Bug 1816074 - Prevent activating menubar without a selectable menu item. r=smaug

We might not have an active item if all items are disabled.

Add the null-check just to be safe too.

Differential Revision: https://phabricator.services.mozilla.com/D169638

dom/xul/MenuBarListener.cpp

@@ -109,7 +109,7 @@ void MenuBarListener::ToggleMenuActiveState(ByKeyboard aByKeyboard) {
     if (aByKeyboard == ByKeyboard::Yes) {
       menuBar->SetActiveByKeyboard();
     }
-    menuBar->SetActive(true);
+    // This will activate the menubar if needed.
     menuBar->SelectFirstItem();
   }
 }
@@ -226,9 +226,10 @@ nsresult MenuBarListener::KeyPress(Event* aKeyEvent) {
 
       if (mMenuBar && mMenuBar->IsActive()) {
 #  ifdef MOZ_WIDGET_GTK
-        RefPtr child = mMenuBar->GetActiveMenuChild();
-        // In GTK, this also opens the first menu.
-        child->OpenMenuPopup(false);
+        if (RefPtr child = mMenuBar->GetActiveMenuChild()) {
+          // In GTK, this also opens the first menu.
+          child->OpenMenuPopup(false);
+        }
 #  endif
         aKeyEvent->StopPropagation();
         aKeyEvent->PreventDefault();
@@ -270,7 +271,7 @@ nsresult MenuBarListener::KeyPress(Event* aKeyEvent) {
 
   RefPtr menuBar = mMenuBar;
   menuBar->SetActiveByKeyboard();
-  menuBar->SetActive(true);
+  // This will activate the menubar as needed.
   menuForKey->OpenMenuPopup(true);
 
   // The opened menu will listen next keyup event.

toolkit/content/tests/widgets/popup_shared.js

@@ -52,6 +52,9 @@ function startPopupTests(tests) {
   document.addEventListener("DOMMenuBarActive", eventOccurred);
   document.addEventListener("DOMMenuBarInactive", eventOccurred);
 
+  // This is useful to explicitly finish a test that shouldn't trigger events.
+  document.addEventListener("TestDone", eventOccurred);
+
   gPopupTests = tests;
   gWindowUtils = SpecialPowers.getDOMWindowUtils(window);
 

toolkit/content/tests/widgets/window_menubar.xhtml

@@ -930,6 +930,30 @@ var popupTests = [
   },
 },
 
+{
+  testname: "Trying to activate menubar without activatable items shouldn't crash",
+  events: [ "TestDone menubar" ],
+  test() {
+    const items = document.querySelectorAll("menubar > menu");
+    let wasDisabled = {};
+    for (let item of items) {
+      wasDisabled[item] = item.disabled;
+      item.disabled = true;
+    }
+
+    synthesizeKey("KEY_F10");
+    setTimeout(function() {
+      synthesizeKey("KEY_F10");
+
+      for (let item of items) {
+        item.disabled = wasDisabled[item];
+      }
+
+      document.getElementById("menubar").dispatchEvent(new CustomEvent("TestDone", { bubbles: true }));
+    }, 0);
+  }
+},
+
 // bug 625151
 {
   testname: "Alt key state before deactivating the window shouldn't prevent " +