> Sure, we can make others do compositor's job, so compositor doesn't have to, but that's pretty ridiculous if you ask me.
The difference is that the compositor doesn't necessarely have a toolkit for buttons and stuff like that at hand, while (most) applications already have. Also applications which actually use the space (i.e. GtkHeaderBar, Chrome, stuff like that) need to implement those window management functions anyway, so it would be duplicated work. Also: Theme development is easier if you don't have to write a window manager theme, too.
Yes, CSD result in other duplicated work: Qt vs. Gtk+. And they come with lots of other disadvantages, e.g. as you've pointed out that it's hard to integrate Gtk+'s main loop and the difference of appearance between different toolkits.
Regarding arrogance: You said that your solution is "proper". You called the pro-CSD folks "stubborn" and "irresponsible". You are the one dismissing all pro-CSD arguments.
> Why don't we do kernel's job in every userspace app then, say, for filesystems? This will make kernel devs' life easier after all.
No, the reality is that on desktop, where window decorations should be drawn, the compositor usually has a toolkit for buttons and stuff at hand, since it's closely related to the whole DE being used - like in GNOME, Plasma or Enlightenment. What's more, this relation in Wayland world is even tighter than it was in X11, since under X you could easily replace the window manager and still be able to configure stuff like screens and input with tools from your DE. With Wayland, unless DEs agree on standard way to configure their compositors (there's no sign of it yet), you can't and that's by design. Those compositors who don't have a toolkit at hand usually aren't targeted for desktop at all. On mobile, embedded, automobile etc. you don't usually need a toolkit, cause you won't draw decorations anyway. Wayland is supposed to go deeper than desktop, you know, and now with popular compositor being CSD-only you need to adjust all the toolkits and apps to not draw them if you want to launch them there, instead of doing it once in the compositor. And yes, while for majority of them it doesn't make sense, there are plenty of desktop apps or games that can run just fine on mobile without any modification, I've used bunch of them on my Openmoko and Maemo phones.
FUSE is exactly the situation like it is now on KDE Plasma, which I fully support - the compositor provides decorations for any app to use, but if the app is interested in doing them itself, it's free to. Just like the kernel which provides the filesystem support, but if you want to implement some fs by yourself in userspace, you're free to - there's little point in doing sshfs in kernel, after all, just like there's little point in doing browser tabs in compositor.
What GNOME is doing, however, is putting all filesystems into FUSE - no, it doesn't even provide common API to access them - and that's just a terrible idea.
Also, to use your own argument - last time I checked, majority of the apps don't customize their window decoration space.
Sorry, I've heard those pro-CSD-only arguments multiple times already, they just don't provide enough merit to be taken seriously (they're also often mixed with just pro-CSD, which I have absolutely nothing against). At times it starts to look like it's a conscious sabotage of the Linux desktop, but more realistically (I hope!) it's probably just bunch of influential people not having wide enough perspective to put things into proper context. I still fully stand behind my words on being irresponsible.
[edit]
Oh, just thought about it - on desktop, you probably need a toolkit in the compositor anyway if you want to provide good UX, cause when some app freezes, you need to have some way to signalize that to the user and give them a way to choose between closing the app, waiting for it to unfreeze, moving it away etc.
Plus, there's XWayland which won't go away anytime soon, where you obviously still need to draw decorations.
> What's more, this relation in Wayland world is even tighter than it was in X11, since under X you could easily replace the window manager and still be able to configure stuff like screens and input with tools from your DE.
What you would loose is the ability to configure the appearance of the decorations because the WM might do it differently. With CSD this is done by Gtk+ regardless of the WM.
> Those compositors who don't have a toolkit at hand usually aren't targeted for desktop at all. On mobile, embedded, automobile etc. you don't usually need a toolkit, cause you won't draw decorations anyway.
A toolkit is still needed for buttons, text, etc.
> I've used bunch of them on my Openmoko and Maemo phones.
Both come with Gtk+.
> Also, to use your own argument - last time I checked, majority of the apps don't customize their window decoration space.
Have a look at Windows and you'll see that most apps will do it if they are able to. All web browsers, the file manager, Office, ...
Also most GNOME apps are already using GtkHeaderBar. And let's not forget the most used applications: Chrome and Firefox (still behind a config flag atm).
> Oh, just thought about it - on desktop, you probably need a toolkit in the compositor anyway if you want to provide good UX, cause when some app freezes, you need to have some way to signalize that to the user and give them a way to choose between closing the app, waiting for it to unfreeze, moving it away etc.
> What you would loose is the ability to configure the appearance of the decorations because the WM might do it differently.
WM is the place where I want to configure the appearance and behavior of window decorations. So that's expected and positive. Point to me.
> With CSD this is done by Gtk+ regardless of the WM.
No, it's done by every toolkit separately regardless of the WM. You have one WM, and you have many toolkits. This is how the user looses the ability to configure the appearance of window decorations. Point to me.
> A toolkit is still needed for buttons, text, etc.
Some compositors don't need it. But yeah, most do. Point to me anyway.
> Both come with Gtk+.
Yeah, Gtk+2, which doesn't do CSD at all. And in both Openmoko 2008 and Maemo 6, GTK+ apps were already looking out of place, superseded by Qt and/or EFL. I'm not even sure if it was installed by default anymore.
With CSD-only, stuff like Illume in Openmoko wouldn't be possible at all. It was already horrible to make it work well on X, don't make it even harder on Wayland!
> Have a look at Windows and you'll see that most apps will do it if they are able to. All web browsers, the file manager, Office, ...
Taking a look at Windows apps is the best point against CSD :) GNOME is following the example and starts to look awful and inconsistent as well, and let's not even speak about UX. Thankfully, I don't have to use it.
> Chrome and Firefox
Both configurable. For a reason. Even though they are actually in the minority of apps where CSD totally makes sense. Go figure.
Anyway, this discussion went far off topic now. If you want to, use CSD in your app or your toolkit. I don't care. It will look ugly, have bad UX and it will add to the configuration mess, but I don't have to use it, so it will be problem of your users, not me. CSD works under X already, with a few caveats, but under Wayland it's already fixed, there's no issue with it at all.
However, when you make a compositor for the desktop and you make it require CSD from every app out there, that's just evil, mean and creates problems. Don't do it.
> The appearance won't match with GtkHeaderBar apps then.
If your app have special needs and has to use CSD, it's up to you to provide (or not) matching appearance for your users, by toolkit or any other means to achieve that. With CSD-only, you're guaranteed to get non-matching appearance. It's way easier to provide all-matching appearance with SSD, since it's only minority of toolkits that decided to go full CSD, so you just have to match your Gtk+ style.
> ...
Let me remind you - the idea that compositor theoretically does not need a toolkit was yours, as an argument for CSD-only compositor. I have showed you that while theoretically it might have some merit, especially on mobile, in practice it doesn't work that way with desktop environments on Wayland - so it can't really be taken as a case in this point.
> The idea is to have only one toolkit: Gtk+.
Wow. Just, no. The only Gtk+3 app I usually run on my desktop is Firefox, and it's not even exactly a Gtk+ app. Let's keep such crazy ideas as science fiction, please.
That might explain some attitudes on this topic (and some others - interoperability was always a somewhat poor side of the GNOME camp) though. Not a happy thought to be honest.
> If your app have special needs and has to use CSD, [...]
Who defines what's special and what's normal though?
> I have showed you that while theoretically it might have some merit, especially on mobile, in practice it doesn't work that way with desktop environments on Wayland - so it can't really be taken as a case in this point.
Because of Xwayland and interactions with the user?
> Who defines what's special and what's normal though?
Typical app does not need to touch its window decoration, only some need. The distinction is natural. Even Gtk+ knows that distinction and lets you disable CSD for apps that don't customize the header bar.
> Because of Xwayland and interactions with the user?
Because it's tightly related to the whole DE, even more than under X, and that DE already has a toolkit for the compositor to use, be it Gtk+, Qt, Evas, St or whatever else. Plus, interactions. Plus, XWayland.
The difference is that the compositor doesn't necessarely have a toolkit for buttons and stuff like that at hand, while (most) applications already have. Also applications which actually use the space (i.e. GtkHeaderBar, Chrome, stuff like that) need to implement those window management functions anyway, so it would be duplicated work. Also: Theme development is easier if you don't have to write a window manager theme, too.
Yes, CSD result in other duplicated work: Qt vs. Gtk+. And they come with lots of other disadvantages, e.g. as you've pointed out that it's hard to integrate Gtk+'s main loop and the difference of appearance between different toolkits.
Regarding arrogance: You said that your solution is "proper". You called the pro-CSD folks "stubborn" and "irresponsible". You are the one dismissing all pro-CSD arguments.
> Why don't we do kernel's job in every userspace app then, say, for filesystems? This will make kernel devs' life easier after all.
Have you heard of FUSE?