TaskPane black rectangle flickering for the first visiable state change

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TaskPane black rectangle flickering for the first visiable state change
 
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Daniel Lutz




Posts: 33
 Joined: 2023-02-27
Hello Support,

maybe some of you can reproduce it or have an idea to handle it. I created a new addin express word add and create an empty usercontrol and add it to a new created taskpane (over the addinexpress designer). The taskpane is invisible at word start and can made visible with an ribbon button.

For the (only) first visible state change (false > true) there is a short black rectangle renderer in the top area of the usercontrol for an short time. It could be that there is rendered something before hwnd is created but i cannot stop it. Maybe some of you have an idea.

Best regards
Daniel
Posted 07 Apr, 2026 09:21:35 Top
Andrei Smolin


Add-in Express team


Posts: 19218
 Joined: 2006-05-11
Hello Daniel,

Could you please send me a test project reproducing this issue? Use the contact form at https://www.add-in-express.com/support/askus.php.

Regards from Poland (GMT+2),

Andrei Smolin
Add-in Express Team Leader
Posted 07 Apr, 2026 12:41:42 Top
Andrei Smolin


Add-in Express team


Posts: 19218
 Joined: 2006-05-11
Thank you, Daniel.

You use Custom Task Panes. That functionality is controlled by Microsoft and developers can't do anything about that behavior.

Regards from Poland (GMT+2),

Andrei Smolin
Add-in Express Team Leader
Posted 10 Apr, 2026 11:51:20 Top
Andrei Smolin


Add-in Express team


Posts: 19218
 Joined: 2006-05-11
I don't reproduce this issue in Word Version 2603 (Build 19822.20142 Click-to-Run) Current Channel.

Regards from Poland (GMT+2),

Andrei Smolin
Add-in Express Team Leader
Posted 10 Apr, 2026 12:58:58 Top
Daniel Lutz




Posts: 33
 Joined: 2023-02-27
Mhmm a colleague could reproduce it. We use the same Word version. I test it on a Laptop (4k, but disabled) and a separate display (4k, 150 % dpi).
Posted 10 Apr, 2026 13:21:44 Top
Andrei Smolin


Add-in Express team


Posts: 19218
 Joined: 2006-05-11
Oh, I see the issue on my secondary display.

Regards from Poland (GMT+2),

Andrei Smolin
Add-in Express Team Leader
Posted 10 Apr, 2026 13:27:10 Top
Andrei Smolin


Add-in Express team


Posts: 19218
 Joined: 2006-05-11
Hello Daniel,

I suggest that you create a VSTO-based add-in showing such a custom task pane; preferably that you use an example they published on VSTO and/or CTP and contact them using the description at https://learn.microsoft.com/en-us/microsoft-365/admin/get-help-support?view=o365-worldwide.

Regards from Poland (GMT+2),

Andrei Smolin
Add-in Express Team Leader
Posted 22 Apr, 2026 08:47:28 Top