RFR: 8202990: javafx webview css filter property with display scaling

[Kevin Rushforth]

On Sat, 29 Aug 2020 00:31:51 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> The fix and test looks good.
>
> I spent some time this afternoon going over the fix in more detail and doing extensive testing on both Windows and Mac.
> 
> I believe the fix is good. Both by inspection and by instrumenting the code, there are no race conditions or other
> problems that I can see.
> The problem appears to be in the test, or else somewhere in the test harness or the SW pipeline exposed by the test. If
> I run the new CSSTest in a loop on either Mac or Windows, it will crash intermittently. I then reverted your fix,
> running the new test (which will throw an expected assertion error), and it still crashes intermittently.  My
> recommendation is to use a system test, similar to what
> [SVGTest.java](https://github.com/openjdk/jfx/blob/master/tests/system/src/test/java/test/javafx/scene/web/SVGTest.java)
> does, rather than a unit test in the javafx.web module, which uses `WebPage::paint`.

I believe that the problem noted above is with the test harness, specifically the `WebPageShim::paint` method. I filed
[JDK-8252596](https://bugs.openjdk.java.net/browse/JDK-8252596) to track fixing the tests.

So the fix for _this_ PR should avoid using it, as suggested above.

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PR: https://git.openjdk.java.net/jfx/pull/279