I got something working with a HorizontalPanel, but I had to wrap each element in a FitLayout in order to get them to use the available space... And the total width is broken somehow... I had to set the table width to match the parent width... If I set it to 100% it overflowed the parent.
There has to be some easier way to lay items out horizontally... I realize CSS is a mess, but can't we write a container with some logic to adjust the layout based on the space available? I have a feeling that I could have done so in less time than I spent trying to figure out how to use three different GXT layout, none of which worked as expected.