The following replaces any current css class names. It appears to call setStyleName.
<g:DecoratorPanel styleName="{style.myCssClass}">
What I really want to do is add a class name, like calling addStyleName.
Is it possible to do what I'm attempting?
Use addStyleNames in such situations, like this:
<g:DecoratorPanel addStyleNames="{style.myCssClass}">
It's a little trick I picked up on the GWT's Google Group - too bad it's not (?) mentioned in the official documentation.
PS: I'm actually missing a really comprehensive documentation for UiBinder. I grepped the GWT sources for addStyleNames and found this file: WidgetBasedUi.ui.xml - it seems to contain some interesting use cases for UiBinder, including the one with addStyleNames.
If someone knows any other good/secret references for UiBinder, please share :)
Yes addStyleNames is the solution. And it is actually mentioned in the documentation: UiObject. See section "Use in UiBinder Templates".