SWT: A Developer's Notebook

Responding to Shift-Click Events

Sometimes you must respond to mouse events that occur in combination with keystrokes. For example, some interfaces select text when the user holds the Shift key while dragging the mouse. For these times, there must be a mechanism that enables you to determine if a key is being pressed simultaneously with a mouse button.

How do I do that?

For this purpose MouseEvent contains a field known as stateMask . This field is populated only when the user is holding down one of the keyboard keys at the same time the mouse is being clicked. If you want to code some action that occurs only when the user is holding the Shift key while clicking a mouse button:

s.addMouseListener(new MouseAdapter( ) {
       public void mouseDown(MouseEvent e) {
           if(e.stateMask==SWT.SHIFT)
           {    
                Label l = new Label(s, SWT.FLAT);
                l.setText("Mouse Button Down at:" + e.x + " " + e.y);
                l.setBounds(e.x,e.y, 150,15);
           }
                
       }
       public void mouseUp(MouseEvent e) {
           Label l = new Label(s, SWT.FLAT);
           l.setText("Mouse Button up at:" + e.x + " " + e.y);
           l.setBounds(e.x,e.y, 150,15);
       }
});

This code results in the Label being created in the mouseDown( ) method only if the user is also holding down the Shift key. The mouseUp( ) method creates the Label even if the Shift key is not pressed.