layout: Layout for column flex-basis and minimum automatic size determination (#33068)

This change adds an expensive layout for the determination of minimum
automatic size and flex basis in process of flexbox layout. Currently,
the layout is not cached, so may be performed up to 2 more times than
necessary.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Oriol Brufau <obrufau@igalia.com>

components/layout_2020/flexbox/mod.rs

@@ -2,24 +2,105 @@
  * 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 geom::{FlexAxis, MainStartCrossStart};
 use serde::Serialize;
 use servo_arc::Arc as ServoArc;
+use style::properties::longhands::align_items::computed_value::T as AlignItems;
+use style::properties::longhands::flex_direction::computed_value::T as FlexDirection;
+use style::properties::longhands::flex_wrap::computed_value::T as FlexWrap;
 use style::properties::ComputedValues;
+use style::values::computed::{AlignContent, JustifyContent};
+use style::values::specified::align::AlignFlags;
 
 use crate::cell::ArcRefCell;
 use crate::formatting_contexts::IndependentFormattingContext;
+use crate::fragment_tree::BaseFragmentInfo;
 use crate::positioned::AbsolutelyPositionedBox;
 
 mod construct;
 mod geom;
 mod layout;
 
+/// A structure to hold the configuration of a flex container for use during layout
+/// and preferred width calculation.
+#[derive(Clone, Debug, Serialize)]
+pub(crate) struct FlexContainerConfig {
+    container_is_single_line: bool,
+    flex_axis: FlexAxis,
+    flex_direction: FlexDirection,
+    flex_direction_is_reversed: bool,
+    flex_wrap: FlexWrap,
+    flex_wrap_reverse: bool,
+    main_start_cross_start_sides_are: MainStartCrossStart,
+    align_content: AlignContent,
+    align_items: AlignItems,
+    justify_content: JustifyContent,
+}
+
+impl FlexContainerConfig {
+    fn new(container_style: &ComputedValues) -> FlexContainerConfig {
+        let flex_direction = container_style.clone_flex_direction();
+        let flex_axis = FlexAxis::from(flex_direction);
+        let flex_wrap = container_style.get_position().flex_wrap;
+        let container_is_single_line = match flex_wrap {
+            FlexWrap::Nowrap => true,
+            FlexWrap::Wrap | FlexWrap::WrapReverse => false,
+        };
+        let flex_direction_is_reversed = match flex_direction {
+            FlexDirection::Row | FlexDirection::Column => false,
+            FlexDirection::RowReverse | FlexDirection::ColumnReverse => true,
+        };
+        let flex_wrap_reverse = match flex_wrap {
+            FlexWrap::Nowrap | FlexWrap::Wrap => false,
+            FlexWrap::WrapReverse => true,
+        };
+
+        let align_content = container_style.clone_align_content();
+        let align_items = AlignItems(match container_style.clone_align_items().0 {
+            AlignFlags::AUTO | AlignFlags::NORMAL => AlignFlags::STRETCH,
+            align => align,
+        });
+        let justify_content = container_style.clone_justify_content();
+        let main_start_cross_start_sides_are =
+            MainStartCrossStart::from(flex_direction, flex_wrap_reverse);
+
+        FlexContainerConfig {
+            container_is_single_line,
+            flex_axis,
+            flex_direction,
+            flex_direction_is_reversed,
+            flex_wrap,
+            flex_wrap_reverse,
+            main_start_cross_start_sides_are,
+            align_content,
+            align_items,
+            justify_content,
+        }
+    }
+}
+
 #[derive(Debug, Serialize)]
 pub(crate) struct FlexContainer {
     children: Vec<ArcRefCell<FlexLevelBox>>,
 
     #[serde(skip_serializing)]
     style: ServoArc<ComputedValues>,
+
+    /// The configuration of this [`FlexContainer`].
+    config: FlexContainerConfig,
+}
+
+impl FlexContainer {
+    pub(crate) fn new(
+        style: &ServoArc<ComputedValues>,
+        children: Vec<ArcRefCell<FlexLevelBox>>,
+    ) -> Self {
+        Self {
+            children,
+            style: style.clone(),
+            config: FlexContainerConfig::new(style),
+        }
+    }
 }
 
 #[derive(Debug, Serialize)]
@@ -37,4 +118,8 @@ impl FlexItemBox {
     fn style(&self) -> &ServoArc<ComputedValues> {
         self.independent_formatting_context.style()
     }
+
+    fn base_fragment_info(&self) -> BaseFragmentInfo {
+        self.independent_formatting_context.base_fragment_info()
+    }
 }