[Webkit-unassigned] [Bug 30442] New: Add helper methods to determine whether a transformation matrix is only scaled or translated

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=30442

           Summary: Add helper methods to determine whether a
                    transformation matrix is only scaled or translated
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: Platform
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: jpetsovits at rim.com


In order to determine whether a rectangle is still a rectangle after some
transformation, it's sufficient to check if the transformation matrix only
consists of scale and translation. That's a useful check to have, as you can,
for example, use that knowledge to follow an optimized code path or a generic
one. I think that check should be a helper method in TransformationMatrix - so
far, I made use of that kind of check twice.

I could also imagine checks for scale-only and translation-only to be useful
for some cases, so I'm adding those too as they're very straightforward.

Patch attached below.

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