Hello, Despite it being 2016 and gtk2 pretty much dead, buried and forgotten upstream, many applications still support only gtk2, have subtle issues with their gtk3 port, or support both, with some of our userbase clinging to gtk2 for dubious political or aesthetical reasons.
For the latter cases, despite GNOME teams policy and strong preference on not providing a choice and just choosing gtk2 or gtk3 (gtk3 if it's working as good as gtk2), some cases exist where the maintainers want to provide such choice. In some cases it is understandable for a short while during transition, e.g firefox. In other cases, it is purely for the sake of providing the choice of working with a deprecated toolkit, apparently. My highly biased essay aside, we need to finally globally agree on what we do in this situation. If we allow this choice at all, only for special cases, or widespread. And if this choice is provided, how do we name the USE flag. Historically, for very good reasons in past and present GNOME team members opinion, USE=gtk has always meant to mean to provide support for gtk in general, not any particular version. This is opposite to what the Qt team has been doing. In our opinion, in a perfect world, only USE=gtk would exist, and no USE=gtk2 or USE=gtk3 would be necessary. But as we don't live in a perfect world, we have made use of USE=gtk3 for providing gtk3 support from library packages to mean to build gtk3 support. Sadly that overloads USE=gtk in many cases to then mean to build gtk2 support. This would ideally not be needed, as the package would instead be slotted and parallel installable for gtk2 and gtk3, which should be theoretically possible in all cases, because gtk2 and gtk3 may not live in the same process, so not the same library either. Due to some packages needing too much manpower effort to do such a split, USE flags are used in such a case. Good examples of such slot splits existing are for example the libappindicator stack. This used to be the case with almost all GNOME libraries as well, but most of them only provide gtk3 now, as gtk2 is, well, dead. Bad examples would be e.g avahi and gtk-vnc, which deemed too hard to split up into separate SLOTs. In some cases it might have been meant as a transitional thing, until all consumers are ported to gtk3, but it has been lingering on due to consumer apps not being ported or we haven't yet noticed to remove the gtk2 support in the library package. Now these are libraries, and despite some USE flag confusion, it's not a huge issue, because consumers are USE depending on what is required. This all is written out in https://wiki.gentoo.org/wiki/Project:GNOME/Gnome_Team_Ebuild_Policies#gtk3 since the GNOME project pages moving to wiki, and also long before that in GuideXML era, and we've pointed people towards that. And then we have applications that support building against either gtk2 or gtk3. In most cases, any requests to provide the choice to have an application use gtk2 instead of gtk3 gets instantly marked as duplicate of https://bugs.gentoo.org/374057 but in some cases the maintainer has chosen to provide this choice for now, and here is the problem - we don't really have a good agreed on way to name such a choice in USE flags, if we should provide such a choice at all. USE=gtk2 is not good, due to the confusion issues with USE=gtk3 and USE=gtk and it being problematic. The GNOME team shall probably veto such USE flag usage if we are deemed to have such an authority as gtk+ maintainers, unless we rework it all in expectations of gtk2 corpse being carried around for a decade as well... I have quite a few bugs against packages to file already for this, afair. I kind of like what firefox did there, going in the spirit of the force-openrc flag we have for avoiding systemd dependency, even if it currently means worse user experience. So if we provide such a choice for apps at all, I might agree to USE=force-gtk2 for this for apps. And we would like to eventually (or immediately) p.use.mask this and once it's 2017 and gtk2 truly dead and buried and full of known security holes, get rid of it again. But this highlighted the inconsistency we are having, ending up with QA initiated bug https://bugs.gentoo.org/581662 tl;dr and my proposal would be the following: * USE=gtk means providing support for GTK+; because we don't have a USE=gui, this also means "provide a GUI version built on top of gtk+" for packages where a GUI is optional. * USE=gtk3 may be used only for controlling extra libraries to be shipped for gtk3 support (the extra library file will link to gtk3), _in addition_ to gtk2 version. This is a temporarily measure until gtk2 support can be dropped and it will only ship gtk3 version of the library. This gives a flag to be able to USE depend on by gtk3 apps. This leaves the question about the opposite open, however. This is why USE=gtk2 would be bad for apps, maybe we need to use it for this library case, when gtk3 version is primary and we just have 1 app remaining that needs the gtk2 version or something. The concept of library is broad here, covering also gtk theme engines (x11-themes/gtk-engine-*, but they shouldn't be hard to split) and modules (e.g caribou, libcanberra) * Applications may only use a gtk2 based stack or gtk3 based stack in a given version/revision. gtk3 is strongly preferred when it is deemed to not have any regressions compared to gtk2 build, but the choice is ultimately with the maintainer. Once the application converts to using gtk3 in our distribution, it should try hard to stay that way in upcoming versions as well. * Some exceptions to the above may exist under heavy consideration, especially in cases where the toolkit usage is complex and may have some issues for some, but in general gtk3 support is deemed good by upstream. Most notable here would be browsers like firefox and chromium, which are using gtk dependency more for emulating the theme it uses, rather than using it as its real toolkit. If such exceptions are allowed, the USE flag naming here must be consistent amongst the exceptions. My proposal would be USE=force-gtk2 then, as I have no better ideas without stomping on the USE=gtk{2,3} historical meaning. When arguing in favor of supporting gtk2 builds more for apps, please do keep in mind that gtk2 really is pretty much dead. And no, MATE, XFCE and others are NOT continuing its support; they are just slow in fully converting to gtk3, but they are doing so and I expect both of those to be fully done this year, around autumn. If the issue is political or just a general gnome3 or gtk3 hate, then I would ask you to keep your political opinions or hate outside this thread and go contemplate on more important life issues. If the issue is lack of themes, then I would like you to help package more gtk3 themes. gtk3.20 now has a stable CSS based theme API and themes shouldn't be breaking anymore beyond this point, theoretically. And gtk3 theme packages should pretty much just be CSS files and some metadata. Though we have yet to get over that bumpy thing yet (a main reason gtk3.20 isn't in main tree yet). Thoughts? Agreements? Suggestions? I'm particularly interested in QA opinion here. I believe WilliamH wanted to spearhead this from their side. Regards, Mart Raudsepp Gentoo developer, GNOME team
