From what I can tell, you must use a backgroundColor on a
container that will be a drop target. A workaround for needing a
transparent container is to set the alpha attribute to 0, but any
children you drag into the container will be invisible as well
since they inherit the 0 alpha setting.
My layout is like so:
* a Tile of image thumbnails that are draggable
* a large, "outer" canvas with a background image
* smaller canvases inside this outer canvas that should be
transparent so as to see the underlying background image
The dragging and dropping on the inner canvases works fine
except for the fact that they disappear when dropped - all because
of the 0 alpha setting.
Does anyone know of a workaround or a totally different way
of achieving this effect?