How can I create a shape based on contiguous color area in Inkscape?

Question

I have a bunch of (crummily composed) SVG images with shapes that look like they have various bounded areas, but actually don't have very useful paths. The shapes are composed of various other shapes, clips, groups and lines on various layers. Here's one of the simplest:

I need to be able to fill the various fully enclosed spaces with various shadings. Since the parts are all on different layers the flood fill does nothing.

Area is not bounded, cannot fill.

I've tried making copies of all the objects and putting them on a layer together, then trying to convert everything to paths with the hopes of using unions to get shapes, but everything just goes haywire.

If this was a raster image a flood fill on contiguous color areas would work perfectly. In fact the shapes here are so frustrating I'm contemplating doing this is ImageMagick post processing, but it seems like there should be a proper way to do this.

How can I make new shapes for areas based on the apparent visual contiguous color regions?

Answer 1

After hours and hours bashing my head of this seemingly simple problem and chasing my tail around the internet, I actually figured this out.

The problem has nothing to do with the paths themselves, it has to do with the background. Inkscape will not find regions if you click on transparent background areas no matter what might be bounding them.

If you change the document properties to have anything but a pure transparent background the tool will work, then you can change it back when you're done.