ImageLink.java

package com.sksamuel.jqm4gwt.html;

import com.google.gwt.dom.client.AnchorElement;
import com.google.gwt.dom.client.Document;
import com.google.gwt.dom.client.Element;
import com.google.gwt.dom.client.ImageElement;
import com.google.gwt.dom.client.SpanElement;
import com.google.gwt.dom.client.Style;
import com.google.gwt.dom.client.Style.Display;
import com.google.gwt.dom.client.Style.Unit;
import com.google.gwt.dom.client.Style.VerticalAlign;
import com.google.gwt.event.dom.client.ClickEvent;
import com.google.gwt.event.dom.client.ClickHandler;
import com.google.gwt.event.dom.client.HasClickHandlers;
import com.google.gwt.event.shared.GwtEvent.Type;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.user.client.ui.HasEnabled;
import com.google.gwt.user.client.ui.UIObject;
import com.google.gwt.user.client.ui.Widget;
import com.sksamuel.jqm4gwt.Empty;
import com.sksamuel.jqm4gwt.HasText;
import com.sksamuel.jqm4gwt.JQMCommon;
import com.sksamuel.jqm4gwt.Orientation;
import com.sksamuel.jqm4gwt.events.HasTapHandlers;
import com.sksamuel.jqm4gwt.events.JQMComponentEvents;
import com.sksamuel.jqm4gwt.events.JQMHandlerRegistration;
import com.sksamuel.jqm4gwt.events.JQMHandlerRegistration.WidgetHandlerCounter;
import com.sksamuel.jqm4gwt.events.TapEvent;
import com.sksamuel.jqm4gwt.events.TapHandler;

/**
 * @author Stephen K Samuel samspade79@gmail.com 17 Jul 2011 15:38:47
 * <br>
 * An implementation of an anchor tag that wraps an image tag and optional text.
 * <pre> <a href='mylink'><img src='myimage'/></a> </pre>
 *
 */
public class ImageLink extends Widget implements HasClickHandlers, HasTapHandlers, HasEnabled,
        HasText<ImageLink> {

    protected static final String JQM4GWT_IMAGE_LINK_A = "jqm4gwt-image-link-a";
    protected static final String JQM4GWT_IMAGE_LINK_IMG = "jqm4gwt-image-link-img";
    protected static final String DATA_RESIZE_PRIORITY = "data-resize-priority";

    protected ImageElement img;
    protected AnchorElement a;
    protected SpanElement txt;

    private Boolean external;

    public ImageLink() {
        a = Document.get().createAnchorElement();
        setElement(a);
        initA();
        img = Document.get().createImageElement();
        initImg();
        a.appendChild(img);
    }

    protected void initA() {
        JQMCommon.setDataRole(a, "none");
        // Let's set proper initial default href value.
        // If no real href is defined later, then something is expected in onClick handler.
        a.setAttribute("href", "javascript:;");
        setStyleName(a, JQM4GWT_IMAGE_LINK_A);
    }

    protected void initImg() {
        setStyleName(img, JQM4GWT_IMAGE_LINK_IMG);
        setImageResizePriority(Orientation.HORIZONTAL);
        img.getStyle().setVerticalAlign(VerticalAlign.TOP); // eliminates excessive/strange margin at the bottom
        img.getStyle().setDisplay(Display.NONE);
    }

    public ImageLink(String href, String src) {
        this();
        setHref(href);
        setSrc(src);
    }

    public String getSrc() {
        return img.getAttribute("src");
    }

    public String getHref() {
        return a.getAttribute("href");
    }

    /**
     * The URL of the source image
     *
     * @param src
     */
    public void setSrc(String src) {
        JQMCommon.setAttribute(img, "src", src);
        refreshPositioning();
    }

    private void refreshPositioning() {
        String src = getSrc();
        String text = getText();
        Style imgSt = img.getStyle();
        if (src == null || src.isEmpty()) {
            imgSt.setVerticalAlign(VerticalAlign.TOP);
            imgSt.clearMarginRight();
            imgSt.setDisplay(Display.NONE);
            if (txt != null) txt.getStyle().setVerticalAlign(VerticalAlign.TOP);
        } else {
            imgSt.setVerticalAlign(VerticalAlign.MIDDLE);
            imgSt.clearDisplay();
            if (txt != null) txt.getStyle().setVerticalAlign(VerticalAlign.MIDDLE);
            if (text == null || text.isEmpty()) imgSt.clearMarginRight();
            else imgSt.setMarginRight(0.3d, Unit.EM);
        }
    }

    /**
     * The destination URL of the link
     *
     * @param href
     */
    public void setHref(String href) {
        JQMCommon.setAttribute(a, "href", href);
        if (external == null /*only if not explicitly set*/ && !Empty.is(href)
                && (href.startsWith("http:") || href.startsWith("https:"))) {
            setExternal(true);
        }
    }

    public boolean isExternal() {
        return external != null ? external : false;
    }

    public void setExternal(boolean value) {
        this.external = value;
        if (value) {
            a.setAttribute("rel", "external");
            a.setAttribute("data-rel", "external");
        } else {
            a.removeAttribute("rel");
            a.removeAttribute("data-rel");
        }
    }

    /**
     * Set the width of the image
     */
    @Override
    public void setWidth(String width) {
        img.getStyle().setProperty("width", width);
    }

    /**
     * Set the height of the image
     */
    @Override
    public void setHeight(String height) {
        img.getStyle().setProperty("height", height);
    }

    public Orientation getImageResizePriority() {
        String s = img.getAttribute(DATA_RESIZE_PRIORITY);
        if (s == null || s.isEmpty()) return null;
        if (Orientation.HORIZONTAL.getJqmValue().equals(s)) return Orientation.HORIZONTAL;
        if (Orientation.VERTICAL.getJqmValue().equals(s)) return Orientation.VERTICAL;
        return null;
    }

    /**
     * Defines how to resize image in case of limited/explicit button size.
     * <p> HORIZONTAL - width is 100% and height is auto (default mode). </p>
     * <p> VERTICAL - height is 100% and width is auto. </p>
     * <p> See <a href="http://stackoverflow.com/a/16217391">Flexible images</a></p>
     */
    public void setImageResizePriority(Orientation value) {
        if (value == null) img.removeAttribute(DATA_RESIZE_PRIORITY);
        else img.setAttribute(DATA_RESIZE_PRIORITY, value.getJqmValue());
    }

    @Override
    public HandlerRegistration addClickHandler(ClickHandler handler) {
        return addDomHandler(handler, ClickEvent.getType());
    }

    @Override
    public HandlerRegistration addTapHandler(TapHandler handler) {
        // this is not a native browser event so we will have to manage it via JS
        return JQMHandlerRegistration.registerJQueryHandler(new WidgetHandlerCounter() {
            @Override
            public int getHandlerCountForWidget(Type<?> type) {
                return getHandlerCount(type);
            }
        }, this, handler, JQMComponentEvents.TAP_EVENT, TapEvent.getType());
    }

    @Override
    public boolean isEnabled() {
        return JQMCommon.isEnabled(this);
    }

    @Override
    public void setEnabled(boolean enabled) {
        JQMCommon.setEnabled(this, enabled);
    }

    /**
     * Gives realistic visibility (parent chain considered, ...)
     * If you need logical visibility of this particular widget,
     * use {@link UIObject#isVisible(Element elem)}
     */
    @Override
    public boolean isVisible() {
        return super.isVisible() && JQMCommon.isVisible(this);
    }

    @Override
    public String getText() {
        return txt != null ? txt.getInnerText() : null;
    }

    @Override
    public void setText(String text) {
        boolean emptyText = text == null || text.isEmpty();
        if (emptyText) {
            if (txt != null) txt.setInnerText(text);
        } else {
            if (txt == null) {
                txt = Document.get().createSpanElement();
                a.appendChild(txt);
            }
            txt.setInnerText(text);
        }
        refreshPositioning();
    }

    @Override
    public ImageLink withText(String text) {
        setText(text);
        return this;
    }
}