When clicking a link in an email in KMail, the message view layout is destroyed and cannot be recovered unless you close KMail's main window and open it again. This happens for *every* link, but only happens on HiDPI screens (QT_SCREEN_SCALE_FACTOR=2 or higher). This has been happening since the switch to QtWebEngine. It has never worked with it. Steps to reproduce: 1) close kmail (killall kmail to be sure) 2) from a terminal, open kmail in HiDPI mode: QT_SCREEN_SCALE_FACTOR=2 kmail 3) select an email that has a web link 4) click it Expected results: Browser opens and KMail window remains as it was before clicking the link (see "before" screenshot) Actual results: Browser opens, but KMail window layout is destroyed (see "after" screenshot).
Created attachment 104078 [details] "Before" screenshot
Created attachment 104079 [details] "After" screenshot
I was able to reproduce the same bug in webengine's demobrowser, so it's a Qt bug. https://bugreports.qt.io/browse/QTBUG-59017
Note: if `kcmshell5 componentchooser` says the webbrowser is firefox, the bug doesn't happen. If OTOH it says "based on the contents of the URL" (i.e. KMail uses KIO), then the bug happens. That's a workaround for now, and an indication that something in KIO is triggering it.