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Virtual Mode and Scroll

Hi Alex,

I observed that grid repaints the rows even with single row scroll. Is this by design?

The only benefit of pre-rendering (20 rows above and 20 rows below the display window, i.e. 20 + 20 + 20 = 60 for window size of 20) is that they do not appear blank while repainting the scrolled window. But this blank row is not noticeable if we render fewer rows (20 + 2 + 2 = 24). Just wondering why 20-up and 20-down is needed!!!

I was implementing AJAX based server side paging and rendering 20-up and 20-down was real pain. Since grid is repainting the rows anyway, reducing it to 2-up and 2-down was giving better result.

When showing record 40-60, we fetch data from 18-82 and paint from 38-62. This is performing extremely well. Giving this extra buffer of 20 for data loading is making more sense.

Alex, any comments?

Sudhaker Raj
Monday, August 28, 2006
Monday, August 28, 2006

Alex, I think 2 rows above display window and 2 rows below display window will also perform equally well? Isn't it?
Sudhaker Raj
Tuesday, August 29, 2006
I was thinking that ideally one should pre-fetch data for 2-3 pages ahead and pre-render rows for 1 page ahead (in case the user presses PageDown key and not just down arrow). This is where 20 rows up and down came from. I guess these parameters should be exposed via public properties because the 'best' behavior usually depends upon lots of other factors.
Alex (ActiveWidgets)
Tuesday, August 29, 2006

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