thispoints to the widget node invoking the macro.
Note that if the params array is missing or blank, then all the supplied parameters are passed to the
Macros are just used to return a chunk of wikitext for further processing. They should not make modifications to tiddlers in the wiki store. The reason is that you cannott control when the macro is called; it may be called repeatedly as part of refresh processing. So it is important that macros do not have any other side effects beyond generating their text.