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 text control that displays the text.
			 */
			private Text text;
			/*
			 * The String shown in the popup.
			 */
			private String contents = EMPTY;
			/*
			 * Construct an info-popup with the specified parent.
			 */
			InfoPopupDialog(Shell parent) {
				super(parent, PopupDialog.HOVER_SHELLSTYLE, false, false,
						false, false, null, null);
			}