lisp-gui-examples VS bintracker

The Allegro egg is accompanied by a couple of examples but no examples showing the use of the audio addon. The Allegro library itself comes with an example showing how to generate a saw wave, but being a C library, the example is, of course, in C. I ported that example to Scheme. I would have contributed the example back to the Allegro egg, but the repo is marked as "archived by the owner" and read-only on GitHub. I've included the example in the repo alongside the rest of the code for this tutorial in case someone finds it useful.

You can check out the entire example on GitHub. This started as a personal learning project to explore the state of GUI programming in Lisp and has become a series of tutorials on building GUIs with various dialects of Lisp.

If you look at the activity on GitHub (https://github.com/bintracker/bintracker/graphs/contributors), they have been working on the project since mid 2018, with almost continuous commits until mid 2021, and then some activity at the start of 2022, and considerably more at the start of 2023. So there seems to have been some loss of momentum, but I wouldn't give up hope yet. It's just unfortunate that there is only one single contributor - but I guess finding fellow LISP Jedi knights (referring to the XKCD comic someone else linked) to work on this project is not that easy...

Let's extend the function that returns our labeled spin box to bind a validation function to the FocusOut event on the spin box. The spin box does have a validatecommand option, but I wasn't able to get it working. I looked through the examples that have come with the various variations of PS/Tk and couldn't find a single example of a spin box with a validatecommand. I even looked at the source code for Bintracker, a chiptune audio workstation written in Chicken Scheme with a PS/Tk GUI and developed by the current maintainer of the PS/Tk egg. Even it binds a validate-new-value function to the Return and FocusOut events of the spin box rather than using validatecommand.