Re: Proposing _NET_WM_STATE_FULLSCREEN_EXCLUSIVE

["Ryan C. Gordon" <icculus icculus org>]

> Also in the case of KDE Plasma Workspaces the window manager is not at all
> responsible for handling the resolution. This is done by a daemon called
> krandr. I will not add code to change the resolution as that is nicely handled
> by krandr. So we would need to announce the support only if the daemon is
> present - this is something we would most likely not be able to guarantee
> correctly as in session start KWin should be started before krandr and it's
> possible that KWin is run outside a KDE Plasma session.

To be clear, I don't think _any_ window manager currently has code to 
change resolutions (indeed, the core of the problem is that the app is 
doing that itself without any coordination with the system). I think 
it's great that KDE has a clear chain of responsibility for who is 
allowed to interact with XRandR, which means this can be cleaner for you 
than it might be for, say, Gnome.

How I would envision this working is something like this (I have no 
experience with KDE source code, so this might be pure fantasy on my 
part)...

- krandr sends a notification to KWin once it starts up, and then KWin 
can begin advertising the appropriate atoms. If a fullscreen app wants 
to start up in the very first seconds of the KDE session: too bad, but 
if we're being really fancy, KWin could stall that app until krandr is 
ready.
- If you run KWin outside of a Plasma session--and therefore never have 
krandr--KWin never advertises the atoms and never supports the 
extension. That's what you get for not running KDE the way God intended.  :)
- An app requests the _NET_WM_STATE_FULLSCREEN_EXCLUSIVE atom, KWin asks 
krandr to change resolutions, and does NOT resize any of the windows or 
move around desktop icons (etc) when it gets the resolution change 
event. It makes the appropriate window the top of the Z-order, etc. 
Other apps have no idea anything has changed for the most part.
- When the window loses focus (user alt-tabbed out of the game, window 
is legitimately being destroyed, etc), repeat this process, telling 
krandr to return to the original resolution.

I'm ignoring some of the minutiae here, but that's the basic gist of it. 
Does this sound like a reasonable approach for KWin?

--ryan.