Re-implement Surge::UserInteractions::promptError

[baconpaul]

Right now Surge::UserInteractions::promptError pops up an error dialog.

It's called all over the place - including in non gui code. So the somewhat optimistic default null SurgeGUIEditor reference we added at the very start of the UserINteractions API is not going to help.

Here's an idea though.

Have S::UI::promptError rather the pop an error update an append only per storage instance (so we have to thread a a storage reference through the api) data structure which has a form like

{ std::array<256, pair<error,.errorno>> q, std::atomic_int count; }

so UserInteractions does { q[count] = ( error, errorno ); count++; }. Fine. And of course checks count vs 256 with an atomic swap and so on. You know std::atomic reader writer thingies where it's OK if you are late in the reader.

Then SGE keeps a 'how far have i got' and checks in the idle loop and reacts if it is behind by splatting the next error over the screen.

If you press ok do mycount++ and check with count; if they are the same set storage count ack to zero otherwise show the next message.

That's basically my late night idea on how to chip out more of this API into local code. Probably won't do it for 172 since it's not really in the way like the spawn_miniedit was. But still.

[baconpaul]

I want to do this one early; it matters a lot for the juce ports too.

[baconpaul]

I'm gonna push this one out of 19. I want to do it a bit differently and am still pondering.