Implement the size presentational hint for <hr> elements (#37211)

This presentational hint either sets the width values of all borders,
removes the bottom border or sets the height of the element, depending
on the context.

This change also implements the corresponding idl attribute (and the
`noshade` attribute, which does nothing in html5)

Testing: Adds new web platform tests

---------

Signed-off-by: Simon Wülker <simon.wuelker@arcor.de>

components/script/dom/element.rs

@@ -121,7 +121,7 @@ use crate::dom::htmlelement::HTMLElement;
 use crate::dom::htmlfieldsetelement::HTMLFieldSetElement;
 use crate::dom::htmlfontelement::{HTMLFontElement, HTMLFontElementLayoutHelpers};
 use crate::dom::htmlformelement::FormControlElementHelpers;
-use crate::dom::htmlhrelement::{HTMLHRElement, HTMLHRLayoutHelpers};
+use crate::dom::htmlhrelement::{HTMLHRElement, HTMLHRLayoutHelpers, SizePresentationalHint};
 use crate::dom::htmliframeelement::{HTMLIFrameElement, HTMLIFrameElementLayoutMethods};
 use crate::dom::htmlimageelement::{HTMLImageElement, LayoutHTMLImageElementHelpers};
 use crate::dom::htmlinputelement::{HTMLInputElement, LayoutHTMLInputElementHelpers};
@@ -1306,6 +1306,47 @@ impl<'dom> LayoutElementHelpers<'dom> for LayoutDom<'dom, Element> {
                 PropertyDeclaration::PaddingRight(cellpadding),
             ));
         }
+
+        // https://html.spec.whatwg.org/multipage/#the-hr-element-2
+        if let Some(size_info) = self
+            .downcast::<HTMLHRElement>()
+            .and_then(|hr_element| hr_element.get_size_info())
+        {
+            match size_info {
+                SizePresentationalHint::SetHeightTo(height) => {
+                    hints.push(from_declaration(
+                        shared_lock,
+                        PropertyDeclaration::Height(height),
+                    ));
+                },
+                SizePresentationalHint::SetAllBorderWidthValuesTo(border_width) => {
+                    hints.push(from_declaration(
+                        shared_lock,
+                        PropertyDeclaration::BorderLeftWidth(border_width.clone()),
+                    ));
+                    hints.push(from_declaration(
+                        shared_lock,
+                        PropertyDeclaration::BorderRightWidth(border_width.clone()),
+                    ));
+                    hints.push(from_declaration(
+                        shared_lock,
+                        PropertyDeclaration::BorderTopWidth(border_width.clone()),
+                    ));
+                    hints.push(from_declaration(
+                        shared_lock,
+                        PropertyDeclaration::BorderBottomWidth(border_width),
+                    ));
+                },
+                SizePresentationalHint::SetBottomBorderWidthToZero => {
+                    hints.push(from_declaration(
+                        shared_lock,
+                        PropertyDeclaration::BorderBottomWidth(
+                            specified::border::BorderSideWidth::from_px(0.),
+                        ),
+                    ));
+                },
+            }
+        }
     }
 
     fn get_span(self) -> Option<u32> {

components/script/dom/htmlhrelement.rs

@@ -2,11 +2,17 @@
  * 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 std::str::FromStr;
+
 use dom_struct::dom_struct;
 use html5ever::{LocalName, Prefix, local_name, ns};
 use js::rust::HandleObject;
 use style::attr::{AttrValue, LengthOrPercentageOrAuto};
 use style::color::AbsoluteColor;
+use style::values::generics::NonNegative;
+use style::values::specified::border::BorderSideWidth;
+use style::values::specified::length::Size;
+use style::values::specified::{LengthPercentage, NoCalcLength};
 
 use crate::dom::bindings::codegen::Bindings::HTMLHRElementBinding::HTMLHRElementMethods;
 use crate::dom::bindings::inheritance::Castable;
@@ -65,6 +71,18 @@ impl HTMLHRElementMethods<crate::DomTypeHolder> for HTMLHRElement {
     // https://html.spec.whatwg.org/multipage/#dom-hr-color
     make_legacy_color_setter!(SetColor, "color");
 
+    // https://html.spec.whatwg.org/multipage/#dom-hr-noshade
+    make_bool_getter!(NoShade, "noshade");
+
+    // https://html.spec.whatwg.org/multipage/#dom-hr-noshade
+    make_bool_setter!(SetNoShade, "noshade");
+
+    // https://html.spec.whatwg.org/multipage/#dom-hr-size
+    make_getter!(Size, "size");
+
+    // https://html.spec.whatwg.org/multipage/#dom-hr-size
+    make_dimension_setter!(SetSize, "size");
+
     // https://html.spec.whatwg.org/multipage/#dom-hr-width
     make_getter!(Width, "width");
 
@@ -72,9 +90,20 @@ impl HTMLHRElementMethods<crate::DomTypeHolder> for HTMLHRElement {
     make_dimension_setter!(SetWidth, "width");
 }
 
+/// The result of applying the the presentational hint for the `size` attribute.
+///
+/// (This attribute can mean different things depending on its value and other attributes)
+#[allow(clippy::enum_variant_names)]
+pub(crate) enum SizePresentationalHint {
+    SetHeightTo(Size),
+    SetAllBorderWidthValuesTo(BorderSideWidth),
+    SetBottomBorderWidthToZero,
+}
+
 pub(crate) trait HTMLHRLayoutHelpers {
     fn get_color(self) -> Option<AbsoluteColor>;
     fn get_width(self) -> LengthOrPercentageOrAuto;
+    fn get_size_info(self) -> Option<SizePresentationalHint>;
 }
 
 impl HTMLHRLayoutHelpers for LayoutDom<'_, HTMLHRElement> {
@@ -92,6 +121,35 @@ impl HTMLHRLayoutHelpers for LayoutDom<'_, HTMLHRElement> {
             .cloned()
             .unwrap_or(LengthOrPercentageOrAuto::Auto)
     }
+
+    fn get_size_info(self) -> Option<SizePresentationalHint> {
+        // https://html.spec.whatwg.org/multipage/#the-hr-element-2
+        let element = self.upcast::<Element>();
+        let size_value = element
+            .get_attr_val_for_layout(&ns!(), &local_name!("size"))
+            .and_then(|value| usize::from_str(value).ok())
+            .filter(|value| *value != 0)?;
+
+        let hint = if element
+            .get_attr_for_layout(&ns!(), &local_name!("color"))
+            .is_some() ||
+            element
+                .get_attr_for_layout(&ns!(), &local_name!("noshade"))
+                .is_some()
+        {
+            SizePresentationalHint::SetAllBorderWidthValuesTo(BorderSideWidth::from_px(
+                size_value as f32 / 2.0,
+            ))
+        } else if size_value == 1 {
+            SizePresentationalHint::SetBottomBorderWidthToZero
+        } else {
+            SizePresentationalHint::SetHeightTo(Size::LengthPercentage(NonNegative(
+                LengthPercentage::Length(NoCalcLength::from_px((size_value - 2) as f32)),
+            )))
+        };
+
+        Some(hint)
+    }
 }
 
 impl VirtualMethods for HTMLHRElement {