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
* The listener installed on the target control.
		 */
		private Listener targetControlListener;
		/*
		 * The listener installed in order to close the popup.
		 */
		private PopupCloserListener popupCloser;
		/*
		 * The table used to show the list of proposals.
		 */
		private Table proposalTable;
		/*
		 * The proposals to be shown (cached to avoid repeated requests).
		 */
		private IContentProposal[] proposals;
		/*
		 * Secondary popup used to show detailed information about the selected
		 * proposal..
		 */
		private InfoPopupDialog infoPopup;
		/*
		 * Flag indicating whether there is a pending secondary popup update.
		 */
		private boolean pendingDescriptionUpdate = false;
		/*
		 * Filter text - tracked while popup is open, only if we are told to
		 * filter
		 */
		private String filterText = EMPTY;
		/**