[OpenJDK 2D-Dev] Review Request: JDK-6457721: Stroke width incorrect while printing

[Jim Graham]

The calculations are still not correct.  Consider a transform that zooms 
Y coordinates and shrinks X coordinates, you will think that the 
resulting line width is large, and it will be for horizontal lines.  But 
vertical lines will experience a smaller line width.

The only real calculation to see if the point size needs to be adjusted 
is one of:

- if the direction is known, use an N-length vector perpendicular to the 
direction of the path.  This might work for drawLine(), but not for 
drawPolygon() and draw(Shape).

- if the direction is not known, or varies as in a polygon or path, then 
you need to use computations to compute the size of the minor axis of 
the ellipse produced by transforming the unit circle, which is not an 
easy problem (you can look at the code in the Marlin renderer to see how 
it handles this, I don't recall how it does it off-hand).

Also, you fixed the computations of "is the line width too thin", but 
there are also computations for "if it is too thin, then what is the 
correct minimum line width?" that still use the old computations, but in 
reverse...

			...jim

On 6/7/2016 4:32 AM, prasanta sadhukhan wrote:
> Fix looks good to me. But, do we not need to do the same for
>
> 209                     minLineWidth = Math.max(Math.abs(minPenSize.x)
>  210                                             Math.abs(minPenSize.y));
>
> For the test the instruction textarea is editable which needs to be made
> read-only.
> Also, if the user does not do any manual intervention, the test passes.
> The test should have provision of failing if there is no user
> interaction. I guess there is no need of using Robot class in a manual
> test, you can use sleep if it is just meant to delay main() closing.
> The test has some wildcard imports which can be changed to specific imports.
>
> Regards
> Prasanta
> On 6/7/2016 3:42 PM, Prahalad Kumar Narayanan wrote:
>>
>> Hello Everyone on Java2D
>>
>>
>>
>> Good day to you.
>>
>>
>>
>> Please find herewith: Webrev changes for the bug
>>
>>       Bug ID     : JDK-6457721
>>
>>       Bug Link : https://bugs.openjdk.java.net/browse/JDK-6457721
>>
>>
>>
>> As per the Bug:
>>
>> 1.       With rotation angle set to Graphics2D object, the printed
>> Lines, Rectangles or Shapes have incorrect stroke width
>>
>> 2.       The behavior is typically noticed at a rotation of 45’
>>
>> 3.       The issue is reproducible on JDK 9 and is applicable for
>> windows platform.
>>
>>
>>
>> Quick Description on Changes
>>
>> 1.       Thanks to Phil for adding his detailed comments on JBS. They
>> were really helpful.
>>
>> a.       Root Cause: The formula for stroke width calculation was
>> incorrect in the WPathGraphics.java code.
>>
>>
>>
>> 2.       Following changes have been incorporated-
>>
>> a.       Correction to the stroke width calculation.
>>
>>                                                                i.
>> As Phil suggested in his JBS comments, the logic has been modified to
>> use distance formula after being rotated by theta.
>>
>>                                                              ii.
>> Since many other places also use the same logic, correction has been
>> taken up wherever necessary
>>
>>
>>
>> b.      Fallback path for Lines and Rectangles when Custom stroke
>> implementation is set.
>>
>>                                                                i.
>> It was observed that when lines or rectangles are drawn with custom
>> stroke object, the code does not print any of these shapes.
>>
>>                                                              ii.
>> A fallback logic is now provided that prints the lines and rectangles
>> as ‘Shapes’.
>>
>>                                                             iii.
>> The same fallback logic is being taken up in other sections of code,
>> when GDI fails to instantiate a pen with required Attributes.
>>
>>          Hence the introduced fallback will be consistent with
>> existing code.
>>
>>
>>
>> c.       Manual Test Case to detect the bug and verify the fix
>>
>>                                                                i.
>> A manual jtreg test case has been provided for users to run, print and
>> verify the fix.
>>
>>
>>
>> Detailed comments have been added for changes in the code.
>>
>> Kindly review the changes at your convenience and provide your
>> suggestions.
>>
>>          Webrev Link:
>> <http://cr.openjdk.java.net/%7Epnarayanan/6457721/webrev.00/>http://cr.openjdk.java.net/~pnarayanan/6457721/webrev.00/
>>
>>
>>
>> Thank you for your time in review
>>
>> Have a good day
>>
>>
>>
>> Prahalad N.
>>
>>
>>
>>
>>
>>
>>
>