Do Style properties matter for leaf node?

[coderedart]

From what I understand, leaf nodes use the measure closure to calculate its size (based on the constraints provided to it). Then, does taffy ever care about the style props of the leaf node? Or are all style props ignored on leaf nodes?

[nicoburns]

Yes:

• They control it's position in it's parent layout. Things like grid_row and flex-basis apply to leaf nodes.
• Padding, borders, and margin are applied on top of the size the measure function returns.
• Aspect ratio applies to leaf nodes

[nicoburns]

Yes they do. The sizes returned by the measure function are the node's "intrinsic sizes" (min-content size, max-content size, and fit-content size depending on the AvailableSpace parameter passed). In many cases those will be overriden by size, min_size, max_size, flex_basis, etc.

[Hexlord]

Aspect ratio applies to leaf nodes

On that topic, is there a reason compute_leaf_layout does not call maybe_apply_aspect_ratio for style_max_size, but compute_flexbox_layout does for max_size?
fyi @nicoburns

[nicoburns]

@Hexlord IIRC there were issues with Taffy not having access to the leaf node's "intrinsic aspect ratio" (e.g. the aspect ratio generated by an image's native dimensions). The decision at the time was the pass &Style into the measure function to let it apply aspect ratio rather than have the measure function pass up it's intrinsic aspect ratio into Taffy. Partly because we didn't fully understand the requirements, and that was a more flexible option.

Part of the plan here is to add a built-in "replaced" layout mode for things like images/videos/etc that are truly "leaf" content (the web specs call these "replaced"). That would be based on an upstreamed version of this function in Blitz https://github.com/DioxusLabs/blitz/blob/3df989ebed39b21f104f2357a90f508f793c5c13/packages/blitz-dom/src/layout/replaced.rs.

The measure function would then likely be expanded to support arbitrary layout modes (by for example returning LayoutOutput rather than just a size).

[Hexlord]

@nicoburns I see your reasoning, however 1) it (style_max_size) seems to be the only place that ignores aspect ratio (size and min_size do respect it in both functions, and max_size respects it in flex); 2) aspect ratio should not be dynamic based on layout, it is a value that should just be set inside Style by Image/Video directly, so it should not relate to measure function in any way?

Your point might be valid (also I am new to all of this), but in this scenario it feels like a simple typo of missing the aspect ratio application for max_size specifically

[nicoburns]

Perhaps images/video could just set the aspect_ratio style. But I suspect we'd need to add an additional "intrinsic aspect ratio" style to account for differences in priority of user-specific aspect ratios and intrinsic aspect ratios.