ZynAddSubFX can't create a new instrument bank

[SeleDreams]

I'm posting this issue because this issue that was present since some times in LMMS and was thought fixed #3886 still exists

the steps to reproduce this bug are pretty easy :

• Starting LMMS on Ubuntu (this bug also exists on the stable 1.1.3 build)
• Adding a ZynAddSubFX track to the project
• Creating a new bank

screenshot of the issue :

[tresf]

So I'm not sure if this is just an old bug inside ZynAddSubFX (it is, see #4642 (comment)), but when I add a debug line to the method which creates the bank folder, it's attempting to write to a location called ~/banks at precisely this location of code.

Although from a casual observer, the directory ~/banks appears to be a user-writable location, I don't believe ~ is a valid directory as it is interpreted literally as a folder named with tilde character.
For home, I would (instead expect to see a helper function for resolving to $HOME.

Attempts to fix this hard-coded value will initially fail unless .zynaddsubfxXML.cfg is purged because Zyn always prefers the value from the config file so as long as the first element isn't blank.

A temporary workaround is the following:

sed -i -e 's/~\/banks/\/tmp/' ~/Documents/lmms/.zynaddsubfxXML.cfg

This will allow the banks to be written temporarily to /tmp, which is a writable directory.

[musikBear]

Actually zasfx 'banks' are nothing but a normal folder, with at least one zasfx preset inside. If you make that zasfx will understand it as a bank, and it will be accessible from both zasfx, and indeed lmms -at least in windows....

[tresf]

@musikBear thanks, but this is about the bug where the folder cannot be created on Linux. When testing, Windows does not suffer this problem.

[tresf]

Apparently upstream patched this ~ behavior three years ago... :)

[tresf]

@fundamental can you explain what the permanence of ~/banks should be? For example, if we patch this to use /tmp would there be any ramifications? I ask because even if we cherry-picked zynaddsubfx/zynaddsubfx@ca9ec78, we'd still run into the problem where $HOME/banks/foo's parent $HOME/banks wouldn't exist, right?

[fundamental]

User data should not be stored in /tmp So, setting the default bank directory to be within /tmp would not be advisable.

[tresf]

Pardon my lack of understanding, I didn't understand if this was something that must be kept persistent. Assuming is is we'll have to find a portable home for it. This means we'll have to write our own mkdir logic. How is it done in modern zyn? How does the plugin get past $HOME/banks not existing?

[fundamental]

For implementation details I would recommend checking the source directly. The majority of the bank logic in zyn is in Bank.cpp with a very small amount in MiddleWare.cpp (in the bankports).

[tresf]

It appears newbank() does attempt to create the directory. To be consistent with upstream, $HOME/banks is a quick fix with the disadvantage of not being portable (as well as being non-standard, user folders should always be identified by the application name).

#ifdef WIN32
    if(mkdir(bankdir.c_str()) < 0)
#else
    if(mkdir(bankdir.c_str(), S_IRWXU | S_IRWXG | S_IROTH | S_IXOTH) < 0)
#endif

But it's still too late I feel. LMMS already attempts to setup a sane bank location (we set it to the presets location) as long as one of them is empty. Are we too late? We can attempt to overwrite the value of ~/banks if it's found in the config but is this going to break the loading of banks that are built-in? Is this a matter of needing TWO bank locations? First being ones we ship, second being ones we create?

[tresf]

After re-reading the source, I think it's safe to simply add a call to LocalZynAddSubFx::setPresetDir(...) from within LocalZynAddSubFx::setLmmsWorkingDir(...). Why? Well:

• Zyn allows 100 bank directories.
• We already loop over the hard-coded ones before appending.
• We already have the ConfigManager::inst()->userPresetsDir() + "/ZynAddSubFX" value as part of the call to LocalZynAddSubFx::setLmmsWorkingDir(...).

Edit: Well, unfortunately Zyn is hard-coded to use ~/banks in slot 0 as the only user-writable bank location. 🤔. We'll have to hard-code it as well.

[tresf]

It appears newbank() does attempt to create the directory.

Correction... no, it doesn't. It DOES create the new bank directory, but not the parent directory. This means on systems without $HOME/banks, zynaddsubfx/zynaddsubfx@ca9ec78 still doesn't fix it.

@fundamental how does Zyn handle this? Is there a startup task in newer versions that we're missing that creates this directory? How does $HOME/banks get created on a new system? This portion of the code appears largely untouched, even in 3.0.

We can still handle this LMMS-side, but we'd be creating a user directory that's only ever used by Zyn. I'd expect Zyn to have the code to create this somewhere since new banks aren't possible without it.

[tresf]

Ended up adding an additional mkdir which I still feels is an upstream bug. @JohannesLorenz is investigating if 3.0 has this bug too, but in the meantime, we're patched. This will be patched in 1.2.0-RC9 (or higher). If it doesn't work, try deleting ~/lmms/.zynaddsubfxXML.cfg and trying again.

Ideally, (long-term) we'd like to make these settings portable and store banks somewhere inside <LMMS_WORKING_DIR>, but for now -- as a stop-gap -- we'll at least allow the "New Bank" button to work as it would normally.