Separate contained grid contributions from stretch

vendor/taffy/src/compute/grid/types/grid_item.rs

@@ -31,6 +31,8 @@ pub(in super::super) struct GridItem {
     /// Is it a compressible replaced element?
     /// https://drafts.csswg.org/css-sizing-3/#min-content-zero
     pub is_compressible_replaced: bool,
+    /// Whether descendants are ignored for intrinsic size contributions in each axis.
+    pub intrinsic_size_containment: Size<bool>,
     /// The item's overflow style
     pub overflow: Point<Overflow>,
     /// The item's box_sizing style
@@ -108,6 +110,7 @@ impl GridItem {
             row: row_span,
             column: col_span,
             is_compressible_replaced: style.is_compressible_replaced(),
+            intrinsic_size_containment: style.intrinsic_size_containment(),
             overflow: style.overflow(),
             box_sizing: style.box_sizing(),
             size: style.size(),
@@ -425,6 +428,13 @@ impl GridItem {
         available_space: Size<Option<f32>>,
     ) -> f32 {
         let known_dimensions = self.known_dimensions(tree, grid_area_size);
+        if self.intrinsic_size_containment.get(axis) {
+            let padding =
+                self.padding.resolve_or_zero(grid_area_size.width, |val, basis| tree.calc(val, basis));
+            let border =
+                self.border.resolve_or_zero(grid_area_size.width, |val, basis| tree.calc(val, basis));
+            return known_dimensions.get(axis).unwrap_or((padding + border).sum_axes().get(axis));
+        }
         // The child sees the grid area as its containing block during intrinsic measurement, so
         // percentage box properties resolve against the grid area when that size is definite.
         // Spec:
@@ -469,6 +479,13 @@ impl GridItem {
         available_space: Size<Option<f32>>,
     ) -> f32 {
         let known_dimensions = self.known_dimensions(tree, grid_area_size);
+        if self.intrinsic_size_containment.get(axis) {
+            let padding =
+                self.padding.resolve_or_zero(grid_area_size.width, |val, basis| tree.calc(val, basis));
+            let border =
+                self.border.resolve_or_zero(grid_area_size.width, |val, basis| tree.calc(val, basis));
+            return known_dimensions.get(axis).unwrap_or((padding + border).sum_axes().get(axis));
+        }
         // See the min-content path above. Max-content measurement uses the same containing-block
         // basis so percentage-dependent item geometry is measured from the grid area rather than
         // from the container.

vendor/taffy/src/style/grid.rs

@@ -237,6 +237,12 @@ pub trait GridContainerStyle: CoreStyle {
 
 /// The set of styles required for a CSS Grid item (child of a CSS Grid container)
 pub trait GridItemStyle: CoreStyle {
+    /// Whether descendants are ignored for intrinsic size contributions in each axis.
+    #[inline(always)]
+    fn intrinsic_size_containment(&self) -> Size<bool> {
+        Size { width: false, height: false }
+    }
+
     /// Defines which row in the grid the item should start and end at
     #[inline(always)]
     fn grid_row(&self) -> Line<GridPlacement<Self::CustomIdent>> {

vendor/taffy/src/style/mod.rs

@@ -442,6 +442,11 @@ pub struct Style<S: CheapCloneStr = DefaultCheapStr> {
     /// Is it a replaced element like an image or form field?
     /// <https://drafts.csswg.org/css-sizing-3/#min-content-zero>
     pub item_is_replaced: bool,
+    /// Whether descendants are ignored for intrinsic size contributions in each axis.
+    ///
+    /// Ordinary final layout is unaffected, allowing an auto-sized grid item to
+    /// retain stretch alignment after its contained intrinsic contribution is removed.
+    pub intrinsic_size_containment: Size<bool>,
     /// Should size styles apply to the content box or the border box of the node
     pub box_sizing: BoxSizing,
     /// Sets the direction of text, table and grid columns, and horizontal overflow.
@@ -591,6 +596,7 @@ impl<S: CheapCloneStr> Style<S> {
         display: Display::DEFAULT,
         item_is_table: false,
         item_is_replaced: false,
+        intrinsic_size_containment: Size { width: false, height: false },
         box_sizing: BoxSizing::BorderBox,
         direction: Direction::Ltr,
         overflow: Point { x: Overflow::Visible, y: Overflow::Visible },
@@ -1150,6 +1156,10 @@ impl<T: GridContainerStyle> GridContainerStyle for &'_ T {
 
 #[cfg(feature = "grid")]
 impl<S: CheapCloneStr> GridItemStyle for Style<S> {
+    #[inline(always)]
+    fn intrinsic_size_containment(&self) -> Size<bool> {
+        self.intrinsic_size_containment
+    }
     #[inline(always)]
     fn grid_row(&self) -> Line<GridPlacement<S>> {
         // TODO: Investigate eliminating clone
@@ -1172,6 +1182,10 @@ impl<S: CheapCloneStr> GridItemStyle for Style<S> {
 
 #[cfg(feature = "grid")]
 impl<T: GridItemStyle> GridItemStyle for &'_ T {
+    #[inline(always)]
+    fn intrinsic_size_containment(&self) -> Size<bool> {
+        (*self).intrinsic_size_containment()
+    }
     #[inline(always)]
     fn grid_row(&self) -> Line<GridPlacement<Self::CustomIdent>> {
         (*self).grid_row()
@@ -1208,6 +1222,7 @@ mod tests {
             display: Default::default(),
             item_is_table: false,
             item_is_replaced: false,
+            intrinsic_size_containment: Size { width: false, height: false },
             box_sizing: Default::default(),
             #[cfg(feature = "float_layout")]
             float: Default::default(),