Contributing to Zynthian Development

1 Contributing to Zynthian

1.1 What we expect of you

We would appreciate you to use the tools we use for developing, as it's a lot easier for coordinating the tasks, having traceability, testing, merging changes and of course, attributing the merit of every fix or improvement.

We use git as versioning tool and github as repository server and issue/task tracker: Zynthian's Repository Index

If you are a punctual contributor, you should follow this procedure:

• fork the repository
• make the changes
• test it
• make a pull request

When you are a habitual contributor, you will receive write access to the repositories you master and would use development branches instead of forking/pull-requesting.

Also, it's a good habit to create a task/issue associated with more relevant changes, specially if you are a newcomer. In such a way other developers will be informed of your intention of implementing a new feature or fixing a bug and will avoid overlapping efforts, at same time allowing other developer to contribute to your task by adding useful knowledge and alternative approaches.

2 A first time developer

It is perfect understandable if you are approaching this for the first time, with a burning desire to solve a specific musical dilemma with code. Treat it as an opportunity to learn. It is a process that can, at first, appear overly involved and, perhaps, a little bureaucratic, but there are good reasons for the approach that's taken. It has succeeded to keep track of enormous code bases securely, sometimes in the face of actively hostile actions by others. It is this very characteristic that means that many open source projects operate that way, and may give people an insight into quite what 'open source code visible to all really' means for us. Also this robustness should resolve you of fears about 'doing some damage'. This well walked path of forking a repository, and making a Pull request protects you the community from yourself in an agreed fashion.

2.1 Could you tell me about the codebase?

This project, Zynthian, is based. predominately, in the python language with various whirling bits of C & C++ doing the heavily mechanical tasks down in the bowls where life is cheap, and code turns precisely. The python is a much more starter friendly world where you define what you want to do, and this gets translated into the sort of coal one can feed into the boilers down below.

This code resides and runs within a Debian (https://www.debian.org/) based linux distribution, on a Raspberry Pi of various vintages, (but not 5's yet-19/01/2024). A zynth, without sound connections doesn't make a lot of sense so there will be some audio out device at the very least, providing an audio output that can be amplified and played to people, yourself or both.

2.2 So what kind of thing do people do?

It's open source. Absolutely whatever they want to do . . .

Personally I do soundscapes, church bells and cajon enhancement, and much of this built without any direct purchase from the zynthian site. The Hardware designs are up on the site if you want to make your own. You'd probably even get advise on how to do it on the forum if you ask ...

2.3 So why might you want to write some code for a zynthian?

Probably to do something with a particular piece of equipment that you want to customise to aid you in your sound based endeavours. The output of MIDI based equipment presents it's self easily to a python code base that allows messages to be detected in an orderly fashion and then pretty much any aspect of the zynthian can be modified to obey your will. This has grown up from user dialog within the forum Zynthian Forumwhich is an excellent place to start with questions, suggestions and the truly crazy range of things people do with these machines.

2.4 Can I do damage to MY zynthian with the code I write ?

Yes, absolutely. With power comes responsibility.

But there is an important distinction between hardware and software. You can produce an inoperable zynthian with a badly placed code edit, but, you can't actively mechanically damage the machine itself by typing garbage. You simply correct the code fault and the damage its done, or at worst put in your backup ssd and things are good again.

This doesn't mean plugging the output of your 100W amp into the audio input of a zynth isn't going to damage it. It will and that's the world of hardware...

It's an important distinction.

2.5 Can I do damage to The whole zynthian code system with the code I write ?

No. Your code will be checked by people who control access to the core repository that you get your code from. They will not allow anything into the code base that they don't trust or that doesn't meet house rules about how stuff is written and presented.

2.6 How is code of the zynthian maintained?

You can log onto a Zynthian itself as the root user if you have the password (it's set to raspberry), but you might well change it on a performance machine. People will find it very amusing to log onto your machine pre or during performance if they can, and if you don't change the password....

You and they (if you haven't changed the password) can, and do pretty much anything you want as it it nothing more or less than a raspberry Pi of various vintages running an operating system. So you can edit files to your hearts content and very quickly render your Zynthian unplayable if you don't know what you are doing. There is an entire linux world built around what is called a terminal, which contains a command line that you literally type commands into and press enter to get them todo things. Zynthian has one of these,

and there are code editors that operate entirely round the command line, allowing you to change the contents of files on the machine.

Here there is no protection. it's your machine and you can break it as you wish, and whilst you will almost certainly get help on the discourse forum, this is not the sort of activity to indulge in twenty five minutes before your performance. It easy to become the essential technician beloved and feared in equal measure, but probably the first concept to learn is stable . . .

2.6.1 So what is a branch?

It's a slightly different version of the code files that a programme running on the zynth keeps track of, allowing you to move around between your different versions and accept of reject changes you have made. This all operates under a programme of some renown and reputation called git, which was written by the same bloke who was largely responsible for the Linux code base, which is used to house the linux code base itself, you are building on the work of giants. ... and riban.

There are many, many introductions to git Getting started with git and it has a certain reputation for complexity, but it rigorously hangs on to any code it is asked to look after even thou' this can be a mixed blessing if you are messy as I am. But it can be operated from the command line but it's better to use an IDE (Integrated Development Environment) which makes it all push button, more on this later.

Git also works peer to peer. This simply mean that rather than some of the older repository managers, every git instance running on a machine has a similar level of importance to every other, so you don't need a running central server to allow you to operate. That is a big feature that you don't appreciate until you DO work with the mega server in the middle with all it's associated limitations. This doesn't mean there isn't a a central repository where all the good stuff lives but it does mean that git allows you to make your own little development world where you do no damage to anybody else and you get all the control of being able to set up branches that are differing version of the code

2.6.2 Is Stable the best Branch to use?

Stable is the particular branch of code that is know good and behaves in a fashion that will match the documentation. It wont be cutting edge, but it will behave itself, precisely as you expect, during the performance so this is what you should be initially taking on stage.

The good news is if you can get enough of a Zynthian running to open up it's inbuilt webserver, forever known as webconf in these parts, you can select an option that will allow you to return to the stable state.

In the above example, where a little development is being done, the zynthian-ui ( the main zynthian code that controls the Touchscreen display and the main audio and midi functionality is set to another branch. Selecting the stable check box will get you back to your stable structure, and not destroy your edited code in this separate 'branch' called DUO Piano code if you have behaved properly in setting this up.

This is your protection from your own misdeeds with code. In fact it is sensible to keep at least two ssd's with a known good stable version on so you can give the zynth a brain change and keep a separate ssd for your code projects, but if you trash a part of webconf, then you have little or no easy way onto the machine, and you will need your backup... You have been warned!

So now we know how to switch between different branches of code how do we actually set up this new branch?

2.6.3 So what is an IDE ?

We could operate all of this using the commaand line and git commands, but unless you really want to, don't. Use an IDE.

an IDE (Integrated Development Environment) is a collection of programmes that work together to ease the difficulties of acquiring, writing, modifying, testing, debugging code you write along with the possibility of many, many other functions you probably never considered. At the moment there is one that seems to be really sweeping the board with this ( yes, i know, emacs users, but I worked on pycharm and intellij and I know which I prefer out of the three).

It's Microsoft's Visual Studio code, https://code.visualstudio.com/ know to friends and enemies alike as VSC.

2.6.4 So what is a host machine?

Visual studio code is a considerable piece of software, Microsoft know an awful lot about writing code and they have realised presenting an suberb, well maintained IDE into the hands of absolutely anybody with a desire to write code. If you date back far enough to remember "a computer on every desk running Microsoft software" you might generate a rye smile at this point, but the software world is a very different place now, and Microsoft are perfectly willing to produce their IDE for every conceivable platform and operating system they come across and make it work. Anyone who plays around with Arduino's and such will find vsc's platformIO plugin is a considerable improvement on the Arduino's own IDE, and plugins like this are the secret of VSC. The Python environment is a plugin, tools to view git repositories are a plugin, remote access components are a plug in . I haven't looked but I don't doubt there is something MIDI related plugin out there . . . So we have a considerable chunk of code to run, which we are going to use to write a considerable chunk of code on a Raspberry Pi... Can you run VSC on a Raspberry Pi? Well yes you can, indeed I have run my vsc environment on a Pi4. But I wouldn't run zynthian and the VSC code on a zynthian. There is a cleverer way. You use the remote connection plugin, to access a separate Zynthian doing musical stuff. The vsc remote component installs itself onto the pi, once you present it with the correct password ( Did I mention about getting your passwords sorted out...?), and it handles many, many areas of this process that you can lose yourself into setting up yourself. I have written this process up for other environments and it was ..... Involved. OK vsc advert over.

So Our development environment consists of two machines, one is the zynthian itself, and the other is another computer running the vsc code.

This other machine is the host computer and it can be any number of bizarre, powerful, stylish, home built, clapped out, PC's and goodness knows what else, but as long as it runs VSC you are good to go. As I say my host machine is now a Pi5 running VSC very effectively, but your's could be MAC or a PC or goodness knows what else. This is why using a specific IDE provides dividends because we don't need to explain all the different access mechanisms for all these machines. Look up how you install VSC on your host machine and do that. It's pretty easy and if anyone wants to write up specific versions then great! just say so on the forum.

2.6.5 How do I install VSC on my host machine?

Go to VSC Download page and pick the appropriate version. For your particular Pi OS. If you are running 64 bit software pick .deb arm64, if you are on a 32 bit Pi OS then pick .deb arm32.If you are on MAC or PC then download accordingly.

VSC Download Page

This will download the selected version and you install as appropriate to your operating system. ON my Pi5 I open the download folder

Pi Desktop Download Folder

and right click on the downloaded file and select Package Install.

It will and you will have a new icon appear in your desktop menu in the Programming section.

Pi Desktop VSC menu item

simply pressing on the icon will run Visual Studio Code, but for the moment there is a bit more to consider...

2.6.6 Where are the zynthian source files located on a zynthian?

The zynthian software exists as a set of directories ( or folders if you prefer) in a directory on the zynthian called ...../zynthian.

Zynthian home directory

But it is a little more involved than this and this is linked to the directory /home/pi. Don't worry too much about this it just is part of the overall desire to no longer run the software as the root user and move to more modern versions of the operating system and is an ongoing process. It is however relevant when you try to run the code locally outside of the normal linux tools, specifically systemd.

The GUI software running on the zynth that operates the touchscreen are located within the zynthian ui directory. and there is a file called zynthian.sh. This is a shell script which isn't written in python but in a language, generally called shell script. It is a collection of commands one runs on the terminal we mentioned earlier an allows various things to be configured, before the actual python script that does the work, which is called zynthian_main.py, is run.

Zynthian-ui directory

One of the main things the shell script set up is the debugging level which decides what level of message the zynthian generates when it encounters a logging command in the python script. . .

2.6.7 What happens if zynthian crashes and how do I stop it restarting on errors ?

When a zynthian starts up, most of the early functions and what gets run gets handled by a linux tool called systemd. This organises what order things happen in and nursemaids programmes, setting up procedures for what to do when programmes crash or misbehave. For instance there is no point in starting up the network devices if there is no network, and this is the sort of thing systemd does on your behalf. In the zynthian case it starts up the zynthian programme using the scripts we discussed in /zynthian/zynthian-ui and handles a zynthian by restarting the GUI if the software crashes for some reason. This is what you want if you are performing but is decidedly irritating if you are trying to write and test code. There are magic incantations to control zynthian via systemd

systemctl stop zynthian systemctl start zynthian systemtl status zynthian

So to stop a running zynthian you issue the first of these and this will tell systemd to ignore the restart so you can take over the running of it.

2.6.8 How do I tell the world about my contribution...?

You put it on Github because that is where the zynthian software itself resides ...

Zynthian page at Github

But that is where Zynthian tells the world about its contribution and you need the good people at zynthian to approve your contribution, and they wont do that till you ask in the right way. . .

You need to submit a pull request.

This is a concept within the github environment, and to do that you need to have an account at github yourself. So you need to dance your way throu their act of anointing (www.github.com).

Now a Pull request is not a specific git command, it's an agreement amongst mortals that the submitted code is suitable to be included in what zynthian publish to the world. One of these mortals then performs a git merge to take your offering, It's called a branch, it has a name, and it contains the code you have written, and combines it into the 'testing' branch so it can be tested.

But, you say, How do I get my code up to github in the first place, and that is, unfortunately, the wrong way to think of it.

You don't put the code there, you make your own copy of the whole zynthian code base in your own github account and download it from there to your machine.

This is called a fork and it means that your submission is derived from the original git hub zynthian site and can, assuming there aren't disagreements of changes two people make (a conflict), then be merged into the code base, using the git merge command and your code is now in testing ...

Congratulations if you get this far. You have just won an open source gold star by having a PR accepted by an open source project.!

So we better write some code.

2.7 It is 'suggested' one creates a task/issue? how do I do that ?

"it's a good habit to create a task/issue associated with more relevant changes"

Goto the zynthian issue tracker github page...

Then fill out something relevant

2.7.1 So what have we gained here ?

Well, the communal Zynthian entity gains an area of interest. Even if the task, dies on the vine, and nothing more gets done, there is a possible development signposted. Because these could be allocated to somebody else at some later time which means the code magically appears from someone you probably would never have met. Of course if you go ahead yourself and write it then so much the better. You move that one step closer to the "Had An Open Source PR accepted"

The github environment allows these relationships to be managed and the more structured this stuff is the less intimidating it becomes. . .

2.7.2 How Do I fork the Zynthian github repository?

The github write up is here... But in summary it's done from the appropriate zynthian page end of the process.

Zynthian page at Github

And here are the default options which will suit nearly all circumstances. You should only strike from the testing branch.

Here is the confirmation in my personal github space.

2.7.3 Can I view files on my Zynthian-ui github repository?

In fact there is a very useful github element that allows you to view code on gihub within a browser based tool that is nothing more or less than VSC.

It's no coincidence Microsoft bought github...

To operate this feature simple select the appropriate repository home page... https://github.com/wyleu/zynthian-ui/

and press the . key...

and here in VSC in github showing a ctldev file ready to be examined.

2.8 How Do I pass code from my Zynthian-ui github repository to my Zynthian on my desk?

This is where we return to applications running on our host computer as opposed to browser based github tools . . and use Visual Studio Code(VSC) actually as an application running on our host machine...

So we start it up, select Clone git repository and it's clever enough to populate the drop down if you ask it to select from GitHub.

Give it a local directory. I store my stuff under Code but it really is up to you. Try to be structural.

And there we have a git repository located on our host machine, which is useful upto a point but isn't actually located on the zynthian . . .

2.8.1 How Do I access code on my zynthian from my host machine?

We need to use Visual Studio Code(VSC) Remote Explorer to allow us to add on to the zynthian and install enough of an environment to allow VSC to seamlessly pass code between the environment and the desktop machine.Frankly sometimes it feels like magic, and for anyone who has read my previous attempts to do this sort of thing you spent a lot of time making sure the shaky old connections required behaved as machines are restarted and stopped and broken and goodness knows what lse. VSC relly sorts this out nicely, and it's a blessing. Indeed it is so tenacious in how it manages connections that the following image is actual a bit of a manufactured effort, but worry no it does it all very well.

select Connect to and enter root@zynthian.local or if you have renamed your zynthian as I tend to do to something like root@zynthian-rack2.local you put that in and enter the password for the machine. You will find yourself doing this password entry a fair bit. There are ways to make this once only per machine turning on but we will skip over that for now.

And we now get a new item in the Remote Explorer desktop and are returned to the VSC setup page to describe where we want to locate this connection to the remote machine and it is important that you put

/home/pi/zynthian-ui in here. If you have /zynthian/zynthian-ui in her which might seem like it should work it wont for reasons to do with the long term migration to a more structured system. Don't worry it's in hand.

So we now can examine and edit the code on the zynthian as thou' it is on our desktop... Which is kind of cool.

2.8.2 How Do I stop being asked for my password?

on your host machine type:

ssh-copy-id root@zynthian-your-machine-name.local

This will copy the key from your host computer to your remote host, where it will allow you to log on without providing the machine password each time, just a first confirmation by asking for your passphrase NOT your password. and when you need to enter the password the first time you will be asked for you pass phrase, if you set one, and since you have probably set this up for github you will have done, This should reduce the chatter a fair bit, but it may still occasionally ask just out of a certain degree of paranoia.. .

2.8.3 How Do I redirect the zynthian code in zynthian-ui to my personnal repository rather than the zynthian master I forked from ?

We need to edit a specific file on the zynthian within the zynthian-ui folder. It's in a hidden directory .git within the /home/pi/zynthian-ui folder so it won't show up with the ls command, use the ls -las form instead to see it.. Now all this can be done from within VSC using a terminal os you have a nicely set up ssh connection to the machine all maintained by VSC. This terminal is in the lower right hand of the window and it saves you the trouble of having to set up separate connections to do basic housekeeping. Because this file is actually specifically kept out of the repository it doesn't appear in the VSC code listing so we have to go and abuse it by hand, which is why we are using the terminal . . . The terminal opens up in the zynthian-ui folder because that's how we configured it so all we have to do is type

cd .git

if you now type

ls -las 

you should see this sort of thing ...

root@zynthian-rack2:/home/pi/zynthian-ui/.git# ls -las total 92

 4 drwxr-xr-x   8 root root  4096 Jan 20 21:46 .
 4 drwxr-xr-x  14 root root  4096 Jan 15 11:21 ..
 4 -rw-r--r--   1 root root    16 Jan 19 15:47 COMMIT_EDITMSG
 4 -rw-r--r--   1 root root   220 Jan 20 21:02 FETCH_HEAD
 4 -rw-r--r--   1 root root    24 Jan 20 21:44 HEAD
 4 -rw-r--r--   1 root root    41 Jan 20 21:02 ORIG_HEAD
 4 drwxr-xr-x   2 root root  4096 Sep  6  2020 branches
 4 -rw-r--r--   1 root root   726 Jan 20 20:55 config
 4 -rw-r--r--   1 root root    73 Sep  5  2020 description
 4 drwxr-xr-x   2 root root  4096 Sep  6  2020 hooks
32 -rw-r--r--   1 root root 32619 Jan 20 21:45 index
 4 drwxr-xr-x   2 root root  4096 Sep  6  2020 info
 4 drwxr-xr-x   3 root root  4096 Sep  6  2020 logs
 4 drwxr-xr-x 133 root root  4096 Jan 19 15:47 objects
 4 -rw-r--r--   1 root root   334 Aug 25 00:11 packed-refs
 4 drwxr-xr-x   5 root root  4096 Sep  6  2020 refs

we want to modify the config file in this folder... So lets ook at this file first to see whats in it . . .

cat config 

root@zynthian-rack2:/home/pi/zynthian-ui/.git# cat config

[core]
       repositoryformatversion = 0
       filemode = true
       bare = false
       logallrefupdates = true
[remote "origin"]   
       url = https://github.com/zynthian/zynthian-ui.git
       fetch = +refs/heads/*:refs/remotes/origin/*
[branch "master"]
       remote = origin
       merge = refs/heads/master
[branch "testing"]
       remote = origin
       merge = refs/heads/testing
[branch "staging-2209"]
       remote = origin
       merge = refs/heads/staging-2209
[branch "stable"]
       remote = origin
       merge = refs/heads/stable
[branch "staging-2307"]
       remote = origin
       merge = refs/heads/staging-2307
[branch "chain_manager"]
       remote = origin
       merge = refs/heads/chain_manager

We want to change the line

url = https://github.com/zynthian/zynthian-ui.git

to point to our own repository, which in my case is

url = https://github.com/wyleu/zynthian-ui.git

to do this we use a little command line text editor called nano... so we type

nano config

Control-X to leave Control-O to write out the file and arrow keys move you around in the file

And you have now redirected your zynthian to look at your repository on github as it's ultimate origin file . . .

git pull will now cement this relationship.

2.8.4 How Do I Start a new branch and what should I call it ?

The VSC status bar at the very bottom of the screen contains a lit of useful information. It shows the remote machine you are logged onto and it shows the current branch you are located on.

Indeed there are useful plugins that can be added that will show git tram lines and such which are very useful . . . but if you press on the testing button in the status bar you will be presented with a dialog for adding a new branch .

Quite what to call it is upto you but remember it will live long in the github zynthian home, so choose something relevant that you can remember what it's about at some point in the future. If it's too scurrilous your Pull Request will be rejected and you will be asked to change it to something more aligned with house style ... Benevolent dictators are perfectly entitled to behave like that .

In summary. git doesn't forget unless you beat it very hard with a stick cos remembering what happened is it's very purpose in life.

2.8.5 How do I switch to different branches when I'm developing?

Simply use the branch name switch down on the status line at the bottom left of the vsc window. Here is is set to the branch name I created Duo-piano-device

You can also see that I have added three device files into the ctrldev directory which is the code I working on...

2.8.6 Can I see a diagram of the various branches?

Here is the git graph vsc plugin showing tramlines for this repository. You will need to install this plugin to get this.

2.8.7 Can I see a diagram of the various branches in the zynthian github page ?

From the github.com/zynthian/zynthian-ui/ you can select insights in the top menu and then Network in the left hand vertical menu. Github will chug away for a little while having a think then show you this, which now features the duo-piano-device branch waiting for me to submit the completion of the code with some more commits and then the pull request which, if successful will result in the branch being merged into testing, and at some later date in stable . . .