Developer diary: plans and progress reports.

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Positively agog Sunday 21st October 2012

So when I said back in July that I was taking a break because of real-life commitments, that was a teeny tiny fib. In fact I was beavering away undercover with the fine people at to help them launch their DOS games catalogue on Mac.

On October 18th the fruits of our labours were finally revealed, and I can finally gush about what I’ve been working on all this time: Boxer standalone. This is a streamlined and state-of-the-art Boxer built for one purpose: releasing DOS games as individual apps. It's also a peek into Boxer’s future.

Why a separate version?

When we were figuring out how to deploy's DOS games on the Mac, it became abundantly clear that Boxer in its current form wasn't gonna cut it. It sticks you with a folder full of sample games to help you figure out the emulator. Its gameboxes are document files that can’t be played without downloading a separate application. Its emulation is studded with peripheral features to help you install new games and configure them and add new drives to them and all that jazz. The entire app is designed around turning your box of old CDs into a games collection.

But are selling games, not raw materials for someone else’s curated emulation experience. Their games already come ready to play, so they don't need any of the features to help you get there. Each game needs nothing but to look and feel like a native Mac game.

So I began macheteing off all the bits of Boxer that weren’t part of that experience. Sample games and game importing were the first to go; the preferences window, inspector panel and drag-drop drive addition all hit the cutting-room floor. The UI was tailored to clean away everything that smelled like emulator infrastructure instead of a native game.

Putting together a game app isn’t as easy as making a gamebox – there’s resources to bundle, app IDs to choose, help links to define, behaviour to tweak, branding to slap on – so I also developed a bundler utility that takes a gamebox and wraps it into an app according to your specifications. It’s not as slick as Boxer’s game importer and it’s not intended for end-users: you’ll need to build it and Boxer standalone from source yourself.

With Boxer’s dead weight liposuctioned away and gamebox-to-app conversion a reality, new challenges came to light. Ones that required exciting and shiny new features.

The launcher, rethought

Boxer’s program panel was designed for one task: choosing the right executable once and never touching it again.

But many of’s games don’t have just one true executable: there may be a main game and expansion packs, there may be separate singleplayer and multiplayer options, there may be setup utilities and campaign editors. Boxer’s program panel was woefully inadequate for switching back and forth between different launch options.

Even worse, the program panel insisted on appearing alongside the wretched old DOS prompt, and it wouldn’t even appear at all in fullscreen mode. In a standalone game app, that makes for a terrible user experience.

So I threw it away and started again.

The first time you launch one of these games, you’ll be greeted with a tidy list of predefined launch options. Click an option to launch that program; quit back to DOS, and the app will return to the launch options. (You can also get back to the launch options at any time from the File menu.)

If you quit the app while a program is still running, the app will remember which launch option you’d chosen and start up with that next time. This way, it’s easy to switch back and forth between launch options, without needing to choose one every time you start up.

The launch options panel only appears in GOG games that actually have multiple options. For games with only a single launch option, the game will start up straight away and exiting to DOS will quit the app instead of returning to the launch options.

Shadow boxing

As you’d expect, inside each game app are all the files for that game. And as you also know, DOS games like to dump their savegames in the same place as all their other program files.

These two facts are on a head-on collision course. OS X apps aren’t expected to be self-modifying: and if you’re not running as an administrator, then apps in the Applications folder are not even allowed to write to themselves. This would prevent you from saving your game and in many cases would prevent the game from running at all.

The solution is one I’ve discussed in the past: write shadowing. Attempts to write to game files are instead written to a ‘shadow’ location inside the current user’s Application Support folder. The app reads changes from there first, before reading the original game files from inside the app. This way noone’s trying to modify the app itself and everyone’s happy.

This has several knock-on benefits:

Shaders a-go-go

Dropping OSX 10.5 support let me pull the trigger on a feature I’ve had in my sights for a long time: pixel shaders for rendering styles. Shaders are programmable effects that run on the GPU, and they allow for faster and considerably fancier scaling effects.

The game apps ship with three shader-powered rendering styles: the original untouched output, a 5xBR smoothing shader by Hyllian and crazy46guy, and a simply awesome curved CRT shader by cgwg, Themaister and DOLLS. I cherry-picked these from the thriving BSNES shader community; the coders deserve much love for creating such great-looking shaders.

For older Macs that can’t run pixel shaders at an acceptable speed, Boxer standalone falls back on the old software rendering styles you get in Boxer 1.3.

Naturally, the game apps also natively support those newfangled retina displays.

There’s always a but

The game apps are slick as hell, but that comes in exchange for flexibility and features. Hence some caveats:

Each game app has a gamebox inside, so if you prefer you can just run the gamebox in Boxer 1.3.2 instead. However, Boxer 1.3.2 does not utilise the new launch option structure, nor does it support write shadowing: your game state will not be consistent between Boxer and the game app, and any changes you make in Boxer will be saved permanently into the app.

So when do I get to see all this neat stuff in Boxer itself?

Soon! But there’s still a bunch of work to do before these features are ready to appear in Boxer 1.4:

For now, buy the hell out of’s DOS game collection and get the goodies right away. If you don’t mind wet paint and you’re familiar with XCode, you could build Boxer 1.4pre from source and take advantage of all the new features; or even build Boxer standalone and its bundler utility and start churning out your own game apps (some assembly required!)

Closing remarks

It's been a huge pleasure to collaborate with the cool guys at and big ups to them for choosing Boxer. By doing so, they’ve ensured that their Mac gamers get the best DOS gaming experience across any platform.

Design by 40watt.