[gentoo-dev] FHS compliant KDE install and multi-version support

[Jorge Manuel B. S. Vicetto]

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Hello.

Some members of the KDE team have been talking for some time about
having a FHS compliant install (define KDE prefix as /usr instead of
/usr/kde/<version>). The most important consequence of that option is
that it won't be possible to have 2 or more KDE versions installed at
the same time - it's important to note this restriction doesn't affect
kde-3.5 as it uses different eclasses that install it under /usr/kde/3.5
and the live version as everyone on the team seems to agree that it
should always be installed into /usr/kde/<live-version>.
We've been trying to find a way that will allow users to do an FHS
compliant install if they want it, while at the same time still allowing
those that are not interested in it to keep using the current scheme.
Our first attempt was to use a multislot use flag[1]. According to that
flag, we would set the SLOT and the PREFIX for the install. That has the
a very important problem - it breaks the invariancy of the SLOT and as
thus been put aside.
The next step was to use a kdeprefix use flag[2]. This flag no longer
touches the SLOT that is set to "4" for all kde-4.X versions. It only
determines if the package will be installed under the FHS compliant
location (/usr) or under the old location (/usr/kde/<version>). This
however means the users will no longer have the option to have more than
one kde-4.X version installed.
I've been thinking on a different method. With this method [3], we would
keep using the <major>.<minor> slots (4.1, 4.2, etc) so we also wouldn't
break the invariancy. We would allow users to select whether to have an
FHS compliant install or not (the way to allow that still needs to be
discussed) and we would set the prefix based on that. In case the user
wants an FHS compliant install, the eclasses would block all kde
packages on other slots - except 3.5 (uses other eclasses) and the live
versions (for the above reason that it will always be installed under
/usr/kde/<live-version>). One way to decide whether to install on an FHS
compliant location would be to add a use flag, but I don't think adding
that flag for 200+ ebuilds makes sense as it doesn't make sense to have
1 version of some packages and possibly 2 or more of other packages.

So, what am I after in this email? After having an internal discussion
and then opening it up to users in #gentoo-kde and a few other people on
#gentoo-portage, it was suggested I sent a mail here to open this
discussion to everyone and to present the case in a more clear manner.
So, can anyone suggest a good way to accomplish what were trying to do?
At least a better solution than the ones I've presented above? I would
also welcome suggestions on how to configure if the user wants an FHS
compliant install or not (I've thought about setting this var on /etc).
In case someone is thinking on suggesting it, ignoring FHS or not
allowing the install of multiple versions are not valid solutions to
this problem.


~ [1] - The commit where it was added was
http://git.overlays.gentoo.org/gitweb/?p=proj/kde.git;a=commitdiff;h=e3a8156bd504e4a377d4eedee123252136da821d

It boiled down to the following:

# setting the slot dep
~                if [[ "${KDEBASE}" == "kde-base" ]]; then
~                        case ${PV} in
~                                3.9*)   _kdedir="3.9" ;;
- -                               4.0.8*| 4.0.9* | 4.1*)  _kdedir="4.1"
- -                                       _pv="-${PV}:4.1" ;;
+                               4.0.8*| 4.0.9* | 4.1*)
+                                       _kdedir="4.1"
+                                       if use multislot; then
+                                               _pv="-${PV}:4.1"
+                                       else
+                                               _pv="-${PV}:4"
+                                       fi
+                                       ;;

# setting the prefix
- -       KDEDIR="/usr/kde/${_kdedir}"
- -       KDEDIRS="/usr:/usr/local:${KDEDIR}"
+       # If the multislot USE flag is set use multiple slots for minor
versions
+       if use multislot; then
+               KDEDIR="/usr/kde/${_kdedir}"
+               KDEDIRS="/usr:/usr/local:${KDEDIR}"
+       else
+               KDEDIR="/usr"
+               KDEDIRS="/usr:/usr/local"
+       fi

# setting the slot
+       # The svn versions always need their own slot
~        if [[ -n ${KDEBASE} ]]; then
~                if [[ ${NEED_KDE} = svn ]]; then
~                        SLOT="kde-svn"
~                else
- -                       case ${PV} in
- -                               4.0.8* | 4.0.9* | 4.1*) SLOT="4.1" ;;
- -                               *) SLOT="kde-4" ;;
- -                       esac
+                       # Assign the slot
+                       if use multislot; then
+                               case ${PV} in
+                                       4.0.8* | 4.0.9* | 4.1*)
+                                               SLOT="4.1" ;;
+                                       *) SLOT="kde-4" ;;
+                               esac
+                       else
+                               SLOT="4"
+                       fi
~                fi
~        fi


~ [2] - The commit where it was added was
http://git.overlays.gentoo.org/gitweb/?p=proj/kde.git;a=commitdiff;h=e13fabc21a97634c3c9467e02380c99f07f7defe

It boiled down to the following:

# setting the slot dep
~                                4.0.8*| 4.0.9* | 4.1*)
~                                        _kdedir="4.1"
- -                                       if use multislot; then
- -                                               _pv="-${PV}:4.1"
- -                                       else
- -                                               _pv="-${PV}:4"
- -                                       fi
+                                       _pv="-${PV}:4"
~                                        ;;

# setting the prefix
- -       # If the multislot USE flag is set use multiple slots for minor
versions
- -       if use multislot; then
+       # If the kdeprefix USE flag is set use the /usr/kde/ prefix
+       if use kdeprefix; then
~                KDEDIR="/usr/kde/${_kdedir}"
- -               KDEDIRS="/usr:/usr/local:${KDEDIR}"
+               KDEDIRS=":${KDEDIR}:/usr:/usr/local"

# setting the slot
- -                       if use multislot; then
- -                               case ${PV} in
- -                                       4.0.8* | 4.0.9* | 4.1*)
- -                                               SLOT="4.1" ;;
- -                                       *) SLOT="kde-4" ;;
- -                               esac
- -                       else
- -                               SLOT="4"
- -                       fi
+                       case ${PV} in
+                               4.0.8* | 4.0.9* | 4.1*) SLOT="4" ;;
+                               *) SLOT="kde-4" ;;
+                       esac

~ [3] - I haven't commited this anywhere yet, so there's no diff to link to.

The basic idea is the following though:

# relevant vars
FHS_Install        # If set to true the user wants to have KDE installed
under /usr and not /usr/kde/<version>
KDE_SLOTS          # The SLOTS used by KDE (this won't include 3.5 as it
uses other eclasses and the live-ebuilds that will use the following
var. If there's no reason not to, it will include kde-5.X SLOTS when we
get there)
KDE_LIVE_SLOTS     # The slots for live ebuilds (why a var for this? We
currently use kde-svn, but I think we should think on moving to live as
KDE is talking about switching to other SCMs, possibly GIT)

# setting the slot dep
~                if [[ "${KDEBASE}" == "kde-base" ]]; then
~                        case ${PV} in
~                                3.9*)   _kdedir="3.9" ;;
~                                4.0.8*| 4.0.9* | 4.1*)
~                                        _kdedir="4.1"
~                                        _pv="-${PV}:4.1"
~                                        ;;

# setting the prefix
~        # If the user wants a FHS compliant install
~        if FHS_Install; then
~                KDEDIR="/usr"
~                KDEDIRS="/usr:/usr/local"
~        else
~                KDEDIR="/usr/kde/${_kdedir}"
~                KDEDIRS="/usr:/usr/local:${KDEDIR}"
~        fi

# setting the slot
~                        case ${PV} in
~                                4.0.8* | 4.0.9* | 4.1*)
~                                        SLOT="4.1" ;;
~                                *) SLOT="kde-4" ;;
~                        esac

# setting the slot vars
KDE_SLOTS=( "kde-4" "4.1" )
KDE_LIVE_SLOTS=( "kde-svn" )

# setting the blocks if FHS_Install is set
if [[ ${FHS_Install} == "true" ]]; then
~        for KDE_SLOT in ${KDE_SLOTS[@]}; do
~                # block other slots
~                if [[ ${SLOT} != ${KDE_SLOT} ]]; then
~                        DEPEND="${DEPEND} !kde-base/*:${KDE_SLOT}"
~                        RDEPEND="${RDEPEND} !kde-base/*:${KDE_SLOT}"
~                fi
~        done
fi

- --
Regards,

Jorge Vicetto (jmbsvicetto) - jmbsvicetto at gentoo dot org
Gentoo- forums / Userrel / Devrel / SPARC / KDE
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