Virtualize WinForms ScrollableControl - Expensive Child Items

Question

I am building a PDF Viewer using the Atalasoft DotImage libraries. They have a PDF Viewing component, but it doesn't support the Acrobat style PDF continuous layout, I have to display the pages a page at a time.

I need to build sort of a virtualizing scrollable control which has probably 3 PDFViewers in it, the current frame, and the ones immediately before and after. So my question is - how would I do this?

[I've been doing WPF for the last 3 years, and my WinForms experience has turned to mental mush.]

I need to be able to detect which viewers to open, and which to close. How?

Answer 1

You can do this with a Panel. Set AutoScroll = true and AutoScrollMinSize.Height = pages x control.Height. Implement the Scroll event handler and look at the -AutoScrollPosition.Y property to find out what the user is looking at. Change the Location property of the 3 controls and their Page property as necessary.