Credit not being added to lightbox. showOnScreen is being ignored

[cmcleese]

Trying to add a custom credit to the lightbox.
From the documentation link
https://cesium.com/learn/cesiumjs/ref-doc/Credit.html?classFilter=cred
showOnScreen seems to have no effect for either addCredit or addDefaultCredit.

None of the following work as intented:

viewer.scene.frameState.creditDisplay.addCredit(new Cesium.Credit('<a>My New Credit1</a>', true));
viewer.scene.frameState.creditDisplay.addCredit(new Cesium.Credit('<a>My New Credit2</a>', false));
viewer.scene.frameState.creditDisplay.addDefaultCredit(new Cesium.Credit('<a>My New Credit3</a>', true));
viewer.scene.frameState.creditDisplay.addDefaultCredit(new Cesium.Credit('<a>My New Credit4</a>', false));

Sandcastle example:
https://sandcastle.cesium.com/#c=tZI/a8MwEMW/yuElNgSJtN2imIIz9s8Q6OTlIp1bUVkO0tnB/fR1HBdCmqEpZNDw3t27Hw+kGx8ZOkt7CrACT3soKNq2Fm+jl5aJHnXReEbrKZRJtiz9MSGiJk+iCljThpFJ6EDG8trGncNeoDHFaKQnhydnpjB/7uHlMBidhZKYz+bAoaXsRoy7iVGhi1dC1lRh6/jvrPt/97ka9XBWK5knZTIQAX4egIrcO8qPAuDR1rsmMLTBpUJIpnqgM0W5bfUnsdAxZsspKU+jytgOrFld+BigHcY4TKrWuY39ojLJlRz2f0Vdg8b699eOwtD5sPaxyJ+OphBCyUFeTnLTuC2Gs8vf

[ggetz]

Hi @cmcleese, I believe this is a duplicate of #6215. That issue goes into further discussion of what addCredit and addDefault credit do, and how showOnScreen applies to both. The public API and docs are not entirely clear about the behavior.

We'd be happy to review a PR if you have some availability to take a look.

I'm going to close this issue to keep discussion in one place. Thanks!