As you already imagined, migrating code to the recommended servlet thread is a nightmare. Anyway, since ZK deprecated the event thread, I thought reasonable to start the migration now. Here are some issues I encountered while doing so.

Close without saving?

Are you capturing the onClose event of a container to prevent user from exiting without saving its content?

This piece of code does capture the event, ask user if really want to exit loosing modifications. If user says no, the event method stopPropagation() is called and the tab remains open.

Tab tab = container.getLinkedTab();
tab.addEventListener(9000, Events.ON_CLOSE, new EventListener() {
  @Override
  public void onEvent(Event event) throws Exception {
    if(modified) {
      if(!ZkossUtils.confirmMessage(ElLabel.getLabel("lCloseWithoutSaving"))) {
         event.stopPropagation();
      }
    }
  }
});

...

public static boolean confirmMessage(String message) {
  if(Messagebox.show(message, ElLabel.getLabel("lQuestion"),
           Messagebox.OK | Messagebox.CANCEL, Messagebox.QUESTION) == Messagebox.OK) {
    return true;
  }
  return false;
}

With servlet thread this code no longer works. The method stopPropagation() gets never called. Messagebox.show() returns immediately and there is no chance that confirmMessage() returns true.

We need to make some changes. In the example I choose commons-chain, but Runnable is also a choice.

final Tab tab = container.getLinkedTab();
tab.addEventListener(9000, Events.ON_CLOSE, new EventListener() {
  @Override
  public void onEvent(final Event event) throws Exception {
    if(modified) { // check whether tab content has been changed
      event.stopPropagation();
      ZkossUtils.confirmMessage(ElLabel.getLabel("lCloseWithoutSaving"), new Command() {
        @Override
        public boolean execute(Context context) throws Exception {
          tab.close();
          return Command.PROCESSING_COMPLETE;
        }
      });
    }
  }
});

...

public static void confirmMessage(String message, final Command command) {
  Messagebox.show(message, ElLabel.getLabel("lQuestion"),
            Messagebox.OK | Messagebox.CANCEL, Messagebox.QUESTION,
            new EventListener() {
    @Override
    public void onEvent(Event event) throws Exception {
      Context ctx = new ContextBase();
      switch ((Integer) event.getData()) {
        case Messagebox.OK: command.execute(ctx); break;
      }
    }
  });
}

First modification is to use Messagebox's EventListener. There we put the code we want to execute when the OK button gets clicked.

The onClose event has changed some more. Fist, we call stopPropagation() when modified is true. This ensures the tab will remain open. Then, we close the tab. Doing so programmatically prevents from entering an endless loop. Notice that in real-world applications, the tab may have its own listeners and perform some stuff.

Before you get mad with modal windows

Setting the modal state. With the event thread enabled you could do setMode("modal") before attaching the window to the page. With the servlet thread that's no longer true. It will throw a not attached exception. So, if you set the window mode somewhere before setPage(page), simply remove the call to setMode() and use doModal() once the page has been set.

It was 2008 and I needed a wiki editor for Elephant-Wiki syntax. The JavaScript source code can be located here editor.txt. For those interested, there is a wiki-bar, coded into a JSP file, which was sensible of caret position as to interact with the user. The code, conveniently renamed to TXT, is here wikiBar.txt

Was quite an effort and never since I have been able to find time to improve it.

Turning to ZK7

Early this year, 2015, BrightSide migrated from ZK6 to ZK7. As usual, guys at Potix had made a great work. ZK7 is fast, slim and a good looking piece of software. Could it be the moment to give a close review to Elephant-Wiki editor?

First requirements

Before trying to write an editor, you have to make sure you'll have what it needs to start with.

• Caret position
• Editor content's value
• Ability to change this content

You might find this list really short for what I'm pretending to do. What about the events, moving data from client to server and so on? Here is where ZK makes difference. I'm not worried at all.

Caret position

Let's use a simple Textbox for our editor. By default, Textbox does not inform of where the caret is. Thus, we are going to use a trick that was first pointed at ZK forums. Transform a JavaScript event into a ZK event and pass through selection values. That is, selection start and selection end. When both values are the same, there is the caret position. When values differ, then they point to selected text.

wikibox.setWidgetListener("onBlur",  
	"zAu.send(new zk.Event(this,"onCaret",zk(this.$n()).getSelectionRange()+"",{toServer:true}));");

This example uses the onBlur event to send an onCaret to ZK Textbox component. The event's data is the selection range. The string has this format "selectionStart,selectionEnd", for example "0,0".

On the server side, we need a listener for the onCaret event.

@Listen("onCaret = *")
public void onCaret(Event event) {
  String v[] = ((String) event.getData()).split(",");
  selectionStart = Integer.valueOf(v[0]);
  selectionEnd = Integer.valueOf(v[1]);
}  

The example uses two variables to store selection range for future uses.

Dealing with editor's value

Textbox component has methods that will make things really easy. To ensure the example interesting we'll suppose the user has clicked on the Bold button and wiki syntax for bold text is to surround the value with double asterisk. The example uses wikibox variable as the Textbox component.

@Listen("onClick = #bold")
public void onBold() {
  wikibox.setSelectedText(selectionStart, selectionStart, "**", false);
  selectionStart += "**".length();
  selectionEnd += "**".length();
  wikibox.setSelectedText(selectionEnd, selectionEnd, "**", false);
  wikibox.setSelectionRange(selectionStart, selectionStart);
  wikibox.setFocus(true);
  Events.postEvent(new InputEvent("onChange", this, wikibox.getValue(), null));
}

If there is no text selected, the text "****" will be inserted, with caret positioned exactly in the middle, as to start typing. If some text is selected, the result will be this text surrounded by double asterisk, as in "**bold text**".

Looking at the code, line by line, the setSelectedText method, inserts "**" at selection range's start. Then increases variables so they point to the same location at text. The next setSelectedText inserts "**" at selection range's end. If there was no text selected, then the four asterisk will stay together, otherwise will surround the selection. Calling setSelectionRange method ensures the caret position will be exactly after the first two asterisk. The method setFocus, as it reads, put focus on the editor. Last line posts an onChange event, to inform composer that something in editor has changed.

Let's write the component

In order to give an appearance to our editor we need some zul code and wrap the above examples into a class. We start with the zul code at file wikiInput.zul.

<zk>
  <menubar>
    <menuitem id="bold" iconSclass="z-icon-bold"/>
  </menubar>
  <textbox id="wikibox" multiline="true" tabbable="true" style="-moz-tab-size:4;-o-tab-size:4;tab-size:4;width:100%;height:100%;"/>
</zk>

The code is quite simple. The reason why I prefer a menubar instead of a toolbar will be more evident when you see the real-world example. For now, it makes no difference what the bold element is. The important things to remember are the id attributes, which are wired to ZK components in the Java class at server-side.

See now the Java class WikiEditor.

public class WikiEditor extends Div implements IdSpace {

  private int selectionStart, selectionEnd;
  
  @Wire private Textbox wikibox;
  
  public WikiEditor() {
    Executions.createComponents("/WEB-INF/_zul/comps/editor/wikiInput.zul", this, null);
    Selectors.wireComponents(this, this, false);
    Selectors.wireEventListeners(this, this);
    wikibox.setWidgetListener("onBlur", 
		"zAu.send(new zk.Event(this,"onCaret",zk(this.$n()).getSelectionRange()+"",{toServer:true}));");

    wikibox.addEventListener(Events.ON_CHANGE, new EventListener() {
      @Override
      public void onEvent(InputEvent event) throws Exception {
        Events.postEvent(WikiEditor.this, event);
      }
    });
  }

  @Listen("onClick = #bold")
  public void onBold() {
    wikibox.setSelectedText(selectionStart, selectionStart, "**", false);
    selectionStart += "**".length();
    selectionEnd += "**".length();
    wikibox.setSelectedText(selectionEnd, selectionEnd, "**", false);
    wikibox.setSelectionRange(selectionStart, selectionStart);
    wikibox.setFocus(true);
    Events.postEvent(new InputEvent("onChange", this, wikibox.getValue(), null));
  }
}

The magic of making Java class aware of zul code is performed in the first three lines of the constructor. Notice that we indicate where to find the zul file in the createComponents method.

Using the component in zul pages

Now you can put the component in your zul pages like this, changing the package org.turro for this where you put the class.

<div width="100%" height="100%" use="org.turro.WikiEditor"/>

Real-world component

As promised, here is the real-world zul page.

<zk>
  <style>
    .font14px * {
      font-size: 14px;
    }
    .fontBold * {
      font-weight: bold;
    }
  </style>
  <menubar sclass="font14px">
    <menuitem id="header1" label="H1" class="fontBold"/>
    <menuitem id="header2" label="H2" class="fontBold"/>
    <menuitem id="header3" label="H3" class="fontBold"/>
    <menuitem id="header4" label="H4" class="fontBold"/>
    
    <menuitem id="bold" iconSclass="z-icon-bold"/>
    <menuitem id="italic" iconSclass="z-icon-italic"/>
    <menuitem id="regular" iconSclass="z-icon-text-width"/>
    
    <menuitem id="alignleft" iconSclass="z-icon-align-left"/>
    <menuitem id="aligncenter" iconSclass="z-icon-align-center"/>
    <menuitem id="alignright" iconSclass="z-icon-align-right"/>
    <menuitem id="alignjustify" iconSclass="z-icon-align-justify"/>
    <menuitem id="floatleft" iconSclass="z-icon-chevron-left"/>
    <menuitem id="floatright" iconSclass="z-icon-chevron-right"/>
    
    <menuitem id="ullist" iconSclass="z-icon-list-ul"/>
    <menuitem id="ollist" iconSclass="z-icon-list-ol"/>
    
    <menu iconSclass="z-icon-tint">
      <menupopup>
        <menu id="color" content="#color=#333333" label="${el_label['wbar.color']}"/>
        <menu id="background" content="#color=#ffffff" label="${el_label['wbar.background']}"/>
      </menupopup>
    </menu>
    <menu iconSclass="z-icon-table">
      <menupopup>
        <menuitem id="thl" label="${el_label['wbar.newheader']}: ${el_label['wbar.left']}"/>
        <menuitem id="thr" label="${el_label['wbar.newheader']}: ${el_label['wbar.right']}"/>
        <menuitem id="trl" label="${el_label['wbar.newrow']}: ${el_label['wbar.left']}"/>
        <menuitem id="trr" label="${el_label['wbar.newrow']}: ${el_label['wbar.right']}"/>
        <menuitem id="tcl" label="${el_label['wbar.newcolumn']}: ${el_label['wbar.left']}"/>
        <menuitem id="tcr" label="${el_label['wbar.newcolumn']}: ${el_label['wbar.right']}"/>
        <menuitem id="tet" label="${el_label['wbar.endtable']}"/>
      </menupopup>
    </menu>
    <menu iconSclass="z-icon-code">
      <menupopup>
        <menuitem id="block" label="${el_label['wbar.createblock']}"/>
        <menuitem id="span" label="${el_label['wbar.createspan']}"/>
        <menuitem id="note" label="${el_label['wbar.createnote']}"/>
        
        <menuitem id="startcolumn" label="${el_label['wbar.addcolumn']}"/>
        <menuitem id="endcolumns" label="${el_label['wbar.endcolumns']}"/>
        
        <menuitem id="tabulator" label="${el_label['wbar.createtabulator']}"/>
        <menuitem id="blind" label="${el_label['wbar.createblind']}"/>
        
        <menu label="Wiki syntax">
          <menupopup>
            <menuitem id="startwiki" label="${el_label.lStart}"/>
            <menuitem id="stopwiki" label="${el_label.lStop}"/>
          </menupopup>
        </menu>
        <menu label="Java syntax">
          <menupopup>
            <menuitem id="startjava" label="${el_label.lStart}"/>
            <menuitem id="stopjava" label="${el_label.lStop}"/>
          </menupopup>
        </menu>
        <menu label="XML syntax">
          <menupopup>
            <menuitem id="startxml" label="${el_label.lStart}"/>
            <menuitem id="stopxml" label="${el_label.lStop}"/>
          </menupopup>
        </menu>
      </menupopup>
    </menu>
    <menuitem id="eraser" iconSclass="z-icon-eraser"/>
    
    <menuitem id="image" iconSclass="z-icon-picture-o"/>
    <menuitem id="link" iconSclass="z-icon-link"/>
    
    <menuitem id="preview" iconSclass="z-icon-eye"/>
  </menubar>
  <textbox id="wikibox" multiline="true" tabbable="true" style="-moz-tab-size:4;-o-tab-size:4;tab-size:4;width:100%;height:100%;"/>
</zk>

Java source code (update 26/04/2015)

WikiEditor.java
WikiElement.java

And finally, the editor while writing this blog.

BrightSide is now running on top of ZK new version, ZK 6.0.1. Code upgrade went smoothly, as if previous issues were all solved, an effect of the ZK project activity. Some improvements shine by themselves:

• Speed, new version runs faster.
• Control over UI, components layout is close to perfection, while composers handle the hard part. 

ZK is a Java Framework for building web applications, with over 1,500,000 downloads worldwide. BrightSide uses ZK as primary user front-end.

We are proud to announce that now, BrightSide is a Case Study on ZK web site.

I have been disconnected  from this site quite long. It seems that time isn't working the right way with me. You know, the more I'm supposed to understand the more complicated to write about it. Well, this time I made a break and gathered myself in order to put my two cents saying something about Zkoss.

First, I would like you to notice that this goes about web application frameworks. Java Server Faces, Flex, Google Web Toolkit, Wicket and those of that kind. I have stressed most of them in my way of being productive writing web applications. Difficult, let me tell you.