IE8 problem when using Singleton and DockLayoutPanel

[Fernando Barbat]

Hi everyone,

I have a "Welcome Screen" which is made by hand from the entry point.
On the other side, I have Widget named Main which uses the Singleton
pattern: this Widget encapsulates the application funcionality and
there should be only one instance in the application. This Widget is a
composite over a DockLayoutPanel, which has north, west and center
panels. The unit used to define the size of these panels is EM.

The problem raises in IE8. If I use the Widget the first time I call
Main.getInstance(), everything is fine. However, if I use it (add it
to RootLayoutPanel) after the first time, IE8 only shows the center
panel.

If I use PX insted of EM, everything works fine.

Here is the code:

//BugTest.java
package com.bugtest.clearadd.client;

import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.event.dom.client.ClickEvent;
import com.google.gwt.event.dom.client.ClickHandler;
import com.google.gwt.user.client.ui.Button;
import com.google.gwt.user.client.ui.FlowPanel;
import com.google.gwt.user.client.ui.Label;
import com.google.gwt.user.client.ui.PopupPanel;
import com.google.gwt.user.client.ui.RootLayoutPanel;
import com.google.gwt.user.client.ui.RootPanel;

public class BugTest implements EntryPoint {

@Override
public void onModuleLoad() {
Button prefetchButton = new Button("Prefetch!");
prefetchButton.addClickHandler(new ClickHandler() {

@Override
public void onClick(ClickEvent event) {
//Invoke the function but do nothing.
Main.getInstance();

PopupPanel popupPanel = new PopupPanel(true);
popupPanel.setWidget(new Label("Prefetching
finished!"));
popupPanel.center();
}
});

Button switchButton = new Button("Switch!");
switchButton.addClickHandler(new ClickHandler() {

@Override
public void onClick(ClickEvent event) {
//Here I use the result if the function
Main result = Main.getInstance();
RootPanel.get().clear();
RootLayoutPanel.get().add(result);
}
});

FlowPanel flowPanel = new FlowPanel();
flowPanel.add(new Label("Bug test!"));
flowPanel.add(prefetchButton);
flowPanel.add(switchButton);

RootPanel.get().add(flowPanel);
}

}

//Main.java
package com.bugtest.clearadd.client;

import com.google.gwt.dom.client.Style.Unit;
import com.google.gwt.user.client.ui.DockLayoutPanel;
import com.google.gwt.user.client.ui.Label;
import com.google.gwt.user.client.ui.ResizeComposite;

public class Main extends ResizeComposite {

private static Main instance = null;

public static Main getInstance() {
if (instance == null) {
instance = new Main();
}
return instance;
}

private Main() {
DockLayoutPanel dockLayoutPanel = new
DockLayoutPanel(Unit.EM);
dockLayoutPanel.addNorth(new Label("North!"), 7);
dockLayoutPanel.addWest(new Label("West!"), 15);
dockLayoutPanel.add(new Label("Center! :D"));
initWidget(dockLayoutPanel);
}

}

Is it a bug or I am just missing something?

I posted this problem in another place, but now I realize that I
should have posted here first. :P Anyway, I haven't received any
comment on that post, so that's why I'm here.

This problem showed up when I was trying to use code splitting. I was
using the Async Provider pattern, but the singleton pattern is a
simplified version which has the same issue. The first call to
Main.getInstance() correspond to a prefetch when I know there's little
network activity.

Thanks in advance.