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
*         auto-activation characters) should be propagated to the adapted
	 *         control when the proposal popup is open. Default value is
	 *         <code>true</code>.
	 */
	public boolean getPropagateKeys() {
		return propagateKeys;
	}
	/**
	 * Set the boolean that indicates whether key events (including
	 * auto-activation characters) received by the content proposal popup should
	 * also be propagated to the adapted control when the proposal popup is
	 * open.
	 * 
	 * @param propagateKeys
	 *            a boolean that indicates whether key events (including
	 *            auto-activation characters) should be propagated to the
	 *            adapted control when the proposal popup is open.
	 */
	public void setPropagateKeys(boolean propagateKeys) {
		this.propagateKeys = propagateKeys;
	}
	/**
	 * Return the content adapter that can get or retrieve the text contents
	 * from the adapter's control. This method is used when a client, such as a
	 * content proposal listener, needs to update the control's contents
	 * manually.
	 * 
	 * @return the {@link IControlContentAdapter} which can update the control
	 *         text.
	 */