[csb6]

Wasn't one of Wayland's key design features combining the window manager and compositor? I am not too familiar with its history but surely there have been presentations or papers about the Wayland designers' reasoning for doing so.

[wmf]

When the window manager is a separate process with async communication between the WM and display server things can get out of sync for a frame or two which leads to visual artifacts. In Wayland the window manager works synchronously with the compositor so that it's never out of sync.

[csb6]

Yeah, that makes sense. It seems like instead of introducing another IPC protocol like this project does, there could be a compositor that loads different window managers as plugins. Then everything is in the same process and there is no need for async communication. Of course a crash in the window manager would take down the compositor, but this is already true for Wayland compositors that combine both.

[WhyNotHugo]

> It seems like instead of introducing another IPC protocol like this project does

It doesn't introduce a new IPC, it uses the Wayland protocol with the river-window-management-v1 extension. The extension mainly defines new objects and verbs for them, but it's the same protocol.

Separate process means that the window manager can be written in any language (even, e.g.: Python).

[csb6]

Interpreters for Python, Lua, etc. can be embedded so using them does not require a separate process.

[MarsIronPI]

What about Emacs? That's the usecase I care about. Until I can get Emacs to manage my Wayland windows ala EXWM, I'm sticking to X.

[donaldihunter]

You'll be looking for https://code.tvl.fyi/about/tools/emacs-pkgs/reka

[DonHopkins]

Or PostScript, even!

https://en.wikipedia.org/wiki/NeWS

Everything old is new again.

Alan Kay on “Should web browsers have stuck to being document viewers?” and a discussion of Smalltalk, HyperCard, NeWS, and HyperLook:

https://donhopkins.medium.com/alan-kay-on-should-web-browser...

Window Management -- Overview: F R A Hopgood, D A Duce, E V C Fielding, K Robinson, A S Williams. 29 April 1985.

This is the Proceedings of the Alvey Workshop at Cosener's House, Abingdon that took place from 29 April 1985 until 1 May 1985. It was input into the planning for the MMI part of the Alvey Programme.

The Proceedings were later published by Springer-Verlag in 1986.

James Gosling: SunDew - A Distributed and Extensible Window System.

https://www.chilton-computing.org.uk/inf/literature/books/wm...

The X-Windows Disaster: This is Chapter 7 of the UNIX-HATERS Handbook. The X-Windows Disaster chapter was written by Don Hopkins.

https://donhopkins.medium.com/the-x-windows-disaster-128d398...

As a result, one of the most amazing pieces of literature to come out of the X Consortium is the “Inter Client Communication Conventions Manual,” more fondly known as the “ICCCM”, “Ice Cubed,” or “I39L” (short for “I, 39 letters, L”). It describes protocols that X clients must use to communicate with each other via the X server, including diverse topics like window management, selections, keyboard and colormap focus, and session management. In short, it tries to cover everything the X designers forgot and tries to fix everything they got wrong. But it was too late — by the time ICCCM was published, people were already writing window managers and toolkits, so each new version of the ICCCM was forced to bend over backwards to be backward compatible with the mistakes of the past.

The ICCCM is unbelievably dense, it must be followed to the last letter, and it still doesn’t work. ICCCM compliance is one of the most complex ordeals of implementing X toolkits, window managers, and even simple applications. It’s so difficult, that many of the benefits just aren’t worth the hassle of compliance. And when one program doesn’t comply, it screws up other programs. This is the reason cut-and-paste never works properly with X (unless you are cutting and pasting straight ASCII text), drag-and-drop locks up the system, colormaps flash wildly and are never installed at the right time, keyboard focus lags behind the cursor, keys go to the wrong window, and deleting a popup window can quit the whole application. If you want to write an interoperable ICCCM compliant application, you have to crossbar test it with every other application, and with all possible window managers, and then plead with the vendors to fix their problems in the next release.

In summary, ICCCM is a technological disaster: a toxic waste dump of broken protocols, backward compatibility nightmares, complex nonsolutions to obsolete nonproblems, a twisted mass of scabs and scar tissue intended to cover up the moral and intellectual depravity of the industry’s standard naked emperor.

Using these toolkits is like trying to make a bookshelf out of mashed potatoes. - Jamie Zawinski

X Myths

X is a colletion of myths that have become so widespread and so prolific in the computer industry that many of them are now accepted as “fact,” without any thought or reflection.

Myth: X Demonstrates the Power of Client/Server Computing At the mere mention of network window systems, certain propeller heads who confuse technology with economics will start foaming at the mouth about their client/server models and how in the future palmtops will just run the X server and let the other half of the program run on some Cray down the street. They’ve become unwitting pawns in the hardware manufacturers’ conspiracy to sell newer systems each year. After all, what better way is there to force users to upgrade their hardware than to give them X, where a single application can bog down the client, the server, and the network between them, simultaneously!

The database client/server model (the server machine stores all the data, and the clients beseech it for data) makes sense. The computation client/server model (where the server is a very expensive or experimental supercomputer, and the client is a desktop workstation or portable computer) makes sense. But a graphical client/server model that slices the interface down some arbitrary middle is like Solomon following through with his child-sharing strategy. The legs, heart, and left eye end up on the server, the arms and lungs go to the client, the head is left rolling around on the floor, and blood spurts everywhere.

The fundamental problem with X’s notion of client/server is that the proper division of labor between the client and the server can only be decided on an application-by-application basis. Some applications (like a flight simulator) require that all mouse movement be sent to the application. Others need only mouse clicks. Still others need a sophisticated combination of the two, depending on the program’s state or the region of the screen where the mouse happens to be. Some programs need to update meters or widgets on the screen every second. Other programs just want to display clocks; the server could just as well do the updating, provided that there was some way to tell it to do so.

The right graphical client/server model is to have an extensible server. Application programs on remote machines can download their own special extension on demand and share libraries in the server. Downloaded code can draw windows, track input events, provide fast interactive feedback, and minimize network traffic by communicating with the application using a dynamic, high-level protocol.

As an example, imagine a CAD application built on top of such an extensible server. The application could download a program to draw an IC and associate it with a name. From then on, the client could draw the IC anywhere on the screen simply by sending the name and a pair of coordinates. Better yet, the client can download programs and data structures to draw the whole schematic, which are called automatically to refresh and scroll the window, without bothering the client. The user can drag an IC around smoothly, without any network traffic or context switching, and the server sends a single message to the client when the interaction is complete. This makes it possible to run interactive clients over low-speed (that is, slow-bandwidth) communication lines.

Sounds like science fiction? An extensible window server was precisely the strategy taken by the NeWS (Network extensible Window System) window system written by James Gosling at Sun. With such an extensible system, the user interface toolkit becomes an extensible server library of classes that clients download directly into the server (the approach taken by Sun’s TNT Toolkit). Toolkit objects in different applications share common objects in the server, saving both time and memory, and creating a look-and-feel that is both consistent across applications and customizable. With NeWS, the window manager itself was implemented inside the server, eliminating network overhead for window manipulation operations — and along with it the race conditions, context switching overhead, and interaction problems that plague X toolkits and window manager.

Ultimately, NeWS was not economically or politically viable because it solved the very problems that X was designed to create.

[sly010]

... or the WM loads the compositor, or the WM links to a compositor library (i.e. wlroots). The point is there are options...

Honestly, every time this topic comes up, I feel like the person complaining just doesn't want to put in the work and they are angry that they don't get an easy win. And maybe that's a good thing. Do we really need more half baked WMs?

[sprash]

This also means low-performing clients can make the whole Desktop stutter/freeze and it is one of the many reasons the Wayland architecture is beyond idiotic. High responsiveness is obviously far more important than avoiding the occasional artifact.

[ChocolateGod]

This has nothing to do with Wayland, only a poor implementation of a display server running a Javascript shell, namely called GNOME.

[wmf]

Clients (apps) should still be async in Wayland; it's just the window manager that's tightly integrated. Wayland compositors should probably use some kind of fair queuing to prevent misbehaving apps from spamming the event loop but they probably don't.

[sprash]

Example: Windows can only be resized when the client finished drawing the new resized window. Otherwise you would get "visual artifacts". So typical operations dealing with window management can not be async when the insistence on the nonsensical "every frame is perfect" mantra is upheld.

[gf000]

Graceful degradation is a thing. If you don't get a response from a client that you are redrawing, you may just put a translucent shader on the window, show the user the changing borders immediately, and then resume whenever it's ready.

[diegocg]

Well, that's exactly what the article is about. Wayland put all together into one process I order to avoid unnecessary context switch. This protocol aims to keep the performance advantages of Wayland without giving up on separation of graphics c server and window manager.

[csb6]

I was responding to this comment in the article and wondering about the historical context:

> Although, I do not know for sure why the original Wayland authors chose to combine the window manager and Wayland compositor, I assume it was simply the path of least resistance.

[em-bee]

already in X11 time, compositor and window manager were one unit: https://en.wikipedia.org/wiki/Compiz

why? because the compositor completely changed the geometry of the desktop. being 3-dimensional. now, today most wayland compositors are 2 dimensional, but they don't have to be. a window manager that works with a 2 dimensional compositor would not work with a 3 dimensional one and vice versa. the window managers listed in the article are only compatible with this particular compositor.

it seems to me that separating window managers from compositors from the start would have created the expectation that all window managers work on all compositors. that is not and will not be the case.

if all compositors start separating out the window manager then the result would be that as a user i now have to choose two components, a compositor and a window manager, and i have to make sure they are compatible.

[Quekid5]

I think wmf's comment in this thread was absolutely correct and succinct, so I won't repeat, but I think it's worth noting that many (all?) of the Wayland devs were actually Xorg devs. Make of that what you will.