Using the first frame delay based on the display refresh rate instead of

hardcoding it to 16ms

> Creating a utility class for caching display property changes

Bug: 128940249
Change-Id: I6f9a214548de65bd1c8530508d665ee88312da4a

src/com/android/launcher3/util/DefaultDisplay.java

@@ -0,0 +1,166 @@
+/*
+ * Copyright (C) 2019 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.launcher3.util;
+
+import android.content.Context;
+import android.graphics.Point;
+import android.hardware.display.DisplayManager;
+import android.hardware.display.DisplayManager.DisplayListener;
+import android.os.Handler;
+import android.os.Message;
+import android.util.Log;
+import android.view.Display;
+import android.view.WindowManager;
+
+import java.util.ArrayList;
+
+/**
+ * Utility class to cache properties of default display to avoid a system RPC on every call.
+ */
+public class DefaultDisplay implements DisplayListener {
+
+    public static final MainThreadInitializedObject<DefaultDisplay> INSTANCE =
+            new MainThreadInitializedObject<>(DefaultDisplay::new);
+
+    private static final String TAG = "DefaultDisplay";
+
+    public static final int CHANGE_SIZE = 1 << 0;
+    public static final int CHANGE_ROTATION = 1 << 1;
+    public static final int CHANGE_FRAME_DELAY = 1 << 2;
+
+    private final Context mContext;
+    private final int mId;
+    private final ArrayList<DisplayInfoChangeListener> mListeners = new ArrayList<>();
+    private final Handler mChangeHandler;
+    private Info mInfo;
+
+    private DefaultDisplay(Context context) {
+        mContext = context;
+        mInfo = new Info(context);
+        mId = mInfo.id;
+        mChangeHandler = new Handler(this::onChange);
+
+        context.getSystemService(DisplayManager.class)
+                .registerDisplayListener(this, new Handler(UiThreadHelper.getBackgroundLooper()));
+    }
+
+    @Override
+    public final void onDisplayAdded(int displayId) {  }
+
+    @Override
+    public final void onDisplayRemoved(int displayId) { }
+
+    @Override
+    public final void onDisplayChanged(int displayId) {
+        if (displayId != mId) {
+            return;
+        }
+
+        Info oldInfo = mInfo;
+        Info info = new Info(mContext);
+
+        int change = 0;
+        if (info.hasDifferentSize(oldInfo)) {
+            change |= CHANGE_SIZE;
+        }
+        if (oldInfo.rotation != info.rotation) {
+            change |= CHANGE_ROTATION;
+        }
+        if (info.singleFrameMs != oldInfo.singleFrameMs) {
+            change |= CHANGE_FRAME_DELAY;
+        }
+
+        if (change != 0) {
+            mInfo = info;
+            mChangeHandler.sendEmptyMessage(change);
+        }
+    }
+
+    public static int getSingleFrameMs(Context context) {
+        return INSTANCE.get(context).getInfo().singleFrameMs;
+    }
+
+    public Info getInfo() {
+        return mInfo;
+    }
+
+    public void addChangeListener(DisplayInfoChangeListener listener) {
+        mListeners.add(listener);
+    }
+
+    public void removeChangeListener(DisplayInfoChangeListener listener) {
+        mListeners.remove(listener);
+    }
+
+    private boolean onChange(Message msg) {
+        for (int i = mListeners.size() - 1; i >= 0; i--) {
+            mListeners.get(i).onDisplayInfoChanged(mInfo, msg.what);
+        }
+        return true;
+    }
+
+    public static class Info {
+
+        public final int id;
+        public final int rotation;
+        public final int singleFrameMs;
+
+        public final Point realSize;
+        public final Point smallestSize;
+        public final Point largestSize;
+
+        private Info(Context context) {
+            Display display = context.getSystemService(WindowManager.class).getDefaultDisplay();
+
+            id = display.getDisplayId();
+            rotation = display.getRotation();
+
+            float refreshRate = display.getRefreshRate();
+            singleFrameMs = refreshRate > 0 ? (int) (1000 / refreshRate) : 16;
+
+            realSize = new Point();
+            smallestSize = new Point();
+            largestSize = new Point();
+            display.getRealSize(realSize);
+            display.getCurrentSizeRange(smallestSize, largestSize);
+        }
+
+        private boolean hasDifferentSize(Info info) {
+            if (!realSize.equals(info.realSize)
+                    && !realSize.equals(info.realSize.y, info.realSize.x)) {
+                Log.d(TAG, String.format("Display size changed from %s to %s",
+                        info.realSize, realSize));
+                return true;
+            }
+
+            if (!smallestSize.equals(info.smallestSize) || !largestSize.equals(info.largestSize)) {
+                Log.d(TAG, String.format("Available size changed from [%s, %s] to [%s, %s]",
+                        smallestSize, largestSize, info.smallestSize, info.largestSize));
+                return true;
+            }
+
+            return false;
+        }
+    }
+
+    /**
+     * Interface for listening for display changes
+     */
+    public interface DisplayInfoChangeListener {
+
+        void onDisplayInfoChanged(Info info, int flags);
+    }
+}