[8.x] [Core Rendering Styles] Fix bug with kibanaFullBodyHeight calcu…

…lation (#193798) (#195146)

# Backport

This will backport the following commits from `main` to `8.x`:
- [[Core Rendering Styles] Fix bug with kibanaFullBodyHeight calculation
(#193798)](#193798)

<!--- Backport version: 9.4.3 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sqren/backport)

<!--BACKPORT [{"author":{"name":"Tim
Sullivan","email":"[email protected]"},"sourceCommit":{"committedDate":"2024-10-04T21:00:57Z","message":"[Core
Rendering Styles] Fix bug with kibanaFullBodyHeight calculation
(#193798)\n\nA variable for the page height was not being calculated
correctly when\r\nthe Kibana chrome is invisible. This PR fixes the
issue by adding `px`\r\nas a unit to a variable used as input in the
calculation.\r\n\r\nUnblocks:
https://github.com/elastic/kibana/pull/193647\r\n\r\n## Testing\r\nIt
will help to test within
the\r\nhttps://github.com//pull/193647 PR branch. The
following\r\nscreenshots show the before and after effects of having
this
fix:\r\n\r\n**before**\r\n\r\n![ghjkgjghgkhjgjgkjg-1](https://github.com/user-attachments/assets/d684bc77-dcc0-40ef-9271-8ae198582eea)\r\n\r\n**after**\r\n\r\n![ghjkgjghgkhjgjgkjg-2](https://github.com/user-attachments/assets/5198cc43-b721-4ce8-92f0-0b2bac9f5eb5)\r\n\r\nCo-authored-by:
Elastic Machine
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Rendering Styles] Fix bug with kibanaFullBodyHeight calculation
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correctly when\r\nthe Kibana chrome is invisible. This PR fixes the
issue by adding `px`\r\nas a unit to a variable used as input in the
calculation.\r\n\r\nUnblocks:
https://github.com/elastic/kibana/pull/193647\r\n\r\n## Testing\r\nIt
will help to test within
the\r\nhttps://github.com//pull/193647 PR branch. The
following\r\nscreenshots show the before and after effects of having
this
fix:\r\n\r\n**before**\r\n\r\n![ghjkgjghgkhjgjgkjg-1](https://github.com/user-attachments/assets/d684bc77-dcc0-40ef-9271-8ae198582eea)\r\n\r\n**after**\r\n\r\n![ghjkgjghgkhjgjgkjg-2](https://github.com/user-attachments/assets/5198cc43-b721-4ce8-92f0-0b2bac9f5eb5)\r\n\r\nCo-authored-by:
Elastic Machine
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Rendering Styles] Fix bug with kibanaFullBodyHeight calculation
(#193798)\n\nA variable for the page height was not being calculated
correctly when\r\nthe Kibana chrome is invisible. This PR fixes the
issue by adding `px`\r\nas a unit to a variable used as input in the
calculation.\r\n\r\nUnblocks:
https://github.com/elastic/kibana/pull/193647\r\n\r\n## Testing\r\nIt
will help to test within
the\r\nhttps://github.com//pull/193647 PR branch. The
following\r\nscreenshots show the before and after effects of having
this
fix:\r\n\r\n**before**\r\n\r\n![ghjkgjghgkhjgjgkjg-1](https://github.com/user-attachments/assets/d684bc77-dcc0-40ef-9271-8ae198582eea)\r\n\r\n**after**\r\n\r\n![ghjkgjghgkhjgjgkjg-2](https://github.com/user-attachments/assets/5198cc43-b721-4ce8-92f0-0b2bac9f5eb5)\r\n\r\nCo-authored-by:
Elastic Machine
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BACKPORT-->

Co-authored-by: Tim Sullivan <[email protected]>

src/core/public/styles/rendering/_base.scss

@@ -67,7 +67,8 @@
 }
 
 .kbnBody--chromeHidden {
-  --euiFixedHeadersOffset: 0;
+  // stylelint-disable-next-line length-zero-no-unit
+  --euiFixedHeadersOffset: 0px;
 
   &.kbnBody--hasHeaderBanner {
     --euiFixedHeadersOffset: var(--kbnHeaderBannerHeight);