More documentation of Layers features

[gregpalaci]

I've gone through the source to find more about layers and found things like the undocumented fact you can use an image instead of a colour overlay and whatnot.

I can't find how you might choose where the layer lands (The X and Y position) as well as the Width and Height of it, compared to its parent.

Specifically I'm adding polaroid backgrounds to photos but since both the layer and the parent stretch to fill the full width I can't achieve this.

I was wondering where all the options are listed for Layers. this.width and this.height and this.crop dont seem to work.