Auto merge of #14518 - mbrubeck:rowspan2, r=notriddle

Fix inline layout of table cells impacted by rowspan

This is part of the fix for #11297. This PR fixes the inline layout of table cells impacted by row-spanning cells from previous rows. A separate PR to follow will fix the table block size calculations to account for rowspan.

This PR doesn't yet include any test changes. If it doesn't cause any existing tests to pass, I will add a new test to it.

r? @pcwalton

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/14518)
<!-- Reviewable:end -->

components/script/dom/element.rs

@@ -325,6 +325,8 @@ pub trait LayoutElementHelpers {
     #[allow(unsafe_code)]
     unsafe fn get_colspan(self) -> u32;
     #[allow(unsafe_code)]
+    unsafe fn get_rowspan(self) -> u32;
+    #[allow(unsafe_code)]
     unsafe fn html_element_in_html_document_for_layout(&self) -> bool;
     fn id_attribute(&self) -> *const Option<Atom>;
     fn style_attribute(&self) -> *const Option<Arc<RwLock<PropertyDeclarationBlock>>>;
@@ -628,6 +630,17 @@ impl LayoutElementHelpers for LayoutJS<Element> {
         }
     }
 
+    #[allow(unsafe_code)]
+    unsafe fn get_rowspan(self) -> u32 {
+        if let Some(this) = self.downcast::<HTMLTableCellElement>() {
+            this.get_rowspan().unwrap_or(1)
+        } else {
+            // Don't panic since `display` can cause this to be called on arbitrary
+            // elements.
+            1
+        }
+    }
+
     #[inline]
     #[allow(unsafe_code)]
     unsafe fn html_element_in_html_document_for_layout(&self) -> bool {

components/script/dom/htmltablecellelement.rs

@@ -18,6 +18,7 @@ use html5ever_atoms::LocalName;
 use style::attr::{AttrValue, LengthOrPercentageOrAuto};
 
 const DEFAULT_COLSPAN: u32 = 1;
+const DEFAULT_ROWSPAN: u32 = 1;
 
 #[dom_struct]
 pub struct HTMLTableCellElement {
@@ -42,6 +43,12 @@ impl HTMLTableCellElementMethods for HTMLTableCellElement {
     // https://html.spec.whatwg.org/multipage/#dom-tdth-colspan
     make_uint_setter!(SetColSpan, "colspan", DEFAULT_COLSPAN);
 
+    // https://html.spec.whatwg.org/multipage/#dom-tdth-rowspan
+    make_uint_getter!(RowSpan, "rowspan", DEFAULT_ROWSPAN);
+
+    // https://html.spec.whatwg.org/multipage/#dom-tdth-rowspan
+    make_uint_setter!(SetRowSpan, "rowspan", DEFAULT_ROWSPAN);
+
     // https://html.spec.whatwg.org/multipage/#dom-tdth-bgcolor
     make_getter!(BgColor, "bgcolor");
 
@@ -75,6 +82,7 @@ impl HTMLTableCellElementMethods for HTMLTableCellElement {
 pub trait HTMLTableCellElementLayoutHelpers {
     fn get_background_color(&self) -> Option<RGBA>;
     fn get_colspan(&self) -> Option<u32>;
+    fn get_rowspan(&self) -> Option<u32>;
     fn get_width(&self) -> LengthOrPercentageOrAuto;
 }
 
@@ -97,6 +105,14 @@ impl HTMLTableCellElementLayoutHelpers for LayoutJS<HTMLTableCellElement> {
         }
     }
 
+    fn get_rowspan(&self) -> Option<u32> {
+        unsafe {
+            (&*self.upcast::<Element>().unsafe_get())
+                .get_attr_for_layout(&ns!(), &local_name!("rowspan"))
+                .map(AttrValue::as_uint)
+        }
+    }
+
     fn get_width(&self) -> LengthOrPercentageOrAuto {
         unsafe {
             (&*self.upcast::<Element>().unsafe_get())
@@ -116,6 +132,7 @@ impl VirtualMethods for HTMLTableCellElement {
     fn parse_plain_attribute(&self, local_name: &LocalName, value: DOMString) -> AttrValue {
         match *local_name {
             local_name!("colspan") => AttrValue::from_u32(value.into(), DEFAULT_COLSPAN),
+            local_name!("rowspan") => AttrValue::from_u32(value.into(), DEFAULT_ROWSPAN),
             local_name!("bgcolor") => AttrValue::from_legacy_color(value.into()),
             local_name!("width") => AttrValue::from_nonzero_dimension(value.into()),
             _ => self.super_type().unwrap().parse_plain_attribute(local_name, value),

components/script/dom/webidls/HTMLTableCellElement.webidl

@@ -5,8 +5,8 @@
 // https://html.spec.whatwg.org/multipage/#htmltablecellelement
 [Abstract]
 interface HTMLTableCellElement : HTMLElement {
-             attribute unsigned long colSpan;
-  //         attribute unsigned long rowSpan;
+  attribute unsigned long colSpan;
+  attribute unsigned long rowSpan;
   //         attribute DOMString headers;
   readonly attribute long cellIndex;