ModalPopupExtender blurring when scrolling in Chromium browsers

[neillg]

The AJAX Control Toolkit <18, 19, 20>

The installation method

• [ ] Installer
• [x] NuGet package
• [ ] A custom build from the source code

Minimal steps to reproduce the bug

Create a panel that is controlled by the ModalPopupExtender. The content must overflow in order to allow for vertical scrolling. IE and Firefox works fine, Chrome and Edge both have problems.

Actual result

When scrolling, controls appear on top of one another giving a blurred visual and making the content illegible. Example:

#546 describes a somewhat similar issue.

Expected result

No blurring, normal scrolling like other browsers

Browser(s) used

Chrome - issue occurs Edge - issue occurs IE - OK Firefox - OK

A site deployment method

• [x] VS development web-server,
• [x] IIS