What's the "correct" way to keep references to widgets? It looks like Scene ends up taking ownership when you call add, which makes sense, since you need the widgets to live at least as long as the scene. Assuming a single main scene which lasts the entire lifetime of the program, it seems like it doesn't matter all that much, so storing raw pointers is perfectly reasonable, e.g.

class App {
public:
  ui::Text * textWidget;
  App() {
    auto scene = ui::make_scene();
    textWidget = new ui::Text(...); // nobody owns this yet
    scene->add(myText);             // now scene owns this
    ui::MainLoop::set_scene(scene); // scene owned by MainLoop, so textWidget won't be destroyed
  }
};

I'm getting a little tripped up with widgets that use overlays, like Dialog. I think Dialog and Scene have a circular reference? I added some logging and never saw a Dialog get destroyed, unless I deleted it myself, which led to unpredictable behavior (since Scene still thought it owned the dialog).

// Like other widgets, this starts out unowned
auto dlg = new Dialog(...);

// Showing a dialog does roughly this:
dlg->scene = ui::make_scene(); // scene owned by dlg
dlg->scene->add(dlg);          // dlg owned by scene
ui::MainLoop::show_overlay(dlg->scene); // scene owned by MainLoop