Bug#550042: xscreensaver still starts automatically in KDE..

> With XscreenSaver 5.10-3 we shipped xdg and the Xsession.d file wasn't
> removed,

Yes, thanks. I did figure that out though.

> please remove the Xsession.d and test.

I did that. The problem still occurs. When I
also remove xscreensaver-daemon.desktop,
the problem is fixed.

>> In my opinion, this package should not cause any
>> automatic startup at all of the xscreensaver
>> daemon.

> So KDE will provide it only for kscreensaver

No, KDE will not provide it at all. KDE runs
xscreensaver hacks inside its own screen saver
service. The xscreensaver daemon should never
run in a KDE session.

> and GNOME only gnome-screensaver.

I don't know how GNOME's screen saver service
works, but I suspect that also for GNOME it is
a bug for xscreensaver daemon to run. It's not
clear yet if that bug is so severe that the system
freezes up in GNOME as it does in KDE, but it's
still a bug. See #519061.

> If someone is new and doesn't know how to set it up
> automatic startup for xscreensaver it can't do it. Right?

It depends what kind of environment they are using. In
KDE and GNOME, the desktop manager will automatically
set up whatever needs to be set up. In fact, they already
do that - without us trying to force xscreensaver daemon
down their throats. The same is true for any other environment
that is designed for screen savers to work without configuration,
each in its own way.

In raw X with a minimalist window manager, such as
xmonad or dwm or twm, it is definitely the user's
responsibility to start xscreensaver daemon. That matches
the "stay out of my way" philosophy of those environments,
and it is clearly explained in their documentation. So it is
also a bug to start xscreensaver daemon automatically in
that type of environment. Someone who is "new and doesn't
know how to set it up" - and doesn't want to learn how -
should not be using xmonad and friends.

There are many other window managers and desktop
environments, each with its own philosophy. For some,
perhaps it may be right for xscreensaver daemon to
launch automatically. For many it is definitely very wrong.
It is impossible for this package to do exactly the
right thing for every environment every time. Just install
xscreensaver, and let each environment decide for itself
if and how it gets launched.

> With the xdg.desktop it's suppossed you can deactivate
> it on your window manager - startup manager.

No, xdg autostart items are just that - they start automatically.
If you put "crash_my_system.desktop" into that folder, the
system will crash, and that is a serious bug. Similarly, if
you put "works_for_gnome_but_crashes_kde.desktop"
in there, it will do just that. The only things you can install
into that folder are things that are guaranteed to work
for *every* desktop environment. In this case, it breaks
KDE, and I suspect that it also breaks GNOME.

Some environments do have a "startup manager" UI to
manage start-up items, but that doesn't give us permission
to install broken things there.

Actually, I think you have pointed out another possible
issue. The X startup procedure for Debian should
not launch the items in the xdg autostart folder unless an
xdg-compliant desktop environment is being launched.
For people who are only running a simple window manager
and not running a desktop environment, these items should
not be run.

But in our case, that is irrelevant. xscreensaver daemon
should *never* start automatically, unless a specific
window manager or desktop environment calls for it.

Thanks,
Yitz



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Yitz,
Both KDE and GNOME ship by default their own screensaver daemons
(kscreensaver and gnome-screensaver). I am most familiar with
gnome-screensaver so I will use it as the example, but I think
kscreensaver does the same. The gnome-screensaver package ships its
own desktop file which is active by default. It is not the "desktop
environment" which is activating it, it is the desktop file from the
screensaver package which makes it start.

We offer the xscreensaver as a substitute, for those who do not like
gnome-screensaver for some reason. If they remove the
gnome-screensaver package and install xscreensaver instead, they
expect xscreensaver to be activated by default. This is also the case.
Otherwise it would be considered a security issue that a screensaver
package is not active after installation.

Users of any other xdg-compliant desktop environment will also expect
that xscreensaver is starting if they install it.

We expect those who install both packages, to have a special reason
for this, because a normal user on the other hand will just use
gnome-screensaver which comes with GNOME. The special users will have
to choose which one to use in their sessions.

I don't know if you fall into any of those categories. Why do you
install the xscreensaver package?

If you have an elegant solution which caters for all needs, I would be
very interested. I don't see why xscreensaver should be more defensive
than gnome-screensaver in the both-installed corner case. Maybe the
desktop environments (whatever function is sourcing the desktops)
should note that two screensavers are installed and only start one of
them?



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We are waiting for your answer.

On Mon, Nov 9, 2009 at 11:08 AM, Tormod Volden <debian.tormod.DeleteThis@gmail.com> wrote:
> Yitz,
> Both KDE and GNOME ship by default their own screensaver daemons
> (kscreensaver and gnome-screensaver). I am most familiar with
> gnome-screensaver so I will use it as the example, but I think
> kscreensaver does the same. The gnome-screensaver package ships its
> own desktop file which is active by default. It is not the "desktop
> environment" which is activating it, it is the desktop file from the
> screensaver package which makes it start.
>
> We offer the xscreensaver as a substitute, for those who do not like
> gnome-screensaver for some reason. If they remove the
> gnome-screensaver package and install xscreensaver instead, they
> expect xscreensaver to be activated by default. This is also the case.
> Otherwise it would be considered a security issue that a screensaver
> package is not active after installation.
>
> Users of any other xdg-compliant desktop environment will also expect
> that xscreensaver is starting if they install it.
>
> We expect those who install both packages, to have a special reason
> for this, because a normal user on the other hand will just use
> gnome-screensaver which comes with GNOME. The special users will have
> to choose which one to use in their sessions.
>
> I don't know if you fall into any of those categories. Why do you
> install the xscreensaver package?
>
> If you have an elegant solution which caters for all needs, I would be
> very interested. I don't see why xscreensaver should be more defensive
> than gnome-screensaver in the both-installed corner case. Maybe the
> desktop environments (whatever function is sourcing the desktops)
> should note that two screensavers are installed and only start one of
> them?
>
>
>



--
Jose Luis Rivas. San Cristóbal, Venezuela.
GPG 0xCACAB118 0x7C4DF50D
http://joseluisrivas.net/acerca - http://ghostbar.ath.cx/about



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> We are waiting for your answer.

Hi Jose and Tormod, sorry for the delay.

Tormod Volden wrote:
>> The gnome-screensaver package ships its
>> own desktop file which is active by default. It is not the "desktop
>> environment" which is activating it, it is the desktop file from the
>> screensaver package which makes it start.

OK. It is from a package that is specifically for gnome though.
That's what I meant by the "provided by desktop environment".
Sorry for being imprecise.

>> We offer the xscreensaver as a substitute, for those who do not like
>> gnome-screensaver for some reason.

No, that's not why we offer it. xscreensaver daemon is not
designed to run in a desktop environment. It is not a substitute
for gnome-screensaver or kscreensaver.

We offer this package to use with classic X Windows, *without*
a desktop manager like Gnome or KDE running on top. That's what
xscreensaver was designed for, and that's how it's still used today.
Increasingly so - with a number simple but powerful window managers
available today, many people are going back to classic X Windows.

People using a desktop manager who want a screen saver
should install the special package for their desktop manager -
like gnome-screensaver or kscreensaver. That will provide
them with the capability to run all of the xscreensaver hacks in a
way that fits in with their desktop manager. And that is what happens
by default in the standard Gnome and KDE installations.

>> If they remove the
>> gnome-screensaver package and install xscreensaver instead, they
>> expect xscreensaver to be activated by default.

Why would anyone expect that? The xscreensaver daemon has nothing
to do with Gnome. If they remove gnome-screensaver, then their
Gnome screen saver won't run, what's so surprising?

Anyway, KDE and Gnome users expect all screen saver configuration
to happen inside the GUI provided for that, not by installing
or removing packages.

>> Otherwise it would be considered a security issue that a screensaver
>> package is not active after installation.

If they install packages without knowing what they are,
there will be plenty of security issues.

xscreensaver is not a replacement for the native screen saver
service in a desktop environment.

>> Users of any other xdg-compliant desktop environment will also expect
>> that xscreensaver is starting if they install it.

The xscreensaver daemon was never designed to run in a general
xdg-compliant environment.

>> We expect those who install both packages, to have a special reason
>> for this, because a normal user on the other hand will just use
>> gnome-screensaver which comes with GNOME. The special users will have
>> to choose which one to use in their sessions.

I agree.

>> I don't know if you fall into any of those categories. Why do you
>> install the xscreensaver package?

Because some of my users use X Windows without any
desktop manager, just a window manager. (I myself am
one of those - I use xmonad.) Some of those want to run
the xscreensaver daemon - so I have it installed on the system.
Any of those users who want to use xscreensaver can run it from their
..xinit file. That has always been the standard in X Windows, and
it's what those people expect.

Other users on the system are running KDE. They get kscreensaver
by default, as is standard for KDE. They can turn it off if they
want, using the KDE Control Center. They would be shocked
if xscreensaver then runs - they turned *off* the screen saver!

>> If you have an elegant solution which caters for all needs, I would be
>> very interested.

I really think that simple is best here. xscreensaver is designed to
be started manually. Leave it that way, and there won't be any
problems.

Perhaps add text to the package description, like:
"If you are using Gnome or KDE, consider using gnome-screensaver
or kscreensaver instead."

>> I don't see why xscreensaver should be more defensive
>> than gnome-screensaver in the both-installed corner case.

Why is that a corner case? Most multi-user systems that give
their users a choice of session type - which is built-in to kdm
by default - will be set up that way.

And it's not being defensive. It's just configuring xscreensaver
the way it was designed to work, and the way it has always worked,
for years.

>> Maybe the
>> desktop environments (whatever function is sourcing the desktops)
>> should note that two screensavers are installed and only start one of
>> them?

Why implement buggy behavior and then write scripts to try
to work around it?

Thanks,
Yitz



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I wrote:
>> No, that's not why we offer it. xscreensaver daemon is not
>> designed to run in a desktop environment. It is not a substitute
>> for gnome-screensaver or kscreensaver.

Jamie Zawinski wrote:
> As the author of xscreensaver, I can tell you that your ideas about what it
> is designed for, and what it is suitable for, are categorically false.

OK, that's great news!

So we currently have the following issues:

1. It is a serious bug for two screen saver daemons to *run* simultaneously.
That bug must be fixed.

2. We should support several screen savers *installed* simultaneously,
because different users on a system may have different needs for
configuring their sessions.

3. We need an interface to determine which screen saver daemon
runs.

For regular X Windows, (3) is easy - no screen saver should run unless
you configure it manually.

For desktop environments, Jose was assuming that the interface should
be that whichever is installed should run. That won't work because of (2).

Here are some alternative proposals:

A. There is a package "xscreensaver-gnome" that configures Gnome to
use xscreensaver daemon instead of gnome-screensaver. Similarly
for KDE.

B. Provide a debconf script where one can configure this.

Neither of those seem very satisfying to me, because this should
be a per-session setting, not a global setting. But for Gnome and
KDE, the way to configure sessions is within the interface they provide,
and they do not provide a way to disable their own screen saver
services in favor of something else.

One way to configure this per session would be:

C. Define session types Gnome-Xscreensaver and KDE-Xscreensaver.

Thanks,
Yitz



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I am also not totally happy with shipping a desktop file in /etc/xdg,
I would have preferred if there was a /usr/share/xdg to put it in, so
a system administrator could override it easily in /etc/xdg if he
installs several screensavers or just wants to hide it. Note that also
gnome-screensaver ships its activated desktop file in /etc/xdg, but it
is maybe not a good example to follow.

We should have a way that people can easily make the screensaver
active by turning it on in their desktop environment autostart manager
(like gnome-session-properties), unless it is enabled by default.
Coping system files around is not really satisfactory.

Back to the original issue, xscreensaver will refuse to start if
another screensaver like xscreensaver or gnome-screensaver is already
running. Maybe kscreensaver is missing this check? If kscreensaver
would be fixed, this whole story would be a non-issue. Seems like
xscreensaver is the only intelligent and "polite" one among its peers.



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