VST3: implement setComponentState (fixes state restore in Ableton Live)

[olilarkin]

Fixes #475.

Ableton Live restores a set by calling setState on the processor, then handing the same stream to the controller via setComponentState to initialize its parameter view. As a SingleComponentEffect the wrapper inherited EditController's kNotImplemented, so Live's parameter layer stayed at default values after a reload and wrote those defaults back over the plugin's restored state (Live Log.txt: couldn't initialize controller with processor state ... not implemented).

setComponentState now:

• loads the handed state into the CLAP plugin — idempotent when setState already ran, and covers hosts that call the controller side first;
• refreshes the VST3 parameter cache from the live CLAP values, the same sync param_rescan(CLAP_PARAM_RESCAN_VALUES) performs.

Tested:

• Ableton Live 12.4 (macOS arm64): set reload now restores parameter values and plugin state correctly; device panel matches the plugin.
• pluginval strictness 8 incl. GUI/state-restoration tests: SUCCESS (no regressions; note it passed before this fix too — it doesn't exercise setComponentState the way Live does).
• clang-format clean against the repo .clang-format.

[olilarkin]

This issue and PR were entirely generated by fable. I'll look a bit more deeply into it next week.

[defiantnerd]

thanks. but probably Claude missed the macro redefinition of the function name when being compiled as single component.

[olilarkin]

Good thought, but setComponentState isn't affected by that macro. The workaround in vstsinglecomponenteffect.h is:

// work around for the name clash of IComponent::setState and IEditController::setState
#define setState setEditorState
#define getState getEditorState
#include "public.sdk/source/vst/vsteditcontroller.h"
#include "pluginterfaces/vst/ivsteditcontroller.h"
#undef setState
#undef getState

It only renames the setState/getState tokens (the controller's own state methods) during that include — setComponentState is a distinct token and keeps its name. Two pieces of evidence the override lands in the right vtable slot:

1. It's declared with the override keyword, so a rename or signature mismatch would be a compile error.
2. nm on the built plugin shows the expected three symbols side by side:

T ClapAsVst3::setComponentState(Steinberg::IBStream*)        <- this PR's override
T ClapAsVst3::setState(Steinberg::IBStream*)                 <- IComponent (processor) state
T Steinberg::Vst::EditController::setEditorState(...)        <- macro-renamed controller state, SDK default

The macro is relevant to the adjacent gap though: Live's log also prints couldn't get controller state: not implemented — that's IEditController::getState (= getEditorState under the macro), the controller's private state, which remains at the EditController default. That's a separate, harmless thing for a single-component wrapper (there's no controller-only state to persist) — probably why the setComponentState gap next to it went unnoticed.

Re-confirmed with the patched build in Ableton Live 12.4: state now transfers correctly (duplicating a device carries its state over; that goes through the same processor-state → controller handoff that was returning kNotImplemented).

[olilarkin]

(says fable). It might be a Live bug. I'll check next week.

[CrushedPixel]

Can confirm this fixes the issue, but might be worth testing what @Quant1um posted in the issue:
#475 (comment)

[CrushedPixel]

@defiantnerd I disagree with closing this - we haven't conclusively resolved the issue yet. I am still investigating

[defiantnerd]

oops - sorry, that was by mistake.

[defiantnerd]

Implemented in #499 because because this one didn't merge anymore.