Implement `selectedIndex` property on `<select>`.

1 files changed, 30 insertions, 0 deletions

diff --git a/components/script/dom/htmlselectelement.rs b/components/script/dom/htmlselectelement.rs
index 03d10e117f4..c44dac71000 100644
--- a/components/script/dom/htmlselectelement.rs
+++ b/components/script/dom/htmlselectelement.rs
@@ -299,6 +299,36 @@ impl HTMLSelectElementMethods for HTMLSelectElement {
             opt.set_selectedness(false);
         }
     }
+
+    // https://html.spec.whatwg.org/multipage/#dom-select-selectedindex
+    fn SelectedIndex(&self) -> i32 {
+        self.upcast::<Node>()
+            .traverse_preorder()
+            .filter_map(Root::downcast::<HTMLOptionElement>)
+            .enumerate()
+            .filter(|&(_, ref opt_elem)| opt_elem.Selected())
+            .map(|(i, _)| i as i32)
+            .next()
+            .unwrap_or(-1)
+    }
+
+    // https://html.spec.whatwg.org/multipage/#dom-select-selectedindex
+    fn SetSelectedIndex(&self, index: i32) {
+        let mut opt_iter = self.upcast::<Node>()
+                               .traverse_preorder()
+                               .filter_map(Root::downcast::<HTMLOptionElement>);
+        for opt in opt_iter.by_ref().take(index as usize) {
+            opt.set_selectedness(false);
+        }
+        if let Some(opt) = opt_iter.next() {
+            opt.set_selectedness(true);
+            opt.set_dirtiness(true);
+            // Reset remaining <option> elements
+            for opt in opt_iter {
+                opt.set_selectedness(false);
+            }
+        }
+    }
 }
 
 impl VirtualMethods for HTMLSelectElement {