[Lazarus] TDBGrid vertical scrolling for sequenced datasets

[Max Vlasov]

Hi,

I don't know what parts of TDBGrid are still in progress, so I'm not sure
whether I should fill a report

I have a TDataSet descendant that IsSequenced = true, so the scrolling
should obey the position inside the dataset. But there are moments when
scrolling jumps to the zero position although should stay at some current,
non-zero (checked both windows and linux). In my case it shows when I
release the scroller at some new pos (and Resync is called for some reason),
but I also could reproduce this for \examples\address_book\addrbook.lpi
project.

For addrbook.lpi
- run the program
- decrease the width of the program so the horizontal scrolling in the upper
grid appears
- scroll down to some place when the vertical scroller is in the middle of
the scroll area (for example when MTH_NAME=January)
- click anything in the horizontal scrolling (button or area)
Now the vertical one jumps to the top (=0). To force it jump back click at
some nearby line (but not the same)

As I suppose looking at the sources, this is because TDBGrid does many
things itself and don't want some of TCustomGrid functionality working.
Neverthelesss sometimes TCustomGrid.UpdateScrollbarPos is called where
ScrollBarPosition uses calculated zero position regardless of the TDBGrid
own state.

Should I feel a report?

Thanks

Max Vlasov
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