How to access the "Loading..." overlay.

I have been searching for the setting in the Cesium Viewer to make the "Loading..." overlay appear while the code is preparing as visible in the Sandcastle examples, but with no luck. Is there a setting in the Viewer, or is this controlled in js with a promise, then, etc? Many thanks

This is not specifically related to Cesium. The sandcastle framework uses basic everyday HTML/CSS/JS for this. You can accomplish in your app many other ways, but the way it works in Sandcastle is:

The body has the “sandcastle-loading” class on it by default, and includes the loadingOverlay div in the HTML:

The CSS only shows the loadingOverlay when its a descendant of the sandcastle-loading class:

The sandcastle-loading class is removed in the finishedLoading function:

which is inserted at the end of the Sandcastle example code:

Bah! I apologies for spending your time.