message: When loading an HDRI, set background color to black.
diff: @@ -1735,6 +1735,10 @@ void MainWindow::buildWindowLightEditor()
  auto &hdriTex = hdri.createChild("map", "texture_2d");
  auto ast2d = hdriTex.nodeAs<sg::Texture2D>();
  ast2d->load(texFileName, false, false);
  + // When using an HDRI, set background color to black. It's otherwise
  + // confusing. The user can still adjust it afterward.
  + auto &r = frame->childAs<sg::Renderer>("renderer");
  + r["backgroundColor"] = vec4f(0.f);
  }
  } else {
  lightNameWarning = true;
  