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
.createImageWithDefault(image));
			
			
			disposeOldImages();
			imageManager = localManager;
			return image != null;
		} else if (widget instanceof Item || widget instanceof Button) {
			
			ImageDescriptor image = action.getHoverImageDescriptor();
			if (image == null) {
				image = action.getImageDescriptor();
			}
			
			if (image == null && forceImage) {
				image = ImageDescriptor.getMissingImageDescriptor();
			}
			
			
			LocalResourceManager localManager = new LocalResourceManager(
					parentResourceManager);
			if (widget instanceof Item) {
				((Item) widget).setImage(image == null ? null : localManager
						.createImageWithDefault(image));
			} else if (widget instanceof Button) {
				((Button) widget).setImage(image == null ? null : localManager
						.createImageWithDefault(image));
			}
			
			
			disposeOldImages();