TweetFollow Us on Twitter

X11: A C of Window Systems

Volume Number: 19 (2003)
Issue Number: 3
Column Tag: Section 7

X11: A C of Window Systems

or possibly a Fortran?

by Rich Morin

Taken on its own terms, X11 is a stunning success. As www.x.org/X11.htm proclaims:

    The X Window System, more simply 'X' or 'X11', is judged worldwide to be one of the most successful open source, collaborative technologies developed to date. It is the de facto standard graphical engine for the UNIX and Linux operating systems and provides the only common windowing environment bridging the heterogeneous platforms in today's enterprise computing. The inherent independence of the X Window System from operating system and hardware, its network-transparency, and its support for a wide range of popular desktops are responsible for its continuing and growing popularity.

    All major hardware vendors support the X Window System. Many third parties provide technologies for integrating X Window System applications into network or personal computer environments under DOS, Windows, Windows 9x, and Windows NT, while thousands of independent software developers provide X Window System applications. The worldwide community of users of the X Window System currently exceeds 30 million.

X11 is such a dominant technology in Unix circles that shipping a Unix system without an integral copy of X11 would be like omitting a C compiler or, erm, hiding the command line. Nonetheless, Apple's initial position was fairly plausible: "X11 support is an opportunity for third-party developers".

Several developers, indeed, accepted the challenge. Tenon Intersystems (www.tenon.com) has produced a well-regarded proprietary X11 implementation for OSX. OroborOSX (oroborosx.sf.net), XDarwin (www.xdarwin.org), and XonX (www.mrcla.com/XonX) provide free distributions of X11 for OSX.

Nonetheless, Apple's release of an "official" implementation of X11 is certain to interest many users, including some who have been wary of trying X11. And, indeed, Apple is in a position to make X11 interoperate with Aqua in ways that a third-party vendor might not have been able to duplicate. I would expect, however, to see the third-party developers adopt any enabling technologies that Apple makes available.

The Apple implementation includes "standard X11 display server software, client libraries, and developer toolkits". The intention, as confirmed by an Apple spokesman, is to place X11 at about the same level of OS support as, say, Carbon. That is, better integrated than Classic, but possibly missing some Cocoa functionality.

So, we can expect to see X11 apps appearing commonly on OSX. Despite the best efforts of all concerned, however, it is not clear that the fit will be all that good: the goals, designs, and philosophy of the two systems are wildly different. Let's look at each of these, using OSX as our point of reference.

X VS. X

The goals of X11, as noted above, are "network transparency" and "bridging heterogeneous platforms". An X11 user can access an X11-based application on either the local machine or on any machine which is reachable over the network.

Apple Remote Desktop, SSH, Timbuktu, and VNC all allow remote access, but none of these provides the level of integration and performance that X11 does. In short, if you want network-transparent, cross-platform support for GUI-based apps, X11 is your answer.

X11's design differences reflect its differing goals. An X11 "client" application sets up callback functions and issues UI requests, just as a Cocoa or Carbon app would. In X11, however, everything is translated into a serial stream of data, suitable for sending over the network.

In place of Apple's Cocoa and Carbon APIs, X11 has "widget sets" (e.g., GTK+, Motif, Qt, Xaw). In place of the Finder, X11 has "window managers" (e.g., fvwm, kvm, mwm, sawfish, twm) and "desktop environments" (e.g., CDE, Gnome, KDE).

Making all of this play nicely with Aqua (e.g., supporting drag and drop) isn't going to be an easy job. In fact, some things will simply fail to translate. If X11 has a widget that Aqua doesn't (or vice versa), there isn't much that a "glue layer" can do about it.

X11's basic philosophy is likely to cause the worst dislocations, however. Apple has worked for years to develop, document, and promote the Macintosh "Human Interface Guidelines". As a result, Mac users feel comfortable starting up a new app, knowing that the command keys and menus will all be familiar. No such guidelines are present in X11:

With no central authority specifying policy, no consistent user interface developed. Each of X11's widget sets, window managers, desktop environments, and applications was free to go off in its own direction. The resulting inconsistency will grate on seasoned Mac users.

Porting X11 apps

Now that Apple is providing an X11 development system, porting an X11 app shouldn't be much harder than porting any other Unix-based app. Nonetheless, I'd like to see Apple provide an X11 and Unix analog to the "Carbon Dater" (an analysis tool for Carbonizing Classic apps); this could ease the task of identifying the OSX equivalents to unavailable include files, library calls, system calls, etc.

While I'm fantasizing, I'd also like a way for Aqua apps to be accessible via the X11 protocol and an X11 toolkit that implements the Aqua look and feel. Both technical and legal issues surround these pipe dreams, however, so I'd best get back to reality.

If an app is written for certain X11 toolkits (e.g., GTK+, Qt, Tk), it may be possible to link it to Carbon or Cocoa. This could provide access to useful Cocoa features and/or improvement in appearance and/or performance. Look around for interface libraries, ala:

If the app only needs to run on a single machine, a port to native Cocoa may be appropriate. If the app has a clean separation between its Model and View code, the rework shouldn't be all that hard. Unfortunately, the real problems may not be obvious at the beginning of the effort.

X11, Layer by Layer

I have made some hand-waving claims about the differences between the OSX model and the X11 model. For those that may be interested, here is a (somewhat) detailed discussion of X11's structure.

At the bottom layer, X11 is a communication protocol. The units of discourse are user events (e.g., mouse and keyboard actions) and displayable items (e.g., characters and pixel rectangles, also known as "pixrects"). An X11 "server" runs on the user's desktop, making the screen and input devices available to the "client" application.

The low level of the X protocol limits the amount of processing power that the server can usefully provide. Once items display instantly, extra computing power is irrelevant. Compare this to Aqua, Display PostScript, Java, Javascript, or Sun's ill-fated NeWS, all of which can offload rendering and other processing to a separate processor.

In addition, X11 is not well suited to displaying shapes other than rectangles. Although any shape can be rendered as a set of rectangles, a PDF-based description of an arbitrary shape is likely to be a lot shorter than the pixrect equivalent.

At the next level, programming interfaces, X11 provides only the bare essentials. You can draw characters and pixrects, as implied above, but doing anything else requires "widgets". The good news is that there are a lot of widgets to choose from; the bad news is that there are a lot of widget sets to choose from. The sets all do roughly the same things, but the look, feel, and APIs vary.

Similarly, window management can be performed by any of a few dozen "window managers" (really, special-purpose X11 clients). These are similar to "skins" and "themes", but their influence extends into the feel, as well as the look, of the apps they are presenting.

Moving up to the application level, we see even more diversity. Historically, X11 app designers picked their own "hot keys", menu layouts, and other UI options. As a result, there was little consistency at this level.

Recently, some X11-based "desktop environments" have begun to promote more consistency in widgets, window management, and applications. The good news is that these environments are becoming popular; the bad news is that there are several desktop environments to choose from. Gnome and KDE are the most popular in Open Source circles. CDE is found on many proprietary Unix systems, but Sun intends to transition Solaris and its users to Gnome.

In Summary

The X mantra of "mechanism, not policy" has resulted in a prolific, but anarchic collection of APIs, window managers, and look and feel decisions. Like the many variations of the C programming language (e.g., C, C++, Objective-C), X11 has evolved into a "sea" of window systems, each with its own vagaries.

Apple's frameworks may be appallingly complex, but they are internally consistent, logical, and produce consistent results on the desktop. Where Microsoft Windows is simple (nay, simplistic), consistent, and ugly, X11 is powerful, inconsistent, and ugly.

This inconsistency, appearing at all levels of X11, means that users cannot build reliable habits. Apple's developer community has spent a great deal of time and effort on making sure that OSX apps act in a consistent manner; the X11 developer community has not, and it shows.

Co-existence?

Many OSX users and programmers will be inclined to ignore X11 entirely, but there are reasons why you might wish to consider a co-existence strategy. If you need a particular X11 app or some of the capabilities that X11 provides, you'll have to allow X11 into your world. Another reason might be the plethora of free (both libre and gratis) X11 apps.

Some institutions will find X11 unavoidable, because critically necessary apps are only available under it. The engineering and scientific communities have been using Unix and X11 for decades; OSX and Aqua are still (largely unproven) newcomers. Until the apps you need get ported to Cocoa, there really isn't any alternative to using X11.

There is also the possibility that you will need to create an OS-independent and/or network-capable application. As noted above, Apple has no real solution in this area; Apple Remote Desktop is fine for sharing a remote screen, but it isn't capable of supporting generic, distributed applications.

Even if your work doesn't require a specialized app, however, you may be interested in trying out some X11 packages. You can pick these up off the Internet (e.g., via Fink or the GNU-Darwin project), but you'll probably have less trouble with a pre-packaged collection.

BSDMall (www.bsdmall.com) has produced a set of X11-based "Office Applications for Mac OS X". The set includes word processors, spreadsheets, graphics tools, games, and more. You may recognize tools such as AbiWord, Calc, Chimera, Draw, Gaim, Gimp, Impress, Math, and OpenOffice. If you're interested in trying X11, this might be a good starting point.

More generally, for a good list of X11 resources, try Kenton Lee's "Technical X Window System and Motif WWW Sites" page, http://www.rahul.net/kenton/xsites.html. He has done a really fine job of collecting and organizing X11-related links!


Rich Morin has been using computers since 1970, Unix since 1983, and Mac-based Unix since 1986 (when he helped Apple create A/UX 1.0). When he isn't writing this column, Rich runs Prime Time Freeware (www.ptf.com), a publisher of books and CD-ROMs for the Free and Open Source software community. Feel free to write to Rich at rdm@ptf.com.

 
AAPL
$97.57
Apple Inc.
+0.54
MSFT
$44.55
Microsoft Corpora
+0.15
GOOG
$590.40
Google Inc.
-2.95

MacTech Search:
Community Search:

Software Updates via MacUpdate

TinkerTool 5.3 - Expanded preference set...
TinkerTool is an application that gives you access to additional preference settings Apple has built into Mac OS X. This allows to activate hidden features in the operating system and in some of the... Read more
Audio Hijack Pro 2.11.0 - Record and enh...
Audio Hijack Pro drastically changes the way you use audio on your computer, giving you the freedom to listen to audio when you want and how you want. Record and enhance any audio with Audio Hijack... Read more
Intermission 1.1.1 - Pause and rewind li...
Intermission allows you to pause and rewind live audio from any application on your Mac. Intermission will buffer up to 3 hours of audio, allowing users to skip through any assortment of audio... Read more
Airfoil 4.8.7 - Send audio from any app...
Airfoil allows you to send any audio to AirPort Express units, Apple TVs, and even other Macs and PCs, all in sync! It's your audio - everywhere. With Airfoil you can take audio from any... Read more
Microsoft Remote Desktop 8.0.8 - Connect...
With Microsoft Remote Desktop, you can connect to a remote PC and your work resources from almost anywhere. Experience the power of Windows with RemoteFX in a Remote Desktop client designed to help... Read more
xACT 2.30 - Audio compression toolkit. (...
xACT stands for X Aaudio Compression Toolkit, an application that encodes and decodes FLAC, SHN, Monkey’s Audio, TTA, Wavpack, and Apple Lossless files. It also can encode these formats to MP3, AAC... Read more
Firefox 31.0 - Fast, safe Web browser. (...
Firefox for Mac offers a fast, safe Web browsing experience. Browse quickly, securely, and effortlessly. With its industry-leading features, Firefox is the choice of Web development professionals... Read more
Little Snitch 3.3.3 - Alerts you to outg...
Little Snitch gives you control over your private outgoing data. Track background activityAs soon as your computer connects to the Internet, applications often have permission to send any... Read more
Thunderbird 31.0 - Email client from Moz...
As of July 2012, Thunderbird has transitioned to a new governance model, with new features being developed by the broader free software and open source community, and security fixes and improvements... Read more
Together 3.2 - Store and organize all of...
Together helps you organize your Mac, giving you the ability to store, edit and preview your files in a single clean, uncluttered interface. Smart storage. With simple drag-and-drop functionality,... Read more

Latest Forum Discussions

See All

Modern Combat 5: Blackout Review
Modern Combat 5: Blackout Review By Brittany Vincent on July 25th, 2014 Our Rating: :: LESS QQ, MORE PEW PEWUniversal App - Designed for iPhone and iPad The fifth entry into the blockbuster Modern Combat series is what mobile... | Read more »
Watch and Share Mobile Gameplay Videos W...
Watch and Share Mobile Gameplay Videos With Kamcord Posted by Jennifer Allen on July 25th, 2014 [ permalink ] iPhone App - Designed for the iPhone, compatible with the iPad | Read more »
THE KING OF FIGHTERS '98 (Games)
THE KING OF FIGHTERS '98 1.0 Device: iOS Universal Category: Games Price: $3.99, Version: 1.0 (iTunes) Description: Series’ masterpiece “KOF ’98” finally joins the battle on iPhone! FEATURES:■ The best game balance in the “KOF”... | Read more »
LEX Goes Free For One Day In Honor of Ne...
LEX Goes Free For One Day In Honor of New Update Posted by Jennifer Allen on July 24th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Thomas Was Alone Goes Universal, Slashes...
Thomas Was Alone Goes Universal, Slashes Price to $3.99 Posted by Ellis Spice on July 24th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Meerkatz Challenge Review
Meerkatz Challenge Review By Jennifer Allen on July 24th, 2014 Our Rating: :: FONDLY PUZZLINGUniversal App - Designed for iPhone and iPad Cute and challenging, Meerkatz Challenge is a fun puzzle game, particularly for fans of... | Read more »
Book Your Appointment with F.E.A.R. this...
Book Your Appointment with F.E.A.R. | Read more »
It Came From Canada: Epic Skater
For all the hate that it gets for being a pastime for slackers, skateboarding really does require a lot of skill. All those flips and spins take real athleticism, and there’s all the jargon to memorize. Fortunately for us less extreme individuals,... | Read more »
Cultures Review
Cultures Review By Jennifer Allen on July 24th, 2014 Our Rating: :: SLOW-PACED EMPIRE BUILDINGiPad Only App - Designed for the iPad Cute it might seem, but Cultures is a bit too slow paced when it comes to those pesky timers to... | Read more »
More Paintings Have Been Added to Paint...
More Paintings Have Been Added to Paint it Back! Posted by Jessica Fisher on July 24th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »

Price Scanner via MacPrices.net

Mac minis on sale for $100 off MSRP, starting...
Best Buy has Mac minis on sale for $100 off MSRP. Choose free shipping or free instant local store pickup. Prices are for online orders only, in-store prices may vary: 2.5GHz Mac mini: $499.99 2.3GHz... Read more
Global Tablet Market Grows 11% in Q2/14 Notwi...
Worldwide tablet sales grew 11.0 percent year over year in the second quarter of 2014, with shipments reaching 49.3 million units according to preliminary data from the International Data Corporation... Read more
New iPhone 6 Models to Have Staggered Release...
Digitimes’ Cage Chao and Steve Shen report that according to unnamed sources in Apple’s upstream iPhone supply chain, the new 5.5-inch iPhone will be released several months later than the new 4.7-... Read more
New iOS App Helps People Feel Good About thei...
Mobile shoppers looking for big savings at their favorite stores can turn to the Goodshop app, a new iOS app with the latest coupons and deals at more than 5,000 online stores. In addition to being a... Read more
Save on 5th generation refurbished iPod touch...
The Apple Store has Apple Certified Refurbished 5th generation iPod touches available starting at $149. Apple’s one-year warranty is included with each model, and shipping is free. Many, but not all... Read more
What Should Apple’s Next MacBook Priority Be;...
Stabley Times’ Phil Moore says that after expanding its iMac lineup with a new low end model, Apple’s next Mac hardware decision will be how it wants to approach expanding its MacBook lineup as well... Read more
ArtRage For iPhone Painting App Free During C...
ArtRage for iPhone is currently being offered for free (regularly $1.99) during Comic-Con San Diego #SDCC, July 24-27, in celebration of the upcoming ArtRage 4.5 and other 64-bit versions of the... Read more
With The Apple/IBM Alliance, Is The iPad Now...
Almost since the iPad was rolled out in 2010, and especially after Apple made a 128 GB storage configuration available in 2012, there’s been debate over whether the iPad is a serious tool for... Read more
MacBook Airs on sale starting at $799, free s...
B&H Photo has the new 2014 MacBook Airs on sale for up to $100 off MSRP for a limited time. Shipping is free, and B&H charges NY sales tax only. They also include free copies of Parallels... Read more
Apple 27″ Thunderbolt Display (refurbished) a...
The Apple Store has Apple Certified Refurbished 27″ Thunderbolt Displays available for $799 including free shipping. That’s $200 off the cost of new models. Read more

Jobs Board

*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
Sr. Project Manager for *Apple* Campus 2 -...
…the design and construction of one building or building components of the New Apple Campus located in Cupertino, CA. They will provide project management oversight for Read more
WW Sales Program Manager, *Apple* Online St...
**Job Summary** Imagine what you could do here. At Apple , great ideas have a way of becoming great products, services, and customer experiences very quickly. Bring Read more
*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
Project Manager / Business Analyst, WW *Appl...
…a senior project manager / business analyst to work within our Worldwide Apple Fulfillment Operations and the Business Process Re-engineering team. This role will work Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.