For a desktop application looking for an extension language, the two most important things to optimize for are the likelihood that your users will create plugins, and the chance they’ll actually enjoy it. This gives a few guidelines when choosing an extension language:

• Adoption matters. There should be a reasonable chance that users already know the language, or if they don’t, learning it is at least a worthy investment.
• Unicode matters. How much depends on the application, but if users can’t even write a script that opens a file in their home directory because of Unicode issues, you won’t be winning any friends.
• Libraries matter. File access, date / time, socket programming, subprocesses, etc. If you’re writing a general purpose desktop application, then most plugins your users will want to write will involve using APIs other that what you’ve explicitly exposed.
• Ease matters. Any language requiring a separate compilation step isn’t a contender.

There are also several criteria that don’t matter for a typical desktop application extension language:

• If you’re going to depend on the scripting language having fast runtime performance, then Python may well not be for you: Lua or Scheme are both typically much faster, and have a lower memory footprint.
• If you’re depending on the language for security, such as a web browser running untrusted code, or a server running code submitted by users, then you have an entirely different set of considerations.
• If the application is only going to be used in house, then it doesn’t matter terribly much what percentage of users are familiar with the language, because they’re going to be forced to use it anyway.

At first glance, it appears that desktop application developers are spoiled for choice of extension languages, but caveat programmer:

Scheme, despite having reasonable libraries and Unicode support, is far from mainstream. Using Scheme or another Lisp dialect as an extension language is an effective way to make sure you won’t have any extensions. Early versions of Sublime Text used Scheme as an extension language, but it was dropped for this reason. Just because you like a language, doesn’t mean your users will.

Lua is another candidate, which has a lot of uptake in games. It has a very small code footprint, and excellent runtime speed. However, its paucity of libraries, weak Unicode support, and small-medium user base make it hard to justify as an extension language for desktop applications.

What about JavaScript? It’s an underrated, elegant language, with a huge number of people acquainted with its syntax. Its weakness is that it’s not used as a general purpose language, so there’s no selection of libraries your users will be able to build on. No libraries and no built-in standard APIs (file system access, I’m looking at you) rule JavaScript out.

We come to Python and Ruby. Which language is better really isn’t relevant, both are fine languages with pleasant syntax and semantics. In terms of ecosystems, both are popular and have a good selection of libraries. Python, however, is the bigger gorilla, with a larger user base and more libraries.

Python, however, has a secret weapon: Python has ctypes, and Ruby doesn’t ⁽¹⁾. ctypes provides an ad-hoc way to call functions in any shared library in the system. This means that the platform’s entire native API is available with no C extensions required. Take, for example, a user who wants to launch another application, then set the input focus back to yours. With Python and ctypes on Windows, it’s only a few lines of code to call GetForegroundWindow and SetForegroundWindow. That’s pretty awesome.

Summary: Your users will be happiest if you choose Python. It’s pretty hard to argue with that.

1. Not strictly true, as pointed out in the comments, Ruby has a similar library called Ruby/DL 2. That’s pretty cool.

Lets start with the simplest case: Ship python25.dll, and python25.zip (containing the standard libraries) with your application, and provide some means for users to enter Python code.

Golden, right? Not so much. It’ll work fine right up until someone with an international version of Windows tries to install your application to a localized version of “C:\Program Files” that contains a unicode character. Then everything falls over.

Oh, you thought Python supported unicode? Well, it does. Sort of. Provided you don’t expect to be able to put unicode paths within sys.path, the list of directories python files may be loaded from. Ouch!

There are still options though: you can set sys.path to load from the current directory, and just set the current directory appropriately before making any calls into Python.

Now, let’s take a look at loading user supplied plugins from .py files. You could just place them in the same directory that the application is installed to, but that’s not a great solution on Vista, as users generally won’t have write access to Program Files. A better location is to place them within the Application Data folder, contained within the user’s home directory.

This raises some more problems: It’s not uncommon for users to have unicode characters in their username, and hence in their Application Data path. So we can’t simply add that to sys.path. We also can’t use the current directory trick any longer, as there are now two directories to load things from.

For Sublime Text, I’ve implemented a half way solution: Do some sys.path_hooks mangling to get modules loading from python25.zip, and use the current directory trick for user supplied modules (Drop me an email if you’re interested in the code). It’s not pretty, but it does work.

Aside from current directory wrangling, there’s another option I’ve yet to try: short path names. Windows has a notion of short path names, where every file has its full path name, and a short one (see GetShortPathName) in 8.3 format for archaic programs. The noteworthy part is that the 8.3 name uses ASCII characters, so they’ll be safe to use as Python module paths. There are a few caveats with this approach:

• Not every file has a short path name. Generation of them may be turned off.
• Some file systems don’t support 8.3 file names: They presumably won’t exist on Samba shares, for instance.

It’s unfortunate that Python has this limitation. My understanding is that it is not going to be fixed for Python 3.0, though there has been some work in this direction. Despite this, I still think you’d be mad to use anything else as an extension language.

So what options do you have? If you’re on a Mac, you can use WriteRoom, and which has a Windows clone called Dark Room. Other options are PyRoom, JDarkRoom and Vroom. These are all great for editing prose, but none support editing LaTeX, let alone code.

If, like Mark Pilgrim, all this makes you wonder why someone would want a text editor with no features, then I do suggest giving one of them a try, it’s a pleasant experience.

Prompted by a suggestion on the forums, the current beta supports this very style. In this setup, there’s nothing at all on the screen but your text in the center, and a muted scrollbar on the right. The cursor doesn’t even blink. You can think of it as WriteRoom for Windows, with regular expressions, Python plugins and code editing.

Here’s a screen shot of it in action:

Note the lack of menu, status bar, toolbar, line numbers, rulers etc.

Unlike multi pane editing, the objective here isn’t to fit as much information as possible on the screen, but to block out everything that you don’t need right now. It also works seamlessly with multiple monitors, with each one able to edit a different file in a similar fashion.

There are several extra settings to configure for this setup, so I’ve put together a quick plugin that will toggle them as a group. I’ve packaged it up with along with a key map that binds Shift+F11 to toggle the extra full screen mode. If you’ve got the latest beta, you can download and install it.

Enjoy!

PS., If you’re writing the next great literary work, then you may also be interested in the very handy Automatic Backups plugin.

PPS., Did I mention Sublime Text has LaTeX syntax highlighting out of the box?

Steve also wrote a great review of Sublime Text, which you should go and read right now if you’ve yet to try Sublime.

Coinciding with this release, the much requested forum is up now too. Drop by and say hi!

The first part of the documentation is up too, detailing how Selection works. It’s available via the Support page. More to come!

Like any bit of software, it’s a long road to release, though in truth it’s only the beginning. There’s already a long list of features to add, and it’s only going to get longer with your feedback.

As feedback comes in, the feature list is going to get re-prioritised and added to, so the sooner you give it a try, the better chance you have of seeing your wish list come true!

Sometimes its the little things that make the difference. When you’re entering a regular expression, you get syntax highlighting in the text box:

You can see in the bottom of the screenshot, the regex operators and character classes are rendered nicely.

My background is in building tools for games. I’ve encountered some beautifully designed tools for artists, such as Modo, ArtRage and Silo. At the time I was using Vim in its 16 colour, 80 column glory, and the very colourful Visual Studio. It occurred to me: why couldn’t the humble text editor get some of this love?

I’ve tried to put some of this user interface craftsmanship into Sublime Text. There are three principles I felt would be required:

• Unobtrusive, minimal chrome. The focus should be on the text, not fourteen different toolbars.
• Don’t obscure the text with dialogs.
• Use the pixels you’ve got. Full screen, multi monitor and editing files side by side should all be possible.

Below is a short tour showing how I’ve applied these rules in building Sublime Text. First, here’s the basic day-to-day level of chrome you are presented with:

There’s not much there, and it’s certainly not yelling at you.

Functionality like find and replace, that would generally be implemented via dialogs, is instead presented as a panel at the bottom of the screen.

The crown jewel, however, is how it works when you start to get serious. The full screen mode does away with a maximum amount of chrome, and works seamlessly with multiple monitor setups. Here you can see Sublime Text running on two monitors, full screen on each, with five files being edited side-by side.

Here’s a screenshot of the large monitor in the above photo, editing three files side by side in full screen. (Warning: 2560×1600 pixels ahead!)

Have I missed any principles? Have I adhered to the ones I set? I’d love your thoughts and feedback.

(Subscribe to the blog, so you don’t miss part two!)