21.12.2012 6:05, Sergey Bylokhov пишет:
Hi, Jim.
21.12.2012 4:59, Jim Graham wrote:
The Object.equals() method is not intended to compare geometries.
While Area.equals() attempts to perform geometric comparison I think
that was a bad idea in retrospect for many reasons:
- In practice you can only really compare within a tolerance due to
the many ways for computations to every so slightly shift the results
- There is no decent way to satisfy the equals/hashcode contract with
such a comparison so Area is forever broken with respect to that
contract.
- It's a complicated test that can only serve to convince developers
to invite performance drains into their code by making them think it
is a reasonable thing to compare.
For testing we should probably use Shape.contains() to verify answers
for rectangle arguments and if we want to perform verification on
arbitrary shape arguments then we'd need to write our own fuzzy
comparator.
But why fix is incorrect? It just use the same code as sffd for the
correct shapes and have additional code for incorrect. Only
conditionchanged from width/height should be positive, to
width/height should be the same direction as incoming rectangle.
There isn't even any guarantee that we will hand them back a rectangle
from getClip().
One of the jck tests expect this, but I think that this is the wrong
test.
There is nothing in the documentation that guarantees a specific type
returned from the method. If a JCK test was written to expect a
Rectangle from the method then that is a separate problem that we'll
have to address at some point. For now I'm only suggesting modifying
the process for negative-empty rectangles. Does that trigger the JCK
failure? If so, we are still satisfying the documented spec and so
we will simply have to confince JCK to allow this exception.
Problem in jck come from the fact that Rectangle differs from
Rectangle2d. Note that everything is ok if graphics is not transformed
or just translated. But if we scale graphics we get:
1 getClip() return non equivalent object.
2 getClipBounds for Rectangle return it as is, but for Rectangle2D it
is call getBounds, which return an empty bounds or wrong bounds if
rectangle2d was normalized by sffd.
3 Some tests expects class equivalence between set/get clip. I'll
prepare CR for them soon.
Also there is the difference in the real clip, if we use type for the
empty Rectangle to Rectangle2D the real clip became correct.
typo: Also there is the difference in the real clip, if we change type
from the empty Rectangle to the empty Rectangle2D, the real clip will
become correct.
All these issues are carried out in the testcase.
After all, if you end up in the drop through case then we hand the
paths to Area to do intersections and Area will do all sorts of
surgery on the geometry.
But I sure this area will be equal to the user's clip?
For all practical purposes it should be, but not only will the Area
code encapsulate the answer in a different class (even if the result
is a rectangle), it may reverse the order of the segments, it may
represent the area as two separate rectangles that abut each other in
a way that they are equivalent to one larger rectangle, but the Area
code failed to notice that optimization, etc. All it will guarantee
is that it returns a shape that describes the same interior, it will
make no guarantees about minimalism or association of segments...
...jim
--
Best regards, Sergey.
--
Best regards, Sergey.
