Last night, I checked in a change to the way drag and drop works.
Gergely had originally written code that required the return value from
an on_drop method to be exactly true or false (the ruby objects by those
names).
When I integrated the code, I had converted this to use the existing
IsTrue test which follows the Ruby convention of false and nil being
treated as false, and *anything else* being treated as true.
In this case, if the user did a move-drag, and the intent was to reject
the drop, it would be dangerous if we thought we were rejecting it but
the system thought we were accepting it. The data would be lost. This
might happen, for example, if the coder returned 0, thinking that 0 was
a non-true value as it is in C++.
So I changed it to still allow either nil or false to mean reject, but
to allow only true to mean accept. Any other value will raise an
exception, similar to how Gergely had originally coded it.
Kevin
