HTMLViewer Performance Issue (max cpu)

Does anyone know how to mitigate this issue when using the HTMLViewer?

When loading the URL “” with no account logged in there is a video/animation at the top of the page I believe is the culprit but the CPU will max out via the VTDecoderXPCService process. as indicated in the Activity Viewer on a Mac running macOS 10.15 or even 10.13.6

This does not happen on Windows as the video/animation stops on initial load regardless of using native or webkit renderer.

Interesting, I do get the same behavior here built on Xojo 2020R1.2 on macOS 10.15.7, but not when opening the URL in Safari 14.0.

Right, even though the native renderer is basically Safari on a Mac when you load the page in Safari itself you do not get the odd behavior. So I’m assuming it’s a “bug” in the HTMLViewer where it cannot handle the page correctly.

The built-in implementation of WebKit on macOS is the only renderer available on that platform. This issue is likely the result of the recent switch to WKWebView.

To add more data to this, I don’t see this issue on 10.14 or 10.15 when loading a local JavaScript-heavy file.

Wondering if anyone know the cause of this issue

I also see this when loading the specified URL in to an HTMLViewer on 10.14:

It would appear to the animation causing the issue. You should open a Feedback Case.

here on macos 10.12 the VTDecoder service stays under 50%, with safari or opera.

Is Apple’s video transcoder (of sorts). When working with video on Apple platforms, this process pops up to convert the video file into a series of images and audio.

It may be a question of compatibility, or needing some security protocol, or even that Apple simply uses one thing for you and I, and different thing for Safari.