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
ti.setText(textToSet);
					}
				}
				if (imageChanged) {
					
					updateImages(!showText);
				}
				if (tooltipTextChanged || textChanged) {
					String toolTip = action.getToolTipText();
					if ((toolTip == null) || (toolTip.length() == 0)) {
						toolTip = text;
					}
					ExternalActionManager.ICallback callback = ExternalActionManager
							.getInstance().getCallback();
					String commandId = action.getActionDefinitionId();
					if ((callback != null) && (commandId != null)
							&& (toolTip != null)) {
						String acceleratorText = callback
								.getAcceleratorText(commandId);
						if (acceleratorText != null
								&& acceleratorText.length() != 0) {
							toolTip = JFaceResources.format(
									"Toolbar_Tooltip_Accelerator", 
									new Object[] { toolTip, acceleratorText });
						}
					}