Implement shrink-to-fit for abspos

components/layout_2020/positioned.rs

@@ -7,6 +7,7 @@ use crate::dom_traversal::{Contents, NodeExt};
 use crate::formatting_contexts::IndependentFormattingContext;
 use crate::fragments::{AnonymousFragment, BoxFragment, CollapsedBlockMargins, Fragment};
 use crate::geom::flow_relative::{Rect, Sides, Vec2};
+use crate::sizing::shrink_to_fit;
 use crate::style_ext::{ComputedValuesExt, Direction, DisplayInside, WritingMode};
 use crate::{ContainingBlock, DefiniteContainingBlock};
 use rayon::iter::{IntoParallelRefIterator, ParallelIterator};
@@ -51,8 +52,15 @@ impl AbsolutelyPositionedBox {
         display_inside: DisplayInside,
         contents: Contents<impl NodeExt<'dom>>,
     ) -> Self {
-        let request_content_sizes =
-            style.inline_size_is_auto() && !style.inline_box_offsets_are_both_auto();
+        // "Shrink-to-fit" in https://drafts.csswg.org/css2/visudet.html#abs-non-replaced-width
+        let request_content_sizes = {
+            // If inline-size is non-auto, that value is used without shrink-to-fit
+            style.inline_size_is_auto() &&
+            // If it is, then the only case where shrink-to-fit is *not* used is
+            // if both offsets are non-auto, leaving inline-size as the only variable
+            // in the constraint equation.
+            !style.inline_box_offsets_are_both_non_auto()
+        };
         Self {
             contents: IndependentFormattingContext::construct(
                 context,
@@ -278,8 +286,20 @@ impl<'a> AbsolutelyPositionedFragment<'a> {
                 Anchor::End(end) => cbis - end - pb.inline_sum() - margin.inline_sum(),
             };
 
-            // FIXME(nox): shrink-to-fit.
+            if self
+                .absolutely_positioned_box
+                .contents
+                .as_replaced()
+                .is_ok()
+            {
+                // FIXME: implement https://drafts.csswg.org/css2/visudet.html#abs-replaced-width
                 available_size
+            } else {
+                shrink_to_fit(
+                    &self.absolutely_positioned_box.contents.inline_content_sizes,
+                    available_size,
+                )
+            }
         });
 
         let containing_block_for_children = ContainingBlock {

components/layout_2020/sizing.rs

@@ -65,10 +65,7 @@ pub(crate) fn outer_inline_content_sizes_and_percentages(
     let specified = specified.map(|lp| lp.as_length());
     // The (inner) min/max-content are only used for 'auto'
     let mut outer = match specified.non_auto().flatten() {
-        None => inner_content_sizes
-            .as_ref()
-            .expect("Accessing content size that was not requested")
-            .clone(),
+        None => expect(inner_content_sizes).clone(),
         Some(length) => ContentSizes {
             min_content: length,
             max_content: length,
@@ -96,3 +93,20 @@ pub(crate) fn outer_inline_content_sizes_and_percentages(
 
     (outer, pbm_percentages)
 }
+
+/// https://drafts.csswg.org/css2/visudet.html#shrink-to-fit-float
+pub(crate) fn shrink_to_fit(
+    content_sizes: &Option<ContentSizes>,
+    available_size: Length,
+) -> Length {
+    let content_sizes = expect(content_sizes);
+    available_size
+        .max(content_sizes.min_content)
+        .min(content_sizes.max_content)
+}
+
+fn expect(content_sizes: &Option<ContentSizes>) -> &ContentSizes {
+    content_sizes
+        .as_ref()
+        .expect("Accessing content size that was not requested")
+}

components/layout_2020/style_ext.rs

@@ -45,7 +45,7 @@ pub(crate) trait ComputedValuesExt {
     fn writing_mode(&self) -> (WritingMode, Direction);
     fn writing_mode_is_horizontal(&self) -> bool;
     fn inline_size_is_auto(&self) -> bool;
-    fn inline_box_offsets_are_both_auto(&self) -> bool;
+    fn inline_box_offsets_are_both_non_auto(&self) -> bool;
     fn box_offsets(&self) -> flow_relative::Sides<LengthPercentageOrAuto>;
     fn box_size(&self) -> flow_relative::Vec2<LengthPercentageOrAuto>;
     fn padding(&self) -> flow_relative::Sides<LengthPercentage>;
@@ -78,7 +78,7 @@ impl ComputedValuesExt for ComputedValues {
         matches!(size, Size::Auto)
     }
 
-    fn inline_box_offsets_are_both_auto(&self) -> bool {
+    fn inline_box_offsets_are_both_non_auto(&self) -> bool {
         let position = self.get_position();
         let offsets = if self.writing_mode_is_horizontal() {
             (position.left, position.right)
@@ -87,7 +87,10 @@ impl ComputedValuesExt for ComputedValues {
         };
         matches!(
             offsets,
-            (LengthPercentageOrAuto::Auto, LengthPercentageOrAuto::Auto)
+            (
+                LengthPercentageOrAuto::LengthPercentage(_),
+                LengthPercentageOrAuto::LengthPercentage(_),
+            )
         )
     }
 

tests/wpt/metadata-layout-2020/css/CSS2/box-display/containing-block-008.xht.ini

@@ -1,2 +0,0 @@
-[containing-block-008.xht]
-  expected: FAIL

tests/wpt/metadata-layout-2020/css/CSS2/box-display/containing-block-010.xht.ini

@@ -1,2 +0,0 @@
-[containing-block-010.xht]
-  expected: FAIL