Cross Platform Compiling

Thanks for the quick answer.
So even if I develop under Windows, if I want my plugin to run under macOS, I have to BUY a Mac?
And if I buy a Mac and setup the development environment, I suppose it’s not just a “build” to make it work flawlessly on macOS…
If I needed six months to develop the Windows version, how much additional development time should I calculate with? Any guess?

Well, native software development speaks for itself - you need to get it working natively, as in per platform!

It never is that easy, but JUCE makes that a much simpler task.

Well, that’s up to you to gauge by figuring out which desktops/versions and DAWs you want to target with your plugin. If you want it to work on everything, all OSs, all DAWs, then you should test against… well, all of that! So you should have a lot of time buffered for just that.

JUCE is intended to strip away that low-level complexity by abstracting most of it out, providing native wrapping facilities.

The Projucer helps with bringing a project to a new desktop platform and using the typical IDEs, so you should start a JUCE project out using the Projucer to make the process much simpler.