In the desktop app, when a window is maximized it covers the taskbar. That is not the spected behavior, it should cover all the desktop, but not the taskbar.

I have a workaround to fix it:

In the class com.sencha.gxt.desktop.client.widget.Desktop when adding the window to the desktop in the method addWindow, the container should be the desktop and not the desktopcontainer

public void addWindow(Window window) {
    if (getWindowManager().add(window)) {
      // Note: callback via onShow

Also in the Window class (com.sencha.gxt.widget.core.client.Window)
in the method fitContainer() you should add 6 px to the height (not the best solution)

        protected void fitContainer() {
        if (getContainer() != null) {
          Rectangle bounds = ((XElement)getContainer()).getBounds();
          setPagePosition(bounds.getX(), bounds.getY());
          setPixelSize(bounds.getWidth(), bounds.getHeight() 6);          
        } else {
          setPosition(0, 0);
          setPixelSize(XDOM.getViewportWidth(), XDOM.getViewportHeight());

I know that is not the most elegant solution but it solves temporally this problem.