private void updatePreviewPane() {
		if (!previewPane.isShowing()) {
			return;
		}

		TreePath path = archiveGTree.getSelectionPath();
		GTreeNode node = null;
		if (path == null) {
			if (lastPreviewNode == null) {
				return; // never shown a preview--nothing to update
			}
			node = lastPreviewNode;
		}
		else {
			node = (GTreeNode) path.getLastPathComponent();
			lastPreviewNode = node;
		}

		if (node instanceof DataTypeNode) {
			showDataTypePreview((DataTypeNode) node);
			return;
		}

		String toolTip = node.getToolTip();
		if (toolTip != null) {
			// Make the text big enough to see easily
			toolTip = "<html><font size=\"5\">" + toolTip + "</font>";
		}

		previewPane.setText(toolTip);
		previewPane.setCaretPosition(0);
	}
This creates all the actions for opening/creating data type archives.
It also creates the action for refreshing the built-in data types
from the class path.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/datamgr/DataTypesProvider.java