Created attachment 126719 [details]
The log of Weston with WAYLAND_DEBUG=server, and standarddialogs connected to it

It seems to be a very weird issue with Qt 5.7.x and Qt 5.8 when using QtWayland with the default wl_shell integration (doesn't seem to happen when it's using xdg_shell, but xdg_shell is not the default for QtWayland without an env var

(and EFL if you export EFL_WAYLAND_DONT_USE_XDG_SHELL=1, I was able to replicate this, however the only EFL application that I know of, and have that actually utilizes child windows is the elementary_test that comes with EFL)

I can replicate this by even unsetting QT_WAYLAND_DECORATION, and KDE_FULL_SESSION to get minimal Qt.

I can test with an example client, standarddialogs
https://quickgit.kde.org/?p=qt%2Fqtbase.git&a=tree&h=ffe4a1df1c641df4b3738887d02214082aa7aa12&hb=25e9bde2d665866f7a9a40d1ed3aa8fabcf2ac2f&f=examples%2Fwidgets%2Fdialogs%2Fstandarddialogs

With standarddialogs, I start the application up, open, and then close a dialog, and then leave the mouse pointer on the main surface. After a few seconds, the cursor changes to a busy cursor, and it stops responding to mouse input, as if though it's not responding to wl_pings (where the whole window becomes draggable). 

The whole surface stops responding to mouse input.


It does however appear to respond to Keyboard input, I can press tab to move the selection around, and press space to press a button to open another dialog. The dialog seems to respond to input, but the main surface that stops responding to mouse input, never responds to it again