Before I convince myself this is a TechSupport issue I want to understand the difference between the Scroll Time control and the Time Period Back control - because there is a difference. The help file for Processbook states the opposite from when comparing functions of Time Period & Scroll Time bar controls:
This operation is the same as would happen if the "forward/backward one period toolbar buttons" were clicked.
This seems to have crept in since Processbook became SDK based and not API.
Let me give a quick example, create a blank display add a trend showing SINSUOID with an 8h time span (*, *-8h).
Add a "Value" object to the display pointing to a tag with attribute STEP = 1, which contains data like:
-So go to the scroll time bar and click in the empty space of the bar to go back in time (same as One Time Period Back) and you will notice the Value updates as expected (as if ValueAtOrBefore is being used for an Archive value).
-Revert the time back to current time.
-Now use "One Time Period Back" button and the value doesn't update the same..! It takes lots more clicks to get to the same data that a couple of clicks on the scroll time control.