Show icons for apps bypassing DND

(Several things pending, such as the +n icon and the correct pending icons, but it's a start).

Test: atest com.android.settings.notification.modes
Bug: 346551087
Flag: android.app.modes_ui
Change-Id: Ifd2ab6a8bb447739dc8ffe400c3960779d477fd6

src/com/android/settings/notification/modes/CircularIconSet.java

@@ -0,0 +1,98 @@
+/*
+ * Copyright (C) 2024 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.settings.notification.modes;
+
+import android.graphics.Color;
+import android.graphics.drawable.ColorDrawable;
+import android.graphics.drawable.Drawable;
+
+import androidx.annotation.VisibleForTesting;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.util.concurrent.ListenableFuture;
+import com.google.common.util.concurrent.ListeningExecutorService;
+import com.google.common.util.concurrent.MoreExecutors;
+
+import java.util.List;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.function.Function;
+
+/**
+ * A set of icons to be displayed in a {@link CircularIconsPreference}
+ *
+ * @param <T> The type of the items in the set. Can be an arbitrary type, the only requirement
+ *           being that the {@code drawableLoader} supplied to the constructor is able to produce
+ *           a {@link Drawable} from it (for example a resource id, a Content Uri, etc).
+ */
+class CircularIconSet<T> {
+
+    @VisibleForTesting // Can be set by tests, before creating instances.
+    static ExecutorService sExecutorService = Executors.newCachedThreadPool();
+
+    static final CircularIconSet<?> EMPTY = new CircularIconSet<>(ImmutableList.of(),
+            unused -> new ColorDrawable(Color.BLACK));
+
+    private final ImmutableList<T> mItems;
+    private final Function<T, Drawable> mDrawableLoader;
+    private final ListeningExecutorService mBackgroundExecutor;
+
+    private final ConcurrentHashMap<T, Drawable> mCachedIcons;
+
+    CircularIconSet(List<T> items, Function<T, Drawable> drawableLoader) {
+        mItems = ImmutableList.copyOf(items);
+        mDrawableLoader = drawableLoader;
+        mBackgroundExecutor = MoreExecutors.listeningDecorator(sExecutorService);
+        mCachedIcons = new ConcurrentHashMap<>();
+    }
+
+    int size() {
+        return mItems.size();
+    }
+
+    /**
+     * Loads all icons from the set, using the supplied {@code drawableLoader}, in a background
+     * thread.
+     */
+    List<ListenableFuture<Drawable>> getIcons() {
+        return getIcons(Integer.MAX_VALUE);
+    }
+
+    /**
+     * Loads up to {@code maxSize} icons from the set, using the supplied {@code drawableLoader}, in
+     * a background thread.
+     */
+    List<ListenableFuture<Drawable>> getIcons(int maxNumber) {
+        return mItems.stream().limit(maxNumber)
+                .map(this::loadIcon)
+                .toList();
+    }
+
+    private ListenableFuture<Drawable> loadIcon(T item) {
+        return mBackgroundExecutor.submit(() -> {
+            if (mCachedIcons.containsKey(item)) {
+                return mCachedIcons.get(item);
+            }
+            Drawable drawable = mDrawableLoader.apply(item);
+            if (drawable != null) {
+                mCachedIcons.put(item, drawable);
+            }
+            return drawable;
+        });
+    }
+}