Lv2 instruments looses automation on export

[zonkmachine]

Bug Summary

Lv2 instruments looses control from Automation Track on export.

Steps to reproduce

Connect an LV2 plugin control to an Automation Track and make a distinct pattern. Make sure it works under lmms live with a distinct change in sound. Export it. The exported project sees no variation in the controller.

Here is a demo project using DISTRHO/DPF-Plugins Kars, automating the Release. lv2automationexport.mmp.zip

Issue introduced in f48dd0fb1f424e06cd7bff1cb3d4c37f5d9a11a7 Fixes #6401: Reload Lv2 plugin on SR change @JohannesLorenz

[JohannesLorenz]

In #6419 we implemented this code:

void Lv2Proc::reload()
{
    // save controls, which we want to keep
    QDomDocument doc;
    QDomElement controls = doc.createElement("controls");
    saveValues(doc, controls);
    // backup construction variables
    const LilvPlugin* plugin = m_plugin;
    Model* parent = Model::parentModel();
    // destroy everything using RAII ...
    this->~Lv2Proc();
    // ... and reuse it ("placement new")
    new (this) Lv2Proc(plugin, parent);
    // reload the controls
    loadValues(controls);
}

As can be seen, the whole Lv2 processor is being destroyed and re-inited, but before, we save the values of all the models (knobs, spinboxes, LEDs etc). However, the connections themselves are not saved - they are in the automation clips or controllers, which reference the corresponding models by ID. On reloading the knobs (AutomatableModel::loadSettings), the models should get the same IDs as before (changeID( nodeElement.attribute( "id" ).toInt() );). However, when reloading, the "object" reference in the automation clip to those models gets deleted, too:

<automationclip pos="0" len="384" mute="0" tens="1" name="Cutoff" prog="1">
          <time pos="0" outValue="1449.762" value="1449.762"/>
          <time pos="192" outValue="7568.4004" value="7568.4004"/>
          <time pos="384" outValue="15136.801" value="15136.801"/>
          <object id="7357890"/>
</automationclip>

Here, <object id="7357890"/> gets lost in the reloading process. We need to find out why...

[JohannesLorenz]

Info: Still present with Lv2 Worker PR.