1 files changed, 129 insertions, 0 deletions
diff --git a/components/layout_2020/style_ext.rs b/components/layout_2020/style_ext.rs
new file mode 100644
index 00000000000..bb0b0411dec
--- /dev/null
+++ b/components/layout_2020/style_ext.rs
@@ -0,0 +1,129 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+use crate::geom::{flow_relative, physical};
+use style::properties::ComputedValues;
+use style::values::computed::{
+    Display as PackedDisplay, Length, LengthPercentage, LengthPercentageOrAuto, Size,
+};
+
+pub use style::computed_values::direction::T as Direction;
+pub use style::computed_values::position::T as Position;
+pub use style::computed_values::writing_mode::T as WritingMode;
+pub use style::values::specified::box_::{DisplayInside, DisplayOutside};
+
+#[derive(Clone, Copy, Eq, PartialEq)]
+pub(crate) enum Display {
+    None,
+    Contents,
+    GeneratingBox(DisplayGeneratingBox),
+}
+
+#[derive(Clone, Copy, Eq, PartialEq)]
+pub(crate) enum DisplayGeneratingBox {
+    OutsideInside {
+        outside: DisplayOutside,
+        inside: DisplayInside,
+        // list_item: bool,
+    },
+    // Layout-internal display types go here:
+    // https://drafts.csswg.org/css-display-3/#layout-specific-display
+}
+
+pub(crate) trait ComputedValuesExt {
+    fn writing_mode(&self) -> (WritingMode, Direction);
+    fn box_offsets(&self) -> flow_relative::Sides<LengthPercentageOrAuto>;
+    fn box_size(&self) -> flow_relative::Vec2<LengthPercentageOrAuto>;
+    fn padding(&self) -> flow_relative::Sides<LengthPercentage>;
+    fn border_width(&self) -> flow_relative::Sides<Length>;
+    fn margin(&self) -> flow_relative::Sides<LengthPercentageOrAuto>;
+}
+
+impl ComputedValuesExt for ComputedValues {
+    fn writing_mode(&self) -> (WritingMode, Direction) {
+        let inherited_box = self.get_inherited_box();
+        let writing_mode = inherited_box.writing_mode;
+        let direction = inherited_box.direction;
+        (writing_mode, direction)
+    }
+
+    #[inline]
+    fn box_offsets(&self) -> flow_relative::Sides<LengthPercentageOrAuto> {
+        let position = self.get_position();
+        physical::Sides {
+            top: position.top,
+            left: position.left,
+            bottom: position.bottom,
+            right: position.right,
+        }
+        .to_flow_relative(self.writing_mode())
+    }
+
+    #[inline]
+    fn box_size(&self) -> flow_relative::Vec2<LengthPercentageOrAuto> {
+        let position = self.get_position();
+        physical::Vec2 {
+            x: size_to_length(position.width),
+            y: size_to_length(position.height),
+        }
+        .size_to_flow_relative(self.writing_mode())
+    }
+
+    #[inline]
+    fn padding(&self) -> flow_relative::Sides<LengthPercentage> {
+        let padding = self.get_padding();
+        physical::Sides {
+            top: padding.padding_top.0,
+            left: padding.padding_left.0,
+            bottom: padding.padding_bottom.0,
+            right: padding.padding_right.0,
+        }
+        .to_flow_relative(self.writing_mode())
+    }
+
+    fn border_width(&self) -> flow_relative::Sides<Length> {
+        let border = self.get_border();
+        physical::Sides {
+            top: border.border_top_width.0,
+            left: border.border_left_width.0,
+            bottom: border.border_bottom_width.0,
+            right: border.border_right_width.0,
+        }
+        .to_flow_relative(self.writing_mode())
+    }
+
+    fn margin(&self) -> flow_relative::Sides<LengthPercentageOrAuto> {
+        let margin = self.get_margin();
+        physical::Sides {
+            top: margin.margin_top,
+            left: margin.margin_left,
+            bottom: margin.margin_bottom,
+            right: margin.margin_right,
+        }
+        .to_flow_relative(self.writing_mode())
+    }
+}
+
+impl From<PackedDisplay> for Display {
+    fn from(packed_display: PackedDisplay) -> Self {
+        if packed_display == PackedDisplay::None {
+            return Self::None;
+        }
+        if packed_display == PackedDisplay::Contents {
+            return Self::Contents;
+        }
+        Self::GeneratingBox(DisplayGeneratingBox::OutsideInside {
+            outside: packed_display.outside(),
+            inside: packed_display.inside(),
+            // list_item: packed_display.is_list_item(),
+        })
+    }
+}
+
+fn size_to_length(size: Size) -> LengthPercentageOrAuto {
+    match size {
+        Size::LengthPercentage(length) => LengthPercentageOrAuto::LengthPercentage(length.0),
+        Size::Auto => LengthPercentageOrAuto::Auto,
+    }
+}