Allow Group blocks to transform into Cover blocks

[kjellr]

It's currently possible to transform a Cover block into a group block, but not the other way around. It would be great to add that option in.

Transform options for Cover Block	Transform options for Group Block

[Soean]

You can't transform a Cover block into a Group block, only wrap a group block around the Cover block (This is possible for every block). You can use ungroup to remove the group around the block.

If we add the ungroup option to the transfer dropdown, we should build for all blocks, not just for the cover block.

[ntsekouras]

I personally can't find much value in this transform, as Cover block needs user input to initialize and we'll have to make arbitrary choices about them. This can confuse users I think. Maybe by having extra checks for having an Image block in group's InnerBlocks and use that as the Cover's background 🤔 ?

Even that would need more changes since the isMatch from transforms API would need to be extended to provide the innerBlocks as well and not only the attributes.

Reference: https://developer.wordpress.org/block-editor/reference-guides/block-api/block-transforms/#block

[getsource]

I'm not sure if it's better for me to reply here or in the PR.

It's worth noting that this does not require user input if there is an existing background of some sort, but I hear you.
I'm mostly thinking it might be easier for a user to take this path, if they started out with a group, and decided to move to a cover block. Could also only allow the transform when that's the case, but that blocks users from migrating a group when they intend to add an image to the background.

I thought about adding something to migrate an image from innerBlocks, but I also wonder if that would be confusing, since it'd be difficult to know which image to pick, and could generate user surprise. I suppose with the previews, it would show the user what would happen, though. I can try to put together a path of some sort to do that, if folks think it'd be helpful.

[kjellr]

Perhaps we only make this available for Group Blocks that have a solid color background set? Then there's a clear 1:1 cover block equivalent to transition to. (Once #14744 is resolved, there should be more possibilities here too).

[ntsekouras]

It's worth noting that this does not require user input if there is an existing background of some sort

Perhaps we only make this available for Group Blocks that have a solid color background set?

Handling Group blocks that have background/gradient should work well with the current API isMatch. Agreed.

Also I'm not aware if we can extract the theme's main background color programmatically to set as background to Cover if not one is set..

[kjellr]

Also I'm not aware if we can extract the theme's main background color programmatically to set as background to Cover if not one is set..

Yeah, I'm not sure that we can. Though it might get easier to do that if the theme's defined a background via theme.json.

[getsource]

Updated the PR to only offer transformation to cover when a background color or gradient is available in the Group block.