The Mac users of the Mojave lab are pleased to announce a handy new app: Forget-Me-Not!

FMN is an app that evolved from a hack I wrote a while back to solve one of the myriad annoyances of the OS X window manager. If you’ve got a PowerBook or MacBook (ick. I still can’t stand that name) that you connect to an external monitor you’ve probably noticed that the layout of your windows doesn’t survive a connect/disconnect cycle. If you go from dual-head to single-head back to dual-head all your windows end up in a corner of one monitor afterwards. A similar thing happens if you connect to a low-resolution 800×600 projector, or a TV—you find your windows tiny and bunched up when you get back to your normal desktop. Well, FMN solves that problem.

You can get FMN and find out more about what it does here, but I thought I’d mention a bit of its history in this blog post. Oh, and if you have any comments or bug reports, feel free to skip this stuff and post a comment below.

I first developed FMN in a couple of hours as a plugin for Desktop Manager, exploiting the fact that DM injects code into the Dock process and can thus be used for all sorts of mischief. My lab-mate David Noblet was jealous of my machine’s newly-found super powers but not a DM user, so he ported my code to a stand-alone app. After a bit of noodling we found out about Apple’s Accessibility API and Dave rewrote the app to use it, thus ending our reliance on Dock-injection haxiness. But there was still one problem: X11.app doesn’t export its windows to the Accessibility system¹, and I can’t live without X11 support. So the next step was to write an “X11 bridge,” which I did without too much difficulty. In the process I converted the app to have a plugin architecture².

At this point everything was working, but we wanted to release FMN to the public and the interface was not ideal. The proper way to interact with something like FMN is a preference pane—it’s basically a per-user preference. So next we set about learning how to write preference panes, how to use distributed objects to communicate with background apps from them, and how to hide an app’s UI. Along the way Dave whipped up some artwork for us to work with, and we started using DARCS as our revision control system.

So anyway, after a lot of messing about with XCode, Interface Builder, Inkscape, and all the rest we’ve got something we think you’ll like. Let us know how it could be better!

¹ This, by the way, is the reason why nice apps like Witch don’t work on X11 windows, making them useless to lots of people. It’s a pity that one’s not open source because I’ll probably end up rewriting it myself one of these days. If I had the source it probably wouldn’t be hard to write a simple X11 bridge.

² This wasn’t just architectural masturbation, by the way. If a user doesn’t have the X11 libraries installed you don’t want to be shipping an app that’s dynamically linked to them—your app will crash. If you ship a plugin that’s linked to them it just won’t load, which is no big deal.