MultiComboBox can't load more than 500 selected items

[gero1992]

Hi all! First of all great component, very good job:).

Unfortunately I found a very serious bug, when the user selects more than 500 items and then try to open the popup again. It's not a common usecase, but I think there shouldn't be situations when the component can break like this.

Steps to reproduce:

• Create an instance of the combo box with 500+ items.
• Press select all button
• Close the popup
• Open the popup again

Result:

• The spinner is shown
• Items are loading and the popup is getting scrolled up and down
• The user is not able to use the component anymore

Expected result:

• The items load and the user can continue with his selection

Code snippet:

MultiComboBox<String> multiComboBox = new MultiComboBox<>();

List<String> list = IntStream.range(0, 501)
                .mapToObj(index -> "Dummy item " + index)
                .collect(Collectors.toList());
multiComboBox.setItems(list);
add(multiComboBox);

Demo:

Best regards, Gero

[jcgueriaud1]

Hi,

I can reproduce the error. Currently the component is trying to focus the first unselected item. When you have a lot of selected items, the focus is navigating from 0 to 500 then loop back to 0 ...

As a workaround you can increase the pageSize (= the size of the list) but it will send all the items to the client side.

I'll try to, at least, avoid the infinite loop.

[jcgueriaud1]

I've added a condition to avoid an infinite loop when more than 500 items are selected: https://github.com/vaadin-component-factory/multiselect-combo-box/issues/23

It's released in 0.4.0

[gero1992]

Hi, sorry for the late response and thanks for your fast reaction!

Yes now it doesn't break, but I don't know if that's the best way to solve the problem. I really like the focus functionality, but maybe the best solution is to remove it, because it's slow and with more than 500 items it doesnt work that good.

Another solution, which I can propose would be to get the focused index on the server side and set it from there.

On the other hand I noticed another bug, which comes from the key mapper which can generate a new key for an already checked item. Whenever the item receives a new key, it won't be shown as checked. If the items have unique keys, which don't change, this will not occur.