4 files changed, 45 insertions, 2 deletions
diff --git a/components/script/dom/activation.rs b/components/script/dom/activation.rs
index ff8d59aac96..5c59393f766 100644
--- a/components/script/dom/activation.rs
+++ b/components/script/dom/activation.rs
@@ -10,6 +10,9 @@ use dom::event::{Event, EventBubbles, EventCancelable};
 use dom::eventtarget::EventTarget;
 use dom::mouseevent::MouseEvent;
 use dom::node::window_from_node;
+use dom::window::ReflowReason;
+use script_layout_interface::message::ReflowQueryType;
+use style::context::ReflowGoal;
 
 /// Trait for elements with defined activation behavior
 pub trait Activatable {
@@ -29,6 +32,25 @@ pub trait Activatable {
 
     // https://html.spec.whatwg.org/multipage/#implicit-submission
     fn implicit_submission(&self, ctrlKey: bool, shiftKey: bool, altKey: bool, metaKey: bool);
+
+    // https://html.spec.whatwg.org/multipage/#concept-selector-active
+    fn enter_formal_activation_state(&self) {
+        self.as_element().set_active_state(true);
+
+        let win = window_from_node(self.as_element());
+        win.reflow(ReflowGoal::ForDisplay,
+                   ReflowQueryType::NoQuery,
+                   ReflowReason::ElementStateChanged);
+    }
+
+    fn exit_formal_activation_state(&self) {
+        self.as_element().set_active_state(false);
+
+        let win = window_from_node(self.as_element());
+        win.reflow(ReflowGoal::ForDisplay,
+                   ReflowQueryType::NoQuery,
+                   ReflowReason::ElementStateChanged);
+    }
 }
 
 /// Whether an activation was initiated via the click() method
diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index 8c3ee29bf1a..f0a77d85f39 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -735,9 +735,22 @@ impl Document {
         // https://w3c.github.io/uievents/#trusted-events
         event.set_trusted(true);
         // https://html.spec.whatwg.org/multipage/#run-authentic-click-activation-steps
+        let activatable = el.as_maybe_activatable();
         match mouse_event_type {
             MouseEventType::Click => el.authentic_click_activation(event),
-            _ => {
+            MouseEventType::MouseDown => {
+                if let Some(a) = activatable {
+                    a.enter_formal_activation_state();
+                }
+
+                let target = node.upcast();
+                event.fire(target);
+            },
+            MouseEventType::MouseUp => {
+                if let Some(a) = activatable {
+                    a.exit_formal_activation_state();
+                }
+
                 let target = node.upcast();
                 event.fire(target);
             },
@@ -904,6 +917,7 @@ impl Document {
                                          .inclusive_ancestors()
                                          .filter_map(Root::downcast::<Element>) {
                     element.set_hover_state(false);
+                    element.set_active_state(false);
                 }
             }
 
diff --git a/components/script/dom/element.rs b/components/script/dom/element.rs
index 479a73dee86..939561e9d1a 100644
--- a/components/script/dom/element.rs
+++ b/components/script/dom/element.rs
@@ -2519,8 +2519,13 @@ impl Element {
         self.state.get().contains(IN_ACTIVE_STATE)
     }
 
+    /// https://html.spec.whatwg.org/multipage/#concept-selector-active
     pub fn set_active_state(&self, value: bool) {
-        self.set_state(IN_ACTIVE_STATE, value)
+        self.set_state(IN_ACTIVE_STATE, value);
+
+        if let Some(parent) = self.upcast::<Node>().GetParentElement() {
+            parent.set_active_state(value);
+        }
     }
 
     pub fn focus_state(&self) -> bool {
diff --git a/components/script/dom/window.rs b/components/script/dom/window.rs
index 6f012e9c31e..2fc1824cde0 100644
--- a/components/script/dom/window.rs
+++ b/components/script/dom/window.rs
@@ -129,6 +129,7 @@ pub enum ReflowReason {
     FramedContentChanged,
     IFrameLoadEvent,
     MissingExplicitReflow,
+    ElementStateChanged,
 }
 
 pub type ScrollPoint = Point2D<Au>;
@@ -1753,6 +1754,7 @@ fn debug_reflow_events(id: PipelineId, goal: &ReflowGoal, query_type: &ReflowQue
         ReflowReason::FramedContentChanged => "\tFramedContentChanged",
         ReflowReason::IFrameLoadEvent => "\tIFrameLoadEvent",
         ReflowReason::MissingExplicitReflow => "\tMissingExplicitReflow",
+        ReflowReason::ElementStateChanged => "\tElementStateChanged",
     });
 
     println!("{}", debug_msg);