Qt does not set WM_NAME property

Qt does not set the WM_NAME property for window titles, only _NET_WM_NAME.

It seems it's not strictly required according to ICCCM/[EWMH|http://standards.freedesktop.org/wm-spec/wm-spec-1.3.html#idm140130317621408]:

Regarding WM_NAME:

The WM_NAME property is an uninterpreted string that the client wants the window manager to display in association with the window

Regarding _NET_WM_NAME:

The Client SHOULD set this to the title of the window in UTF-8 encoding. If set, the Window Manager should use this in preference to WM_NAME.

I also opened a discussion on the wm-spec-list@gnome.org list about this, where Martin Gräßlin said:

Qt 5's XCB backend doesn't support many "deprecated" features where there is a
EWMH replacement. For example it also doesn't support setting a window icon
through the WM_HINTS (ICCCM section 4.1.2.4) property. Given that I
interpreted this as a design decision to not support the "deprecated" hints in
the new implementation.

However, unfortunately not setting WM_NAME causes problems in the wild, for example:

• herbstluftwm (a window manager) not updating titles correctly.
• KeePassX (a password manager) not reading the titles correctly.
• Probably anything not implementing EWMH not reading the title correctly, which might affect some other minimal or older WMs.

I understand the argument of not maintaining "deprecated" things, but here it seems it really causes trouble at a lot of other places - of course I'll submit bug reports there as applicable as well.