So I've been playing with the new 11.1 documentation style and I noticed that there's something seemingly odd with the openers.
If we open any doc page:
Documentation`HelpLookup@"TaggingRules"
And look at any of the section openers we see they're something custom:
But they work totally normally. And looking at how they're implemented we see a general pattern like:
Dynamic@ CurrentValue[EvaluationNotebook[], {TaggingRules, "Openers", style}, Closed] (where style is sometimes more deeply nested, like "ExamplesSection", "0").
And interestingly we can open and close the groups via:
CurrentValue[EvaluationNotebook[], {TaggingRules, "Openers", style}] = Open | Closed And this gets updated when the cell group is opened and closed by hand, too.
If we copy and paste one of these cells the behavior is preserved, but if we take the cell expression and reprint it using NotebookWrite it no longer works. The cell group will open and close because it has WholeCellGroupOpener->True but the opener won't toggle states and we can't close it via CurrentValue.
If I look at the Cell expressions there's no difference, so what causes this?
Update for clarity:
I expected to see grouping from the automatic grouping that Mathematica applies. I figured the grouping behavior would be handled somehow in the Cell expression because copying one of the CellObjects yielded the opening behavior I originally saw. It turns out the CellObject simply remembered the grouping spec.
