Render user's actual workspace in ThemePicker preview (Part 1)

This change takes care of icon rendering. Further work still needs to be done for folders and widgets.

Test: Go to grid options, choose a different grid option, and see user's workspace rendered in the preview
Bug: 144052839
Change-Id: I696153dec1d1f08c5ac82d0c75be5740325c0fc4

src/com/android/launcher3/model/ModelUtils.java

@@ -0,0 +1,112 @@
+/*
+ * 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.model;
+
+import com.android.launcher3.InvariantDeviceProfile;
+import com.android.launcher3.ItemInfo;
+import com.android.launcher3.LauncherSettings;
+import com.android.launcher3.config.FeatureFlags;
+import com.android.launcher3.util.IntSet;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Iterator;
+
+/**
+ * Utils class for {@link com.android.launcher3.LauncherModel}.
+ */
+public class ModelUtils {
+
+    /**
+     * Filters the set of items who are directly or indirectly (via another container) on the
+     * specified screen.
+     */
+    public static <T extends ItemInfo> void filterCurrentWorkspaceItems(int currentScreenId,
+            ArrayList<T> allWorkspaceItems,
+            ArrayList<T> currentScreenItems,
+            ArrayList<T> otherScreenItems) {
+        // Purge any null ItemInfos
+        Iterator<T> iter = allWorkspaceItems.iterator();
+        while (iter.hasNext()) {
+            ItemInfo i = iter.next();
+            if (i == null) {
+                iter.remove();
+            }
+        }
+        // Order the set of items by their containers first, this allows use to walk through the
+        // list sequentially, build up a list of containers that are in the specified screen,
+        // as well as all items in those containers.
+        IntSet itemsOnScreen = new IntSet();
+        Collections.sort(allWorkspaceItems,
+                (lhs, rhs) -> Integer.compare(lhs.container, rhs.container));
+        for (T info : allWorkspaceItems) {
+            if (info.container == LauncherSettings.Favorites.CONTAINER_DESKTOP) {
+                if (info.screenId == currentScreenId) {
+                    currentScreenItems.add(info);
+                    itemsOnScreen.add(info.id);
+                } else {
+                    otherScreenItems.add(info);
+                }
+            } else if (info.container == LauncherSettings.Favorites.CONTAINER_HOTSEAT) {
+                currentScreenItems.add(info);
+                itemsOnScreen.add(info.id);
+            } else {
+                if (itemsOnScreen.contains(info.container)) {
+                    currentScreenItems.add(info);
+                    itemsOnScreen.add(info.id);
+                } else {
+                    otherScreenItems.add(info);
+                }
+            }
+        }
+    }
+
+    /**
+     * Sorts the set of items by hotseat, workspace (spatially from top to bottom, left to right)
+     */
+    public static void sortWorkspaceItemsSpatially(InvariantDeviceProfile profile,
+            ArrayList<ItemInfo> workspaceItems) {
+        final int screenCols = profile.numColumns;
+        final int screenCellCount = profile.numColumns * profile.numRows;
+        Collections.sort(workspaceItems, (lhs, rhs) -> {
+            if (lhs.container == rhs.container) {
+                // Within containers, order by their spatial position in that container
+                switch (lhs.container) {
+                    case LauncherSettings.Favorites.CONTAINER_DESKTOP: {
+                        int lr = (lhs.screenId * screenCellCount + lhs.cellY * screenCols
+                                + lhs.cellX);
+                        int rr = (rhs.screenId * screenCellCount + +rhs.cellY * screenCols
+                                + rhs.cellX);
+                        return Integer.compare(lr, rr);
+                    }
+                    case LauncherSettings.Favorites.CONTAINER_HOTSEAT: {
+                        // We currently use the screen id as the rank
+                        return Integer.compare(lhs.screenId, rhs.screenId);
+                    }
+                    default:
+                        if (FeatureFlags.IS_DOGFOOD_BUILD) {
+                            throw new RuntimeException(
+                                    "Unexpected container type when sorting workspace items.");
+                        }
+                        return 0;
+                }
+            } else {
+                // Between containers, order by hotseat, desktop
+                return Integer.compare(lhs.container, rhs.container);
+            }
+        });
+    }
+}