Question: I have written my own `PopupPanel` in GWT. I want to show the popup relative to an other widget. My implementation of the class looks like the following:

```java
public class Popover extends PopupPanel implements PositionCallback {

    private static final Binder binder = GWT.create(Binder.class);
    private UIObject relative;

    interface Binder extends UiBinder<Widget, Popover> {
    }

    public Popover() {
        setWidget(binder.createAndBindUi(this));
        setStylePrimaryName("popover");
    }

    public void show(UIObject relative) {

        this.relative = relative;
        setPopupPositionAndShow(this);

    }

    public void setPosition(int offsetWidth, int offsetHeight) {

        if (relative != null) {

            int left = relative.getAbsoluteLeft();
            int top = relative.getAbsoluteTop();
            int width = relative.getOffsetWidth();
            int height = relative.getOffsetHeight();

            int topCenter = top + height / 2 - offsetHeight / 2;

            if (offsetWidth < left) {
                setPopupPosition(left - offsetWidth, topCenter);
            } else {
                setPopupPosition(left + width, topCenter);

            }
        }
    }

}

```

The problem is that `offsetWidth` and `offsetHeight` is always `10`?

My `Popover.ui.xml` looks like the following:

```xml
<g:FlowPanel stylePrimaryName="popover">
    <g:FlowPanel stylePrimaryName="arrow" />
    <g:FlowPanel stylePrimaryName="inner">
        <g:Label stylePrimaryName="title" text="New Label" />
        <g:FlowPanel stylePrimaryName="content">
            <g:Label text="Hallo" />
        </g:FlowPanel>
    </g:FlowPanel>
</g:FlowPanel>

```

Answer: 
To solve this issue, I followed the steps used by `PopupPanel`'s `setPopupPositionAndShow()`, but I made the positioning step a deferred command. My code didn't extend `PopupPanel`, hence the `popupPanel` variable:

```java
popupPanel.setVisible(false);
popupPanel.show();

// Pausing until the event loop is clear appears to give the browser
// sufficient time to apply CSS styling.  We use the popup's offset
// width and height to calculate the display position, but those
// dimensions are not accurate until styling has been applied.
Scheduler.get().scheduleDeferred(new ScheduledCommand() {
   @Override
   public void execute() {
      yourMethodToSetPositionGoesHere(popupPanel);
      popupPanel.setVisible(true);
   }
});

```
`getOffsetWidth()` and `getOffsetHeight()` only work if the DOM is fully constructed and the container for which you want to get the value is visible and attached. 

Why don't you use the `showRelativeTo()` function of the `PopupPanel`?

```java
popup.showRelativeTo(SomeWidget);

```