I discussed about this issue 6 years ago, but it still happens with the last release :-(

I need to use the report control (ActiveX) with variable height preview area (each row will have different height than others) with a lot of records (10,000 to 50,000) and with smooth vertical scrolling :-)

I'm testing with a sample application (written from scratch) but I cannot get a good performance in any way (even with lightning fast event handlers when measuring or drawing preview area). I'm testing using virtual and non virtual ways but the control always spend a lot of time when scrolling to the last elements. It works fine with the first ones. It seems than the logic developed to calculate the record for the scroll position has an exponential complexity. I know that you need to calculate the height of every previous rows in order to determine the row at the current scroll offset but you'd have to implement any kind of mechanism to enhance it (caching, using estimated and real row heights, delegate on user to calculate it, etc.)

I know it could be a hard work to solve it, but, please, think about many people are waiting for any solution for years (like me).

Thanks in advance