1 files changed, 36 insertions, 0 deletions
diff --git a/components/layout_2020/style_ext.rs b/components/layout_2020/style_ext.rs
index 8c145f23c6f..5748eac1b02 100644
--- a/components/layout_2020/style_ext.rs
+++ b/components/layout_2020/style_ext.rs
@@ -45,6 +45,9 @@ pub(crate) enum DisplayInside {
 
 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_non_auto(&self) -> bool;
     fn box_offsets(&self) -> flow_relative::Sides<LengthPercentageOrAuto>;
     fn box_size(&self) -> flow_relative::Vec2<LengthPercentageOrAuto>;
     fn min_box_size(&self) -> flow_relative::Vec2<LengthPercentageOrAuto>;
@@ -62,6 +65,39 @@ impl ComputedValuesExt for ComputedValues {
         (writing_mode, direction)
     }
 
+    fn writing_mode_is_horizontal(&self) -> bool {
+        match self.get_inherited_box().writing_mode {
+            WritingMode::HorizontalTb => true,
+            WritingMode::VerticalLr | WritingMode::VerticalRl => false,
+        }
+    }
+
+    fn inline_size_is_auto(&self) -> bool {
+        let position = self.get_position();
+        let size = if self.writing_mode_is_horizontal() {
+            position.width
+        } else {
+            position.height
+        };
+        matches!(size, Size::Auto)
+    }
+
+    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)
+        } else {
+            (position.top, position.bottom)
+        };
+        matches!(
+            offsets,
+            (
+                LengthPercentageOrAuto::LengthPercentage(_),
+                LengthPercentageOrAuto::LengthPercentage(_),
+            )
+        )
+    }
+
     #[inline]
     fn box_offsets(&self) -> flow_relative::Sides<LengthPercentageOrAuto> {
         let position = self.get_position();