this allows using the pagescroller for scrolling elements into view where the rect gets calculated somewhere else
Example: CodeMirror has the `cm.cursorCoords()` function that returns the rect of the textselection (or cursor coordinates)
this scrolls the cursor or text selection into view using tiddlywikis pagescroller:
`$tw.pageScroller.scrollIntoView(undefined, function() { return self.cm.cursorCoords(true,"window"); });`
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