objective-c

GNUstep StepTalk is Alive and Well

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A few years ago, I explored the idea of writing a small interpreter for embedding into McLaren Labs applications. The concept was to extend rtpmidi or a synth application with a scriptable ability to customize controls, behaviors or sound graphs. This would help make each application very slim, but to allow extension through scripting. (This is not a very novel idea: it’s been done many times before. 🙂 )

The Objective-C execution environment (libobjc) provides many hooks that make it fairly easy to call into the ObjC runtime from an interpreter, or even to bridge Objc method calls back to an interpreter. The idea of a scritping environment to accompany a GNUstep ObjC Appplication program seemed promising and I wrote a little interpreter (based on PostScript syntax) to test out some of the ideas.

Along the way, I learned about a much more mature project in libs-steptalk. Among other things, it provides a SmallTalk-like language for extending applications or even gluing them together in the GNUstep workspace. It seemed very old, but there were some tremendous ideas in there: I wondered if I could learn enough about it to use it, and I wondered if it still worked.

(Spoiler Alert! I did and it does.)

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GNUstep Desktop – a refreshed look at NeXT/OpenStep

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There’s a cool project called “GNUstep Desktop” that brings together many old GNUstep technologies, and a few new ones, to provide an entire integrated desktop. We gave it a whirl and are pretty impressed!

GNUstep Desktop on Debian 11

It’s pretty amazing that software that began life 30 years ago is still operational and evolving, but that is the case in the GNUstep project.

At McLaren labs, we have been a fan of modern ObjC on clang, and the ObjC runtime with Foundation libraries and have been slowly learning more about GNUstep GUI and desktop. To be honest, it has been a slow learning process. While there is actually very good information about the various pieces of the GNUstep project, it sometimes seems that there are too many conflicting versions around — there isn’t a single source of truth that brings everything together. But that being said, the quality of many of the components really amazes me.

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Announcing McLaren Synth Kit

The “McLaren Synth Kit” is an Objective-C framework for using MIDI and Audio on Linux computers with the GNUstep programming environment. It is distributed as a project including libraries, headers and example programs at https://github.com/mclarenlabs/libs-mclaren-alpha. You can use it to experiment with sound synthesis for your own personal projects. The project is designed to provide ready-to-compile examples after you clone the repo.

Working with sound is a delicate endeavor. The Synth Kit does a lot of the low-level work of opening devices, managing an audio thread and copying MIDI events to and from dispatch queues. This leaves the audio programmer free to think about designing sounds as a graph of processing units, called Voices.

Standard Voices in the Synth Kit provide envelopes and oscillators of various types, filters and a reverb algorithm. Using the features of modern Objective-C (blocks, ARC and dispatch queues) the Synth Kit makes programming sounds easy, or at least “easier.”

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VSCode, Ubuntu Snaps and ALSA Sound Development

Here at McLaren Labs we like to try all sorts of tools and development environments to see how they work together. We’ve been using vscode (https://code.visualstudio.com/) on and off for about a year, but only recently decided to try using it for a more complete edit/debug/run cycle for an Objective-C Synthesizer project. We ran into an unexpected interaction between the Snap environment of vscode and the ALSA (Advanced Linux Sound Architecture) PCM interface.

The Symptoms

What we discovered was that when running a program that attempted to access an ALSA sound device was that the program malfunctioned. It worked correctly in a “normal” terminal, however.

We reproduced the behavior using the default aplay command that is available in alsa-utils. See the screenshot below for what should appear in a terminal when it is run, playing an Ubuntu standard sound called “Front-Left”. Unless otherwise specified, this command opens the “default” sound device.

If your Ubuntu sound system is set up correctly, you will hear a woman saying “Front Left” … and it will come out of your front-left speaker.

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Why McLaren Labs uses Objective-C

McLaren Labs was started with the idea that music and media creation on Linux should be as easy and fluid as Mac OSX. We had been inspired by AVFoundation and the modular way its pieces fit together. We loved being able to build media pipelines with sources and sinks that cleaned up after themselves when you were done with them them.

Many of the facets of the OSX components we liked were provided by ObjC features enabled by the Clang compiler and LLVM tool suite. LLVM has revolutionized language development by paving the way for Swift and Rust. Back at the time we were getting started, Swift on Linux was gaining traction and we considered adopting it. However, after some initial explorations with Swift and libdispatch, we discovered that libdispatch just wasn’t ready with Swift on Linux. That was in 2015 – Swift on Linux is much more mature. The equation might be different today … but it might not too.

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