Messages for selecting region?

[doc hawk]

I think I used to know this, but . . .

Aren’t there messages for when the mouse is held down and dragged, as if selecting an area?

Or is it something we do with mosueDown, mouseStillDown, and mouseUp?

Specifically, in the new pdf widget, I’m looking to, during development, selecting a region, which may or may not cause scrolling, and using the results of the drag to resize the widget to the selected area, then suppress the boarders, scrollbars, etc.