On Fri, 16 May 2025 14:38:20 GMT, Michael Strauß <mstra...@openjdk.org> wrote:
> When an exception is thrown from `AnimationTimer::handle`, the JavaFX
> application freezes. The reason is that the user exception will bubble up
> into framework code, preventing the normal operation of JavaFX.
>
> The following program demonstrates the defect:
>
>
> public class FailingAnimationTimer extends Application {
> @Override
> public void start(Stage stage) throws Exception {
> var button = new Button("start timer");
> button.setOnAction(_ -> {
> var timer = new AnimationTimer() {
> @Override
> public void handle(long l) {
> throw new RuntimeException("foo");
> }
> };
>
> timer.start();
> });
>
> var root = new HBox();
> root.getChildren().add(new TextField("test"));
> root.getChildren().add(button);
> stage.setScene(new Scene(root));
> stage.show();
> }
> }
>
>
> The solution is to not allow user exceptions to bubble up into animation
> framework code. If an exception occurs, it is instead sent to the current
> thread's uncaught exception handler. This is the same thing that we already
> do for exceptions thrown by invalidation listeners and change listeners.
>
> In addition to that, a failing animation timer has the potential to spam
> logs, which is why I introduced a cut-off value at 100 exceptions for each
> individual timer, after which no further exceptions from this particular
> timer are sent to the uncaught exception handler. After reaching the cut-off
> value, the following warning is logged:
>
> `WARNING: Too many exceptions thrown by AnimationTimer, ignoring further
> exceptions. The cut-off number can be set with the system property
> com.sun.scenario.animation.failingTimerThreshold (current = 100).`
This pull request has now been integrated.
Changeset: 192b8613
Author: Michael Strauß <mstra...@openjdk.org>
URL:
https://git.openjdk.org/jfx/commit/192b86137d9a29c5c420434f8021f8dabd21dccf
Stats: 229 lines in 2 files changed: 205 ins; 4 del; 20 mod
8357157: Exception thrown from AnimationTimer freezes application
Reviewed-by: angorya, kizune
-------------
PR: https://git.openjdk.org/jfx/pull/1811
