style: Implement basic column spans.

This patch provides some of the groundwork for column spans greater than
1. It implements the column-span CSS property (prefixed so as not to be
exposed to content) as well as the corresponding colspan attribute;
although the former is not well-specified outside of CSS multi-column
layout, INTRINSIC refers to it. Although width is distributed to
spanning columns, they do not yet contribute minimum and preferred
widths; this will be implemented in a follow-up.

Additionally, this patch cleans up some miscellaneous formatting issues
and improves the handling of table rowgroups.

components/style/legacy.rs

@@ -8,7 +8,8 @@
 use node::{TElement, TElementAttributes, TNode};
 use properties::{BackgroundColorDeclaration, BorderBottomWidthDeclaration};
 use properties::{BorderLeftWidthDeclaration, BorderRightWidthDeclaration};
-use properties::{BorderTopWidthDeclaration, SpecifiedValue, WidthDeclaration, specified};
+use properties::{BorderTopWidthDeclaration, ServoColumnSpanDeclaration, SpecifiedValue};
+use properties::{WidthDeclaration, specified};
 use selector_matching::{DeclarationBlock, Stylist};
 
 use cssparser::{RGBA, RGBAColor};
@@ -32,6 +33,8 @@ pub enum IntegerAttribute {
 pub enum UnsignedIntegerAttribute {
     /// `<td border>`
     BorderUnsignedIntegerAttribute,
+    /// `<td colspan>`
+    ColSpanUnsignedIntegerAttribute,
 }
 
 /// Legacy presentational attributes that take a simple color as defined in HTML5 § 2.4.6.
@@ -111,6 +114,14 @@ impl PresentationalHintSynthesis for Stylist {
                         *shareable = false
                     }
                 }
+                match element.get_unsigned_integer_attribute(ColSpanUnsignedIntegerAttribute) {
+                    None => {}
+                    Some(value) => {
+                        matching_rules_list.vec_push(DeclarationBlock::from_declaration(
+                                ServoColumnSpanDeclaration(SpecifiedValue(value))));
+                        *shareable = false
+                    }
+                }
                 self.synthesize_presentational_hint_for_legacy_background_color_attribute(
                     element,
                     matching_rules_list,

components/style/lib.rs

@@ -54,9 +54,10 @@ pub use selectors::{PseudoElement, Before, After, SelectorList, parse_selector_l
 pub use selectors::{AttrSelector, NamespaceConstraint, SpecificNamespace, AnyNamespace};
 pub use selectors::{SimpleSelector, LocalNameSelector};
 pub use cssparser::{Color, RGBA};
-pub use legacy::{BgColorSimpleColorAttribute, BorderUnsignedIntegerAttribute, IntegerAttribute};
-pub use legacy::{LengthAttribute, SimpleColorAttribute, SizeIntegerAttribute};
-pub use legacy::{UnsignedIntegerAttribute, WidthLengthAttribute};
+pub use legacy::{BgColorSimpleColorAttribute, BorderUnsignedIntegerAttribute};
+pub use legacy::{ColSpanUnsignedIntegerAttribute, IntegerAttribute, LengthAttribute};
+pub use legacy::{SimpleColorAttribute, SizeIntegerAttribute, UnsignedIntegerAttribute};
+pub use legacy::{WidthLengthAttribute};
 pub use font_face::{Source, LocalSource, UrlSource_};
 
 mod stylesheets;

components/style/properties/mod.rs.mako

@@ -1316,6 +1316,34 @@ pub mod longhands {
 
     ${single_keyword("table-layout", "auto fixed")}
 
+    <%self:single_component_value name="-servo-column-span">
+        // The handling of this property is not well-specified by INTRINSIC, but its presence is
+        // assumed. HTML5 14.3.9 specifies that the `colspan` attribute is to be a nonnegative
+        // integer.
+        pub use super::computed_as_specified as to_computed_value;
+        pub mod computed_value {
+            pub type T = u32;
+        }
+        pub type SpecifiedValue = computed_value::T;
+
+        #[inline]
+        pub fn get_initial_value() -> computed_value::T {
+            1
+        }
+
+        pub fn from_component_value(input: &ComponentValue, _: &Url) -> Result<SpecifiedValue,()> {
+            match input {
+                &Number(ref value) => {
+                    match value.int_value {
+                        None => Err(()),
+                        Some(n) => Ok(n as SpecifiedValue),
+                    }
+                }
+                _ => Err(()),
+            }
+        }
+    </%self:single_component_value>
+
     // CSS 2.1, Section 18 - User interface
 
 

components/style/selector_matching.rs

@@ -802,8 +802,8 @@ pub fn common_style_affecting_attributes() -> [CommonStyleAffectingAttributeInfo
 /// Attributes that, if present, disable style sharing. All legacy HTML attributes must be in
 /// either this list or `common_style_affecting_attributes`. See the comment in
 /// `synthesize_presentational_hints_for_legacy_attributes`.
-pub fn rare_style_affecting_attributes() -> [Atom, ..2] {
-    [ atom!("bgcolor"), atom!("border") ]
+pub fn rare_style_affecting_attributes() -> [Atom, ..3] {
+    [ atom!("bgcolor"), atom!("border"), atom!("colspan") ]
 }
 
 /// Determines whether the given element matches the given single selector.