Royal Hawaiian ladies garment

My grandmother bought this in Hawaii a long time ago. I'm not actually sure what this is... It looks like a dress, but it only fastens to the waste and there are large slits on either side. It's like a combo between a dress and a jacket, so I call it a "dracket".
Anyhow, it's in great shape; no dry rotting or tears. the fabric is a tiny bit faded perhaps, but maybe not. I think this garment was "new" before I was born. My parents stored things for my grandmother and this is one of them. I wore it a couple of times when I was younger (it seemed like a waste not to wear something so neat). It closes with those "frog" things made of cord. It seems Asian in style, but in a Hawaiian patterned fabric.

I've heard that some people collect vintage Hawaiian shirts, but I don't know if anyone collects something like this. Anyhow, if someone could just tell me what this thing is actually called I'd be happy.