From d55424e88f732c663d1ec988a3fbe98d6c9a89e5 Mon Sep 17 00:00:00 2001
From: Josh Matthews <josh@joshmatthews.net>
Date: Fri, 12 Jun 2020 18:19:49 -0400
Subject: [PATCH] Update document focus when element focusability changes.

---
 components/script/dom/document.rs             | 11 +++
 components/script/dom/element.rs              | 72 ++++++++++++++++++-
 components/script/dom/htmlbuttonelement.rs    |  1 +
 components/script/dom/htmlelement.rs          | 56 +--------------
 components/script/dom/htmlfieldsetelement.rs  |  3 +
 components/script/dom/htmlinputelement.rs     |  2 +
 components/script/dom/htmltextareaelement.rs  |  1 +
 .../focus-fixup-rule-one-no-dialogs.html.ini  | 15 ----
 8 files changed, 89 insertions(+), 72 deletions(-)

diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index 97ca60af115..385f7c2139e 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -1025,6 +1025,17 @@ impl Document {
         *self.focus_transaction.borrow_mut() = FocusTransaction::InTransaction(Default::default());
     }
 
+    /// <https://html.spec.whatwg.org/multipage/#focus-fixup-rule>
+    pub(crate) fn perform_focus_fixup_rule(&self, not_focusable: &Element) {
+        if Some(not_focusable) != self.focused.get().as_ref().map(|e| &**e) {
+            return;
+        }
+        self.request_focus(
+            self.GetBody().as_ref().map(|e| &*e.upcast()),
+            FocusType::Element,
+        )
+    }
+
     /// Request that the given element receive focus once the current transaction is complete.
     /// If None is passed, then whatever element is currently focused will no longer be focused
     /// once the transaction is complete.
diff --git a/components/script/dom/element.rs b/components/script/dom/element.rs
index 458f301e238..5518ddd3837 100644
--- a/components/script/dom/element.rs
+++ b/components/script/dom/element.rs
@@ -1300,12 +1300,12 @@ impl Element {
         if self.is_actually_disabled() {
             return false;
         }
-        // TODO: Check whether the element is being rendered (i.e. not hidden).
         let node = self.upcast::<Node>();
         if node.get_flag(NodeFlags::SEQUENTIALLY_FOCUSABLE) {
             return true;
         }
-        // https://html.spec.whatwg.org/multipage/#specially-focusable
+
+        // <a>, <input>, <select>, and <textrea> are inherently focusable.
         match node.type_id() {
             NodeTypeId::Element(ElementTypeId::HTMLElement(
                 HTMLElementTypeId::HTMLAnchorElement,
@@ -1832,6 +1832,67 @@ impl Element {
     pub fn get_name(&self) -> Option<Atom> {
         self.rare_data().as_ref()?.name_attribute.clone()
     }
+
+    fn is_sequentially_focusable(&self) -> bool {
+        let element = self.upcast::<Element>();
+        let node = self.upcast::<Node>();
+        if !node.is_connected() {
+            return false;
+        }
+
+        if element.has_attribute(&local_name!("hidden")) {
+            return false;
+        }
+
+        if self.disabled_state() {
+            return false;
+        }
+
+        if element.has_attribute(&local_name!("tabindex")) {
+            return true;
+        }
+
+        match node.type_id() {
+            // <button>, <select>, <iframe>, and <textarea> are implicitly focusable.
+            NodeTypeId::Element(ElementTypeId::HTMLElement(
+                HTMLElementTypeId::HTMLButtonElement,
+            )) |
+            NodeTypeId::Element(ElementTypeId::HTMLElement(
+                HTMLElementTypeId::HTMLSelectElement,
+            )) |
+            NodeTypeId::Element(ElementTypeId::HTMLElement(
+                HTMLElementTypeId::HTMLIFrameElement,
+            )) |
+            NodeTypeId::Element(ElementTypeId::HTMLElement(
+                HTMLElementTypeId::HTMLTextAreaElement,
+            )) => true,
+
+            // Links that generate actual links are focusable.
+            NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLLinkElement)) |
+            NodeTypeId::Element(ElementTypeId::HTMLElement(
+                HTMLElementTypeId::HTMLAnchorElement,
+            )) => element.has_attribute(&local_name!("href")),
+
+            //TODO focusable if editing host
+            //TODO focusable if "sorting interface th elements"
+            _ => {
+                // Draggable elements are focusable.
+                element.get_string_attribute(&local_name!("draggable")) == "true"
+            },
+        }
+    }
+
+    pub(crate) fn update_sequentially_focusable_status(&self) {
+        let node = self.upcast::<Node>();
+        let is_sequentially_focusable = self.is_sequentially_focusable();
+        node.set_flag(NodeFlags::SEQUENTIALLY_FOCUSABLE, is_sequentially_focusable);
+
+        // https://html.spec.whatwg.org/multipage/#focus-fixup-rule
+        if !is_sequentially_focusable {
+            let document = document_from_node(self);
+            document.perform_focus_fixup_rule(self);
+        }
+    }
 }
 
 impl ElementMethods for Element {
@@ -2751,6 +2812,9 @@ impl VirtualMethods for Element {
         let node = self.upcast::<Node>();
         let doc = node.owner_doc();
         match attr.local_name() {
+            &local_name!("tabindex") | &local_name!("draggable") | &local_name!("hidden") => {
+                self.update_sequentially_focusable_status()
+            },
             &local_name!("style") => {
                 // Modifying the `style` attribute might change style.
                 *self.style_attribute.borrow_mut() = match mutation {
@@ -2917,6 +2981,8 @@ impl VirtualMethods for Element {
             return;
         }
 
+        self.update_sequentially_focusable_status();
+
         if let Some(ref value) = *self.id_attribute.borrow() {
             if let Some(shadow_root) = self.upcast::<Node>().containing_shadow_root() {
                 shadow_root.register_element_id(self, value.clone());
@@ -2945,6 +3011,8 @@ impl VirtualMethods for Element {
             return;
         }
 
+        self.update_sequentially_focusable_status();
+
         let doc = document_from_node(self);
 
         if let Some(ref shadow_root) = self.shadow_root() {
diff --git a/components/script/dom/htmlbuttonelement.rs b/components/script/dom/htmlbuttonelement.rs
index cb6e1d0c056..100d9fb92b7 100755
--- a/components/script/dom/htmlbuttonelement.rs
+++ b/components/script/dom/htmlbuttonelement.rs
@@ -233,6 +233,7 @@ impl VirtualMethods for HTMLButtonElement {
                         el.check_ancestors_disabled_state_for_form_control();
                     },
                 }
+                el.update_sequentially_focusable_status();
             },
             &local_name!("type") => match mutation {
                 AttributeMutation::Set(_) => {
diff --git a/components/script/dom/htmlelement.rs b/components/script/dom/htmlelement.rs
index 1820c4367d5..282e980f2d6 100644
--- a/components/script/dom/htmlelement.rs
+++ b/components/script/dom/htmlelement.rs
@@ -28,7 +28,7 @@ use crate::dom::htmlinputelement::{HTMLInputElement, InputType};
 use crate::dom::htmllabelelement::HTMLLabelElement;
 use crate::dom::htmltextareaelement::HTMLTextAreaElement;
 use crate::dom::node::{document_from_node, window_from_node};
-use crate::dom::node::{BindContext, Node, NodeFlags, ShadowIncluding};
+use crate::dom::node::{Node, ShadowIncluding};
 use crate::dom::text::Text;
 use crate::dom::virtualmethods::VirtualMethods;
 use dom_struct::dom_struct;
@@ -91,53 +91,6 @@ impl HTMLElement {
         let eventtarget = self.upcast::<EventTarget>();
         eventtarget.is::<HTMLBodyElement>() || eventtarget.is::<HTMLFrameSetElement>()
     }
-
-    fn update_sequentially_focusable_status(&self) {
-        let element = self.upcast::<Element>();
-        let node = self.upcast::<Node>();
-        if element.has_attribute(&local_name!("tabindex")) {
-            node.set_flag(NodeFlags::SEQUENTIALLY_FOCUSABLE, true);
-        } else {
-            match node.type_id() {
-                NodeTypeId::Element(ElementTypeId::HTMLElement(
-                    HTMLElementTypeId::HTMLButtonElement,
-                )) |
-                NodeTypeId::Element(ElementTypeId::HTMLElement(
-                    HTMLElementTypeId::HTMLSelectElement,
-                )) |
-                NodeTypeId::Element(ElementTypeId::HTMLElement(
-                    HTMLElementTypeId::HTMLIFrameElement,
-                )) |
-                NodeTypeId::Element(ElementTypeId::HTMLElement(
-                    HTMLElementTypeId::HTMLTextAreaElement,
-                )) => node.set_flag(NodeFlags::SEQUENTIALLY_FOCUSABLE, true),
-                NodeTypeId::Element(ElementTypeId::HTMLElement(
-                    HTMLElementTypeId::HTMLLinkElement,
-                )) |
-                NodeTypeId::Element(ElementTypeId::HTMLElement(
-                    HTMLElementTypeId::HTMLAnchorElement,
-                )) => {
-                    if element.has_attribute(&local_name!("href")) {
-                        node.set_flag(NodeFlags::SEQUENTIALLY_FOCUSABLE, true);
-                    }
-                },
-                _ => {
-                    if let Some(attr) = element.get_attribute(&ns!(), &local_name!("draggable")) {
-                        let value = attr.value();
-                        let is_true = match *value {
-                            AttrValue::String(ref string) => string == "true",
-                            _ => false,
-                        };
-                        node.set_flag(NodeFlags::SEQUENTIALLY_FOCUSABLE, is_true);
-                    } else {
-                        node.set_flag(NodeFlags::SEQUENTIALLY_FOCUSABLE, false);
-                    }
-                    //TODO set SEQUENTIALLY_FOCUSABLE flag if editing host
-                    //TODO set SEQUENTIALLY_FOCUSABLE flag if "sorting interface th elements"
-                },
-            }
-        }
-    }
 }
 
 impl HTMLElementMethods for HTMLElement {
@@ -855,13 +808,6 @@ impl VirtualMethods for HTMLElement {
         }
     }
 
-    fn bind_to_tree(&self, context: &BindContext) {
-        if let Some(ref s) = self.super_type() {
-            s.bind_to_tree(context);
-        }
-        self.update_sequentially_focusable_status();
-    }
-
     fn parse_plain_attribute(&self, name: &LocalName, value: DOMString) -> AttrValue {
         match name {
             &local_name!("itemprop") => AttrValue::from_serialized_tokenlist(value.into()),
diff --git a/components/script/dom/htmlfieldsetelement.rs b/components/script/dom/htmlfieldsetelement.rs
index b2b05cbc5c4..cefee026751 100644
--- a/components/script/dom/htmlfieldsetelement.rs
+++ b/components/script/dom/htmlfieldsetelement.rs
@@ -182,14 +182,17 @@ impl VirtualMethods for HTMLFieldSetElement {
                         let el = field.downcast::<Element>().unwrap();
                         el.set_disabled_state(true);
                         el.set_enabled_state(false);
+                        el.update_sequentially_focusable_status();
                     }
                 } else {
                     for field in fields {
                         let el = field.downcast::<Element>().unwrap();
                         el.check_disabled_attribute();
                         el.check_ancestors_disabled_state_for_form_control();
+                        el.update_sequentially_focusable_status();
                     }
                 }
+                el.update_sequentially_focusable_status();
             },
             &local_name!("form") => {
                 self.form_attribute_mutated(mutation);
diff --git a/components/script/dom/htmlinputelement.rs b/components/script/dom/htmlinputelement.rs
index 6177d4f7831..1078f71d59e 100755
--- a/components/script/dom/htmlinputelement.rs
+++ b/components/script/dom/htmlinputelement.rs
@@ -2291,6 +2291,8 @@ impl VirtualMethods for HTMLInputElement {
                     let read_write = !(self.ReadOnly() || el.disabled_state());
                     el.set_read_write_state(read_write);
                 }
+
+                el.update_sequentially_focusable_status();
             },
             &local_name!("checked") if !self.checked_changed.get() => {
                 let checked_state = match mutation {
diff --git a/components/script/dom/htmltextareaelement.rs b/components/script/dom/htmltextareaelement.rs
index cbdbcec2f0f..c6d9331532f 100755
--- a/components/script/dom/htmltextareaelement.rs
+++ b/components/script/dom/htmltextareaelement.rs
@@ -478,6 +478,7 @@ impl VirtualMethods for HTMLTextAreaElement {
                         }
                     },
                 }
+                el.update_sequentially_focusable_status();
             },
             local_name!("maxlength") => match *attr.value() {
                 AttrValue::Int(_, value) => {
diff --git a/tests/wpt/metadata/html/interaction/focus/processing-model/focus-fixup-rule-one-no-dialogs.html.ini b/tests/wpt/metadata/html/interaction/focus/processing-model/focus-fixup-rule-one-no-dialogs.html.ini
index 19b1435fd03..d3120d0b31f 100644
--- a/tests/wpt/metadata/html/interaction/focus/processing-model/focus-fixup-rule-one-no-dialogs.html.ini
+++ b/tests/wpt/metadata/html/interaction/focus/processing-model/focus-fixup-rule-one-no-dialogs.html.ini
@@ -2,21 +2,6 @@
   [Disabling contenteditable]
     expected: FAIL
 
-  [Hiding the active element]
-    expected: FAIL
-
-  [Disabling the active element (making it expressly inert)]
-    expected: FAIL
-
   [Changing the first legend element in disabled <fieldset>]
     expected: FAIL
 
-  [Disabling <fieldset> affects its descendants]
-    expected: FAIL
-
-  [Removing the tabindex attribute from a div]
-    expected: FAIL
-
-  [Removing the active element from the DOM]
-    expected: FAIL
-