igx-simple-combo: Repeated Switching Between Two Combos Causes Severe Performance Issues

[jsakamotoIGJP]

Description

When there are two or more igx-simple-combo components on a page, clicking each combo component repeatedly causes a significant performance issue.

It occurred even when placing two identical combos on the same page and making them bound to the same simple array. After selecting any item in both combos, repeatedly clicking them alternately to open their dropdown lists causes CPU usage to increase over time. Eventually, the UI becomes sluggish, and the browser freezes completely.

The issue also occurs in the latest version of Ignite UI for Angular (21.0.3).
It occurs in version 20 as well. On the v20, the problem is even more visible, with noticeable UI flickering.

Additional notes:

• The issue does not occur if either combo has no selected item.
• The issue does not occur when closing one combo’s dropdown (via the dropdown button) before opening the other.

• igniteui-angular version: 21.0.3 (also reproducible in 20.x)
• browser: Version 143.0.3650.96 (Official build) (64-bit)

Steps to reproduce

1. Place two igx-simple-combo components on the same page.
2. Bind both combos to the same simple array.
3. Select any item in each combo.
4. Alternately click each combo to open its dropdown list repeatedly (don't close one before opening the other).
5. Observe CPU usage and UI responsiveness.

Result

• CPU usage gradually increases.
• UI interaction becomes noticeably slower.
• Eventually, the browser becomes unresponsive and freezes.
• In version 20.x, the focus line of the combo also flickers visually during the process.

Expected result

• CPU usage should remain stable.
• Opening and closing dropdown lists should not degrade performance.
• The browser should remain responsive regardless of repeated interactions.

Attachments

I will attach two reproducible sample projects (as ZIP files):

• One built with version 21.0.3: 📦c-00245218-ng-app1.zip

• One built with version 20.x: 📦c-00245218-ng-app2.zip

Additionally, I will attach an MP4 video demonstrating the issue in version 20.

2025-12-22_15h33_13.mp4