com.google.gwt.i18n.client.AutoDirectionHandler.java Source code

Introduction

Here is the source code for com.google.gwt.i18n.client.AutoDirectionHandler.java

Source

/*
 * Copyright 2010 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.gwt.i18n.client;

import com.google.gwt.event.dom.client.HasKeyUpHandlers;
import com.google.gwt.event.dom.client.KeyUpEvent;
import com.google.gwt.event.dom.client.KeyUpHandler;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.i18n.client.HasDirection.Direction;
import com.google.gwt.i18n.shared.DirectionEstimator;
import com.google.gwt.i18n.shared.HasDirectionEstimator;
import com.google.gwt.i18n.shared.WordCountDirectionEstimator;
import com.google.gwt.user.client.ui.HasText;

/**
 * Utility class for handling auto-direction adjustment.
 *
 * This class is useful for automatically adjusting the direction of an object
 * that takes text input, while the text is being entered.
 */
public class AutoDirectionHandler implements KeyUpHandler, HasDirectionEstimator {

    /**
     * The interface an object must implement in order to add an
     * AutoDirectionHandler to it.
     *
     * TODO(tomerigo): add Paste and Input events once they're available in GWT.
     */
    public interface Target extends HasText, HasDirection, HasKeyUpHandlers {
    }

    /**
     * Operates like {@link #addTo(Target, DirectionEstimator)}, but always uses
     * a default DirectionEstimator, {@link
     * com.google.gwt.i18n.shared.WordCountDirectionEstimator}.
     *
     * @param target Object whose direction should be automatically adjusted on
     *     relevant events.
     * @return AutoDirectionHandler An instance of AutoDirectionHandler for the
     *     given object.
     */
    public static AutoDirectionHandler addTo(Target target) {
        return addTo(target, true);
    }

    /**
     * Operates like {@link #addTo(Target, DirectionEstimator)}, but uses a
     * default DirectionEstimator, {@link
     * com.google.gwt.i18n.shared.WordCountDirectionEstimator} if {@code enabled},
     * or else a null DirectionEstimator, which means disabling direction
     * estimation.
     *
     * @param target Object whose direction should be automatically adjusted on
     *     relevant events.
     * @param enabled Whether the handler is enabled upon creation.
     * @return AutoDirectionHandler An instance of AutoDirectionHandler for the
     *     given object.
     */
    public static AutoDirectionHandler addTo(Target target, boolean enabled) {
        return addTo(target, enabled ? WordCountDirectionEstimator.get() : null);
    }

    /**
     * Adds auto-direction adjustment to a given object:
     * - Creates an AutoDirectionHandler.
     * - Initializes it with the given DirectionEstimator.
     * - Adds it as an event handler for the relevant events on the given object.
     * - Returns the AutoDirectionHandler, so its setAutoDir() method can be
     * called when the object's text changes by means other than the handled
     * events.
     *
     * @param target Object whose direction should be automatically adjusted on
     *     relevant events.
     * @param directionEstimator A DirectionEstimator object used for direction
     *     estimation (use null to disable direction estimation).
     * @return AutoDirectionHandler An instance of AutoDirectionHandler for the
     *     given object.
     */
    public static AutoDirectionHandler addTo(Target target, DirectionEstimator directionEstimator) {
        AutoDirectionHandler autoDirHandler = new AutoDirectionHandler(target, directionEstimator);
        return autoDirHandler;
    }

    /**
     * A DirectionEstimator object used for direction estimation.
     */
    private DirectionEstimator directionEstimator;

    /**
     * A HandlerRegistration object used to remove this handler.
     */
    private HandlerRegistration handlerRegistration;

    /**
     * The object being handled.
     */
    private Target target;

    /**
     * Private constructor. Instantiate using one of the addTo() methods.
     *
     * @param target Object whose direction should be automatically adjusted on
     *     relevant events.
     * @param directionEstimator A DirectionEstimator object used for direction
     *     estimation.
     */
    private AutoDirectionHandler(Target target, DirectionEstimator directionEstimator) {
        this.target = target;
        this.handlerRegistration = null;
        setDirectionEstimator(directionEstimator);
    }

    /**
     * Returns the DirectionEstimator object.
     */
    public DirectionEstimator getDirectionEstimator() {
        return directionEstimator;
    }

    /**
     * Automatically adjusts hasDirection's direction on KeyUpEvent events.
     * Implementation of KeyUpHandler interface method.
     */
    public void onKeyUp(KeyUpEvent event) {
        refreshDirection();
    }

    /**
     * Adjusts target's direction according to the estimated direction of the text
     * it supplies.
     */
    public void refreshDirection() {
        if (directionEstimator != null) {
            Direction dir = directionEstimator.estimateDirection(target.getText());
            if (dir != target.getDirection()) {
                target.setDirection(dir);
            }
        }
    }

    /**
     * Toggles direction estimation on (using a default estimator) and off.
     */
    public void setDirectionEstimator(boolean enabled) {
        setDirectionEstimator(enabled ? WordCountDirectionEstimator.get() : null);
    }

    /**
     * Sets the DirectionEstimator object.
     */
    public void setDirectionEstimator(DirectionEstimator directionEstimator) {
        this.directionEstimator = directionEstimator;
        if ((directionEstimator == null) != (handlerRegistration == null)) {
            if (directionEstimator == null) {
                handlerRegistration.removeHandler();
                handlerRegistration = null;
            } else {
                handlerRegistration = target.addKeyUpHandler(this);
            }
        }
        refreshDirection();
    }
}