RFR: 8255015: Inconsistent illumination of 3D shape by PointLight

[Andreas Heger]

On Wed, 9 Jun 2021 18:46:16 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> The inconsistent illumination happens on Macs with retina displays only if the 3D shape is placed in a SubScene. The light sources are located with wrong coordinates in sub scenes and this causes a different illumination. The wrong coordinates for the light sources come from the fact that the retina pixel scale factors are not used in a SubScene.
>> 
>> With this pull request, the retina pixel scale factors will be also used in SubScenes and this should resolve the bug [https://bugs.openjdk.java.net/browse/JDK-8255015](url)
>
> @andreas-heger Welcome to the `jfx` project. At a quick glance, the fix looks promising. Have you tested this on Windows with Hi-DPI to make sure there is no impact? Would you be able add an automated test case that fails (only on Mac retina) without the fix and passes (on all platforms) with your fix? Hi-DPI fixes are often tricky to test in an automated test, so if not, we can use the existing manual test.
> 
> @nlisker this is the same problem I noted while testing PR #334. Clearly I had forgotten that it was not only a preexisting bug, but a known bug that was already filed. I intend to test this alone and in connection with your PR.

@kevinrushforth 
> The fix looks good. I tested it both in isolation and with PR #334 and it works on both a retina and non-retina display.
> 
> If you have time to write an automated test, that would be useful, but if not then a manual test would be OK.

Ok, I will try to write an automated test case which draws a sphere in a SubScene and then calculates the average color of the generated image. The test will be passed if the calculated average does not differ from the excepted average color by a certain tolerance value. I'm not sure if I will manage to do this... but I will give it a try.

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PR: https://git.openjdk.java.net/jfx/pull/531