1 files changed, 94 insertions, 1 deletions

diff --git a/components/script/dom/element.rs b/components/script/dom/element.rs
index e14e1af0d97..8fa454c0e73 100644
--- a/components/script/dom/element.rs
+++ b/components/script/dom/element.rs
@@ -19,6 +19,7 @@ use dom::bindings::codegen::Bindings::EventBinding::EventMethods;
 use dom::bindings::codegen::Bindings::HTMLInputElementBinding::HTMLInputElementMethods;
 use dom::bindings::codegen::Bindings::HTMLTemplateElementBinding::HTMLTemplateElementMethods;
 use dom::bindings::codegen::Bindings::NodeBinding::NodeMethods;
+use dom::bindings::codegen::Bindings::WindowBinding::WindowMethods;
 use dom::bindings::codegen::UnionTypes::NodeOrString;
 use dom::bindings::error::{Error, ErrorResult, Fallible};
 use dom::bindings::global::GlobalRef;
@@ -39,6 +40,7 @@ use dom::htmlanchorelement::HTMLAnchorElement;
 use dom::htmlbodyelement::{HTMLBodyElement, HTMLBodyElementLayoutHelpers};
 use dom::htmlbuttonelement::HTMLButtonElement;
 use dom::htmlcollection::HTMLCollection;
+use dom::htmlelement::HTMLElement;
 use dom::htmlfieldsetelement::HTMLFieldSetElement;
 use dom::htmlfontelement::{HTMLFontElement, HTMLFontElementLayoutHelpers};
 use dom::htmlhrelement::{HTMLHRElement, HTMLHRLayoutHelpers};
@@ -86,7 +88,7 @@ use string_cache::{Atom, Namespace, QualName};
 use style::element_state::*;
 use style::error_reporting::ParseErrorReporter;
 use style::properties::DeclaredValue;
-use style::properties::longhands::{self, background_image, border_spacing, font_family, font_size};
+use style::properties::longhands::{self, background_image, border_spacing, font_family, overflow_x, font_size};
 use style::properties::{PropertyDeclaration, PropertyDeclarationBlock, parse_style_attribute};
 use style::selector_impl::{NonTSPseudoClass, ServoSelectorImpl};
 use style::values::CSSFloat;
@@ -164,6 +166,35 @@ impl Element {
             document,
             ElementBinding::Wrap)
     }
+
+    // https://drafts.csswg.org/cssom-view/#css-layout-box
+    // Elements that have a computed value of the display property
+    // that is table-column or table-column-group
+    // FIXME: Currently, it is assumed to be true always
+    fn has_css_layout_box(&self) -> bool {
+        true
+    }
+
+    // https://drafts.csswg.org/cssom-view/#potentially-scrollable
+    fn potentially_scrollable(&self) -> bool {
+        self.has_css_layout_box() &&
+        !self.overflow_x_is_visible() &&
+        !self.overflow_y_is_visible()
+    }
+
+    // used value of overflow-x is "visible"
+    fn overflow_x_is_visible(&self) -> bool {
+        let window = window_from_node(self);
+        let overflow_pair = window.overflow_query(self.upcast::<Node>().to_trusted_node_address());
+        overflow_pair.x == overflow_x::computed_value::T::visible
+    }
+
+    // used value of overflow-y is "visible"
+    fn overflow_y_is_visible(&self) -> bool {
+        let window = window_from_node(self);
+        let overflow_pair = window.overflow_query(self.upcast::<Node>().to_trusted_node_address());
+        overflow_pair.y != overflow_x::computed_value::T::visible
+    }
 }
 
 #[allow(unsafe_code)]
@@ -1452,6 +1483,68 @@ impl ElementMethods for Element {
                      rect.size.height.to_f64_px())
     }
 
+    // https://drafts.csswg.org/cssom-view/#dom-element-scrolltop
+    fn ScrollTop(&self) -> f64 {
+        let node = self.upcast::<Node>();
+
+        // 1. Let document be the element’s node document.
+        let doc = node.owner_doc();
+
+        // 2. If the document is not the active document, return zero and terminate these steps.
+        if !doc.is_fully_active() {
+            return 0.0;
+        } else {
+            // 3. Let window be the value of document’s defaultView attribute.
+            let win = doc.DefaultView();
+
+            // 5. If the element is the root element and document is in quirks mode,
+            //    return zero and terminate these steps.
+            if *self.root_element() == *self {
+                if doc.quirks_mode() == Quirks {
+                    return 0.0;
+                }
+
+                // 6. If the element is the root element return the value of scrollY on window.
+                return (*win).ScrollY() as f64;
+            }
+
+            // 7. If the element is the HTML body element, document is in quirks mode,
+            //    and the element is not potentially scrollable, return the value of scrollY on window.
+            if doc.GetBody().r() == self.downcast::<HTMLElement>() &&
+               doc.quirks_mode() == Quirks &&
+               !self.potentially_scrollable() {
+                   return (*win).ScrollY() as f64;
+            }
+
+
+            // 8. If the element does not have any associated CSS layout box, return zero and terminate these steps.
+            if !self.has_css_layout_box() {
+                return 0.0;
+            }
+
+            // 9. Return the y-coordinate of the scrolling area at the alignment point
+            //    with the top of the padding edge of the element.
+            let point = node.scroll_offset();
+            return -point.y as f64;
+        }
+    }
+
+    // https://drafts.csswg.org/cssom-view/#dom-element-scrolltop
+    fn SetScrollTop(&self, _scroll_top: f64) {
+        unimplemented!()
+    }
+
+    // https://drafts.csswg.org/cssom-view/#dom-element-scrollleft
+    fn ScrollLeft(&self) -> f64 {
+        let point = self.upcast::<Node>().scroll_offset();
+        return -point.x as f64;
+    }
+
+    // https://drafts.csswg.org/cssom-view/#dom-element-scrollleft
+    fn SetScrollLeft(&self, _scroll_left: f64) {
+        unimplemented!()
+    }
+
     // https://drafts.csswg.org/cssom-view/#dom-element-scrollwidth
     fn ScrollWidth(&self) -> i32 {
         self.upcast::<Node>().scroll_area().size.width