com.google.gapid.util.Trees.java Source code

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Here is the source code for com.google.gapid.util.Trees.java

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/*
 * Copyright (C) 2017 Google Inc.
 *
 * 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.google.gapid.util;

import static com.google.gapid.util.GeoUtils.bottom;
import static java.util.Collections.emptySet;

import com.google.common.collect.Sets;

import org.eclipse.swt.widgets.Tree;
import org.eclipse.swt.widgets.TreeItem;

import java.util.Set;

/**
 * Utilities for dealing with {@link Tree Trees} and {@link TreeItem TreeItems}.
 */
public class Trees {
    private Trees() {
    }

    /**
     * @return the {@link TreeItem TreeItems} that are currently visible in the tree.
     */
    public static Set<TreeItem> getVisibleItems(Tree tree) {
        TreeItem top = tree.getTopItem();
        if (top == null) {
            // Work around bug where getTopItem() returns null when scrolling
            // up past the top item (elastic scroll).
            return (tree.getItemCount() != 0) ? null : emptySet();
        }

        int treeBottom = bottom(tree.getClientArea());
        Set<TreeItem> visible = Sets.newIdentityHashSet();
        if (!getVisibleItems(top, treeBottom, visible)) {
            do {
                top = getVisibleSiblings(top, treeBottom, visible);
            } while (top != null);
        }
        return visible;
    }

    /**
     * Adds the given item and all visible descendants into the given set.
     * @return whether the bottom has been reached.
     */
    private static boolean getVisibleItems(TreeItem item, int treeBottom, Set<TreeItem> visible) {
        visible.add(item);
        if (bottom(item.getBounds()) > treeBottom) {
            return true;
        }

        if (item.getExpanded()) {
            for (TreeItem child : item.getItems()) {
                if (getVisibleItems(child, treeBottom, visible)) {
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * Adds all visible siblings (and their visible descendants) into the given set.
     * @return the next parent or {@code null} if the bottom has been reached.
     */
    private static TreeItem getVisibleSiblings(TreeItem item, int treeBottom, Set<TreeItem> visible) {
        TreeItem parent = item.getParentItem();
        TreeItem[] siblings = (parent == null) ? item.getParent().getItems() : parent.getItems();
        int idx = 0;
        for (; idx < siblings.length && siblings[idx] != item; idx++) {
            // Do nothing.
        }
        for (idx++; idx < siblings.length; idx++) {
            if (getVisibleItems(siblings[idx], treeBottom, visible)) {
                return null;
            }
        }
        return parent;
    }
}