Auto merge of #26838 - servo:flexbox, r=nox

Flexbox, the boring parts

I have a local branch starting to implement https://drafts.csswg.org/css-flexbox/#layout-algorithm. It’s not PR-ready yet, but it’s going to be large so here are some of the less interesting parts meaningful by themselves. Landing the module split in particular will help reduce merge conflicts.

CC https://github.com/servo/servo/issues/26639

components/layout_2020/flexbox/construct.rs

@@ -2,36 +2,21 @@
  * 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 super::{FlexContainer, FlexLevelBox};
 use crate::cell::ArcRefCell;
 use crate::context::LayoutContext;
 use crate::dom_traversal::{
     BoxSlot, Contents, NodeAndStyleInfo, NodeExt, NonReplacedContents, TraversalHandler,
 };
 use crate::element_data::LayoutBox;
-use crate::formatting_contexts::{IndependentFormattingContext, IndependentLayout};
+use crate::formatting_contexts::IndependentFormattingContext;
 use crate::fragments::Tag;
-use crate::positioned::{AbsolutelyPositionedBox, PositioningContext};
+use crate::positioned::AbsolutelyPositionedBox;
 use crate::sizing::{BoxContentSizes, ContentSizes, ContentSizesRequest};
 use crate::style_ext::DisplayGeneratingBox;
-use crate::ContainingBlock;
 use rayon::iter::{IntoParallelIterator, ParallelIterator};
 use std::borrow::Cow;
-use style::values::computed::Length;
 use style::values::specified::text::TextDecorationLine;
-use style::Zero;
-
-// FIXME: `min-width: auto` is not zero: https://drafts.csswg.org/css-flexbox/#min-size-auto
-
-#[derive(Debug, Serialize)]
-pub(crate) struct FlexContainer {
-    children: Vec<ArcRefCell<FlexLevelBox>>,
-}
-
-#[derive(Debug, Serialize)]
-pub(crate) enum FlexLevelBox {
-    FlexItem(IndependentFormattingContext),
-    OutOfFlowAbsolutelyPositionedBox(ArcRefCell<AbsolutelyPositionedBox>),
-}
 
 impl FlexContainer {
     pub fn construct<'dom>(
@@ -230,23 +215,3 @@ where
         FlexContainer { children }
     }
 }
-
-impl FlexContainer {
-    pub(crate) fn layout(
-        &self,
-        layout_context: &LayoutContext,
-        positioning_context: &mut PositioningContext,
-        containing_block: &ContainingBlock,
-        tree_rank: usize,
-    ) -> IndependentLayout {
-        // FIXME
-        let _ = layout_context;
-        let _ = positioning_context;
-        let _ = containing_block;
-        let _ = tree_rank;
-        IndependentLayout {
-            fragments: Vec::new(),
-            content_block_size: Length::zero(),
-        }
-    }
-}

components/layout_2020/flexbox/layout.rs

@@ -0,0 +1,33 @@
+/* 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 super::FlexContainer;
+use crate::context::LayoutContext;
+use crate::formatting_contexts::IndependentLayout;
+use crate::positioned::PositioningContext;
+use crate::ContainingBlock;
+use style::values::computed::Length;
+use style::Zero;
+
+// FIXME: `min-width: auto` is not zero: https://drafts.csswg.org/css-flexbox/#min-size-auto
+
+impl FlexContainer {
+    pub(crate) fn layout(
+        &self,
+        layout_context: &LayoutContext,
+        positioning_context: &mut PositioningContext,
+        containing_block: &ContainingBlock,
+        tree_rank: usize,
+    ) -> IndependentLayout {
+        // FIXME
+        let _ = layout_context;
+        let _ = positioning_context;
+        let _ = containing_block;
+        let _ = tree_rank;
+        IndependentLayout {
+            fragments: Vec::new(),
+            content_block_size: Length::zero(),
+        }
+    }
+}

components/layout_2020/flexbox/mod.rs

@@ -0,0 +1,21 @@
+/* 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::cell::ArcRefCell;
+use crate::formatting_contexts::IndependentFormattingContext;
+use crate::positioned::AbsolutelyPositionedBox;
+
+mod construct;
+mod layout;
+
+#[derive(Debug, Serialize)]
+pub(crate) struct FlexContainer {
+    children: Vec<ArcRefCell<FlexLevelBox>>,
+}
+
+#[derive(Debug, Serialize)]
+pub(crate) enum FlexLevelBox {
+    FlexItem(IndependentFormattingContext),
+    OutOfFlowAbsolutelyPositionedBox(ArcRefCell<AbsolutelyPositionedBox>),
+}

components/style/properties/longhands/position.mako.rs

@@ -72,7 +72,8 @@ ${helpers.predefined_type(
 ${helpers.single_keyword(
     "flex-direction",
     "row row-reverse column column-reverse",
-    engines="gecko servo-2013",
+    engines="gecko servo-2013 servo-2020",
+    servo_2020_pref="layout.flexbox.enabled",
     spec="https://drafts.csswg.org/css-flexbox/#flex-direction-property",
     extra_prefixes="webkit",
     animation_value_type="discrete",
@@ -83,7 +84,8 @@ ${helpers.single_keyword(
 ${helpers.single_keyword(
     "flex-wrap",
     "nowrap wrap wrap-reverse",
-    engines="gecko servo-2013",
+    engines="gecko servo-2013 servo-2020",
+    servo_2020_pref="layout.flexbox.enabled",
     spec="https://drafts.csswg.org/css-flexbox/#flex-wrap-property",
     extra_prefixes="webkit",
     animation_value_type="discrete",
@@ -205,7 +207,8 @@ ${helpers.predefined_type(
     "flex-grow",
     "NonNegativeNumber",
     "From::from(0.0)",
-    engines="gecko servo-2013",
+    engines="gecko servo-2013 servo-2020",
+    servo_2020_pref="layout.flexbox.enabled",
     spec="https://drafts.csswg.org/css-flexbox/#flex-grow-property",
     extra_prefixes="webkit",
     animation_value_type="NonNegativeNumber",
@@ -216,7 +219,8 @@ ${helpers.predefined_type(
     "flex-shrink",
     "NonNegativeNumber",
     "From::from(1.0)",
-    engines="gecko servo-2013",
+    engines="gecko servo-2013 servo-2020",
+    servo_2020_pref="layout.flexbox.enabled",
     spec="https://drafts.csswg.org/css-flexbox/#flex-shrink-property",
     extra_prefixes="webkit",
     animation_value_type="NonNegativeNumber",
@@ -278,7 +282,8 @@ ${helpers.predefined_type(
     "flex-basis",
     "FlexBasis",
     "computed::FlexBasis::auto()",
-    engines="gecko servo-2013",
+    engines="gecko servo-2013 servo-2020",
+    servo_2020_pref="layout.flexbox.enabled",
     spec="https://drafts.csswg.org/css-flexbox/#flex-basis-property",
     extra_prefixes="webkit",
     animation_value_type="FlexBasis",

components/style/properties/shorthands/position.mako.rs

@@ -5,7 +5,8 @@
 <%namespace name="helpers" file="/helpers.mako.rs" />
 
 <%helpers:shorthand name="flex-flow"
-                    engines="gecko servo-2013"
+                    engines="gecko servo-2013 servo-2020",
+                    servo_2020_pref="layout.flexbox.enabled",
                     sub_properties="flex-direction flex-wrap"
                     extra_prefixes="webkit"
                     derive_serialize="True"
@@ -45,7 +46,8 @@
 </%helpers:shorthand>
 
 <%helpers:shorthand name="flex"
-                    engines="gecko servo-2013"
+                    engines="gecko servo-2013 servo-2020",
+                    servo_2020_pref="layout.flexbox.enabled",
                     sub_properties="flex-grow flex-shrink flex-basis"
                     extra_prefixes="webkit"
                     derive_serialize="True"