On Wed, 4 Mar 2026 08:07:05 GMT, Lukasz Kostyra <[email protected]> wrote:
>> This change fixes a potential threading issue in RTImage.draw() method in >> WebView. The issue has been theorized back in >> [JDK-8333374](https://bugs.openjdk.org/browse/JDK-8333374), I have not >> managed to figure out a reliable reproducer for it, but the circumstances >> for it to happen are there. >> >> Issue can happen in `RTimage.draw()` method. In 99% of cases >> `RTImage.draw()` will be called only by QuantumRenderer thread (that is >> during regular drawing to a Stage/Scene), however there is also a >> possibility we will call `RTImage.draw()` from a different thread, notably >> with a `PrinterGraphics` object (or in other words, when printing). Then >> there is a chance we will run some of the initial checks in parallel to >> QuantumRenderer thread. I found two places that can be affected - the >> initial checks at the beginning of the method and the `getTexture()` call >> inside the code block responsible for printing. >> >> The first place was fixed by running the checks on the render thread. That >> way we can ensure the render thread will not overwrite the `tex` reference >> from the render thread while the printing thread reads it. To make this >> happen I added `PrismInvoker.callOnRenderThread()` which functions like >> `PrismInvoker.runOnRenderThread()` but with a `Callable<>` instead of a >> `Runnable` object. >> >> Second place can happen if, for some reason, in between previous checks and >> the `getTexture()` call QuantumRenderer will modify or free RTImage's tex >> reference (ex. while pruning the Vram pool) - then the `getTexture()` call >> will return `null` (introduced as NPE prevention from >> [JDK-8333374](https://bugs.openjdk.org/browse/JDK-8333374)) which can cause >> an NPE on QuantumRenderer thread. If that happens, we skip the >> `readPixels()` call which will print an empty RTImage. >> >> I verified these changes on Windows and Linux with our test suite and with >> manual testing via `HelloWebView` and using an old `SimplePrint.java` >> reproducer from [JDK-8118415](https://bugs.openjdk.org/browse/JDK-8118415); >> both regular drawing and printing work as they did. I found simply loading >> `google.com` via both apps works to trigger this draw call multiple times >> (`SimplePrint.java` needed to be adjusted slightly to print out the web page >> instead of predefined HTML code). Test suite completes successfully (there >> were 3 web.test failures on my end but they also happened on master and >> refer to other, unrelated parts of javafx.web) and printing works the same >> way it used to. > > Lukasz Kostyra has updated the pull request incrementally with one additional > commit since the last revision: > > PrismInvoker: Remove redundant type when creating FutureTasks I am getting assertion messages while printing: PrinterJob: JavaFX PrinterJob Printer Print to PDF Collation = UNCOLLATED Copies = 1 Sides = ONE_SIDED JobName = JavaFX Print Job Output file = Page ranges = null Print color = COLOR Print quality = NORMAL Print resolution = Feed res=300dpi. Cross Feed res=300dpi. Paper source = Paper source : Automatic Page layout = Paper=Paper: A4 size=210.0x297.0 MM Orient=PORTRAIT leftMargin=54.0 rightMargin=54.0 topMargin=54.0 bottomMargin=54.0 Job Status = NOT_STARTED *** unexpected PG access java.lang.Exception: Stack trace at java.base/java.lang.Thread.dumpStack(Thread.java:2018) at javafx.graphics/javafx.scene.Node.getPeer(Node.java:2700) at javafx.graphics/javafx.scene.Node$1.getPeer(Node.java:539) at javafx.graphics/com.sun.javafx.scene.NodeHelper.getPeer(NodeHelper.java:213) at javafx.graphics/com.sun.prism.j2d.print.J2DPrinterJob$J2DPageable.printNode(J2DPrinterJob.java:1145) at javafx.graphics/com.sun.prism.j2d.print.J2DPrinterJob$J2DPageable.print(J2DPrinterJob.java:1138) at java.desktop/sun.lwawt.macosx.CPrinterJob$4.run(CPrinterJob.java:878) at java.desktop/sun.lwawt.macosx.CPrinterJob.printAndGetPageFormatArea(CPrinterJob.java:897) at java.desktop/sun.lwawt.macosx.CPrinterJob.printLoop(Native Method) at java.desktop/sun.lwawt.macosx.CPrinterJob.print(CPrinterJob.java:377) at javafx.graphics/com.sun.prism.j2d.print.J2DPrinterJob$PrintJobRunnable.run(J2DPrinterJob.java:863) at java.base/java.lang.Thread.run(Thread.java:1474) the print job succeeds though. ------------- PR Comment: https://git.openjdk.org/jfx/pull/2092#issuecomment-4000110890
