Monocle as a replacement

Danny Gonzalez danny.gonzalez at
Wed Feb 19 07:46:31 UTC 2020

Hi Tres,

We also are suffering from this crash when running our TestFX unit tests, particularly on Java 11.
It is due to a concurrency issue between the JavaFX thread and the QuantumRenderer thread and there is an OpenJDK bug here:

Quoting from this bug report:
“The QuantumRenderer calls the getPixels() method while trying to find a buffer that's not in use, yet in doing so it can inadvertently modify a buffer that's in use."

There is also a related TestFX Bug:

There is a fix for this issue In the first comment of the JDK-8201567, in a link to GitLab:<>

We have used this patch in our local OpenJFX build.

This has never been made into a pull request however but I believe it should.


On 17 Feb 2020, at 19:12, Tres Finocchiaro <tres.finocchiaro at<mailto:tres.finocchiaro at>> wrote:


I'm the developer of a printing plugin which leverages JavaFX for a few
HTML functions.

One of our functions would greatly benefit from being "headless (or more
accurately, "silent") mode that Monocle offers and I'm evaluating the use
of Monocle on (non-headless) Desktops for this.  I'm currently testing a
monocle build by the TestFX team for MacOS.

Although first test was positive, when invoking multiple times, I'm getting
some internal errors similar to this: and the framework grows slower
and slower as it nears its final capture. (I'm using WebView.capture(...))

Is this the right place for such as discussion? Where's the best place to
ask about issues with Monocle?

- Tres.Finocchiaro at<mailto:Tres.Finocchiaro at>

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