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## Summary of the Pull Request
In the focus mode the top border disappears upon resize. While this behavior is expected in the maximized / full screen mode, it should not happen in the focus mode.
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## References
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## PR Checklist
* [x] Closes https://github.com/microsoft/terminal/issues/7012
* [x] CLA signed
* [ ] Tests added/passed - nope, only manual testing
* [ ] Documentation updated - irrelevant
* [ ] Schema updated - irrelevant
* [ ] I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx
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## Detailed Description of the Pull Request / Additional comments
_GetTopBorderHeight method returns 0 when maximized or no title bar is visible. However the existence of top border has nothing to do with whether the title bar is visible. We want to leave the border as long as the window is not in some form of maximizing (maximized / full screen)
<!-- Describe how you validated the behavior. Add automated tests wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed
* Manual - dragging, resizing, maximizing both in focus and non focus modes + full screen testing
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