Start supporting images in layout 2020

8 files changed, 249 insertions, 46 deletions

diff --git a/components/layout_2020/Cargo.toml b/components/layout_2020/Cargo.toml
index 7bfe7cbea16..5a28da8d9ee 100644
--- a/components/layout_2020/Cargo.toml
+++ b/components/layout_2020/Cargo.toml
@@ -22,6 +22,7 @@ gfx_traits = {path = "../gfx_traits"}
 ipc-channel = "0.12"
 libc = "0.2"
 msg = {path = "../msg"}
+net_traits = {path = "../net_traits"}
 range = {path = "../range"}
 rayon = "1"
 rayon_croissant = "0.1.1"
diff --git a/components/layout_2020/display_list.rs b/components/layout_2020/display_list.rs
index 5dc5ecb96ad..16592a8a5d0 100644
--- a/components/layout_2020/display_list.rs
+++ b/components/layout_2020/display_list.rs
@@ -78,6 +78,34 @@ impl Fragment {
                     .wr
                     .push_text(&common, rect.into(), &glyphs, t.font_key, rgba(color), None);
             },
+            Fragment::Image(i) => {
+                use style::computed_values::image_rendering::T as ImageRendering;
+                is_contentful.0 = true;
+                let rect = i
+                    .content_rect
+                    .to_physical(i.style.writing_mode(), containing_block)
+                    .translate(&containing_block.top_left);
+                let common = CommonItemProperties {
+                    clip_rect: rect.clone().into(),
+                    clip_id: wr::ClipId::root(builder.pipeline_id),
+                    spatial_id: wr::SpatialId::root_scroll_node(builder.pipeline_id),
+                    hit_info: None,
+                    // TODO(gw): Make use of the WR backface visibility functionality.
+                    flags: PrimitiveFlags::default(),
+                };
+                builder.wr.push_image(
+                    &common,
+                    rect.into(),
+                    match i.style.get_inherited_box().image_rendering {
+                        ImageRendering::Auto => wr::ImageRendering::Auto,
+                        ImageRendering::CrispEdges => wr::ImageRendering::CrispEdges,
+                        ImageRendering::Pixelated => wr::ImageRendering::Pixelated,
+                    },
+                    wr::AlphaType::PremultipliedAlpha,
+                    i.image_key,
+                    wr::ColorF::WHITE,
+                );
+            },
         }
     }
 }
diff --git a/components/layout_2020/dom_traversal.rs b/components/layout_2020/dom_traversal.rs
index 732dc1afdc9..ee368566bef 100644
--- a/components/layout_2020/dom_traversal.rs
+++ b/components/layout_2020/dom_traversal.rs
@@ -3,18 +3,22 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use crate::element_data::{LayoutBox, LayoutDataForElement};
+use crate::geom::physical::Vec2;
 use crate::replaced::ReplacedContent;
 use crate::style_ext::{Display, DisplayGeneratingBox, DisplayInside, DisplayOutside};
 use crate::wrapper::GetRawData;
 use atomic_refcell::{AtomicRefCell, AtomicRefMut};
+use net_traits::image::base::{Image as NetImage, ImageMetadata};
 use script_layout_interface::wrapper_traits::{LayoutNode, ThreadSafeLayoutNode};
 use servo_arc::Arc as ServoArc;
 use std::convert::TryInto;
 use std::marker::PhantomData as marker;
+use std::sync::Arc;
 use style::context::SharedStyleContext;
 use style::dom::TNode;
 use style::properties::ComputedValues;
 use style::selector_parser::PseudoElement;
+use style::values::computed::Length;
 
 #[derive(Clone, Copy)]
 pub enum WhichPseudoElement {
@@ -90,11 +94,12 @@ fn traverse_element<'dom, Node>(
 ) where
     Node: NodeExt<'dom>,
 {
+    let replaced = ReplacedContent::for_element(element);
     let style = element.style(context);
     match Display::from(style.get_box().display) {
         Display::None => element.unset_boxes_in_subtree(),
         Display::Contents => {
-            if ReplacedContent::for_element(element, context).is_some() {
+            if replaced.is_some() {
                 // `display: content` on a replaced element computes to `display: none`
                 // <https://drafts.csswg.org/css-display-3/#valdef-display-contents>
                 element.unset_boxes_in_subtree()
@@ -107,10 +112,7 @@ fn traverse_element<'dom, Node>(
             handler.handle_element(
                 &style,
                 display,
-                match ReplacedContent::for_element(element, context) {
-                    Some(replaced) => Contents::Replaced(replaced),
-                    None => Contents::OfElement(element),
-                },
+                replaced.map_or(Contents::OfElement(element), Contents::Replaced),
                 element.element_box_slot(),
             );
         },
@@ -287,6 +289,7 @@ impl Drop for BoxSlot<'_> {
 pub(crate) trait NodeExt<'dom>: 'dom + Copy + LayoutNode + Send + Sync {
     fn is_element(self) -> bool;
     fn as_text(self) -> Option<String>;
+    fn as_image(self) -> Option<(Option<Arc<NetImage>>, Vec2<Length>)>;
     fn first_child(self) -> Option<Self>;
     fn next_sibling(self) -> Option<Self>;
     fn parent_node(self) -> Option<Self>;
@@ -315,6 +318,26 @@ where
         }
     }
 
+    fn as_image(self) -> Option<(Option<Arc<NetImage>>, Vec2<Length>)> {
+        let node = self.to_threadsafe();
+        let (resource, metadata) = node.image_data()?;
+        let (width, height) = resource
+            .as_ref()
+            .map(|image| (image.width, image.height))
+            .or_else(|| metadata.map(|metadata| (metadata.width, metadata.height)))
+            .unwrap_or((0, 0));
+        let (mut width, mut height) = (width as f32, height as f32);
+        if let Some(density) = node.image_density().filter(|density| *density != 1.) {
+            width = (width as f64 / density) as f32;
+            height = (height as f64 / density) as f32;
+        }
+        let size = Vec2 {
+            x: Length::new(width),
+            y: Length::new(height),
+        };
+        Some((resource, size))
+    }
+
     fn first_child(self) -> Option<Self> {
         TNode::first_child(&self)
     }
diff --git a/components/layout_2020/flow/mod.rs b/components/layout_2020/flow/mod.rs
index 5c2e3d8e988..4b887abde35 100644
--- a/components/layout_2020/flow/mod.rs
+++ b/components/layout_2020/flow/mod.rs
@@ -15,6 +15,7 @@ use crate::geom::flow_relative::{Rect, Sides, Vec2};
 use crate::positioned::{
     adjust_static_positions, AbsolutelyPositionedBox, AbsolutelyPositionedFragment,
 };
+use crate::replaced::ReplacedContent;
 use crate::style_ext::{ComputedValuesExt, Position};
 use crate::{relative_adjustement, ContainingBlock};
 use rayon::iter::{IndexedParallelIterator, IntoParallelRefIterator, ParallelIterator};
@@ -295,10 +296,12 @@ impl BlockLevelBox {
                 ))
             },
             BlockLevelBox::Independent(contents) => match contents.as_replaced() {
-                Ok(replaced) => {
-                    // FIXME
-                    match *replaced {}
-                },
+                Ok(replaced) => Fragment::Box(layout_in_flow_replaced_block_level(
+                    layout_context,
+                    containing_block,
+                    &contents.style,
+                    replaced,
+                )),
                 Err(non_replaced) => Fragment::Box(layout_in_flow_non_replaced_block_level(
                     layout_context,
                     containing_block,
@@ -360,24 +363,15 @@ fn layout_in_flow_non_replaced_block_level<'a>(
     let box_size = style.box_size();
     let inline_size = box_size.inline.percentage_relative_to(cbis);
     if let LengthOrAuto::LengthPercentage(is) = inline_size {
-        let inline_margins = cbis - is - pb.inline_sum();
-        match (
-            &mut computed_margin.inline_start,
-            &mut computed_margin.inline_end,
-        ) {
-            (s @ &mut LengthOrAuto::Auto, e @ &mut LengthOrAuto::Auto) => {
-                *s = LengthOrAuto::LengthPercentage(inline_margins / 2.);
-                *e = LengthOrAuto::LengthPercentage(inline_margins / 2.);
-            },
-            (s @ &mut LengthOrAuto::Auto, &mut LengthOrAuto::LengthPercentage(e)) => {
-                *s = LengthOrAuto::LengthPercentage(inline_margins - e);
-            },
-            (&mut LengthOrAuto::LengthPercentage(s), e) => {
-                // Either the inline-end margin is auto,
-                // or we’re over-constrained and we do as if it were.
-                *e = LengthOrAuto::LengthPercentage(inline_margins - s);
-            },
-        }
+        let (margin_inline_start, margin_inline_end) = solve_inline_margins_for_in_flow_block_level(
+            containing_block,
+            pb.inline_sum(),
+            computed_margin.inline_start,
+            computed_margin.inline_end,
+            is,
+        );
+        computed_margin.inline_start = LengthOrAuto::LengthPercentage(margin_inline_start);
+        computed_margin.inline_end = LengthOrAuto::LengthPercentage(margin_inline_end);
     }
     let margin = computed_margin.auto_is(Length::zero);
     let mut block_margins_collapsed_with_children = CollapsedBlockMargins::from_margin(&margin);
@@ -476,3 +470,104 @@ fn layout_in_flow_non_replaced_block_level<'a>(
         block_margins_collapsed_with_children,
     }
 }
+
+/// https://drafts.csswg.org/css2/visudet.html#block-replaced-width
+/// https://drafts.csswg.org/css2/visudet.html#inline-replaced-width
+/// https://drafts.csswg.org/css2/visudet.html#inline-replaced-height
+fn layout_in_flow_replaced_block_level<'a>(
+    layout_context: &LayoutContext,
+    containing_block: &ContainingBlock,
+    style: &Arc<ComputedValues>,
+    replaced: &ReplacedContent,
+) -> BoxFragment {
+    let cbis = containing_block.inline_size;
+    let padding = style.padding().percentages_relative_to(cbis);
+    let border = style.border_width();
+    let computed_margin = style.margin().percentages_relative_to(cbis);
+    let pb = &padding + &border;
+    let mode = style.writing_mode();
+    // FIXME(nox): We shouldn't pretend we always have a fully known intrinsic size.
+    let intrinsic_size = replaced.intrinsic_size.size_to_flow_relative(mode);
+    // FIXME(nox): This can divide by zero.
+    let intrinsic_ratio = intrinsic_size.inline.px() / intrinsic_size.block.px();
+    let box_size = style.box_size();
+    let inline_size = box_size.inline.percentage_relative_to(cbis);
+    let block_size = box_size
+        .block
+        .maybe_percentage_relative_to(containing_block.block_size.non_auto());
+    let (inline_size, block_size) = match (inline_size, block_size) {
+        (LengthOrAuto::LengthPercentage(inline), LengthOrAuto::LengthPercentage(block)) => {
+            (inline, block)
+        },
+        (LengthOrAuto::LengthPercentage(inline), LengthOrAuto::Auto) => {
+            (inline, inline / intrinsic_ratio)
+        },
+        (LengthOrAuto::Auto, LengthOrAuto::LengthPercentage(block)) => {
+            (block * intrinsic_ratio, block)
+        },
+        (LengthOrAuto::Auto, LengthOrAuto::Auto) => (intrinsic_size.inline, intrinsic_size.block),
+    };
+    let (margin_inline_start, margin_inline_end) = solve_inline_margins_for_in_flow_block_level(
+        containing_block,
+        pb.inline_sum(),
+        computed_margin.inline_start,
+        computed_margin.inline_end,
+        inline_size,
+    );
+    let margin = Sides {
+        inline_start: margin_inline_start,
+        inline_end: margin_inline_end,
+        block_start: computed_margin.block_start.auto_is(Length::zero),
+        block_end: computed_margin.block_end.auto_is(Length::zero),
+    };
+    let containing_block_for_children = ContainingBlock {
+        inline_size,
+        block_size: LengthOrAuto::LengthPercentage(block_size),
+        mode,
+    };
+    // https://drafts.csswg.org/css-writing-modes/#orthogonal-flows
+    assert_eq!(
+        containing_block.mode, containing_block_for_children.mode,
+        "Mixed writing modes are not supported yet"
+    );
+    let independent_layout = replaced.layout(layout_context, style, &containing_block_for_children);
+    let relative_adjustement = relative_adjustement(
+        style,
+        inline_size,
+        LengthOrAuto::LengthPercentage(block_size),
+    );
+    let content_rect = Rect {
+        start_corner: Vec2 {
+            block: pb.block_start + relative_adjustement.block,
+            inline: pb.inline_start + relative_adjustement.inline + margin.inline_start,
+        },
+        size: Vec2 {
+            block: block_size,
+            inline: inline_size,
+        },
+    };
+    BoxFragment {
+        style: style.clone(),
+        children: independent_layout.fragments,
+        content_rect,
+        padding,
+        border,
+        block_margins_collapsed_with_children: CollapsedBlockMargins::from_margin(&margin),
+        margin,
+    }
+}
+
+fn solve_inline_margins_for_in_flow_block_level(
+    containing_block: &ContainingBlock,
+    padding_border_inline_sum: Length,
+    computed_margin_inline_start: LengthOrAuto,
+    computed_margin_inline_end: LengthOrAuto,
+    inline_size: Length,
+) -> (Length, Length) {
+    let inline_margins = containing_block.inline_size - padding_border_inline_sum - inline_size;
+    match (computed_margin_inline_start, computed_margin_inline_end) {
+        (LengthOrAuto::Auto, LengthOrAuto::Auto) => (inline_margins / 2., inline_margins / 2.),
+        (LengthOrAuto::Auto, LengthOrAuto::LengthPercentage(end)) => (inline_margins - end, end),
+        (LengthOrAuto::LengthPercentage(start), _) => (start, inline_margins - start),
+    }
+}
diff --git a/components/layout_2020/flow/root.rs b/components/layout_2020/flow/root.rs
index 8df332b90d6..f4cb0abafb9 100644
--- a/components/layout_2020/flow/root.rs
+++ b/components/layout_2020/flow/root.rs
@@ -48,7 +48,7 @@ fn construct_for_root_element<'dom>(
     root_element: impl NodeExt<'dom>,
 ) -> (ContainsFloats, Vec<Arc<BlockLevelBox>>) {
     let style = root_element.style(context);
-    let replaced = ReplacedContent::for_element(root_element, context);
+    let replaced = ReplacedContent::for_element(root_element);
     let box_style = style.get_box();
 
     let display_inside = match Display::from(box_style.display) {
@@ -63,21 +63,13 @@ fn construct_for_root_element<'dom>(
         Display::GeneratingBox(DisplayGeneratingBox::OutsideInside { inside, .. }) => inside,
     };
 
-    if let Some(replaced) = replaced {
-        let _box = match replaced {};
-        #[allow(unreachable_code)]
-        {
-            return (ContainsFloats::No, vec![Arc::new(_box)]);
-        }
-    }
-
     let position = box_style.position;
     let float = box_style.float;
     let contents = IndependentFormattingContext::construct(
         context,
         style,
         display_inside,
-        Contents::OfElement(root_element),
+        replaced.map_or(Contents::OfElement(root_element), Contents::Replaced),
     );
     if position.is_absolutely_positioned() {
         (
diff --git a/components/layout_2020/formatting_contexts.rs b/components/layout_2020/formatting_contexts.rs
index 96294947720..06e863da1b1 100644
--- a/components/layout_2020/formatting_contexts.rs
+++ b/components/layout_2020/formatting_contexts.rs
@@ -83,7 +83,7 @@ impl IndependentFormattingContext {
         absolutely_positioned_fragments: &mut Vec<AbsolutelyPositionedFragment<'a>>,
     ) -> IndependentLayout {
         match self.as_replaced() {
-            Ok(replaced) => match *replaced {},
+            Ok(replaced) => replaced.layout(layout_context, &self.style, containing_block),
             Err(ifc) => ifc.layout(
                 layout_context,
                 containing_block,
diff --git a/components/layout_2020/fragments.rs b/components/layout_2020/fragments.rs
index a0ea097abb6..e0c335eb3c9 100644
--- a/components/layout_2020/fragments.rs
+++ b/components/layout_2020/fragments.rs
@@ -10,12 +10,13 @@ use std::sync::Arc;
 use style::properties::ComputedValues;
 use style::values::computed::Length;
 use style::Zero;
-use webrender_api::FontInstanceKey;
+use webrender_api::{FontInstanceKey, ImageKey};
 
 pub(crate) enum Fragment {
     Box(BoxFragment),
     Anonymous(AnonymousFragment),
     Text(TextFragment),
+    Image(ImageFragment),
 }
 
 pub(crate) struct BoxFragment {
@@ -61,6 +62,12 @@ pub(crate) struct TextFragment {
     pub glyphs: Vec<Arc<GlyphStore>>,
 }
 
+pub(crate) struct ImageFragment {
+    pub style: ServoArc<ComputedValues>,
+    pub content_rect: Rect<Length>,
+    pub image_key: ImageKey,
+}
+
 impl AnonymousFragment {
     pub fn no_op(mode: (WritingMode, Direction)) -> Self {
         Self {
diff --git a/components/layout_2020/replaced.rs b/components/layout_2020/replaced.rs
index 04defc26b02..bb003f613fa 100644
--- a/components/layout_2020/replaced.rs
+++ b/components/layout_2020/replaced.rs
@@ -2,20 +2,77 @@
  * 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::context::LayoutContext;
 use crate::dom_traversal::NodeExt;
+use crate::formatting_contexts::IndependentLayout;
+use crate::fragments::{Fragment, ImageFragment};
+use crate::geom::{flow_relative, physical};
+use crate::positioned::AbsolutelyPositionedFragment;
+use crate::ContainingBlock;
+use net_traits::image::base::Image;
+use servo_arc::Arc as ServoArc;
+use std::sync::Arc;
 use style::context::SharedStyleContext;
+use style::properties::ComputedValues;
+use style::values::computed::Length;
+use style::Zero;
 
 #[derive(Debug)]
-pub(super) enum ReplacedContent {
-    // Not implemented yet
+pub(crate) struct ReplacedContent {
+    pub kind: ReplacedContentKind,
+    pub intrinsic_size: physical::Vec2<Length>,
+}
+
+#[derive(Debug)]
+pub(crate) enum ReplacedContentKind {
+    Image(Option<Arc<Image>>),
 }
 
 impl ReplacedContent {
-    pub fn for_element<'dom, Node>(element: Node, _context: &SharedStyleContext) -> Option<Self>
-    where
-        Node: NodeExt<'dom>,
-    {
-        // FIXME: implement <img> etc.
+    pub fn for_element<'dom>(element: impl NodeExt<'dom>) -> Option<Self> {
+        if let Some((image, intrinsic_size)) = element.as_image() {
+            return Some(Self {
+                kind: ReplacedContentKind::Image(image),
+                intrinsic_size,
+            });
+        }
         None
     }
+
+    pub fn layout<'a>(
+        &'a self,
+        layout_context: &LayoutContext,
+        style: &ServoArc<ComputedValues>,
+        containing_block: &ContainingBlock,
+    ) -> IndependentLayout {
+        let (fragments, content_block_size) = match self.kind {
+            ReplacedContentKind::Image(ref image) => {
+                // FIXME(nox): We should not assume block size is known.
+                let block_size = containing_block.block_size.non_auto().unwrap();
+                let fragments = image
+                    .as_ref()
+                    .and_then(|image| image.id)
+                    .map(|image_key| {
+                        Fragment::Image(ImageFragment {
+                            style: style.clone(),
+                            content_rect: flow_relative::Rect {
+                                start_corner: flow_relative::Vec2::zero(),
+                                size: flow_relative::Vec2 {
+                                    inline: containing_block.inline_size,
+                                    block: block_size,
+                                },
+                            },
+                            image_key,
+                        })
+                    })
+                    .into_iter()
+                    .collect::<Vec<_>>();
+                (fragments, block_size)
+            },
+        };
+        IndependentLayout {
+            fragments,
+            content_block_size,
+        }
+    }
 }