WM_NAME vs. _NET_WM_NAME

[Martin Gräßlin]

On Monday 27 October 2014 09:22:15 Florian Bruhin wrote:
> * Martin Gräßlin <mgraesslin at kde.org> [2014-10-27 08:59:17 +0100]:
> > > While developing a Qt application, I noticed some bugs regarding to
> > > window title handling [1][2][3].
> > 
> > I assume that's Qt 5, right?
> 
> Indeed, it works fine with Qt 4.
> 
> > > It seems the Qt toolkit only sets _NET_WM_NAME and doesn't set WM_NAME
> > > at all. Now that raises some questions:
> > > 
> > > - Should a client also set WM_NAME when setting _NET_WM_NAME? Sure,
> > > 
> > >   it's a good idea for backwards-compatiblity, but is it warranted to
> > >   open a bug against Qt? (I'd say yes, but I'd like to hear other
> > >   opinions).
> > 
> > From my reading of the relevant section in ICCCM (4.1.2.1) there is no
> > indication that a client is supposed to set it. Given that it's certainly
> > not a bug on Qt's side. If a window manager has problems with it, it's
> > more because the window manager doesn't support EWMH.
> 
> Okay. I'll still open a bug in Qt then since it seems to raise
> problems in the wild - then it's up to them to decide whether it's
> worth to fix it or not ;)

Fair enough, though I think it's not the task of a toolkit to be bug-to-bug 
compatible with each window manager ;-)

> 
> > 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.
> 
> Do you mean the backend as in a part of Qt, or xcb itself?

The backend in Qt (qtbase/src/plugins/platforms/xcb).

> 
> > At the same time knowing the Qt development I am sure they would accept
> > patches if it improves the interoperability.
> 
> I unfortunately don't feel comfortable enough with C++ to work on Qt
> (I'm using PyQt).
> 
> > > - Should a window manager which implements EWMH act correctly when a
> > > 
> > >   client sets _NET_WM_NAME but not WM_NAME? (see [2])
> > 
> > I do not really understand this question. I looked at the bug report and
> > would say that's a hebstluftwm bug. For comparison KWin handles the
> > situation with Qt 5 windows correctly.
> 
> Okay. The question basically "is it the WM's fault, or Qt's fault" ;)

Then the answer is: WMs fault.

> 
> > Shameless plug: as you are using Qt 5, consider using KF5::WindowSystem
> > which is a nice Qt 5 (only, no further KDE dependencies) library
> > implementing EWMH, supporting fallback to ICCCM if needed. It's the
> > library powering KWin and Plasma (e.g. taskmanager) and also used in
> > LXQt.
> 
> Probably not an option with PyQt, and also that's not really a
> dependency I want to have just to set a window title :D

ah that be more for the case of reading the window title.

Cheers
Martin
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