Add max-content support for width, height, and flex-basis - #2012
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intergalacticspacehighway wants to merge 1 commit into
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Add max-content support for width, height, and flex-basis#2012intergalacticspacehighway wants to merge 1 commit into
max-content support for width, height, and flex-basis#2012intergalacticspacehighway wants to merge 1 commit into
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Implements the CSS max-content sizing keyword (css-sizing-3) for dimensions and flex-basis. The public setters existed but layout treated the keyword as auto; this makes them take effect. Keyword axes are measured with indefinite available space, then laid out at the measured (min/max clamped) size, so descendants resolve percentages against the resolved value and wrap within it. Covers root constraint minting (including a second height measure when a width clamp changes wrapping), the flex-basis cascade, the cross-axis path, the stretch re-layout guards, and absolute layout. Aspect-ratio transfer from a resolved keyword axis is deferred; the browser target is recorded in a disabled fixture case and the current behavior is pinned by MaxContentAspectRatioTest. Root cases that need a definite owner size are hand-written (gentest cannot express one).
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Why
Implements the CSS
max-contentsizing keyword forwidth,height, andflex-basis.The public setter (
YGNodeStyleSetWidthMaxContent) already exist, but layout silently treated the keyword asauto. This PR makes them take effect.We have a feature in Expo UI (RNHostView) that allows mounting a React Native hierarchy inside a SwiftUI hierarchy and allowing it to grow to it's natural size. So
max-contentwould be very useful in that case (autosizes are context dependent and often depend on parent dimensions)How
The
max-contentallows content to be laid out to it's intrinsic size, given an indefinite space in an axis. It requires changes to root, flex-basis, cross-axis (prevent stretch) and absolute layout path.Testing
Test includes browser generated
max-contentspec which aims to test all the control flow that is added in this PR and also some tests (specifying max-content to owner size) which is not supported by gentest yet.TODOs
min-width: max-content,max-width: max-contentnot supported yet.max-contentaxis yet (browsers do this). Documented in the disabledmax_content_with_aspect_ratiofixture case and pinned byMaxContentAspectRatioTest. Currently aspect ratio needs some work to make it spec compliant, it has the same issue when child has percentage dimensions.