Implement non-zero dimension attribute parsing

Fixes #8445

The only attributes I found that we have implemented that uses non-zero
dimenion attributes:

* `width` for `<td>` and `<th>` (table cells)
* `width` for `<table>`

I updated these implementations to use the new non-zero dimension
attribute parsing and added associated regression tests.

components/script/dom/htmltablecellelement.rs

@@ -3,27 +3,25 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use cssparser::RGBA;
-use dom::attr::{Attr, AttrValue};
+use dom::attr::AttrValue;
 use dom::bindings::codegen::Bindings::HTMLTableCellElementBinding::HTMLTableCellElementMethods;
 use dom::bindings::codegen::Bindings::NodeBinding::NodeMethods;
 use dom::bindings::inheritance::Castable;
 use dom::bindings::js::LayoutJS;
 use dom::document::Document;
-use dom::element::{AttributeMutation, Element, RawLayoutElementHelpers};
+use dom::element::{Element, RawLayoutElementHelpers};
 use dom::htmlelement::HTMLElement;
 use dom::htmltablerowelement::HTMLTableRowElement;
 use dom::node::Node;
 use dom::virtualmethods::VirtualMethods;
-use std::cell::Cell;
 use string_cache::Atom;
-use util::str::{self, DOMString, LengthOrPercentageOrAuto};
+use util::str::{DOMString, LengthOrPercentageOrAuto};
 
 const DEFAULT_COLSPAN: u32 = 1;
 
 #[dom_struct]
 pub struct HTMLTableCellElement {
     htmlelement: HTMLElement,
-    width: Cell<LengthOrPercentageOrAuto>,
 }
 
 impl HTMLTableCellElement {
@@ -33,7 +31,6 @@ impl HTMLTableCellElement {
                          -> HTMLTableCellElement {
         HTMLTableCellElement {
             htmlelement: HTMLElement::new_inherited(tag_name, prefix, document),
-            width: Cell::new(LengthOrPercentageOrAuto::Auto),
         }
     }
 
@@ -56,6 +53,12 @@ impl HTMLTableCellElementMethods for HTMLTableCellElement {
     // https://html.spec.whatwg.org/multipage/#dom-tdth-bgcolor
     make_legacy_color_setter!(SetBgColor, "bgcolor");
 
+    // https://html.spec.whatwg.org/multipage/#dom-tdth-width
+    make_getter!(Width, "width");
+
+    // https://html.spec.whatwg.org/multipage/#dom-tdth-width
+    make_nonzero_dimension_setter!(SetWidth, "width");
+
     // https://html.spec.whatwg.org/multipage/#dom-tdth-cellindex
     fn CellIndex(&self) -> i32 {
         let self_node = self.upcast::<Node>();
@@ -101,7 +104,11 @@ impl HTMLTableCellElementLayoutHelpers for LayoutJS<HTMLTableCellElement> {
 
     fn get_width(&self) -> LengthOrPercentageOrAuto {
         unsafe {
-            (*self.unsafe_get()).width.get()
+            (&*self.upcast::<Element>().unsafe_get())
+                .get_attr_for_layout(&ns!(), &atom!("width"))
+                .map(AttrValue::as_dimension)
+                .cloned()
+                .unwrap_or(LengthOrPercentageOrAuto::Auto)
         }
     }
 }
@@ -111,23 +118,11 @@ impl VirtualMethods for HTMLTableCellElement {
         Some(self.upcast::<HTMLElement>() as &VirtualMethods)
     }
 
-    fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
-        self.super_type().unwrap().attribute_mutated(attr, mutation);
-        match *attr.local_name() {
-            atom!("width") => {
-                let width = mutation.new_value(attr).map(|value| {
-                    str::parse_length(&value)
-                });
-                self.width.set(width.unwrap_or(LengthOrPercentageOrAuto::Auto));
-            },
-            _ => {},
-        }
-    }
-
     fn parse_plain_attribute(&self, local_name: &Atom, value: DOMString) -> AttrValue {
         match *local_name {
             atom!("colspan") => AttrValue::from_u32(value, DEFAULT_COLSPAN),
             atom!("bgcolor") => AttrValue::from_legacy_color(value),
+            atom!("width") => AttrValue::from_nonzero_dimension(value),
             _ => self.super_type().unwrap().parse_plain_attribute(local_name, value),
         }
     }

components/script/dom/htmltableelement.rs

@@ -120,7 +120,7 @@ impl HTMLTableElementMethods for HTMLTableElement {
     make_getter!(Width, "width");
 
     // https://html.spec.whatwg.org/multipage/#dom-table-width
-    make_dimension_setter!(SetWidth, "width");
+    make_nonzero_dimension_setter!(SetWidth, "width");
 }
 
 pub trait HTMLTableElementLayoutHelpers {
@@ -195,7 +195,7 @@ impl VirtualMethods for HTMLTableElement {
     fn parse_plain_attribute(&self, local_name: &Atom, value: DOMString) -> AttrValue {
         match *local_name {
             atom!("border") => AttrValue::from_u32(value, 1),
-            atom!("width") => AttrValue::from_dimension(value),
+            atom!("width") => AttrValue::from_nonzero_dimension(value),
             _ => self.super_type().unwrap().parse_plain_attribute(local_name, value),
         }
     }

components/script/dom/macros.rs

@@ -236,6 +236,19 @@ macro_rules! make_dimension_setter(
     );
 );
 
+#[macro_export]
+macro_rules! make_nonzero_dimension_setter(
+    ( $attr:ident, $htmlname:tt ) => (
+        fn $attr(&self, value: DOMString) {
+            use dom::bindings::inheritance::Castable;
+            use dom::element::Element;
+            let element = self.upcast::<Element>();
+            let value = AttrValue::from_nonzero_dimension(value);
+            element.set_attribute(&atom!($htmlname), value)
+        }
+    );
+);
+
 /// For use on non-jsmanaged types
 /// Use #[derive(JSTraceable)] on JS managed types
 macro_rules! no_jsmanaged_fields(

components/script/dom/webidls/HTMLTableCellElement.webidl

@@ -19,7 +19,7 @@ partial interface HTMLTableCellElement {
   //         attribute DOMString align;
   //         attribute DOMString axis;
   //         attribute DOMString height;
-  //         attribute DOMString width;
+  attribute DOMString width;
 
   //         attribute DOMString ch;
   //         attribute DOMString chOff;

components/style/attr.rs

@@ -6,7 +6,7 @@ use cssparser::RGBA;
 use std::ops::Deref;
 use string_cache::{Atom, Namespace};
 use util::str::{DOMString, LengthOrPercentageOrAuto, parse_unsigned_integer, parse_legacy_color, parse_length};
-use util::str::{split_html_space_chars, str_join, parse_integer};
+use util::str::{parse_nonzero_length, split_html_space_chars, str_join, parse_integer};
 use values::specified::{Length};
 
 // Duplicated from script::dom::values.
@@ -96,6 +96,11 @@ impl AttrValue {
         AttrValue::Dimension(string, parsed)
     }
 
+    pub fn from_nonzero_dimension(string: DOMString) -> AttrValue {
+        let parsed = parse_nonzero_length(&string);
+        AttrValue::Dimension(string, parsed)
+    }
+
     /// Assumes the `AttrValue` is a `TokenList` and returns its tokens
     ///
     /// ## Panics

components/util/str.rs

@@ -4,6 +4,7 @@
 
 use app_units::Au;
 use cssparser::{self, Color, RGBA};
+use euclid::num::Zero;
 use js::conversions::{FromJSValConvertible, ToJSValConvertible, latin1_to_string};
 use js::jsapi::{JSContext, JSString, HandleValue, MutableHandleValue};
 use js::jsapi::{JS_GetTwoByteStringCharsAndLength, JS_StringHasLatin1Chars};
@@ -372,6 +373,17 @@ pub fn parse_length(mut value: &str) -> LengthOrPercentageOrAuto {
     }
 }
 
+/// HTML5 § 2.4.4.5.
+///
+/// https://html.spec.whatwg.org/multipage/#rules-for-parsing-non-zero-dimension-values
+pub fn parse_nonzero_length(value: &str) -> LengthOrPercentageOrAuto {
+    match parse_length(value) {
+        LengthOrPercentageOrAuto::Length(x) if x == Au::zero() => LengthOrPercentageOrAuto::Auto,
+        LengthOrPercentageOrAuto::Percentage(0.) => LengthOrPercentageOrAuto::Auto,
+        x => x,
+    }
+}
+
 /// https://html.spec.whatwg.org/multipage/#rules-for-parsing-a-legacy-font-size
 pub fn parse_legacy_font_size(mut input: &str) -> Option<&'static str> {
     // Steps 1 & 2 are not relevant