Running the test javax/swing/Popup/TaskbarPositionTest.java on my Linux machines, I often have it failed because isPopupOnScreen() method is often called immediately after popup triggering robot action and before the popup bounds are fixed. Robot.waitForIdle() cannot be used here since in many cases isPopupOnScreen is called from EDT. Solution would be, wait for some condition -- or just wait some "mouse event time", 50 or 100 ms, before getting the popup geometry.