Hi, I have looked around in a bunch of sources and have come to the conclusion that this is most probably a bug in the bundled chromium version of Qt 5.11.1 Looking around For Chromium it is difficult to track bugs due to its size and due to many users making bogus bug reports, but over the years there have been multiple issues where Chromium print(-preview) results in blank pages.
The changelog of Qt 5.12.x does also not list anything significant related to printing, further supporting this theory. I have also confirmed Qt 5.12.0 resolves the issue. There are two ways to fix this issue as I see it now: 1. Hard: Figure out the difference between Chromium 65.0.3325.230 (Qt 5.11.1 - Qt 5.11.3) and Chromium 69.0.3497.128 (Qt 5.12.0), find upstream bug reports in Chromium and see if there are any relevant patches and/or commits. Then attempt to backport these to fix the bug. 2. Easy: update to QtWebEngine 5.12.0, keep build depends as Qt 5.11.x. Take the earliest Debian 5.12.x release, before build depends were updated, and downgrade to 5.12.0 so the diff is as small as possible. This builds fine in a buster environment and works as expected. The only "issue" is applications still say "QtWebEngine 5.11.3" in their about as they aren't recompiled. Upstream makes the following guarantee[1]: > The Qt version 5.12 series is binary compatible with the 5.11.x series. > Applications compiled for 5.11 will continue to run with 5.12. So, problems could only occur when users still have self-compiled/legacy QtWebEngine applications that were compiled with 5.10.x. If this is of serious concern a NEWS entry could be added. For those that are interested in the fix, I have prepared a source package[2] and a binary package for amd64[3]. This binary package has been used in production for about a week now and I have received no issues regarding it. In most office environments printing is typically used a lot, besides Qt browser printing being broken mail printing being broken is a significant issue. Many users rely on printing for their daily work, which is why I consider this bug to be of severity "important", not "normal". Melvin. [1] https://code.qt.io/cgit/qt/qtwebengine.git/tree/dist/changes-5.12.0 [2] https://git.mel.vin/debian/pkg/qtwebengine [3] https://mel.vin/debian/pool/main/q/qtwebengine-opensource-src/
