RFR: 8176501: Method Shape.getBounds2D() incorrectly includes Bezier control points in bounding box [v12]

[Laurent Bourgès]

On Thu, 16 Dec 2021 18:33:37 GMT, Jeremy <duke at openjdk.java.net> wrote:

>> This removes code that relied on consulting the Bezier control points to calculate the Rectangle2D bounding box. Instead it's pretty straight-forward to convert the Bezier control points into the x & y parametric equations. At their most complex these equations are cubic polynomials, so calculating their extrema is just a matter of applying the quadratic formula to calculate their extrema. (Or in path segments that are quadratic/linear/constant: we do even less work.)
>> 
>> The bug writeup indicated they wanted Path2D#getBounds2D() to be more accurate/concise. They didn't explicitly say they wanted CubicCurve2D and QuadCurve2D to become more accurate too. But a preexisting unit test failed when Path2D#getBounds2D() was updated and those other classes weren't. At this point I considered either:
>> A. Updating CubicCurve2D and QuadCurve2D to use the new more accurate getBounds2D() or
>> B. Updating the unit test to forgive the discrepancy.
>> 
>> I chose A. Which might technically be seen as scope creep, but it feels like a more holistic/better approach.
>> 
>> Other shapes in java.awt.geom should not require updating, because they already identify concise bounds.
>> 
>> This also includes a new unit test (in Path2D/UnitTest.java) that fails without the changes in this commit.
>
> Jeremy has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8176501: Method Shape.getBounds2D() incorrectly includes Bezier control points in bounding box
>   
>   This is a second follow-up response to prrace's code review feedback about method modifiers.
>   
>   This commit more carefully preserves the getBounds2D() method modifiers for all 3 classes: the Path2D.Double, the Path2D.Float, and the Path2D itself.
>   
>   It is possible (if unlikely) that someone previously extended the Path2D class and overrode getBounds2D(), because the Path2D#getBounds2D() method was *not* final. So with this commit: any such existing code will not break. Meanwhile the subclasses (Double and Float) preserve their previous modifiers (final, synchronized).
>   
>   This is in response to prrace's code review:
>   
>   >    You are changing the signature of public API
>   >    src/java.desktop/share/classes/java/awt/geom/Path2D.java
>   >    public final synchronized Rectangle2D getBounds2D() => public Rectangle2D getBounds2D() {
>   >
>   > So no longer final, and no longer synchronized.
>   > This means a CSR is required and we need to think about it ..
>   > the intention was that the subclass not over-ride.
>   > And why remove synchronized ? I am fairly sure it was there to
>   > make sure no one was mutating the Path whilst
>   > bounds are being calculated.
>   > And you are using getPathIterator(AffineTransform) and the docs
>   > for that say it isn't thread safe.
>   > So I think this implementation needs to be thought about very carefully.

Congratulations!

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PR: https://git.openjdk.java.net/jdk/pull/6227