Card thumbnail style: make a field layout's choice apply to every card, with an optional "auto"

[thupsi]

Context

A field layout can set how its element cards show their thumbnail: Normal (a thumbnail in a column beside the content) or Cover (the image fills the card, with the title and controls over it). Asset volumes default to Cover, other element types to Normal.

Cover isn't applied to every card in a source. A card falls back to Normal whenever its thumbnail can't cover it, which for assets currently means any of these:

• the file isn't an image, or the image could be transparent
• the image is smaller than 480×360
• the image is narrower than 3:4 or wider than 2:1

So one source can show a mix of cover and normal cards, depending on each entry's image.

The problem

An editor can't tell why some cards look one way and some another. The cause is the image's size, shape or transparency, but this reasoning is not self-evident to the end-user. Because the setting is per field layout, it looks like it should be consistent within an entry type.

Proposal

1. Enforce the selected style. If the field layout says Cover, every card in that layout is a cover card.
2. Maybe add an "Auto" option that keeps today's behaviour: Cover where the thumbnail can cover the card, Normal otherwise. People who like the current behaviour choose it explicitly.

Open questions

• What does Cover mean when the image can't fill the card? Options: crop it anyway, or show it contained on a neutral background.
• Which should be the default for existing layouts, Auto (nothing changes visibly) or the stored value (enforced)? Asset volumes currently default to Cover, which would suddenly apply to every file, including PDFs and small images.
• Entries without a thumbnail at all. They could stay as plain cards with no image. Option to use the entry type's icon as a thumbnail when an entry has none #20208 suggests an optional setting that shows the entry type's icon as the thumbnail when there is none, which would give a Cover card something to show for those entries.

[thupsi]

For comparison, same index, forced cover style (dark mode, but that's not important, just cooler 🙂)