Server-side sorting symmetrical buffer

I’ve set up dynamic loading from the server. Works great when scrolling down, but when scrolling up it has to fetch from the server every time. How do I set the buffer to be symmetrical?

You can adjust your server side code and treate “posStart” and “count” parameters in necessary way

Normally you output
<rows pos="{posStart}"
… data for row {posStart} - {posStart+count}
but you can output it as

<rows pos="{posStart-some}"
… data for row {posStart-some} - {posStart+count}

where some - count of row , which will be additionally fetched, before current position