com.google.gwt.user.client.ui.HasHorizontalAlignment.java Source code

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Here is the source code for com.google.gwt.user.client.ui.HasHorizontalAlignment.java

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/*
 * Copyright 2008 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.user.client.ui;

import com.google.gwt.core.client.GWT;
import com.google.gwt.i18n.client.HasDirection.Direction;
import com.google.gwt.i18n.client.LocaleInfo;

/**
 * Characteristic interface which indicates that a widget can be aligned
 * horizontally.
 * 
 * <h3>Use in UiBinder Templates</h3>
 * 
 * <p>
 * The names of the static members of {@link HorizontalAlignmentConstant}, as
 * well as simple alignment names (<code>left</code>, <code>center</code>,
 * <code>right</code>, <code>justify</code>), can be used as values for a
 * <code>horizontalAlignment</code> attribute of any widget that implements this
 * interface. (In fact, this will work for any widget method that takes a single
 * HorizontalAlignmentConstant value.)
 * <p>
 * For example,
 * 
 * <pre>
 * &lt;g:Label horizontalAlignment='ALIGN_RIGHT'>Hi there.&lt;/g:Label>
 * &lt;g:Label horizontalAlignment='right'>Hi there.&lt;/g:Label>
 * </pre>
 */
public interface HasHorizontalAlignment {

    /**
     * Type for values defined and used in {@link HasAutoHorizontalAlignment}.
     * Defined here so that HorizontalAlignmentConstant can be derived from it,
     * thus allowing HasAutoHorizontalAlignment methods to accept and return both
     * AutoHorizontalAlignmentConstant and HorizontalAlignmentConstant values -
     * without allowing the methods defined here to accept or return
     * AutoHorizontalAlignmentConstant values.
     */
    public static class AutoHorizontalAlignmentConstant {
        // The constructor is package-private to prevent uncontrolled inheritance
        // and instantiation of this class.
        AutoHorizontalAlignmentConstant() {
        }
    }

    /**
     * Possible return values for {@link #getHorizontalAlignment}, and parameter
     * values for {@link #setHorizontalAlignment}.
     */
    public static class HorizontalAlignmentConstant extends AutoHorizontalAlignmentConstant {

        public static HorizontalAlignmentConstant endOf(Direction direction) {
            return direction == Direction.LTR ? ALIGN_RIGHT
                    : direction == Direction.RTL ? ALIGN_LEFT : ALIGN_LOCALE_END;
        }

        public static HorizontalAlignmentConstant startOf(Direction direction) {
            return direction == Direction.LTR ? ALIGN_LEFT
                    : direction == Direction.RTL ? ALIGN_RIGHT : ALIGN_LOCALE_START;
        }

        private final String textAlignString;

        private HorizontalAlignmentConstant(String textAlignString) {
            this.textAlignString = textAlignString;
        }

        /**
         * Gets the CSS 'text-align' string associated with this constant.
         *
         * @return the CSS 'text-align' value
         */
        public String getTextAlignString() {
            return textAlignString;
        }
    }

    /**
     * Specifies that the widget's contents should be aligned in the center.
     */
    HorizontalAlignmentConstant ALIGN_CENTER = new HorizontalAlignmentConstant("center");

    /**
     * Specifies that the widget's contents should be aligned as justify.
     */
    HorizontalAlignmentConstant ALIGN_JUSTIFY = new HorizontalAlignmentConstant("justify");

    /**
     * Specifies that the widget's contents should be aligned to the left.
     */
    HorizontalAlignmentConstant ALIGN_LEFT = new HorizontalAlignmentConstant("left");

    /**
     * Specifies that the widget's contents should be aligned to the right.
     */
    HorizontalAlignmentConstant ALIGN_RIGHT = new HorizontalAlignmentConstant("right");

    /**
     * In a RTL layout, specifies that the widget's contents should be aligned to
     * the right. In a LTR layout, specifies that the widget's constants should be
     * aligned to the left.
     */
    HorizontalAlignmentConstant ALIGN_LOCALE_START = GWT.isClient() && LocaleInfo.getCurrentLocale().isRTL()
            ? ALIGN_RIGHT
            : ALIGN_LEFT;

    /**
     * In a RTL layout, specifies that the widget's contents should be aligned to
     * the left. In a LTR layout, specifies that the widget's constants should be
     * aligned to the right.
     */
    HorizontalAlignmentConstant ALIGN_LOCALE_END = GWT.isClient() && LocaleInfo.getCurrentLocale().isRTL()
            ? ALIGN_LEFT
            : ALIGN_RIGHT;

    /**
     * Synonym of {@link #ALIGN_LOCALE_START}.
     */
    HorizontalAlignmentConstant ALIGN_DEFAULT = ALIGN_LOCALE_START;

    /**
     * Gets the horizontal alignment.
     *
     * @return the current horizontal alignment (
     *         {@link HasHorizontalAlignment#ALIGN_LEFT},
     *         {@link HasHorizontalAlignment#ALIGN_CENTER},
     *         {@link HasHorizontalAlignment#ALIGN_RIGHT},
     *         {@link HasHorizontalAlignment#ALIGN_JUSTIFY}, or
     *         null).
     */
    HorizontalAlignmentConstant getHorizontalAlignment();

    /**
     * Sets the horizontal alignment.
     * <p> Use {@code null} to clear horizontal alignment, allowing it to be
     * determined by the standard HTML mechanisms such as inheritance and CSS
     * rules.  
     *
     * @param align the horizontal alignment (
     *         {@link HasHorizontalAlignment#ALIGN_LEFT},
     *         {@link HasHorizontalAlignment#ALIGN_CENTER},
     *         {@link HasHorizontalAlignment#ALIGN_RIGHT},
     *         {@link HasHorizontalAlignment#ALIGN_JUSTIFY},
     *         {@link HasHorizontalAlignment#ALIGN_LOCALE_START}, or
     *         {@link HasHorizontalAlignment#ALIGN_LOCALE_END}).
     */
    void setHorizontalAlignment(HorizontalAlignmentConstant align);
}