Bug 148357 [Field Assist] - API - provide access for closing the proposal popup
I think that the field assist API needs more hooks to be customizable. For example : 1) There is no way to manually close/open the popup. Most of the times, this is the easier thing for a user to ask to implement his custom behaviour. 2) There is no way to intercept keystrokes/events directed to the field. 3) There is no way to control focus.
bundles/org.eclipse.jface/src/org/eclipse/jface/fieldassist/ContentProposalAdapter.java
* FILTER_CUMULATIVE, FILTER_NONE.
	 */
	private int filterStyle = FILTER_NONE;
	/*
	 * The listener we install on the control.
	 */
	private Listener controlListener;
	/*
	 * The list of listeners who wish to be notified when something significant
	 * happens with the proposals.
	 */
	private ListenerList proposalListeners = new ListenerList();
	/*
	 * Flag that indicates whether the adapter is enabled. In some cases,
	 * adapters may be installed but depend upon outside state.
	 */
	private boolean isEnabled = true;
	/*
	 * The delay in milliseconds used when autoactivating the popup.
	 */
	private int autoActivationDelay = 0;
	
	/*
	 * A boolean indicating whether a keystroke has been received.  
	 * Used to see if an autoactivation delay was interrupted by 
	 * a keystroke.
	 */
	private boolean receivedKeyDown;
	/*
	 * The desired size in pixels of the proposal popup.