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Provide a RunLoop on Linux

On this page:

• Query IRunLoop from IPlugFrame
• Query IRunLoop from the host context of IPlugFactory3

On Linux, there is no global event run loop like on Windows and macOS. For this reason, the plug-in can query for an Linux::IRunLoop which must be provided by the host application in two different ways.

Query IRunLoop from IPlugFrame

The host application must provide the Linux::IRunLoop via IPlugFrame (by calling IPlugView::setFrame).

// Plug-in implementation
tresult PLUGIN_API MyPlugView::setFrame (Steinberg::IPlugFrame* frame)
{
    ...
    Steinberg::FUnknownPtr<Steinberg::Linux::IRunLoop> runLoop (plugFrame);
    if (runLoop)
    {
        runLoop->registerEventHandler (...);
    }
    ...
}

Query IRunLoop from the host context of IPlugFactory3

A plug-in also needs a way to query for an Linux::IRunLoop without IPlugFrame. This allows to register timers in case the editor is closed or unavailable.

These timers can be used inside Vst::IAudioProcessor for extra computations or sending messages within the UI thread.

The host application must call Vst::IPlugFactory3::setHostContext (context) for this and provide a context. This context can be used to query an Linux::IRunLoop interface.

// Plug-in implementation
tresult PLUGIN_API MyPlugFactory::setHostContext (FUnknown* context)
{
    ...
    Steinberg::FUnknownPtr<Steinberg::Linux::IRunLoop> runLoop (context);
    if (runLoop)
    {
        runLoop->registerTimer (...);
    }
    ...
}