Virtual Scrolling is jumpy

[Chris Hack]

Telerik Version: 2012.1.215.40

I have the following control setup to load on demand 10 items at a time and it works fine except for the jumpiness when using the scroll-bar.  The items seem to shift up once the next batch of 10 are loaded on the client.  Our clients are complaining about this behavior and I was wondering if there is anything I can do to mitigate or preferably illiminate this?                 

<telerik:RadComboBox ID="rcbLocation" runat="server" ClientIDMode="Static"
    Height="175px" Width="200px" EmptyMessage="Enter Location" MarkFirstMatch="true"
    EnableLoadOnDemand="true" EnableVirtualScrolling="true"
    ShowMoreResultsBox="true" OnClientItemsRequesting="MDL.Default.requestingItems"
    OnClientItemsRequestFailed="Main.radComboBoxItemsRequestFailed"
>
    <WebServiceSettings Path="Default.aspx" Method="GetMatchingLocations" />
</telerik:RadComboBox>

If you examine the attached screen snippet you can observe on the left is the state of the dropdown while it is loading and on the right is the state after it has loaded the next 10 items.  Keep in mind that I held the mouse perfectly still while waiting for the control to load, after which, the items are shifted up by 1.  When continuously scrolling, this behavior causes the appearance to be quite jumpy to the eye.

Tested environments: Chrome 21.0.1180.83 m, IE 9.0.8112.16421, FireFox 15.0

[Cat Cheshire]

Did you try the latest Telerik version?

[Chris Hack]

Upgraded to version 2012.2.724.40 and the behavior is the same.  Any other suggestions?

[Nencho]

Hello Chris,

Do you reproduce the problem at our online demo:
http://demos.telerik.com/aspnet-ajax/combobox/examples/populatingwithdata/autocompletesql/defaultcs.aspx?

When the new portion of items are needed, they are loaded at once and the previously loaded items are moved up. In order to rarely observe this behavior, you could enlarge the number of items loaded per request.

Kind regards,
Nencho
the Telerik team

[Chris Hack]

Yes, the behavior there is the same.  Start slowly scrolling the items by dragging the scroll-bar and as soon as it fetches another set of items, the whole list will jump up and your eyes will loose focus on the item you were currently viewing.

[Nencho]

Hi Chris,

Indeed when the new portion of items is loaded, the previous ones are moved up.
We are aware of this behaviour and actually it is by design.

Regards,
Nencho
the Telerik team

[Chris Hack]

Would you consider adding in a setting to turn off this behavior?  Maybe... EnableSmoothVirtualScrolling

Our clients are not going to stop complaining about this, so this is my desperate plea for help.  Is there perhaps a client side script that I can hijack to force it to scroll smoothly?

Thanks

[Nencho]

Hello Chris,

We understand the importance of that behavior in your scenario and I will forward the suggestion for smooth scrolling to our developer team for further consideration. I will notify you as soon as we decide what our further actions would be.

All the best,
Nencho
the Telerik team

[K]

Hi,

Is there any update on this issue?  We have found that as items load next set of data focus jumps back to beginning of the list which is very frustrating for users.

Thanks, K

[Nencho]

Hello,

The problem reported in this thread is already fixed with our latest official release and you can test the behavior with our online demon below:

http://demos.telerik.com/aspnet-ajax/combobox/examples/populatingwithdata/autocompletesql/defaultcs.aspx

Please give it a try and let us know if you encounter any issues with the functionality.

Regards,
Nencho
Telerik