canvas_refresh() not working like described

[ClarkyCat]

Why doesn't canvas_refresh() doesn't work on its own from within a script?

I am trying to make a Canvas object template and a foundation starting point for canvas objects.
When trying to initialise the canvas via canvas_refresh(), the script does not compile.

But when I declare a variable inside the script and make the canvas_refresh() refer to the declaration variable, it works?

So,

Create script > Manual Execution > Touch - Multitouch > Redraw - On demand

Inside Canvas object create a script called 'Test'

Inside script write:
canvas_refresh();

This does not work.

But when you write,

decl this = getobject();
canvas_refresh(this);

The script compiles fine. Why does this happen?

Why is it not possible to manually call canvas_refresh() from it's own script?