Software Version 188.8.131.52, just to get that out of the way...
When a user launches com.amazon.bueller.photos (Amazon Photos), they can view photos uploaded to their Amazon Drive. With a quick click, they can change the folder that com.amazon.ftv.screensaver uses to retrieve files used for screensaver. It seems...seems...that as soon as the "Set as Screensaver" button is pressed, this executes a few [obvious] methods: 1) a change is made to an applicable setting, perhaps in an xml file somewhere and, 2) it brings up the screensaver options screen in case the user wants to change something else.
Importantly, the new photos appear ghosted in the background of the screensaver options screen immediately. (This is important because the click action on that button not only changed the setting, but initiated a download of the new files.
I simply want to do just that...with adb commands. (I want to change that folder as I wish on the fly and initiate that immediate download...let's call it a "reset" of the screensaver).
I found out how to view processes (adb shell ps -a) and services (adb shell service list). Easy enough. I found some presumable references to the screensaver "environment" (android.service.dreams.IDreamManager, com.amazon.ftv.screensaver and app.services.ScreensaverService and looked around for how to kill and then start these services (one and then immediately the other is basically a restart).
An 'adb shell ps | grep \saver' gets me a PID...but I didn't see any visual results. Hope I'm kinda on the right track. ???