BaseDOMElementFactory.java

/*
 * Copyright 2015 Red Hat, Inc. and/or its affiliates.
 *
 * 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 org.uberfire.ext.wires.core.grids.client.widget.dom.multiple.impl;

import java.util.ArrayList;
import java.util.List;

import com.google.gwt.user.client.ui.Widget;
import org.uberfire.client.callbacks.Callback;
import org.uberfire.ext.wires.core.grids.client.widget.context.GridBodyCellRenderContext;
import org.uberfire.ext.wires.core.grids.client.widget.dom.impl.BaseDOMElement;
import org.uberfire.ext.wires.core.grids.client.widget.dom.multiple.MultipleDOMElementFactory;
import org.uberfire.ext.wires.core.grids.client.widget.grid.GridWidget;
import org.uberfire.ext.wires.core.grids.client.widget.layer.GridLayer;

/**
 * Base Factory for multi-instance DOMElements, i.e. there can be more than one "on screen" at any given time.
 * This implementation keeps track of a List of DOMElements used during a render phase. DOMElements are re-used
 * for subsequent render phases, freeing unused DOMElements at the end of the render phase. When a column
 * is not rendered all DOMElements are destroyed.
 * @param <T> The data-type of the cell
 * @param <W> The Widget to be wrapped by the DOMElement.
 * @param <E> The DOMElement type that this Factory generates.
 */
public abstract class BaseDOMElementFactory<T, W extends Widget, E extends BaseDOMElement<T, W>> implements MultipleDOMElementFactory<W, E> {

    protected final GridLayer gridLayer;
    protected final GridWidget gridWidget;

    protected final List<E> domElements = new ArrayList<E>();

    private int consumed = 0;

    public BaseDOMElementFactory(final GridLayer gridLayer,
                                 final GridWidget gridWidget) {
        this.gridLayer = gridLayer;
        this.gridWidget = gridWidget;
    }

    @Override
    public void attachDomElement(final GridBodyCellRenderContext context,
                                 final Callback<E> onCreation,
                                 final Callback<E> onDisplay) {
        E domElement;
        if (consumed + 1 > domElements.size()) {
            domElement = createDomElement(gridLayer,
                                          gridWidget,
                                          context);
            domElements.add(domElement);
        } else {
            domElement = domElements.get(consumed);
        }
        consumed++;

        domElement.setContext(context);
        domElement.initialise(context);
        onCreation.callback(domElement);

        domElement.attach();
        onDisplay.callback(domElement);
    }

    @Override
    public void initialiseResources() {
        consumed = 0;
    }

    @Override
    public void destroyResources() {
        for (E domElement : domElements) {
            domElement.detach();
        }
        domElements.clear();
        consumed = 0;
    }

    @Override
    public void freeUnusedResources() {
        final List<E> freedDomElements = new ArrayList<E>();
        for (int i = consumed; i < domElements.size(); i++) {
            final E domElement = domElements.get(i);
            domElement.detach();
            freedDomElements.add(domElement);
        }
        for (E domElement : freedDomElements) {
            domElements.remove(domElement);
        }
    }
}