Update z-index hierarchy

[renatho]

What?

This PR fixes an issue where the menu would have bad behavior when used inside a cover block. The issue happened when the menu was open on a small screen (the layer on top of the content).

Why?

Many users are having and reporting this issue.
See

• Cover block in content body overlaps mobile menu overlay #45353
• Navigation Block: Overlay Z-index nesting issues with consecutive cover blocks Automattic/wp-calypso#75439
• Navigation block: overlapping(z-index) issue when nested inside Cover Block Automattic/wp-calypso#79317

How?

Before, we had the following index hierarchy inside the cover block:

• Cover (z-index: auto - position: relative;)
  • Cover background (z-index: 1 - position: absolute; z-index: 1;)
  • Cover image (z-index: 0 - position: absolute; z-index: 0;)
  • Cover container (z-index: 1 - z-index: 1;)
    • Content here, where the Navigation could be added and navigation has a position: fixed; z-index: 100000.

It repurposes the hierarchy to also have a z-index: auto (not set) in the Cover container, so the z-index inside it works properly without the interference of a parent (not forming a stacking context).

Considered alternatives

Ideally, the solution would be in the navigation block creating an element in an independent context for the open menu, so the issue would never happen regardless of where the menu is added. But it would have a huge impact and it is probably not worth it.

Another alternative would be to change the order of the elements so that we could clean up a bit the z-index from the elements, but this would demand a deprecation and a migration for users that already saved it, so I decided not to touch this.

Testing Instructions

1. In a template or a post add a Cover block.
2. Inside the cover block, add a Navigation block.
3. After the previously created Cover block, add another Cover block.
4. Visit the site in the frontend, on a small screen.
5. Open the menu, and make sure it's displayed over the whole content.

Please, also test other scenarios that I didn't cover here or in the following video if you see something I missed.

Screenshots or screencast

Screen.Recording.2024-09-25.at.11.47.34.1.mp4

[github-actions]

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Co-authored-by: renatho <renathoc@git.wordpress.org>
Co-authored-by: aaronrobertshaw <aaronrobertshaw@git.wordpress.org>
Co-authored-by: allilevine <firewatch@git.wordpress.org>
Co-authored-by: youknowriad <youknowriad@git.wordpress.org>

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[allilevine]

@oandregal 👋 Who would be best to ask for a review of this cover block fix?

[youknowriad]

I just pinged some people randomly to see if folks can help with review here.

[aaronrobertshaw]

Thanks for wrangling these z-index values @renatho, it appears to be a tricky one with plenty of edge cases 🙂

I could replicate the original issues linked in the description. After checking out this PR some of the issues were resolved but I ran into a number of other z-index related issues. For example, I could:

• Still select cover blocks under the navigation overlay
• See the resize handles on cover blocks over the navigation overlay
• See and interact with the quick inserter of the selected block
• Reach a situation where I couldn't close the navigation overlay at all

Trunk	This PR
Screen.Recording.2024-10-09.at.3.10.40.pm.mp4	Screen.Recording.2024-10-09.at.3.13.38.pm.mp4

Also, I think we can cull the padding-visualizer rule from the z-index styles. I've left a more detailed explanation as an inline comment below.

Please, also test other scenarios that I didn't cover here or in the following video if you see something I missed.

I couldn't find many other blocks that had z-index rules. All I saw when searching were some references to inline toolbars and modals. I'm happy to do further testing if there is anything specific I should be looking at.

[renatho]

Thank you for your review, @aaronrobertshaw!

It seems the issue is reproducible only with multiple clicks in a short period of time. Maybe something related to a double click event in the editor? I recorded a video trying to reproduce it, where I test the clicks in the first 20 seconds, and after this I refresh the page to test the scroll (also happens after the multiple clicks only when the wrong block is selected).

Screen.Recording.2024-10-09.at.11.30.26.1.mp4

I didn't dig into to find the cause of this other issue. Since it's a more specific case, I'd suggest that we go ahead with this PR and create a follow up issue to handle this separately. IMO, a lower priority issue since it's only in the editor using small screens and depending on the multiple clicks to break. WDYT?

[aaronrobertshaw]

Thanks for the quick iterations @renatho 👍

It seems the issue is reproducible only with multiple clicks in a short period of time

It can also be reproduced by using keyboard navigation to move between blocks, the inspector and the canvas etc. Additionally, if a user selects the parent block from the navigation toolbar we reach the same state.

Since it's a more specific case, I'd suggest that we go ahead with this PR and create a follow up issue to handle this separately.

I'm on board if you wish to create issues for these as problems for the navigation block rather than z-index issues. However, I'm not sure all the z-index issues are resolved by this PR.

Things look ok with nested cover and navigation blocks in the editor but they're still out of whack for me on the frontend.

This is what I'm seeing:

Screen.Recording.2024-10-10.at.4.58.00.pm.mp4

Here's the block markup I was testing with but as it uses uploaded media and local nav it might not help other than to illustrate the structure of what I tested with.

Block markup I tested with

<!-- wp:navigation {"ref":4} /-->

<!-- wp:cover {"url":"http://wp-build.test/wp-content/uploads/2024/10/1067-3931-CoreyArnold-UnitedStates-Professional-WildlifeNature-2023.jpg","id":13,"dimRatio":50,"customOverlayColor":"#8f897e","isUserOverlayColor":false,"minHeight":240,"minHeightUnit":"px","isDark":false,"layout":{"type":"constrained"}} -->
<div class="wp-block-cover is-light" style="min-height:240px"><span aria-hidden="true" class="wp-block-cover__background has-background-dim" style="background-color:#8f897e"></span><img class="wp-block-cover__image-background wp-image-13" alt="" src="http://wp-build.test/wp-content/uploads/2024/10/1067-3931-CoreyArnold-UnitedStates-Professional-WildlifeNature-2023.jpg" data-object-fit="cover"/><div class="wp-block-cover__inner-container"><!-- wp:paragraph {"align":"center","placeholder":"Write title…","fontSize":"large"} -->
<p class="has-text-align-center has-large-font-size">Cover Block</p>
<!-- /wp:paragraph -->

<!-- wp:navigation {"ref":4} /-->

<!-- wp:cover {"dimRatio":90,"overlayColor":"accent-4","isUserOverlayColor":true,"minHeight":240,"minHeightUnit":"px","layout":{"type":"constrained"}} -->
<div class="wp-block-cover" style="min-height:240px"><span aria-hidden="true" class="wp-block-cover__background has-accent-4-background-color has-background-dim-90 has-background-dim"></span><div class="wp-block-cover__inner-container"><!-- wp:paragraph {"align":"center","placeholder":"Write title…","fontSize":"large"} -->
<p class="has-text-align-center has-large-font-size">Nested Cover Block</p>
<!-- /wp:paragraph -->

<!-- wp:navigation {"ref":4} /--></div></div>
<!-- /wp:cover --></div></div>
<!-- /wp:cover -->

<!-- wp:cover {"url":"http://wp-build.test/wp-content/uploads/2024/10/file_example_MP4_480_1_5MG.mp4","id":16,"dimRatio":90,"overlayColor":"accent-6","isUserOverlayColor":true,"backgroundType":"video","minHeight":240,"minHeightUnit":"px","layout":{"type":"constrained"}} -->
<div class="wp-block-cover" style="min-height:240px"><span aria-hidden="true" class="wp-block-cover__background has-accent-6-background-color has-background-dim-90 has-background-dim"></span><video class="wp-block-cover__video-background intrinsic-ignore" autoplay muted loop playsinline src="http://wp-build.test/wp-content/uploads/2024/10/file_example_MP4_480_1_5MG.mp4" data-object-fit="cover"></video><div class="wp-block-cover__inner-container"><!-- wp:paragraph {"align":"center","placeholder":"Write title…","fontSize":"large"} -->
<p class="has-text-align-center has-large-font-size">Cover Block</p>
<!-- /wp:paragraph -->

<!-- wp:navigation {"ref":4} /-->

<!-- wp:cover {"url":"http://wp-build.test/wp-content/uploads/2024/10/1067-3931-CoreyArnold-UnitedStates-Professional-WildlifeNature-2023.jpg","id":13,"dimRatio":50,"customOverlayColor":"#8f897e","isUserOverlayColor":false,"minHeight":240,"minHeightUnit":"px","isDark":false,"layout":{"type":"constrained"}} -->
<div class="wp-block-cover is-light" style="min-height:240px"><span aria-hidden="true" class="wp-block-cover__background has-background-dim" style="background-color:#8f897e"></span><img class="wp-block-cover__image-background wp-image-13" alt="" src="http://wp-build.test/wp-content/uploads/2024/10/1067-3931-CoreyArnold-UnitedStates-Professional-WildlifeNature-2023.jpg" data-object-fit="cover"/><div class="wp-block-cover__inner-container"><!-- wp:paragraph {"align":"center","placeholder":"Write title…","fontSize":"large"} -->
<p class="has-text-align-center has-large-font-size">Nested Cover Block</p>
<!-- /wp:paragraph --></div></div>
<!-- /wp:cover --></div></div>
<!-- /wp:cover -->

<!-- wp:navigation {"ref":4} /-->

<!-- wp:cover {"url":"http://wp-build.test/wp-content/uploads/2024/10/1067-3931-CoreyArnold-UnitedStates-Professional-WildlifeNature-2023.jpg","id":13,"dimRatio":50,"customOverlayColor":"#8f897e","isUserOverlayColor":false,"minHeight":240,"minHeightUnit":"px","isDark":false,"layout":{"type":"constrained"}} -->
<div class="wp-block-cover is-light" style="min-height:240px"><span aria-hidden="true" class="wp-block-cover__background has-background-dim" style="background-color:#8f897e"></span><img class="wp-block-cover__image-background wp-image-13" alt="" src="http://wp-build.test/wp-content/uploads/2024/10/1067-3931-CoreyArnold-UnitedStates-Professional-WildlifeNature-2023.jpg" data-object-fit="cover"/><div class="wp-block-cover__inner-container"><!-- wp:paragraph {"align":"center","placeholder":"Write title…","fontSize":"large"} -->
<p class="has-text-align-center has-large-font-size">Cover Block</p>
<!-- /wp:paragraph -->

<!-- wp:navigation {"ref":4} /--></div></div>
<!-- /wp:cover -->

<!-- wp:cover {"dimRatio":80,"overlayColor":"accent-3","isUserOverlayColor":true,"minHeight":240,"minHeightUnit":"px","layout":{"type":"constrained"}} -->
<div class="wp-block-cover" style="min-height:240px"><span aria-hidden="true" class="wp-block-cover__background has-accent-3-background-color has-background-dim-80 has-background-dim"></span><div class="wp-block-cover__inner-container"><!-- wp:paragraph {"align":"center","placeholder":"Write title…","fontSize":"large"} -->
<p class="has-text-align-center has-large-font-size">Cover Block</p>
<!-- /wp:paragraph -->

<!-- wp:navigation {"ref":4} /--></div></div>
<!-- /wp:cover -->

<!-- wp:cover {"url":"http://wp-build.test/wp-content/uploads/2024/10/file_example_MP4_480_1_5MG.mp4","id":16,"dimRatio":50,"customOverlayColor":"#FFF","isUserOverlayColor":false,"backgroundType":"video","minHeight":240,"minHeightUnit":"px","isDark":false,"layout":{"type":"constrained"}} -->
<div class="wp-block-cover is-light" style="min-height:240px"><span aria-hidden="true" class="wp-block-cover__background has-background-dim" style="background-color:#FFF"></span><video class="wp-block-cover__video-background intrinsic-ignore" autoplay muted loop playsinline src="http://wp-build.test/wp-content/uploads/2024/10/file_example_MP4_480_1_5MG.mp4" data-object-fit="cover"></video><div class="wp-block-cover__inner-container"><!-- wp:paragraph {"align":"center","placeholder":"Write title…","fontSize":"large"} -->
<p class="has-text-align-center has-large-font-size">Cover Block</p>
<!-- /wp:paragraph --></div></div>
<!-- /wp:cover -->

<!-- wp:navigation {"ref":4} /-->

[renatho]

Hi @aaronrobertshaw!

In the frontend it should work properly. I recorded a video on my end with your markup (it just doesn't have the images/videos - but I have this in other post I was testing it):

Screen.Recording.2024-10-10.at.10.28.15.mov

I noticed sometimes when configuring the environment to re-test it, it had some kind of cache and it started working after some refreshes. Could you confirm if it's not the issue on your end? If it's not the case, could you confirm what browser and there you are using? I'm using Chrome (although I had also tested with others) and Twenty Twenty-Four.

[aaronrobertshaw]

I noticed sometimes when configuring the environment to re-test it, it had some kind of cache and it started working after some refreshes.

After noticing the issue, I made sure the browser cache was disabled, refreshed multiple times, and rebuilt Gutenberg for good measure. I was testing only in Chrome with TT5 so far.

I'll try and clean the slate again this morning and test further.

[aaronrobertshaw]

Thanks for the patience here @renatho 👍

I spun up a fresh site and clone of Gutenberg this morning, rebuilt everything and re-tested. I can no longer see the issues noted in my last review. On the frontend it works well for me across Chrome, Safari, and Firefox.

Latest demo

Screen.Recording.2024-10-11.at.10.27.17.am.mp4

I find the experience in the editor really easy to get into a broken state but can agree to fixes there being a follow-up. This PR is an improvement so I'm happy to approve to get it into 6.7.

To that end, I've added appropriate labels to this PR including Backport to WP 6.7 Beta/RC.

Nice work here! ✨

[github-actions]

I just cherry-picked this PR to the wp/6.7 branch to get it included in the next release: 7e52f6e

[renatho]

Thank you @aaronrobertshaw! I opened this issue as a follow-up: #66066
Feel free to add anything else there that you consider important. 😉

[juanfra]

Hi @renatho @aaronrobertshaw - I found an issue that could be related to these changes. Could you please take a look when you have time? Thanks 🙌