The X-Windows Disaster

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

How to make a 50-MIPS Workstation Run Like a 4.77MHz IBM PC

If the designers of X-Windows built cars, there would be no fewer than five steering wheels hidden about the cockpit, none of which followed the same principles -- but you'd be able to shift gears with your car stereo. Useful feature, that.
- Marus J. Ranum, Digital Equipment Corporation

X-Windows is the Iran-Contra of graphical user interfaces: a tragedy of political compromises, entangled alliances, marketing hype, and just plain greed. X-Windows is to memory as Ronald Reagan was to money. Years of "Voodoo Ergonomics" have resulted in an unprecedented memory deficit of gargantuan proportions. Divisive dependencies, distributed deadlocks, and partisan protocols have tightened gridlocks, aggravated race conditions, and promulgated double standards.

X has had its share of $5,000 toilet seats -- like Sun's Open Look clock tool, which gobbles up 1.4 megabytes of real memory! If you sacrificed all the RAM from 22 Commodore 64s to clock tool, it still wouldn't have enough to tell you the time. Even the vanilla X11R4 "xclock" utility consumed 656K to run. And X's memory usage is increasing.

X: The First Fully Modular Software Disaster

X-Windows started out as one man's project in an office on the fifth floor of MIT's Laboratory for Computer Science. A wizardly hacker, who was familiar with W, a window system written at Stanford University as part of the V project, decided to write a distributed graphical display server. The idea was to allow a program, called a client, to run on one computer and allow it to display on another computer that was running a special program called a window server. The two computers might be VAXes or Suns, or one of each, as long as the computers were networked together and each implemented the X protocol.

[Footnote: We have tried to avoid paragraph-length footnotes in this book, but X has defeated us by switching the meaning of client and server. In all other client/server relationships, the server is the remote machine that runs the application (i.e., the server provides services, such as database service or computational service). For some perverse reason that's better left to the imagination, X insists on calling the program running on the remote machine "the client." This program displays its windows on the "window server." We're going to follow X terminology when discussing graphical client/servers. So when you see "client" think "the remote machine where the application is running," and when you see "Server" think "the local machine that displays output and accepts user input."]

The Nongraphical GUI

X was designed to run three programs: xterm, xload, and xclock. (The idea of a window manager was added as an afterthought, and it shows.) For the first few years of its development at MIT, these were, in fact, the only programs that ran under the window system. Notice that none of these program have any semblance of a graphical user interface (except xclock), only one of these programs implements anything in the way of cut-and-paste (and then, only a single data type is supported), and none of them requires a particularly sophisticated approach to color management. Is it any wonder, then, that these are all areas in which modern X falls down?

Ten years later, most computers running X run just four programs: xterm, xload, xclock, and a window manager. And most xterm windows run Emacs! X has to be the most expensive way ever of popping up an Emacs window. It sure would have been much cheaper and easier to put terminal handling in the kernel where it belongs, rather than forcing people to purchase expensive bitmapped terminals to run character-based applications. On the other hand, then users wouldn't get all of those ugly fonts. It's a trade-off.

The Motif Self-Abuse Kit

X gave Unix vendors something they had professed to want for years: a standard that allowed programs built for different computers to interoperate. But it didn't give them enough. X gave programmers a way to display windows and pixels, but it didn't speak to buttons, menus, scroll bars, or any of the other necessary elements of a graphical user interface. Programmers invented their own. Soon the Unix community had six or so different interface standards. A bunch of people who hadn't written 10 lines of code in as many years set up shop in a brick building in Cambridge, Massachusetts, that was the former home of a failed computer company and came up with a "solution:" the Open Software Foundation's Motif.

What Motif does is make Unix slow. Real slow. A stated design goal of Motif was to give the X Window System the window management capabilities of HP's circa-1988 window manager and the visual elegance of Microsoft Windows. We kid you not.

Recipe for disaster: start with the Microsoft Windows metaphor, which was designed and hand coded in assembler. Build something on top of three or four layers of X to look like Windows. Call it "Motif." Now put two 486 boxes side by side, one running Windows and one running Unix/Motif. Watch one crawl. Watch it wither. Watch it drop faster than the putsch in Russia. Motif can't compete with the Macintosh OS or with DOS/Windows as a delivery platform.

Ice Cube: The Lethal Weapon

One of the fundamental design goals of X was to separate the window manager from the window server. "Mechanism, not policy" was the mantra. That is, the X server provided a mechanism for drawing on the screen and managing windows, but did not implement a particular policy for human-computer interaction. While this might have seemed like a good idea at the time (especially if you are in a research community, experimenting with different approaches for solving the human-computer interaction problem), it can create a veritable user interface Tower of Babel.

If you sit down at a friend's Macintosh, with its single mouse button, you can use it with no problems. If you sit down at a friend's Windows box, with two buttons, you can use it, again with no problems. But just try making sense of a friend's X terminal: three buttons, each one programmed a different way to perform a different function on each different day of the week -- and that's before you consider combinations like control-left-button, shift-right-button, control-shift-meta-middle-button, and so on. Things are not much better from the programmer's point of view.

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 ust 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 gheads 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 fore suers 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 slies 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 eents, 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 an 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 interfae 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 reating a look-and-feel that is both consistent aross 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 the very problems that X was designed to create.

Myth: X Makes Unix "Easy to Use"

Graphical interfaces can only paper over misdesigns and kludges in the underlying operating system; they can't eliminate them.

The "drag-and-drop" metaphor tires to cover up the Unix file system, but so little of Unix is designed for the desktop metaphor that it's just one kludge on top of another with little holes and sharp edges popping up everywhere. Maybe the "sag-and-drop" metaphor is more appropriate for such ineffective and unreliable performance.

A shining example is Sun's Open Windows File Manager, which goes out of its way to display ore dump files as cute little red bomb icons. When you double-click on the bomb, it runs a text editor on the core dump. Harmless, but not very useful. But if you intuitively drag and drop the bomb on the DBX Debugger Tool, it does exactly what you'd expect if you were a terrorist: it ties the entire system up, as the core dump (including a huge unmapped gap of zeros) is pumped through the server and into the debugger text window, which inflates to the maximum capacity of swap space, then violently explodes, dumping an even bigger core file in place of your original one, filling up the entire file system, overwhelming the file server, and taking out the File Manager with shrapnel. (This bug has since been fixed.)

But that's not all: the File Manager puts even more power at your fingertips if you run it as root! When you drag and drop a directory onto itself, it beeps and prints "rename: invalid argument" at the bottom of the window, then instantly deletes the entire directory trwe without bothering to update the graphical directory browser.

The following message illustrates the X approach to "seurity through obscurity":

Date: Wed, 30 Jan 91 15:35:46 -0800
From: David Chapman <zvona@gang-of-four.stanford.edu>
To: UNIX-HATERS
Subject: MIT-MAGIC-COOKIE-1
[You're going to have to buy the UNIX-HATERS Handbook to read this one -- it's funny but long so I'm not going to type it in.]

Anybody who has ever used X knows that Chapman's error was trying to use xauth in the first place. he should have known better. (Blame the victom, not the program.)

From: Olin Shivers <shivers@bronto.soar.cs.cmu.edu>
Date: Wed, 30 Jan 91 23:49:46 EST
To: ian@ai.mit.edu
Cc: zvona@gang-of-four.stanford.edu, UNIX-HATERS
Subject: MIT-MAGIC-COOKIE-1
[You're going to have to buy the UNIX-HATERS Handbook to read this one -- it's funny but long so I'm not going to type it in.]

Myth: X Is "Customizable"

...And so is a molten blob of pig iron. But it's getting better; at least now you don't hasve to use your bare hands. Hewlett-Packard's Visual User Environment is so cutting-edge that it even has an icon you can click on to bring up the resource manager: it pops up a vi on your .Xdefaults file! Quite a labor-saving contraption, as long as you're omniscient enough to understand X defaults and archaic enough to use vi. The following message describes the awesome flexibility and unbounded freedom of expression that X defaults fail to provide.

Date: Fri, 22 Feb 91 08:17:14 -0800
From: beldar@ips.com (Gardner Cohen)
[You're going to have to buy the UNIX-HATERS Handbook to read this one -- it's funny but long so I'm not going to type it in.]

Myth: X Is "Portable"

...And Iran-Contra wasn't Arms for Hostages.

Even if you can get an X program to compile, there's no guarantee it'll work with your server. If an application requires an X extension that your server doesn't provide, then it fails. X applications can't extend the server themselves -- the exten sion has to be compiled and linkekd into the server. Most interesting extensions actually require extensive modification and recompilation of the X server itself, a deidedly nontrivial task. the e tells how much brain-searing, eye-popping fun compiling "portable" X server extensions can be:

Date: Wed 4 Mar 92 02:53:53 PST
X-Windows: Boy, Is my Butt Sore
From: Jamie Zawinski [jwz@lucid.com]
To: UNIX-HATERS
Subject: X: or, How I Learned to Stop Worring and Love the Bomb
[You're going to have to buy the UNIX-HATERS Handbook to read this one -- it's funny but long so I'm not going to type it in.]

On the whole, X extensions are a failure. The ntable exception that proves the rule is the Shaped Window extension, which was specifically designed to implement round clocks and eyeballs. But most application writers just don't bother using proprietarty extensions like Display PostScript, because X terminals and MIT servers don't support them. Many find it too much of a hassle to use more ubiquitous extensions like shared memory, double buffering, or splines: they still don't work in many cases, so you have to be prepared to do without them. If you really don't need the extension, then why complicate your code wioth the special cases? And most applications that do use extensions just assume they're supported and bomb if they're not.

The most that can be said about the lowest-common-denominator approach that X takes to graphics is that it levels the playing field, allowing incredidibly stupid companies to jump on the bandwaon and sell obsolete junk that's just as unusable as high-end brand-name workstations:

Date: Wed 10 Apr 91 08:14:16 EDT
From: Steve Strassmann <straz@media-lab.mit.edu>
To: UNIX-HATERS
Subject: the display from hell
[You're going to have to buy the UNIX-HATERS Handbook to read this one -- it's funny but long so I'm not going to type it in.]

Myth: X is "Device Independent"

X is extremely device dependent because all X graphics are specified in piel coordinates. graphics drawn on different resulution screens come out at different sizes, so you have to scale all the coordinates yourself if you want to draw at a ertain size. N ot all screens een have square pixels: unless you don't mind rectangular squares and oval circles, you also have to adjust all coordinates according to the pixel aspect ratio.

A task as simple as filing and stroking shapes is quite complicated because of X's bizarre pixel-oriented imaging rules. When you fill a 10x10 square with XFillRectangle, it fills the 100 pixels you expect. But you get extra "bonus pixels" when you pass the same arguments to XDrawRectangle, because it actually draws an 11x11 square, hanging out one pixel below and to the right!!! If you find this hard to believe, look it up in the X manual yourself: Volume 1, Section 6.1.4. The manual patronizingly explains how easy it is to add 1 to the x and y position of the filled rectangle, while subtracting 1 from the width and height to compensate, so it fits neatly inside the outline. Then it points out that "in the case of arcs, however, this is a much more difficult proposition (probably impossible in a portable fashion)." This means that portably filling and stroking an arbitrarily scaled arc without overlapping or leaving gaps is an intractable problem when using the X Window System. Think about that. You can't even draw a proper rectangle with a thick outline, since the line width is specified in unscaled pixel units, so if your display has rectangular pixels, the vertical and horizontal lines will have different thicknesses enen though you scaled the rectangle corner coordinates to compensate for the aspect ratio.

The color situation is a total flying circus. The X approach to device independence is to treat everything like a MicroVAX framebuffer on acid. A truly portable X application is required to act like the persistent customer in Monty Python's "Cheese Shop" sketch, or a grail seeker in "Monty Python and the Holy Grail." Even the simplest applications must answer many difficult questions:

[You're going to have to buy the UNIX-HATERS Handbook to read this one -- it's funny but long so I'm not going to type it in.]

X Graphics: Square Peg in a Round Hole

Programming X-Windows is like trying to find the square root of pi using roman numerals.
- Unknown

The PostScript imaging model, used by NeWS and Display PostScript, solves all these horrible problems in a high-level, standard, device independent manner. NeWS has integrated extensions for input, lightweight processes, networking, and windows. It can draw and respond to input in the same arbitrary coordinate system and define window shapes with PostScript paths. The Display PostScript extension for X is intended for output only and doesn't address any window system issues, which must be dealt with through X. NEXTSTEP is a toolkit written in Objective-C, on top of NeXT's own window server. NEXTSTEP uses Display PostScript for imaging, but not for input. It has an excellent imaging model and well designed toolkit, but the Display PostScript server is not designed to be programmed with interactive code: instead all events are sent to the client for processing, and the toolkit runs in the client, so it does not have the low bandwidth, context-switching, and code-sharing advantages of NeWS. Nevertheless, it is still superior to X, which lacks the device-independent imaging model.

On the other hand, X's spelling has remained constant over the years, while NeXT has at various times spelled their flagship product "NextStep," "NeXTstep," NeXTStep," "NeXTSTEP," "NEXTSTEP", and finally "OpenStep." A standardized, consistent spelling is certainly easier on the marketing 'droids.

Unfortunately, NeWS an d NEXTSTEP were political failures because they suffer from the same two problems: oBNoXiOuS capitalization, and Amiga Persecution Attitude(TM).

X: On the Road to Nowhere

X is just so stupid, why do people use it? Beats us. Maybe it's because they don't have a choice. (See Figure 2)

Nobody really wants to run X: what they do want is a way to run several applications at the same time using a large screen. If you want to run Unix, it's either X or a dumb character-based terminal.

Pick your poison.

Figure 2. Distributed at the X-Windows Conference

Official Notie, Post Immediately

X: Dangerous Virus

[You're going to have to buy the UNIX-HATERS Handbook to read this one -- it's funny but long so I'm not going to type it in.]

Don Hopkins is a seasoned user interface designer and graphics programmer. Don received a BSCS degree from the University of Maryland while working as a researcher at the Human Computer Interaction Lab. Don has worked at UniPress Software, Sun Microsystems, the Turing Institute, and Carnegie Mellon University. He ported SimCity to NeWS and X11 for DUX Software. He now workes for Kaleida. Don wrote the chapter on the X-Windows Disaster. (To annoy X fanatics, Don specifically asked that we include the hyphen after the letter "X,", as well as the plural of the word "Windows," in his chapter title.)