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
*            proposal. If specified, these characters will trigger
	 *            auto-activation of the proposal popup, regardless of whether
	 *            an explicit invocation keyStroke was specified. If this
	 *            parameter is <code>null</code>, then only a specified
	 *            keyStroke will invoke content proposal. If this parameter is
	 *            <code>null</code> and the keyStroke parameter is
	 *            <code>null</code>, then all alphanumeric characters will
	 *            auto-activate content proposal.
	 */
	public ContentProposalAdapter(Control control,
			IControlContentAdapter controlContentAdapter,
			IContentProposalProvider proposalProvider, KeyStroke keyStroke,
			char[] autoActivationCharacters) {
		super();
		
		Assert.isNotNull(control);
		Assert.isNotNull(controlContentAdapter);
		this.control = control;
		this.controlContentAdapter = controlContentAdapter;
		
		this.proposalProvider = proposalProvider;
		this.triggerKeyStroke = keyStroke;
		if (autoActivationCharacters != null) {
			this.autoActivateString = new String(autoActivationCharacters);
		}
		addControlListener(control);
	}
	/**
	 * Get the control on which the content proposal adapter is installed.
	 *