWrappedEngine = wrappedEngine;
+    }
+
+    /**
+     * @see IWallpaperEngine#scalePreview(Rect)
+     */
+    public void scalePreview(Rect scaleToRect) {
+        try {
+            mWrappedEngine.scalePreview(scaleToRect);
+        } catch (RemoteException e) {
+            Log.i(TAG, "Couldn't call scalePreview method on WallpaperEngine", e);
+        }
+    }
+}

packages/SystemUI/shared/src/com/android/systemui/shared/system/WallpaperManagerCompat.java

@@ -36,4 +36,12 @@ public class WallpaperManagerCompat {
     public void setWallpaperZoomOut(IBinder windowToken, float zoom) {
         mWallpaperManager.setWallpaperZoomOut(windowToken, zoom);
     }
+
+    /**
+     * @return the max scale for the wallpaper when it's fully zoomed out
+     */
+    public static float getWallpaperZoomOutMaxScale(Context context) {
+        return context.getResources()
+                .getFloat(com.android.internal.R.dimen.config_wallpaperMaxScale);
+    }
 }