Flow inlines around floats

This implements the rest of the bulk of float support. Now inline
element flow around floats and floats can be pushed down by inline
elements before them.

Co-authored-by: Oriol Brufau <obrufau@igalia.com>

components/layout_2020/flow/float.rs

@@ -307,7 +307,7 @@ impl FloatContext {
     pub fn new(max_inline_size: Length) -> Self {
         let mut bands = FloatBandTree::new();
         bands = bands.insert(FloatBand {
-            top: Length::zero(),
+            top: Length::new(-f32::INFINITY),
             left: None,
             right: None,
         });

components/layout_2020/geom.rs

@@ -105,11 +105,11 @@ where
     }
 }
 
-impl flow_relative::Vec2<Length> {
+impl<T: Zero> flow_relative::Vec2<T> {
     pub fn zero() -> Self {
         Self {
-            inline: Length::zero(),
-            block: Length::zero(),
+            inline: T::zero(),
+            block: T::zero(),
         }
     }
 }
@@ -155,7 +155,7 @@ impl flow_relative::Vec2<Option<&'_ LengthPercentage>> {
     }
 }
 
-impl flow_relative::Rect<Length> {
+impl<T: Zero> flow_relative::Rect<T> {
     pub fn zero() -> Self {
         Self {
             start_corner: flow_relative::Vec2::zero(),
@@ -346,6 +346,17 @@ where
     }
 }
 
+impl<T: Zero> flow_relative::Sides<T> {
+    pub(crate) fn zero() -> flow_relative::Sides<T> {
+        flow_relative::Sides {
+            inline_start: T::zero(),
+            inline_end: T::zero(),
+            block_start: T::zero(),
+            block_end: T::zero(),
+        }
+    }
+}
+
 impl<T> flow_relative::Rect<T> {
     pub fn max_inline_position(&self) -> T
     where

components/layout_2020/lib.rs

@@ -3,6 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 #![deny(unsafe_code)]
+#![feature(once_cell)]
 
 #[macro_use]
 extern crate log;

components/layout_2020/style_ext.rs

@@ -65,6 +65,17 @@ pub(crate) struct PaddingBorderMargin {
     pub padding_border_sums: flow_relative::Vec2<Length>,
 }
 
+impl PaddingBorderMargin {
+    pub(crate) fn zero() -> Self {
+        Self {
+            padding: flow_relative::Sides::zero(),
+            border: flow_relative::Sides::zero(),
+            margin: flow_relative::Sides::zero(),
+            padding_border_sums: flow_relative::Vec2::zero(),
+        }
+    }
+}
+
 pub(crate) trait ComputedValuesExt {
     fn inline_size_is_length(&self) -> bool;
     fn inline_box_offsets_are_both_non_auto(&self) -> bool;