DropdownActionButton.java

package org.ovirt.engine.ui.common.widget.action;

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

import org.ovirt.engine.core.common.utils.Pair;
import org.ovirt.engine.ui.common.CommonApplicationResources;
import org.ovirt.engine.ui.common.gin.AssetProvider;
import org.ovirt.engine.ui.common.utils.ElementTooltipUtils;

import com.google.gwt.core.client.GWT;
import com.google.gwt.resources.client.CssResource;
import com.google.gwt.uibinder.client.UiBinder;
import com.google.gwt.uibinder.client.UiField;
import com.google.gwt.user.client.ui.FocusPanel;
import com.google.gwt.user.client.ui.Image;
import com.google.gwt.user.client.ui.MenuItem;
import com.google.gwt.user.client.ui.ToggleButton;

public class DropdownActionButton<T> extends AbstractActionButton {

    interface WidgetUiBinder extends UiBinder<FocusPanel, DropdownActionButton> {
        WidgetUiBinder uiBinder = GWT.create(WidgetUiBinder.class);
    }

    @UiField
    Style style;

    @UiField
    FocusPanel container;

    @UiField(provided = true)
    ToggleButton dropdownButton;

    MenuPanelPopup menuPopup;

    private List<Pair<MenuItem, ActionButtonDefinition<T>>> items = new ArrayList<>();

    private final SelectedItemsProvider<T> selectedItemsProvider;

    private static final CommonApplicationResources resources = AssetProvider.getResources();

    public DropdownActionButton(List<ActionButtonDefinition<T>> actions, SelectedItemsProvider<T> selectedItemsProvider) {
        this.selectedItemsProvider = selectedItemsProvider;

        initDropdownButton();
        initWidget(WidgetUiBinder.uiBinder.createAndBindUi(this));
        initMenuPopup(actions);
        addMouseHandlers();
    }

    private void initDropdownButton() {
        dropdownButton = new ToggleButton(new Image(resources.triangle_down()));
        dropdownButton.addClickHandler(event -> {
            if (dropdownButton.isDown()) {
                menuPopup.asPopupPanel().showRelativeToAndFitToScreen(container);
            } else {
                menuPopup.asPopupPanel().hide();
            }
        });
    }

    private void initMenuPopup(List<ActionButtonDefinition<T>> actions) {
        menuPopup = new MenuPanelPopup(true);

        for (final ActionButtonDefinition<T> buttonDef : actions) {
            MenuItem menuItem = new MenuItem(buttonDef.getText(), () -> {
                menuPopup.asPopupPanel().hide();
                buttonDef.onClick(selectedItemsProvider.getSelectedItems());
            });
            menuItem.addStyleName(style.menuItem());
            updateMenuItem(menuItem, buttonDef, selectedItemsProvider.getSelectedItems());
            menuPopup.getMenuBar().addItem(menuItem);

            items.add(new Pair<>(menuItem, buttonDef));
        }

        menuPopup.asPopupPanel().setAutoHideEnabled(true);
        menuPopup.asPopupPanel().addAutoHidePartner(dropdownButton.getElement());
        menuPopup.asPopupPanel().addCloseHandler(event -> dropdownButton.setDown(false));
    }

    /**
     * Ensures that the specified action button is visible or hidden and enabled or disabled as it should.
     */
    void updateMenuItem(MenuItem item, ActionButtonDefinition<T> buttonDef, List selectedItems) {
        item.setVisible(buttonDef.isAccessible(selectedItems) && buttonDef.isVisible(selectedItems));
        item.setEnabled(buttonDef.isEnabled(selectedItems));

        if (buttonDef.getTooltip() != null) {
            ElementTooltipUtils.setTooltipOnElement(item.getElement(), buttonDef.getTooltip());
        }
    }

    private void addMouseHandlers() {
        button.addClickHandler(event -> {
            container.removeStyleName(style.buttonMouseOver());
            container.addStyleName(style.buttonMouseOut());
        });

        container.addMouseOverHandler(event -> {
            if (isEnabled()) {
                container.removeStyleName(style.buttonMouseOut());
                container.addStyleName(style.buttonMouseOver());
            }
        });

        container.addMouseOutHandler(event -> {
            container.removeStyleName(style.buttonMouseOver());
            container.addStyleName(style.buttonMouseOut());
        });
    }

    @Override
    public void setEnabled(boolean enabled) {
        button.setEnabled(enabled);
        for (Pair<MenuItem, ActionButtonDefinition<T>> item : items) {
            updateMenuItem(item.getFirst(), item.getSecond(), selectedItemsProvider.getSelectedItems());
        }

        dropdownButton.setEnabled(enabled);
    }

    interface Style extends CssResource {
        String buttonMouseOver();

        String buttonMouseOut();

        String menuItem();
    }

    public interface SelectedItemsProvider<T> {
        List<T> getSelectedItems();
    }

}