Fix Settings bug that occurs when not using JACK by messmerd · Pull Request #8299 · LMMS/lmms

messmerd · 2026-03-13T04:56:18Z

This fixes a regression from #7919.

Opening the Settings would unconditionally try to start the JACK server if it was not already running, even if the user was using an audio backend other than JACK. When it failed to start the JACK server, it would retry a few times which made opening the Settings take several seconds. For me, it also broke my whole system's audio, requiring me to restart pipewire (see the console logs below).

This PR fixes that problem by passing the JackNoStartServer option to jack_client_open() in the setupWidget used by the Settings. AudioJack::initJackClient() continues to use the JackNullOption option, so like before, it will still attempt to start the JACK server if you select the JACK backend and restart LMMS.

I also moved some static free functions into a nearby anonymous namespace, and I removed the server name argument from the jack_client_open() calls since that variadic argument is only supposed to be passed if the JackServerName option is passed (see documentation).

Console output showing the bug that was fixed by this PR

Click to expand

$ ./lmms *** WEAK-JACK: initializing *** WEAK-JACK: OK. (0) lilv_world_add_plugin(): warning: Duplicate plugin lilv_world_add_plugin(): warning: ... found in file:///home/dalton/.lv2/spectmorph.lv2/ lilv_world_add_plugin(): warning: ... and file:///usr/local/lib/lv2/spectmorph.lv2/ (ignored) Lv2 plugin SUMMARY: 18 of 40 loaded in 119 msecs. For details about not loaded plugins, please set environment variable "LMMS_LV2_DEBUG" to nonempty. Cannot connect to server socket err = No such file or directory Cannot connect to server request channel jackdmp 1.9.21 Copyright 2001-2005 Paul Davis and others. Copyright 2004-2016 Grame. Copyright 2016-2022 Filipe Coelho. jackdmp comes with ABSOLUTELY NO WARRANTY This is free software, and you are welcome to redistribute it under certain conditions; see the file COPYING for details no message buffer overruns no message buffer overruns no message buffer overruns JACK server starting in realtime mode with priority 10 self-connect-mode is "Don't restrict self connect requests" audio_reservation_init Acquire audio card Audio0 creating alsa driver ... hw:0|hw:0|1024|2|48000|0|0|nomon|swmeter|-|32bit Cannot connect to server socket err = No such file or directory Cannot connect to server request channel Cannot connect to server socket err = No such file or directory Cannot connect to server request channel Cannot connect to server socket err = No such file or directory Cannot connect to server request channel

ATTENTION: The playback device "hw:0" is already in use. The following applications are using your soundcard(s) so you should check them and stop them as necessary before trying to start JACK again:

pipewire (process ID 2501)

JackTemporaryException : now quits...
Released audio card Audio0
audio_reservation_finish
Cannot initialize driver
JackServer::Open failed with -1
Failed to open server
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
Cannot connect to server socket err = No such file or directory
Cannot connect to server request channel
jack server is not running or cannot be started
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
JackShmReadWritePtr::~JackShmReadWritePtr - Init not done for -1, skipping unlock
jack_client_open() failed, Status: 0x11
Overall operation failed. JACK dependencies might need to be installed.
Could not connect to JACK server.

Opening the settings would unconditionally try to start the JACK server if it was not already running, even if the user was using an audio backend other than JACK. This fixed that problem by passing the JackNoStartServer option to jack_client_open() in the setupWidget. initJackClient() continues to use the JackNullOption option, so it will still attempt to start the JACK server if you select the JACK backend and restart LMMS.

JohannesLorenz

I only left 1 comment.

Review scope:

Functional code review -> OK
Style code review -> OK
Testing -> OK

I tested:

Jack Server not available on system -> Error message on stderr, settings dialog still opens normally
Jack Client is available, but not started -> Jack is being started, dialog works
Jack Client is already started -> No messages, dialog works

JohannesLorenz · 2026-03-17T09:09:49Z

 	: AudioDeviceSetupWidget(AudioJack::name(), parent)
 {
-	const char* serverName = nullptr;
+	// TODO: Add a button to start the JACK server?


So, the disadvantage of this PR is for users who have jack installed properly but don't have it started currently, these users can now not see the option dialogue. I assume that's exactly what this comment proposes. It would be a good solution to this.

I assume it's not much work to add such a button to start (and possibly also to stop) the jack server? I guess it would be a nice compensation to this PR.

Thanks for testing!

So, the disadvantage of this PR is for users who have jack installed properly but don't have it started currently, these users can now not see the option dialogue.

No, if JACK is the selected as the current audio device in the Settings, AudioJack::initJackClient() will be called at startup and start the JACK server if it isn't already. With this PR it just won't try to start the JACK server again when opening the Settings, since should already be started due to AudioJack::initJackClient().

The start/stop button would be useful in the future if we're able to change the audio device without restarting LMMS. We'd want there to be a way to display the JACK server status and provide a button to start the JACK server. Bitwig Studio has such a feature.

But for now having that button would be less useful. For example, if you're currently using the SDL backend but then go into the Settings and switch to JACK, the JACK server might not be running so you'd want to start it. However, even if you start it you wouldn't be able to use it until you restart LMMS, and LMMS already takes care of starting the JACK server at startup, so there wouldn't be much use to having the button right now.

But for now having that button would be less useful. For example, if you're currently using the SDL backend but then go into the Settings and switch to JACK, the JACK server might not be running so you'd want to start it.

Sorry, yes, that was what I meant.

Let's see what Copilot has to say 😆

Copilot

Pull request overview

Fixes a regression where opening the Settings dialog would try to start the JACK server even when JACK isn’t the selected audio backend, causing multi-second delays and potentially disrupting system audio.

Changes:

Open the JACK client from the Settings/setup widget with JackNoStartServer to avoid auto-starting JACK.
Keep AudioJack::initJackClient() behavior unchanged (JackNullOption) so selecting the JACK backend still attempts to start the server as before.
Remove the unused JACK server-name vararg from jack_client_open() calls and refactor local statics into an anonymous namespace.

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JohannesLorenz approved these changes Mar 17, 2026

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JohannesLorenz requested a review from Copilot March 17, 2026 14:05

Copilot started reviewing on behalf of JohannesLorenz March 17, 2026 14:06 View session

Copilot AI reviewed Mar 17, 2026

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Comment thread src/core/audio/AudioJack.cpp Outdated

Don't print error message in setupWidget

ae8d7a5

messmerd merged commit 0f0d972 into LMMS:master Mar 18, 2026
11 checks passed

messmerd deleted the fix-jack-server-start-when-opening-settings branch March 18, 2026 01:21

messmerd mentioned this pull request Mar 23, 2026

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Fix Settings bug that occurs when not using JACK#8299

Fix Settings bug that occurs when not using JACK#8299
messmerd merged 2 commits intoLMMS:masterfrom
messmerd:fix-jack-server-start-when-opening-settings

messmerd commented Mar 13, 2026 •

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messmerd commented Mar 13, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Console output showing the bug that was fixed by this PR

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messmerd commented Mar 13, 2026 •

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