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How to Fix Vertical Lines When Resizing Excel Desktop Add-ins
Question details
The user is experiencing visual rendering glitches where vertical lines remain on the screen after resizing a custom third-party add-in task pane.
- Product
- Microsoft Excel
- Device & OS
- not provided
- Scenario
- Adjusting the window size or section width of a custom third-party add-in within the Excel desktop environment.
- Observed behavior
- Residual vertical lines persistently display in the desktop app after resizing the add-in, despite the exact same add-in functioning normally without glitches in Excel Online.
Ensure your Microsoft Office desktop application is updated to the latest build, as rendering bugs are frequently patched in newer releases.
Isolate the Rendering Issue to the Custom Add-in
Determine if the visual glitch is a systemic Excel problem or isolated solely to the custom third-party code by testing standard add-ins.
Since the custom add-in works flawlessly in Excel Online (which uses web-based DOM rendering) but glitches on desktop, the issue is likely tied to how the specific custom add-in interacts with the desktop rendering engine.
Open Excel, click on File > Options > Add-ins. At the bottom of the window, select 'COM Add-ins' or 'Excel Add-ins' from the Manage dropdown, click Go, and uncheck the custom add-in.
From the same menu, check the box for an official Microsoft add-in (such as the Analysis ToolPak or Solver) and click OK to activate it.
Open the official add-in's task pane, resize the window borders, and observe the screen. If no vertical lines appear, the issue is confirmed to be isolated within your custom third-party add-in.
Gather Diagnostic Data for Developer Support
Collect specific version and environment details to present to your developers or the Microsoft Q&A Office Development forum.
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If rendering bugs and add-in compatibility issues in Microsoft Excel desktop are disrupting your workflow, WPS Office offers a highly stable, lightweight, and free alternative. Experience seamless spreadsheet management without visual glitches.
- 1. Download the software: Visit the official WPS website and download the free WPS Office installation package for your operating system.
- 2. Install WPS Office: Run the installer and follow the straightforward on-screen instructions to set up the lightweight office suite.
- 3. Open your files instantly: Launch WPS Spreadsheets and open your existing .xlsx files directly. Enjoy a smooth, stable editing environment free of rendering errors.
Frequently Asked Questions
Why does my custom Excel add-in work in Excel Online but glitch on the desktop app?
Excel Online operates within a web browser and relies on standard web rendering (HTML/CSS/DOM). The Excel desktop application uses a completely different internal rendering engine. Code that renders perfectly in a browser can sometimes leave visual artifacts, like vertical lines, when interacting with the desktop app's native window manager.
Can hardware graphics acceleration cause vertical lines when resizing add-ins?
Yes. Sometimes, the computer's graphics processor conflicts with Excel's desktop UI updates. You can test this by going to File > Options > Advanced, scrolling to the Display section, and checking 'Disable hardware graphics acceleration' (available in older Excel versions) to see if the lines disappear.
Where should I report a bug regarding a custom Office.js add-in?
If you are a developer or working with developers, the best place to report code-level rendering bugs for modern Office add-ins is the Microsoft Q&A Office Development forum or the official OfficeDev GitHub repository.
