Running a WebView that generates a javascript animation, many times, even without waiting for it to end, can lead to exceptions, especially if the graphic resources are limited. The issue has been found with recent JavaFX versions (21, 23-ea), on Windows and macOS.

On Windows:

May 31, 2024 6:59:25 PM com.sun.javafx.webkit.prism.PrismInvoker runOnRenderThread
SEVERE: RenderJob error
java.util.concurrent.ExecutionException: java.lang.NullPointerException: Cannot invoke "com.sun.prism.RTTexture.contentsUseful()" because "this.txt" is null
        at java.base/java.util.concurrent.FutureTask.report(FutureTask.java:122)
        at java.base/java.util.concurrent.FutureTask.get(FutureTask.java:191)
        at javafx.web@23-ea/com.sun.javafx.webkit.prism.PrismInvoker.runOnRenderThread(PrismInvoker.java:93)
        at javafx.web@23-ea/com.sun.javafx.webkit.prism.RTImage.getPixelBuffer(RTImage.java:203)
        at javafx.web@23-ea/com.sun.webkit.MainThread.twkScheduleDispatchFunctions(Native Method)
        at javafx.web@23-ea/com.sun.webkit.MainThread.lambda$fwkScheduleDispatchFunctions$0(MainThread.java:35)
        at javafx.graphics@23-ea/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:456)
        at java.base/java.security.AccessController.doPrivileged(AccessController.java:400)
        at javafx.graphics@23-ea/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:455)
        at javafx.graphics@23-ea/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
Caused by: java.lang.NullPointerException: Cannot invoke "com.sun.prism.RTTexture.contentsUseful()" because "this.txt" is null
        at javafx.web@23-ea/com.sun.javafx.webkit.prism.RTImage.getTexture(RTImage.java:118)
        at javafx.web@23-ea/com.sun.javafx.webkit.prism.RTImage.getGraphics(RTImage.java:93)
        at javafx.web@23-ea/com.sun.javafx.webkit.prism.WCBufferedContext.getGraphics(WCBufferedContext.java:65)
        at javafx.web@23-ea/com.sun.javafx.webkit.prism.WCGraphicsPrismContext.getPlatformGraphics(WCGraphicsPrismContext.java:127)
        at javafx.web@23-ea/com.sun.javafx.webkit.prism.WCGraphicsPrismContext.isValid(WCGraphicsPrismContext.java:132)
        at javafx.web@23-ea/com.sun.webkit.graphics.WCRenderQueue.decode(WCRenderQueue.java:107)
        at javafx.web@23-ea/com.sun.webkit.graphics.WCImage.flushRQ(WCImage.java:64)
        at javafx.web@23-ea/com.sun.javafx.webkit.prism.RTImage.lambda$getPixelBuffer$2(RTImage.java:209)
        at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:572)
        at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
        at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:572)
        at java.base/java.util.concurrent.FutureTask.runAndReset(FutureTask.java:358)
        at javafx.graphics@23-ea/com.sun.javafx.tk.RenderJob.run(RenderJob.java:58)
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
        at javafx.graphics@23-ea/com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.run(QuantumRenderer.java:126)
        at java.base/java.lang.Thread.run(Thread.java:1583)

on macOS:

May 31, 2024 8:55:16 PM com.sun.javafx.webkit.prism.PrismInvoker runOnRenderThread
SEVERE: RenderJob error
java.util.concurrent.ExecutionException: java.lang.NullPointerException: Cannot invoke "com.sun.prism.RTTexture.contentsUseful()" because "this.txt" is null
        at java.base/java.util.concurrent.FutureTask.report(FutureTask.java:122)
        at java.base/java.util.concurrent.FutureTask.get(FutureTask.java:191)
        at javafx.web@23-ea/com.sun.javafx.webkit.prism.PrismInvoker.runOnRenderThread(PrismInvoker.java:93)
        at javafx.web@23-ea/com.sun.javafx.webkit.prism.RTImage.getPixelBuffer(RTImage.java:203)
        at javafx.web@23-ea/com.sun.webkit.Timer.twkFireTimerEvent(Native Method)
        at javafx.web@23-ea/com.sun.webkit.Timer.fireTimerEvent(Timer.java:84)
        at javafx.web@23-ea/com.sun.webkit.Timer.notifyTick(Timer.java:65)
        at javafx.web@23-ea/javafx.scene.web.WebEngine$PulseTimer.lambda$static$0(WebEngine.java:1205)
        at javafx.graphics@23-ea/com.sun.javafx.application.PlatformImpl.lambda$runLater$10(PlatformImpl.java:456)
        at java.base/java.security.AccessController.doPrivileged(AccessController.java:400)
        at javafx.graphics@23-ea/com.sun.javafx.application.PlatformImpl.lambda$runLater$11(PlatformImpl.java:455)
        at javafx.graphics@23-ea/com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
Caused by: java.lang.NullPointerException: Cannot invoke "com.sun.prism.RTTexture.contentsUseful()" because "this.txt" is null
        at javafx.web@23-ea/com.sun.javafx.webkit.prism.RTImage.getTexture(RTImage.java:118)
        at javafx.web@23-ea/com.sun.javafx.webkit.prism.RTImage.getGraphics(RTImage.java:93)
        at javafx.web@23-ea/com.sun.javafx.webkit.prism.WCBufferedContext.getGraphics(WCBufferedContext.java:65)
        at javafx.web@23-ea/com.sun.javafx.webkit.prism.WCGraphicsPrismContext.getPlatformGraphics(WCGraphicsPrismContext.java:127)
        at javafx.web@23-ea/com.sun.javafx.webkit.prism.WCGraphicsPrismContext.isValid(WCGraphicsPrismContext.java:132)
        at javafx.web@23-ea/com.sun.webkit.graphics.WCRenderQueue.decode(WCRenderQueue.java:107)
        at javafx.web@23-ea/com.sun.webkit.graphics.WCImage.flushRQ(WCImage.java:64)
        at javafx.web@23-ea/com.sun.javafx.webkit.prism.RTImage.lambda$getPixelBuffer$2(RTImage.java:209)
        at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:572)
        at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
        at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:572)
        at java.base/java.util.concurrent.FutureTask.runAndReset(FutureTask.java:358)
        at javafx.graphics@23-ea/com.sun.javafx.tk.RenderJob.run(RenderJob.java:58)
        at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
        at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
        at javafx.graphics@23-ea/com.sun.javafx.tk.quantum.QuantumRenderer$PipelineRunnable.run(QuantumRenderer.java:126)
        at java.base/java.lang.Thread.run(Thread.java:1583)

The attached test reproduces the issue.

Unzip the html file, run the application, and select one row of the tableView to generate the animation. Then go selecting one after the other, without waiting, and at some point the exception will show up. Resizing the stage also helps.

Note that the test has a very low Vram value (40 MB), way lower than the default 512 MB, but this is just to get the exception faster.

While the pool of resources is perfectly capable of dealing with resource management under such limit, the logs show that at some point the resources are pruned from the pool:

Pruning obsolete in pool: D3D Vram Pool
Pruning unuseful older than 1024 in pool: D3D Vram Pool
Pruning unuseful older than 512 in pool: D3D Vram Pool
Pruning unuseful older than 10 in pool: D3D Vram Pool
Pruning all older than 1024 in pool: D3D Vram Pool
Pruning all older than 512 in pool: D3D Vram Pool
Pruning all older than 100 in pool: D3D Vram Pool
Pruning everything in pool: D3D Vram Pool

or

Pruning obsolete in pool: ES2 Vram Pool
Pruning unuseful older than 1024 in pool: ES2 Vram Pool
Pruning unuseful older than 512 in pool: ES2 Vram Pool
Pruning unuseful older than 10 in pool: ES2 Vram Pool
Pruning all older than 1024 in pool: ES2 Vram Pool
Pruning all older than 512 in pool: ES2 Vram Pool
Pruning all older than 100 in pool: ES2 Vram Pool
Pruning everything in pool: ES2 Vram Pool
Last chance pruning in pool: ES2 Vram Pool

there is sometimes a texture that is removed, but it is still being referred down the line, causing the NPE.