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Request a Feature Report a Bug
Completed
Last Updated: 20 Jun 2024 14:11 by Brian
Release 5.0.0 (15 Nov 2023) (R1 PI1)
Constantinos Petridis
Created on: 02 Dec 2021 12:22
Category: ComboBox
Type: Bug Report
30
ComboBox virtual scrolling breaks when you slowly scroll up after selecting an item. The same behavior goes with the virtualization in DropDownList.

I have a ComboBox/DropDownList that gets data from a remote service, using virtualization. When the PageSize property is big enough (in my case 20), I have issues scrolling up the selection box dropdown list. I'm trying to scroll but then resets to the currently selected item making it almost impossible to scroll up. You can use your own demo examples to replicate this issue.

To reproduce the issue, try the ComboBox - Virtualization, in Telerik REPL (Demo), change the PageSize from 10 to 20. Open the dropdown and select an item. Then, open again the dropdown and scroll slowly up.

Duplicated Items
26 comments
Brian
Posted on: 20 Jun 2024 14:11

Hi Dimo,

Thanks for the clarification.
It's worked since I deleted the bin and obj folders as well as cleared the browser cache.
@Anastasia, I did not realise you could change versions on the repl site as well.

Thank you.

ADMIN
Dimo
Posted on: 20 Jun 2024 10:40

Hello Brian,

Please clear the browser cache and delete the bin and obj folders in your app.

I tested your algorithm on our ComboBox Virtualization online demo and it works as expected. Let me know if your observations are different.

Regards,
Dimo
Progress Telerik

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Brian
Posted on: 20 Jun 2024 10:31

Hi Anastasia,

Thanks for your reply.
I tested on the demo link you shared and noticed it works fine if you select an element at the top and scroll to the bottom.
However, if I select an element further down the list, and then try to scroll back to the top it bounces back to the selected item.

I can bypass this by dragging the scrollbar until it passes the selected item, but I don't think it is ideal for the casual user.

 

P.S. I have upgraded to v 6.0.2.

 

Kind regards,

Anastasia
Posted on: 14 Jun 2024 06:35

Brian, testing with this demo, it seems that the issues has been resolved since version 5.0.0

I have tested it with all versions up to 6.0.2 and it is working as expected.

Brian
Posted on: 14 Jun 2024 06:11

Has this issue been resolved?

It seems to be there on Version 5.1.1

ADMIN
Nadezhda Tacheva
Posted on: 02 Oct 2023 08:24

Hi Constantinos,

I agree that the issue you have reported is pretty annoying and I can confirm it is in our backlog with high priority. I reached out to our management once again to consider it for fixing as soon as possible.

Let me now provide some more information about prioritizing the fixes.

Indeed, some bugs can be more blocking than others and this raises their severity and priority in our backlog. In addition, we do track the gathered votes in the prioritization process as this indicates the number of community members affected by the specific bug.

However, there is one other important metric that we take into consideration - whether the reported bug is a regression. In such a case, we strive to prioritize the fix for the earliest possible release.

The reported bug that you linked is essentially a regression and this is why it was scheduled for the upcoming 4.6.0 release.

A concern of mine is that with the current labeling of the issues in the feedback portal, it is not clear to the community whether an item is a bug or a regression. Thus, questions like yours arise.

I started an initiative to make the issue type more clear. For the time being, we will mark the items as regressions in the title. In addition to that, we will consider possible labeling enhancements.

Regards,
Nadezhda Tacheva
Progress Telerik

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Constantinos Petridis
Posted on: 25 Sep 2023 14:27

The reported bug, got scheduled for fixing in the next release (Scheduled for 4.6.0 (11 Oct 2023) (R3 2023))!

I can understand that some issues might be more important than others... but man... the grid bug is reported 7th of Septemper this year... and gets planned with only 2 vote for next release...

Yet, this one remains unfixed & unplanned with 23 votes since 2nd of December 2021... :(

Soon I will have to write a new demo of the issue... the original demo posted stopped working a long time ago (pre 3.0.0 version of blazor controls!). The second version was posted in Feb 2023 (link) and it still works with 4.5.0

Mark
Posted on: 25 Sep 2023 09:17
Similar bug in the Telerik Grid planned to be fixed, Mouse scrolling up a virtual navigable Grid reverts the scroll offset (telerik.com).
ADMIN
Dimo
Posted on: 15 Sep 2023 06:32

Hi Alexander,

Thanks for the detailed description. Yes, you are right that a small PageSize will not work for adaptive scenarios that use a higher list of items.

I agree with you that the problem is serious and I escalated it a few days ago to the developers. We have an imminent product planning and I do hope this will be scheduled for fixing soon.

Please accept my apologies for the trouble.

Regards,
Dimo
Progress Telerik

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Alexander
Posted on: 12 Sep 2023 06:56

Let me summarize this issue: there is a (in my opinion) severe bug in the virtual scroll feature of TelerikComboBox that has been known for almost two years now, that basically prevents its usage, but there are still no plans to fix this.

Yes, you can reduce the page size to some small value as suggested below, but that leads to other problems when also using "AdaptiveMode.Auto"

Take, for example, the small demo from https://demos.telerik.com/blazor-ui/combobox/virtualization and add the following parameter to the TelerikComboBox:

AdaptiveMode="@AdaptiveMode.Auto"

Then run the demo and shrink the right side so the full-screen modal dialog will be used. Now try to scroll all the way down to select the last entry in the list ("Lusaka (Zambia)"). You will find that it is not possible to do so. The last selectable entry I get shown with the given page size of 10 is "Washington, D.C. (United States of America)".

Here is the link to the REPL: https://blazorrepl.telerik.com/QdODlcYK50oMfdoZ56 

Mark
Posted on: 08 Sep 2023 12:22

Hi Hristian

An example from the Telerik documentation that exhibits this behaviour for me is Blazor MultiSelect - Virtualization - Telerik UI for Blazor. I hope that helps.

 

As a sidenote, the MultiColumnComboBox example does not seem to select items until the drop out is closed?

ADMIN
Hristian Stefanov
Posted on: 06 Sep 2023 13:40

Hi Federico,

I have tested the virtualization sample from our MultiColumnComboBox documentation. As a result, I wasn't able to reproduce the bug with it. Could you please share the configuration you are testing with so I can see the behavior with the MultiColumnComboBox firsthand?

I look forward to hearing from you.

Regards,
Hristian Stefanov
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Federico
Posted on: 06 Sep 2023 12:06
I have this undesidered behavior in the MultiColumnComboBox component too.
ADMIN
Hristian Stefanov
Posted on: 06 Sep 2023 11:49

Hello,

I fully empathize with the inconvenience and frustration caused by this problem.

Still, at present, the status of this item is "Unplanned," signifying that it does not currently have a specific timeline assigned. Nevertheless, as we prioritize and transfer the task to our short-term backlog, its status will be updated to "Planned" along with an associated release number. This release number will indicate the future release in which the fix is expected to be incorporated into our Blazor ComboBox/DropDownList.

In the meantime, to ensure that you stay informed about any progress or changes regarding this item, I encourage you to subscribe to it. By subscribing, you will receive email notifications that provide timely updates on the status of the bug.

Additionally, as the only possible workaround, you can set a small PageSize value (e.g. "5").

Regards,
Hristian Stefanov
Progress Telerik

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Sean
Posted on: 05 Sep 2023 17:15

This is also a big problem for us.  I just noticed this and replicated it with your latest 4.5.0 version of blazor controls.

See attached gif showing behavior on YOUR demo page.

 

Thank you.

Attached Files:
Mark
Posted on: 20 Jul 2023 19:46

I have recently posted a bug report for this issue, see the duplicated section. I suppose I was unable to find the existing report in the large backlog of features and bug reports. It was very disconcerting to be referred to a bug report from 2 Dec 2021, status unplanned. I'm sure the original author must be particularly frustrated.

 

For what it is worth I have added my vote.

 

 

ADMIN
Nadezhda Tacheva
Posted on: 15 Jun 2023 15:52

Hi all,

I am stepping in to provide an update. I can confirm I added this issue to our Backlog in March. However, we haven't been able to schedule the fix for a specific release yet.

This is indeed a very unpleasant behavior and the only possible workaround is to set a smaller PageSize value.

I have reached out to our management to escalate the issue but I am still unable to provide a firm estimate. The best way to track the progress of the fix is to follow the thread. Once it is scheduled for fixing, we will update the label and you will receive an email for that change. 

Regards,
Nadezhda Tacheva
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Constantinos Petridis
Posted on: 14 Jun 2023 13:01
Back in March, Nadezhda promised to prioriatize the issue, but still no news I'm affraid :(
Christian
Posted on: 09 Jun 2023 07:27
This feature has to be fixed, how is it in unplanned state? it is unusable as is.
Tate
Posted on: 08 Jun 2023 16:29

Any updates with this issue? Should I file a bug report in hopes that it ups the severity? I would love to see virtualization as a legitimate component feature without arbitrary page size restrictions that only work if you suggest your users scroll at an equally arbitrary speed.

Constantinos Petridis
Posted on: 09 May 2023 13:27

Version 4.2.0 and this bug is still present!

By mistake in my last message I said that, at February 17th 2023, it was 2 months after the initial post of this bug... but it was 1 year and two months and now it is 1 year and 5 months.

I do wonder how much time is needed, for a bug to get fixed... a bug in your virtual list implementation of all selection controls in your blazor suite. The problematic behaviour is not fixed by using a smaller page size but it is just easier to go fast enough to skip a page of ten. Then again I am sure some people out there will not be able to do so...

ADMIN
Nadezhda Tacheva
Posted on: 02 Mar 2023 16:13

Hi Constantinos,

I am sorry that this bug causes so much trouble on your side. I do agree with you that it affects an important component functionality and prevents one from using the full capabilities of the virtualization feature.

I escalated this with the team. We have plugged it into our backlog and will try to prioritize the fix for it.

As for the RTL support, it is currently planned for 4.2.0. You may follow the linked item to get status updates on that.

Regards,
Nadezhda Tacheva
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Constantinos Petridis
Posted on: 24 Feb 2023 17:48

Two and half months is a long time for a bug that prevents all drop down controls to work correctly with virtualization.

You know what, without virtualization, the conrols works fine... no need for a fix at all... or better yet stop using the control.

I think you are missing my point, I did not complain a few days or a week after I reported the bug... but 3 months after. 

Sorry for being bitter... but I'm a bit frustrated with the slow support and progress of blazor controls... I mean, we have been waiting for the AppBar control since 2021 and it is still in the roadmap. And what about RTL support, should I trust that R2 releases will, at last, bring support for it?

 

ADMIN
Nadezhda Tacheva
Posted on: 24 Feb 2023 16:50

Hi Constantinos,

Thank you for the additional details!

It is a good thing that the issue does not occur with smaller PageSize. However, you are correct that the bug still exists when setting a larger PageSize value and it has to be fixed.

The prioritization process of the bug reports in our backlog is a bit different compared to how we prioritize the feature requests. For the bugs, we alto consider their severity - in other words, how badly they are affecting the component behavior. The higher severity, the sooner the bug is planned for fixing.

Apart from that, we also track the community demand for the specific fix. If a couple of bug reports have the same severity level we will first target the fix of the one that has gathered more votes.

I hope this information provides some clarity on how we are prioritizing the bug fixes. As unfortunately all bugs cannot be fixed simultaneously, they have to be organized in an efficient and fair manner.

For the time being, my suggestion would be to use a PageSize value that does not cause problematic behavior. Testing on my end, a value of 10 does seem to work well.

Regards,
Nadezhda Tacheva
Progress Telerik

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Constantinos Petridis
Posted on: 22 Feb 2023 16:40

Demo link of a new working example. The page size is 30, select a city in the middle of the list, then reopen the combo and try to wheel scroll up a few ticks and try to make the select city leave the drop down box... it will always bring the list back to display the selected item at the bottom.

You will need to very quickly move the wheel in order to manage skip more than 30items (page size) to escape the selected item region! The bigger the page size the worse, the smaller the better but still a bug.

Constantinos Petridis
Posted on: 17 Feb 2023 20:36

2 months and still unfixed, 3 versions later!!

This is frustrating to say the least :(

Mind you that the demo is not working with version 4 of the controls but the bug is still present

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