Update README for the new nix world.

README.md

@@ -1,65 +1,126 @@
 noisicaä
 ========
 
-**Important note**: This is project is in pre-APLHA  state, do not expect it to
-be usable in any form or shape.
+**Important note**: This is project is in pre-APLHA state, do not expect it to be usable in any form
+or shape.
 
 * It has bugs.
 * It does not do a lot of useful things.
 * There is no documentation.
-* And most importantly: the save format is not finalized and will change in
-  incompatible ways, i.e. you will not be able to open your work from older
-  versions.
+* And most importantly: the save format is not finalized and will change in incompatible ways,
+  i.e. you will not be able to open your work from older versions.
 
+Follow the development at http://noisicaa.odahoda.de/
 
 What's This?
 ------------
 
-A simple music editor with a focus on classical musical notation.
-
-Follow the development at http://noisicaa.odahoda.de/
+The open source DAW that does not DAW.
 
 License: GPL2 (see file COPYING).
 
-Requirements
-------------
+This project is currenly only designed to run on Linux desktops.
+
+Eventually it should have the general features you would expect from a DAW, like recording and
+editing audio or MIDI, using plugins, etc. I specifically want to have tracks that can be edited
+using musical notation (i.e. notes on staff lines instead of the more common MIDI grid).
 
-This project is currenly only designed to run on Linux desktops. No effort has
-yet been made to make it run on anything else than Ubuntu 16.04 and 18.04
-(which are the distributions used for development).
+But all that is still in the far out future.
+
+The focus will be on electronic music production and sound design (using the broadest possible
+definition of music).
+
+noisicaä should not be a tool to record, edit and mix audio tracks from people playing actual
+instruments - it does not try to compete with [Ardour](https://ardour.org/).
 
 Getting Started
 ---------------
 
-These instructions are not targetted at end users. There are not prebuilt
-binary packages, which you could just install, so you have to build from
-source. It is assumed that you're moderately experienced with software
-development on Linux.
+> There are currently no prebuilt binary packages, which you could just install, so you have to
+> build from source. It is assumed that you're moderately experienced with software development on
+> Linux.
+
+**1. Prerequisites**
+
+You need `git`, which is probably already installed on your system.
+
+Building noisicaä itself does not need a lot of disk space, but Nix (see below) will download and
+install *a lot* of packages, which are going to be stored on your root filesystem. So make sure that
+you have a few gigabytes of free space there. But the upside is that you do not need to manually
+install any other packages.
+
+**2. Set up Nix**
+
+The development setup is currently built around the [Nix package manager](https://nixos.org/). If
+you already use Nix, then you can skip this section.
+
+> *What is Nix?*\
+> Nix is a functional package manager, a configuration language to describe package and a Linux
+> distribution.\
+> For our purposes you only need to think of it as a package manager like `apt`, `pip`, etc. The
+> great thing about it is that you can install and use it on any Linux system and it will not
+> interfere with your normal package manager. We're going to use it to install all the tools and
+> dependencies needed to build noisicaä without messing up your system.\
+> If you want to contribute to the code, you might need to deal with the Nix configuration
+> language.\
+> But you do not need to install Nix as your Linux OS (neither do I).
+
+The most basic Nix installation is done with a single command (the
+[Nix documentation](https://nixos.org/manual/nix/stable/) describes more options, but we
+don't need those):
+
+```bash
+sh <(curl -L https://nixos.org/nix/install)
+```
+
+**3. Get the source code**
+
+Go to some directory where you want to store the source code and clone the git repository:
+
+```bash
+git clone https://git.odahoda.de/pink/noisicaa.git
+```
+
+That should create a directory `noisicaa`, so now go there:
+
+```bash
+cd noisicaa
+```
 
-You need at least `git` and `python3` installed on your system.
+**4. Install the dependencies**
 
-    sudo apt install git python3
+Now we're going to start a "Nix shell".
 
-First grab the latest source code:
+Nix will download all the packages needed to build noisicaa into its "Nix store" and start a
+subshell with environment variables (`$PATH` and so on) setup such that those packages are
+accessible. When you exit that subshell, there will be no trace left of what has been installed,
+except from the disk usage of the Nix store.
 
-    git clone https://github.com/odahoda/noisicaa.git
-    cd noisicaa
+The downloads will take a while and some packages need to be built from source, so grab a cup of
+tea, while you watch it:
 
-Configure the project. This will create a virtual environment and populate it
-with the required 3rd party packages. It will also install missing system
-packages - this assumes that you have `sudo` rights on the system, and it might
-query you for your password.
+```bash
+nix-shell
+```
 
-    ./waf configure --download --install-system-packages
+**5. Configure and build**
 
-Now you can build it:
+Once inside the Nix shell and all dependencies available, the actual build process is pretty simple
+and standard (using [waf](https://waf.io/) as the build system):
 
-    ./waf build
+```bash
+./waf configure
+./waf build
+```
 
-You can either run it from the build directory:
+The output of that process is stored in a `build` directory.
 
-    bin/noisicaä
+**6. Launch noisicaä**
 
-Or install it to `/usr/local`:
+It is not yet possible to properly install noisicaä on your system (i.e. the configuration to make
+`./waf install` work has yet to be written), so use a wrapper script to launch it from the `build`
+directory:
 
-    sudo ./waf install
+```bash
+bin/noisicaa-dev
+```