GWT - Retrieve size of a widget that is not displayed

Question

I need to set the size of an absolutePanel regarding to its child size, but the getOffset* methods return 0 because (i think) the child has not been displayed yet.

A Quick example:

AbsolutePanel aPanel = new AbsolutePanel();
HTML text = new HTML(/*variable lenght text*/);
int xPosition = 20; // actually variable
aPanel.add(text, xPosition, 0);
aPanel.setSize(xPosition + text .getOffsetWidth() + "px", "50px"); // 20px 50px

I could also solve my problem by using the AbsolutePanel size to set the child position and size:

AbsolutePanel aPanel = new AbsolutePanel();
aPanel.setSize("100%", "50px");
HTML text = new HTML(/*variable lenght text*/);
int xPosition = aPanel.getOffsetWidth() / 3; // Once again, getOffsetWidth() returns 0;
 aPanel.add(text, xPosition, 0);

In both case, i have to find a way to either:

• retrieve the size of a widget that has not been displayed
• be notified when a widget is displayed

Answer 1

I think you should try to solve this with css styles. If I were you, I would try to set a style for parent and/or absolute panel, using addStyle or addStyleNames. Maybe something like...

AbsolutePanel aPanel = new AbsolutePanel();
aPanel.setSize("100%", "50px");
HTML text = new HTML(/*variable lenght text*/);
text.addStyleName("my-custom-style");

in css you would create a css style which would then size your widget appropriately.

The other approach would be....

You could create a function that creates a HTML widget exactly the size you need.

Here's some code for you, to get you started:

public native void customizeHTMLElement(Element elem, String widthInPx) /*-{ 
  elem.style.width = widthInPx;   //this is basically pure js. 
}-*/ 

Then somewhere within your widget make a call to the above function like

public void foo() {
  ...
  customizeHTMLElement(someElement, "20");
  ...
}

Some info about JSNI - http://code.google.com/webtoolkit/doc/latest/DevGuideCodingBasicsJSNI.html