F11: xorg decision to disable Ctrl-Alt-Backspace

[Bill Crawford]

On Tuesday 31 March 2009 16:48:13 Adam Jackson wrote:
> On Tue, 2009-03-31 at 10:51 -0400, Colin Walters wrote:
...
> > That's useful.  A lot of the time I have a good idea of what app has a
> > stuck grab, but this is a bit easier.  Ideally there would be a way to
> > forcibly ungrab but I suppose that may confuse application toolkits.
>
> We had an optional bit of config file magic at one point that would let
> you turn on a magic key combo to break the current grab.  Plus a
> matching request in the XFree86-Misc extension to turn it back off,
> since otherwise you can defeat screen locking.  Gone in 1.6 though, that
> extension was pretty much a mistake. [1]

This was actually very, very useful (I get to use it on a fair number of 
occasions, and when the alternatives are (1) wait ten minutes for the app to 
catch up or (2) kill it and lose whatever was in it, I go with (3) break the 
grab and do something else for a bit.

> The problem with the notion of breaking grabs is that it's an arms race.
> X is just broken here.  The only way to fix it is to break out to a
> wayland mini-app that does the moral equivalent of MacOS's Force Quit.
> (And in some sense, by the time you're running a whole new display
> system to fix your old one, it's time to just move on.)

You lose the option to wait for the app to catch up, without it preventing you 
from doing anything else, which is the current behaviour if you *don't* break 
the grab.

We don't always want to quit the app, in other words.

> Since we can't _actually_ fix grabs, the right thing to do is punish
> apps that abuse them.  Server zap doesn't do this.  It punishes the
> whole session.  Even just breaking the grab doesn't get things fixed,
> because the bug stays there in the app forever.  You want the recovery
> path to be such that you can inspect the state of the broken app at the
> moment it's misbehaving.  Grab state dump on VT switch accomplishes this
> better than either zap or grab-break.

But you're actually punishing the *user* here. That is what upsets me, I can't 
speak for anyone else.

I may know very well what the problem is, and that it's fixed by a newer version 
of or replacement for my browser. I may be unable to upgrade to a version of 
the OS that comes with that new version because I have multiple GPUs ... ;o)

> [1] - Not so much that the things it embodied were bad ideas - though
> they all were to some extent - but that the implementation showed a
> willful disregard for the rest of the server.  GrabBreak could easily
> have been a new, possibly even privileged, XKB action, but instead it
> was a magic trapdoor.  Why do anything in the existing design when you
> can add another layer of crap on top.
>
> - ajax