Re: layout.cc: do not draw empty boxes (issue 6450113)

[dak]

http://codereview.appspot.com/6450113/diff/10001/lily/lookup.cc
File lily/lookup.cc (right):

http://codereview.appspot.com/6450113/diff/10001/lily/lookup.cc#newcode172
lily/lookup.cc:172: if (b.x ().length () < blotdiameter)
On 2012/09/03 07:25:53, Keith wrote:
> It is arguably valid to request a box running from right to left, for
which
> length() returns zero.  In this application, the Interval class
abstraction is
> not helping us.  We could defeat the abstraction with
>   if ( abs( b.x().delta() ) < blotdiameter)
>      blotdiameter = abs( b.x().delta() );

Well, "arguably valid" does not mean that we can let some of our code
argue one way, some of our code the other.

If we argue it is invalid, we should deliver a programming error here in
order to make people fix the callers.  If we argue it is valid, the code
needs to be able to deal with it.

Both the code in this function as well as the code in any function it
calls.  Of course, this becomes easier to guarantee if the code in this
function will, when in doubt, transform its input into a "proper"
left-to-right box, giving the followup code better guarantees than those
it contends itself to work with.

http://codereview.appspot.com/6450113/