Just read throught this, very usefule

Though shouldn't
function on.paint(gc)
drawRoundRect(gc, 100, 50, 20, 15, 5)
...
end
in the second code block be
gc:drawRoundRect(100, 50, 20, 15, 5)
then? Because it doesn't seem any different to me

(I may as well be wrong, I'm not that good yet
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)