Fix mobile overlay inert ownership (#1352)

frontend/mobile-insights.js

@@ -8,12 +8,25 @@
   let active = false;
   let previous = '#/my-work';
   let retries = 0;
+  let backgroundInert = null;
 
   function attr(element, name, value) {
     if (value === null) element.removeAttribute(name);
     else element.setAttribute(name, value);
   }
 
+  function containBackground() {
+    if (backgroundInert) return;
+    backgroundInert = new Map(o.backgrounds.map(element => [element, element.inert]));
+    backgroundInert.forEach((_wasInert, element) => { element.inert = true; });
+  }
+
+  function releaseBackground() {
+    if (!backgroundInert) return;
+    backgroundInert.forEach((wasInert, element) => { element.inert = wasInert; });
+    backgroundInert = null;
+  }
+
   function render(open, focus = false) {
     const wasActive = active;
     active = Boolean(open && o.mediaQuery.matches);
@@ -28,7 +41,8 @@
     attr(o.root, 'aria-modal', active ? 'true' : null);
     attr(o.root, 'aria-hidden', active || !o.mediaQuery.matches ? null : 'true');
     o.root.inert = !active && o.mediaQuery.matches;
-    o.backgrounds.forEach(element => { element.inert = active; });
+    if (active) containBackground();
+    else releaseBackground();
     o.dock.hidden = active;
     attr(o.hud, 'data-overlay-hidden', active ? 'true' : null);
     if (active) o.closeButton.focus();

tests/test_mobile_insights.py

@@ -133,6 +133,37 @@ process.stdout.write(JSON.stringify({{current:controller.current(),hash:location
     }
 
 
+def test_late_inactive_route_event_does_not_release_background_owned_by_next_overlay():
+    script = f"""
+const createInsights = require({json.dumps(str(CONTROLLER))});
+const listeners = {{}};
+const element = () => ({{
+  hidden:false, inert:false, attributes:{{}}, focuses:0, listeners:{{}},
+  setAttribute(name,value) {{ this.attributes[name] = String(value); }},
+  removeAttribute(name) {{ delete this.attributes[name]; }},
+  addEventListener(name,fn) {{ this.listeners[name] = fn; }},
+  focus() {{ this.focuses += 1; }},
+}});
+const root=element(), launcher=element(), closeButton=element(), dock=element(), hud=element(), header=element();
+const location={{pathname:'/dashboard/', search:'', hash:'#/insights'}};
+const history={{state:null, pushState() {{}}, back() {{}}, replaceState(state,unused,url) {{
+  this.state=state; location.hash=url.slice(url.indexOf('#'));
+}}}};
+const controller=createInsights({{
+  root,launcher,closeButton,dock,hud,backgrounds:[header],history,location,
+  eventTarget:{{addEventListener(name,fn) {{ listeners[name]=fn; }}}},
+  mediaQuery:{{matches:true,addEventListener() {{}}}},
+}});
+controller.start();
+closeButton.listeners.click();
+header.inert = true;
+listeners.hashchange();
+process.stdout.write(JSON.stringify({{current:controller.current(), headerInert:header.inert}}));
+"""
+
+    assert run_node(script) == {"current": False, "headerInert": True}
+
+
 def test_escape_requests_back_navigation_only_while_insights_is_open():
     script = f"""
 const createInsights=require({json.dumps(str(CONTROLLER))});