[Qemu-devel] SDL_GRAB problem

[Qemu-devel] SDL_GRAB problem

[Richard Zidlicky]

Hi,

the usual grab agony: something goes wrong at the wrong time and
X is completely unusable. No idea what exactly went wrong this
time - luckilly ctrl-alt-f2 saved me. 
Very unpleasant problem, should be fixed or avoided no matter how.

I have no idea about SDL, if I have to grab in X I do at least:
 - handle Enter/Leave, Map/UnMap events
 - add timer and enforce a maximum grab time, eg 45s

Also, if it is not absolutely necessary to grab the mouse
it would be good to avoid this.

Richard

[Qemu-devel] Re: SDL_GRAB problem

[Sami Haahtinen]

Richard Zidlicky wrote:
> the usual grab agony: something goes wrong at the wrong time and
> X is completely unusable.

My X is currently stuck in this state.

> No idea what exactly went wrong this time - luckilly ctrl-alt-f2 saved me.

For me, qemu crashed while focus was grabbed. Also ctrl-alt-backspace is 
a handy command (use with caution, kills your X without asking twice)

> Very unpleasant problem, should be fixed or avoided no matter how.

I agree with you, it would ease the situation if there was a tool to 
ungrab X, but i don't know of any...

Regards, Sami

Re: [Qemu-devel] Re: SDL_GRAB problem

[J. Mayer]

On Wed, 2004-03-17 at 22:03, Sami Haahtinen wrote:
> Richard Zidlicky wrote:
> > the usual grab agony: something goes wrong at the wrong time and
> > X is completely unusable.
> 
> My X is currently stuck in this state.
> 
> > No idea what exactly went wrong this time - luckilly ctrl-alt-f2 saved me.
> 
> For me, qemu crashed while focus was grabbed. Also ctrl-alt-backspace is 
> a handy command (use with caution, kills your X without asking twice)
> 
> > Very unpleasant problem, should be fixed or avoided no matter how.
> 
> I agree with you, it would ease the situation if there was a tool to 
> ungrab X, but i don't know of any...

The solution I found is to relaunch qemu, grab then ungrab the focus and
I get my X usable. 
Qemu should do sthg to leave SDL in a proper way when it crashes...

-- 
J. Mayer <l_indien@magic.fr>
Never organized

Re: [Qemu-devel] Re: SDL_GRAB problem

[Michel Dänzer]

On Wed, 2004-03-17 at 22:49, J. Mayer wrote:
> On Wed, 2004-03-17 at 22:03, Sami Haahtinen wrote:
> > Richard Zidlicky wrote:
> > > the usual grab agony: something goes wrong at the wrong time and
> > > X is completely unusable.
> > 
> > My X is currently stuck in this state.
> > 
> > > No idea what exactly went wrong this time - luckilly ctrl-alt-f2 saved me.
> > 
> > For me, qemu crashed while focus was grabbed. Also ctrl-alt-backspace is 
> > a handy command (use with caution, kills your X without asking twice)
> > 
> > > Very unpleasant problem, should be fixed or avoided no matter how.
> > 
> > I agree with you, it would ease the situation if there was a tool to 
> > ungrab X, but i don't know of any...

>From the XF86Config-4 manpage, about the ServerFlags section:

Option "AllowDeactivateGrabs" "boolean"
       This  option  enables  the use of the Ctrl+Alt+Keypad‐Divide key
       sequence to deactivate any active  keyboard  and  mouse  grabs.
       Default: off.

[...]

       Note  that  the options AllowDeactivateGrabs and AllowClosedown‐
       Grabs will allow  users  to  remove  the  grab  used  by  screen
       saver/locker programs.  An API was written to such cases. If you
       enable this  option,  make  sure  your  screen  saver/locker  is
       updated.

> The solution I found is to relaunch qemu, grab then ungrab the focus and
> I get my X usable. 
> Qemu should do sthg to leave SDL in a proper way when it crashes...

Strictly speaking, it may be an X server bug that the grab persists when
the client goes away.


-- 
Earthling Michel Dänzer      |     Debian (powerpc), X and DRI developer
Libre software enthusiast    |   http://svcs.affero.net/rm.php?r=daenzer

[Qemu-devel] Re: SDL_GRAB problem

[Sami Haahtinen]

Michel Dänzer wrote:
> On Wed, 2004-03-17 at 22:49, J. Mayer wrote: 
>>On Wed, 2004-03-17 at 22:03, Sami Haahtinen wrote:
>>>I agree with you, it would ease the situation if there was a tool to 
>>>ungrab X, but i don't know of any...
> 
> 
>>From the XF86Config-4 manpage, about the ServerFlags section:
> 
> Option "AllowDeactivateGrabs" "boolean"
>        This  option  enables  the use of the Ctrl+Alt+Keypad‐Divide key
>        sequence to deactivate any active  keyboard  and  mouse  grabs.
>        Default: off.

i must have missed that, that looks like a good solution. time to check 
whether my xscreensaver is new enough ;)

>> The solution I found is to relaunch qemu, grab then ungrab the
>> focus and I get my X usable. Qemu should do sthg to leave SDL in a
>> proper way when it crashes...
> 
> Strictly speaking, it may be an X server bug that the grab persists
> when the client goes away.

When you think it through, it does appear so. Why would an application 
that doesn't exist need grab. Although i don't know the full mechanism 
behind grab, so it might be that there is some reason why this hasn't 
been fixed.

Oh well, i'm looking forward to xouvert, somehow i have lost my faith in 
XFree86.

Regards, Sami

Re: [Qemu-devel] Re: SDL_GRAB problem

[Michel Dänzer]

On Thu, 2004-03-18 at 06:23, Sami Haahtinen wrote:
> Michel Dänzer wrote:
> 
> > Strictly speaking, it may be an X server bug that the grab persists
> > when the client goes away.
> 
> When you think it through, it does appear so. Why would an application 
> that doesn't exist need grab. 

I can't think of a reason, but specs don't always follow reason. ;)

> Although i don't know the full mechanism behind grab, so it might be that 
> there is some reason why this hasn't been fixed.

IIRC the spec does define grabs to expire when the client goes away, but
I don't know offhand where this is defined.

> Oh well, i'm looking forward to xouvert, somehow i have lost my faith in 
> XFree86.

You're not alone. Unfortunately, xouvert looked quite dead already last
time I checked. Fortunately, there's a lot going on over at
http://freedesktop.org/Software/Home .


On Thu, 2004-03-18 at 12:18, Richard Zidlicky wrote: 
> Now, excuse for the completely offtopic Q: Once every year or so
> my Xemacs looses sync with the Xserver.. usually there is some
> message suggesting xlib lost some reply or got an unexpected one.
> Is there any way to revive the app in such a case?

Not sure, but I'm afraid not - error recovery isn't exactly a strength of
Xlib and most of its applications.


-- 
Earthling Michel Dänzer      |     Debian (powerpc), X and DRI developer
Libre software enthusiast    |   http://svcs.affero.net/rm.php?r=daenzer

Re: [Qemu-devel] Re: SDL_GRAB problem

[Richard Zidlicky]

On Thu, Mar 18, 2004 at 01:35:36AM +0100, Michel Dänzer wrote:

> Option "AllowDeactivateGrabs" "boolean"
>        This  option  enables  the use of the Ctrl+Alt+Keypad???Divide key
>        sequence to deactivate any active  keyboard  and  mouse  grabs.
>        Default: off.

that looks like an extremely usefull option for developpers, I don't
even recall how often I needed a remote login to debug programs that
use grabs :)

For the average user this is still a bit difficult I am afraid.

> Strictly speaking, it may be an X server bug that the grab persists when
> the client goes away.

client didn't go away in my case so it is not an X bug. An strace
displayed some SIGALRM in qemu and nothing else as far as I could see.
After killing qemu the X server was fine again.

Now, excuse for the completely offtopic Q: Once every year or so
my Xemacs looses sync with the Xserver.. usually there is some
message suggesting xlib lost some reply or got an unexpected one.
Is there any way to revive the app in such a case?

Richard