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.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

f.lux 36.1 - Adjusts the color of your d...
f.lux makes the color of your computer's display adapt to the time of day, warm at night and like sunlight during the day. Ever notice how people texting at night have that eerie blue glow? Or wake... Read more
VirtualBox 5.0.2 - x86 virtualization so...
VirtualBox is a family of powerful x86 virtualization products for enterprise as well as home use. Not only is VirtualBox an extremely feature rich, high performance product for enterprise customers... Read more
File Juicer 4.43 - Extract images, video...
File Juicer is a drag-and-drop can opener and data archaeologist. Its specialty is to find and extract images, video, audio, or text from files which are hard to open in other ways. In computer... Read more
Apple MainStage 3.2 - Live performance t...
MainStage 3 makes it easy to bring to the stage all the same instruments and effects that you love in your recording. Everything from the Sound Library and Smart Controls you're familiar with from... Read more
formZ 8.5 - Solid and surface modeler. (...
formZ pro is a powerful 3D design application featuring a variety of modeling personalities and tools with an easy to use interface to express and communicate your imagination. It is based on... Read more
PopChar 7.2 - Floating window shows avai...
We're also selling a 5-license family pack for only $25.99! PopChar helps you get the most out of your font collection. With its crystal-clear interface, PopChar provides a frustration-free way to... Read more
FileMaker Pro 14.0.2 - Powerful, easy-to...
FileMaker Pro is powerful, easy-to-use software used to create custom solutions for your business that run on iPad, iPhone, Windows, Mac and the web. Use FileMaker Pro to manage and share information... Read more
djay Pro 1.2 - Transform your Mac into a...
djay Pro provides a complete toolkit for performing DJs. Its unique modern interface is built around a sophisticated integration with iTunes and Spotify, giving you instant access to millions of... Read more
Stacks 2.7.2 - New way to create pages i...
Stacks is a new way to create pages in RapidWeaver. It's a plugin designed to combine drag-and-drop simplicity with the power of fluid layout. Features Fluid Layout: Stacks lets you build pages... Read more
Vitamin-R 2.30 - Personal productivity t...
Vitamin-R creates the optimal conditions for your brain to work at its best by structuring your work into short bursts of distraction-free, highly focused activity alternating with opportunities for... Read more

ReBoard: Revolutionary Keyboard (Utilit...
ReBoard: Revolutionary Keyboard 1.0 Device: iOS Universal Category: Utilities Price: $1.99, Version: 1.0 (iTunes) Description: Do everything within the keyboard without switching apps! If you are in WhatsApp, how do you schedule a... | Read more »
Tiny Empire (Games)
Tiny Empire 1.1.3 Device: iOS Universal Category: Games Price: $2.99, Version: 1.1.3 (iTunes) Description: Launch cannonballs and blow tiny orcs into thousands of pieces in this intuitive fantasy-themed puzzle shooter! Embark on an... | Read more »
Astropad Mini (Productivity)
Astropad Mini 1.0 Device: iOS iPhone Category: Productivity Price: $4.99, Version: 1.0 (iTunes) Description: *** 50% off introductory price! ​*** Get the high-end experience of a Wacom tablet at a fraction of the price with Astropad... | Read more »
Emo Chorus (Music)
Emo Chorus 1.0.0 Device: iOS Universal Category: Music Price: $1.99, Version: 1.0.0 (iTunes) Description: Realistic Choir simulator ranging from simple Chorus emulation to full ensemble Choir with 128 members. ### introductory offer... | Read more »
Forest Spirit (Games)
Forest Spirit 1.0.5 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.5 (iTunes) Description: | Read more »
Ski Safari 2 (Games)
Ski Safari 2 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: The world's most fantastical, fun, family-friendly skiing game is back and better than ever! Play as Sven's sister Evana, share... | Read more »
Lara Croft GO (Games)
Lara Croft GO 1.0.47768 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0.47768 (iTunes) Description: Lara Croft GO is a turn based puzzle-adventure set in a long-forgotten world. Explore the ruins of an ancient... | Read more »
Whispering Willows (Games)
Whispering Willows 1.23 Device: iOS Universal Category: Games Price: $4.99, Version: 1.23 (iTunes) Description: **LAUNCH SALE 50% OFF** - Whispering Willows is on sale for 50% off ($4.99) until September 9th. | Read more »
Calvino Noir (Games)
Calvino Noir 1.1 Device: iOS iPhone Category: Games Price: $3.99, Version: 1.1 (iTunes) Description: The film noir stealth game. Calvino Noir is the exploratory, sneaking adventure through the 1930s European criminal underworld.... | Read more »
Angel Sword (Games)
Angel Sword 1.0 Device: iOS Universal Category: Games Price: $6.99, Version: 1.0 (iTunes) Description: Prepare to adventure in the most epic full scale multiplayer 3D RPG for mobile! Experience amazing detailed graphics in full HD.... | Read more »

Price Scanner via MacPrices.net

12-inch 1.1GHz Gold MacBook on sale for $1149...
B&H Photo has the 12″ 1.1GHz Gold Retina MacBook on sale for $1149.99 including free shipping plus NY sales tax only. Their price is $150 off MSRP, and it’s the lowest price available for this... Read more
27-inch 3.3GHz 5K iMac on sale for $1849, sav...
Best Buy has the 27″ 3.3GHz 5K iMac on sale for $1849.99. Their price is $150 off MSRP, and it’s the lowest price available for this model. Choose free shipping or free local store pickup (if... Read more
Worldwide Tablet Shipments Expected to Declin...
Does Apple badly need a touchscreen convertible/hybrid laptop MacBook? Yes, judging from a new market forecast from the International Data Corporation (IDC) Worldwide Quarterly Tablet Tracker, which... Read more
Continued PC Shipment Shrinkage Expected Thro...
Worldwide PC shipments are expected to fall by -8.7 percent in 2015 and not stabilize until 2017, according to the latest International Data Corporation (IDC) Worldwide Quarterly PC Tracker data. The... Read more
Imminent iPhone 6s Announcement Leads To 103%...
NextWorth Solutions, with its online and in-store electronics trade-in programs including http://NextWorth.com, reports that it has experienced a 103 percent surge in quoted trade-in values over the... Read more
Weekend Deal: 13-inch Retina MacBook Pros for...
Save up to $100 on the purchase of a new 2015 13″ Retina MacBook Pro at the following resellers this weekend. Shipping is free with each model: 2.7GHz/128GB MSRP $1299 2.7GHz/... Read more
13-inch 2.5GHz MacBook Pro on sale for $999,...
B&H Photo has the 13″ 2.5GHz MacBook Pro on sale for $999.99 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Read more
Apple refurbished iPad Air 2s available for u...
The Apple Store has Apple Certified Refurbished iPad Air 2s available for up to $140 off the price of new models. Apple’s one-year warranty is included with each model, and shipping is free: - 128GB... Read more
The ‘Book Mystique Still Magic After All Thes...
This column has been called The ‘Book Mystique for what has been a 15 year run so far, and I have no interest in changing the name. The reference is to what I’ve observed is a the near magical... Read more
15-inch Retina MacBook Pros on sale for up to...
B&H Photo has 2015 15″ Retina MacBook Pros on sale for up to $184 off MSRP including free shipping plus NY sales tax only: - 15″ 2.2GHz Retina MacBook Pro: $1815 $184 off - 15″ 2.5GHz Retina... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Software QA Engineer, *Apple* Pay Security...
Changing the world is all in a day039s work at Apple . If you love innovation, here039s your chance to make a career of it. You039ll work hard. But the job comes with Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Solutions Consultant - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail Read more
*Apple* Solutions Consultant - Retail Sales...
**Job Summary** As an Apple Solutions Consultant (ASC) you are the link between our customers and our products. Your role is to drive the Apple business in a retail Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.