Properties of Custom Layout

Hi all,

Similar to Custom Paint, we wanted to start some more discussions on the
mailing list around Custom Layout. Shane & I sat down what we think are
some of the desirable properties.

See https://gist.github.com/bfgeek/93408fe4182d87e92b7b
<https://www.google.com/url?q=https%3A%2F%2Fgist.github.com%2Fbfgeek%2F93408fe4182d87e92b7b&sa=D&sntz=1&usg=AFQjCNGjov9R3QzZqzOuolRqt1BYSkANmQ>

Again feel free to respond here, or directly on the gist.

Thanks,
Ian