add-browser

The JavaFX docs state that a WebView is ready when Worker.State.SUCCEEDED is reached however, unless you wait a while (i.e. Animation, Transition, PauseTransition, etc.), a blank page is rendered.

This suggests that there is an event which occurs inside the WebView readying it for a capture, but what is it?

There's over 7,000 code snippets on GitHub which use SwingFXUtils.fromFXImage but most of them appear to be either unrelated to WebView, are interactive (human masks the race condition) or use arbitrary Transitions (anywhere from 100ms to 2,000ms).

I've tried:

• Listening on changed(...) from within the WebView's dimensions (height and width properties DoubleProperty implements ObservableValue, which can monitor these things)

  • Not viable. Sometimes, the value seems to change separate from the paint routine, leading to partial content.

• Blindly telling anything and everything to runLater(...) on the FX Application Thread.

  • Many techniques use this, but my own unit tests (as well as some great feedback from other developers) explain that events are often already on the right thread, and this call is redundant. The best I can think of is adds just enough of a delay through queuing that it works for some.

• Adding a DOM listener/trigger or JavaScript listener/trigger to the WebView

  • Both JavaScript and the DOM seem to be loaded properly when SUCCEEDED is called despite the blank capture. DOM/JavaScript listeners don't seem to help.

• Using an Animation or Transition to effectively "sleep" without blocking the main FX thread.

  • ⚠️ This approach works and if the delay is long enough, can yield up to 100% of unit tests, but the Transition times seem to be some future moment that we're just guessing and bad design. For performant or mission-critical applications, this forces the programmer to make a tradeoff between speed or reliability, both a potentially bad experience to the user.

When's a good time to call WebView.snapshot(...)?

Usage: