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
if (action.getStyle() == IAction.AS_RADIO_BUTTON) {
					action.setChecked(selection);
				}
			} else if ((style & SWT.DROP_DOWN) != 0) {
				if (e.detail == 4) { 
					if (action.getStyle() == IAction.AS_DROP_DOWN_MENU) {
						IMenuCreator mc = action.getMenuCreator();
						menuCreatorCalled = true;
						ToolItem ti = (ToolItem) item;
						
						
						
						
						
						
						
						
						if (mc != null) {
							Menu m = mc.getMenu(ti.getParent());
							if (m != null) {
								
								Point point = ti.getParent().toDisplay(
										new Point(e.x, e.y));
								m.setLocation(point.x, point.y); 
																	
								
								m.setVisible(true);
								return; 
							}
						}