When tool tip location is very close to the screen edges, then it shows only partially. Tool tip does not get adjusted it-self to show its full length of
text. This happens on windows with Merlin.

This is similar to bug# 4425878 which involves popup menu.

Test case:
public class MyTestW extends Object {
    public static void main (String args[]) {
        javax.swing.JFrame f = new javax.swing.JFrame();
        javax.swing.JButton b = new javax.swing.JButton("whooo");
        b.setToolTipText("Somthing really long 1234567890 1234567890 1234567890
1234567890 1234567890 1234567890 1234567890 1234567890");
        f.getContentPane().add(b);
        f.pack();
        //f.setDefaultCloseOperation(javax.swing.JFrame.EXIT_ON_CLOSE);
        f.show();
    }
}