Bug 36446 [Contributions] widgets: Associating Actions with Buttons
Actions can be associated with Menu items , and tool bar items using MenuManager and ToolBarManager but there is not way to associate Action with a regular button and obtaining a reference to that button the closest thing is creating an ActionContributionItem with the desired action in its constructor , then filling the parent composite with ActionContributionItem.fill(Control parent) this creats the button , but it doesn't return a reference to that button , so for example i can't give it any layout data i suggest the ActionContributionItem.fill(Control parent) returns the created widget
bundles/org.eclipse.jface/src/org/eclipse/jface/action/ActionContributionItem.java
ExternalActionManager.ICallback callback = ExternalActionManager
						.getInstance().getCallback();
				if ((callback != null) && (commandId != null)) {
					callback.addPropertyChangeListener(commandId,
							actionTextListener);
				}
			}
		}
	}
	/**
	 * Returns the action associated with this contribution item.
	 * 
	 * @return the action
	 */
	public IAction getAction() {
		return action;
	}
	/**
	 * Returns the listener for SWT button widget events.
	 * 
	 * @return a listener for button events
	 */
	private Listener getButtonListener() {
		if (buttonListener == null) {
			buttonListener = new Listener() {
				public void handleEvent(Event event) {
					switch (event.type) {
					case SWT.Dispose:
						handleWidgetDispose(event);
						break;