[Bug 28918] New: getClientRects() and getBoundingClientRect() need to be clearer about when the returned DOMRect might contain -0 anywhere

https://www.w3.org/Bugs/Public/show_bug.cgi?id=28918

            Bug ID: 28918
           Summary: getClientRects() and getBoundingClientRect() need to
                    be clearer about when the returned DOMRect might
                    contain -0 anywhere
           Product: CSS
           Version: unspecified
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: CSSOM View
          Assignee: simonp@opera.com
          Reporter: jwalden+w3@mit.edu
        QA Contact: public-css-bugzilla@w3.org

The CSSOM spec is unclear about what the sign of getBoundingClientRect().top
is, when that value is zero.  Is -0 a possibility, or is +0 the only permitted
value?  Could it be either, and if so, when should the different signs be
observed?

This issue applies to all the other fields of DOMRect, as well.  The DOMRect
spec is clear that width/height can be negative, but that could just as easily
be because |new DOMRect| lets you create a rect with arbitrary numeric
components, as because of any real-world reason.  And one could imagine that
"negative" observation to be motivated by "real" negative numbers, not -0.

This issue is pretty nitpickery, of course.  But I raise it because I stumbled
across a Gecko test that inadvertently compared gBCR().top with -0.  It passes
because it ignores the sign on zero, but I'm changing the (general) comparison
mechanism to only equate same-signed zeroes, and it's not clear that the test's
comparison is exactly right or wrong.

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Received on Monday, 6 July 2015 19:17:55 UTC