Kmail, Firefox and HTML-encoded emails

Does anyone know how Kmail displays HTM-encoded emails? Does it use its own rendering utility, or the system’s default browser, or some other external package?

I’m trying to track down the cause of long periods of 100% CPU utilisation which seem to occur when reading HTML-encoded emails containing daily digests from a newspaper and clicking on links which bring up the full stories in Firefox. The only thing I can be fairly sure about is that a task manager (XFCE?) is consuming up to 67% and I suspect “firefox-contentproc” process(es) are taking most of the rest.

The Windows version of Firefox seems to have its own task manager; does the Leap 51.1 version use the XFCE task manager?

A quick web search reveals Kmail uses Qt Webengine to display HTML, which makes total sense since KDE/Plasma is built on the Qt Framework today. And, Qt Webengine is based on Chromium with parts removed

I don’t know what may be causing your problems but I personally found that Firefox’ hardware acceleration has no governor, when it’s activated it can run wild and max out your GPU.

So, I disabled my Firefox hardware acceleration and haven’t had problems since.


Thanks for your reply. I noticed QTWebEngine in the system monitor and wondered about that. The hardware graphics-accelerator was actually disabled, but checking the Firefox “Use recommended performance settings” enabled it and that certainly improved its rendering performance.

However I think I have a much more fundamental problem, and I’ll open another post.