[Bug]: 8.64.2 regresses padding-top styling for Panels with custom header/nav

[dbjorge]

Library

React / v8 (@fluentui/react)

System Info

System:
    OS: Windows 10 10.0.22000
    CPU: (16) x64 Intel(R) Xeon(R) W-11955M CPU @ 2.60GHz
    Memory: 90.52 GB / 127.67 GB
  Browsers:
    Edge: Spartan (44.22000.120.0), Chromium (100.0.1185.39)
    Internet Explorer: 11.0.22000.120
  npmPackages:
    @fluentui/react: ^8.64.2 => 8.64.2

Are you reporting Accessibility issue?

no

Reproduction

https://codepen.io/dbjorge/pen/yLpxJXb

Bug Description

I believe this is a regression introduced by https://github.com/microsoft/fluentui/pull/22408. It changes the implementation of the empty space in question from marginTop to paddingTop, but appears to have missed adjusting the corresponding behavior to suppress the empty space when custom navigation is in play at L271 of Panel.styles.ts - it is still overriding marginTop in that case, rather than the newly-used paddingTop.

Actual Behavior

As of @fluentui/react@8.64.2, there is a new 18px of empty padding applied above custom header+nav rendering passed to <Panel>s. See red-highlighted section of the below screenshot of the provided minimal repro:

Expected Behavior

Behavior should be consistent with @fluentui/react<=8.64.1, where the default 18px of margin-top applied to <Panel> content was suppressed for <Panel>s which use a custom header/nav. See red pointer of the below screenshot of the same repro downgraded to 8.64.1:

Logs

No response

Requested priority

High

Products/sites affected

Accessibility Insights for Web (see https://github.com/microsoft/accessibility-insights-web/pull/5312#issuecomment-1097091341 for more details and a screenshot of the motivating example)

Are you willing to submit a PR to fix?

no

Validations

• [X] Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• [X] The provided reproduction is a minimal reproducible example of the bug.

[micahgodbolt]

@Hotell can you look into the custom header/nav scenario with the fix you made last week? We might need to take a different approach on #22408