Refactor Effect processing

[messmerd]

All LMMS effects share some identical boilerplate code at the beginning and end of their process loop, such as an early return if the effect is not enabled and calling the checkGate method, but these tasks should not be the plugin developer's responsibility. So I created a wrapper method that handles these tasks and simplifies the process method for all effect plugins.

And along the way, I also made a few other minor changes.

Changes made:

• Introduce processImpl and processBypassedImpl methods, and adapt each effect
  plugin to use them
• Move plugin state checks, RMS out sum calculations, and checkGate calls to the processAudioBuffer wrapper method
  • Compressor and LOMM now use double instead of float for RMS out sum
  • checkGate now runs for GranularPitchShifterEffect
• Minor changes to LadspaEffect
• Remove dynamic allocations and VLAs from VstEffect's process method
• Some minor style/formatting fixes

[sakertooth]

We should probably remove the gate feature since it seems to generally be problematic for many plugins (as @LostRobotMusic mentioned), though I'm not sure what that would mean for backwards compatibility (maybe the risk is low enough since its rarely used I'm assuming?)

[Rossmaxx]

I am planning to remove gate knob as a seperate PR. Informed it because there's chance of conflicts

[JohannesLorenz]

Functional review finished.

Outstanding reviews:

• Style review (at least, I did not do it)
• Testing review

When testing, different things should be tested:

• Testing GranularPitchShifterEffect
• Testing a LadspaEffect
• Testing a Lv2Effect (if the respective comment will be changed)
• Trying VstEffect with different (very high?) sampleRates

[PhysSong]

I think there was a suggestion to handle W/D mix and check output level in single place, rather than letting each plugin handles them. This might be in the scope of this PR as well.

[PhysSong]

Also, for sleepImpl: I think something like processBypassedImpl will match what the operation is commonly called.

[messmerd]

I think there was a suggestion to handle W/D mix and check output level in single place, rather than letting each plugin handles them. This might be in the scope of this PR as well.

I like that idea, though I'm not sure if it can be easily done while keeping in-place processing of the buf audio buffer. So that could be left to another PR if it is feasible.

[messmerd]

I think all the reviews have been addressed now.

I was able to move the outSum calculations into the wrapper method, and introduced the ProcessStatus enum to allow plugins to specify what they want to happen after the process loop (continue, continue if not quiet, or sleep). I took this idea from the CLAP API. It makes the interface really clean and avoids the -1.0 magic value.

[JohannesLorenz]

Rework checked, OK from that point of view.
Style checked.
Testing still to be done.

[bratpeki]

I see this needs testing. I would be interested. How exactly does one test this?

[messmerd]

@bratpeki This PR shouldn't change anything from a user's perspective, so testing would just involve using effects plugins (LMMS, VST, Ladspa, Lv2) and verifying that they still work as expected. If there are any regressions, it would probably affect the auto-off/gate

[JohannesLorenz]

I see this needs testing. I would be interested. How exactly does one test this?

See also #7484 (review)

[bratpeki]

Alright, I'll clone it, build it, and use it for a few days, reporting back on any mishaps, if they occur!

[bratpeki]

LB302 seems to not produce sound.

[messmerd]

LB302 seems to not produce sound.

It looks like it doesn't work on master either... strange. Not a bug from this PR fortunately

[sakertooth]

I'm currently looking into the regression reported by @bratpeki that seems to not be from this PR. This PR however looks good to me.

[bratpeki]

Also, please check if TripleOsc is louder than before.
This could just be my mind playing games with me!

It could also be unrelated to this PR, of course!

[messmerd]

@bratpeki This PR doesn't affect any of the instrument plugins so you don't need to test them

[bratpeki]

LADSPA works great, LV2 has also been tested, I'll look at some LinuxVSTs as well!

[bratpeki]

I have done tested a few AirWindows LinuxVST plugins, and they sound perfectly fine! I've tested the audio with Air, Chorus, StereoChorus, ADClip, and a few other plugins from the suite.

I've left a somewhat detailed report and question on the Discord server.

In any case, the audio sounds just fine, so this LGTM, but I'll leave it to you. Please let me know if you would like me to conduct any more testing on this!

[messmerd]

@bratpeki Thank you very much for testing! I'll look into what you mentioned on Discord, though I imagine it won't be an issue.