Bug 1614224 - Fix <dialog> focus wrap-around, and add tests for it. r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D62490

--HG--
extra : moz-landing-system : lando

dom/base/nsFocusManager.cpp

@@ -3491,19 +3491,19 @@ nsresult nsFocusManager::GetNextTabbableContent(
             NS_ADDREF(*aResultContent = contentToFocus);
             return NS_OK;
           }
+          // If we've wrapped around already, then carry on.
+          if (aOriginalStartContent &&
+              currentTopLevelScopeOwner ==
+                  GetTopLevelScopeOwner(aOriginalStartContent)) {
+            // FIXME: Shouldn't this return null instead?  aOriginalStartContent
+            // isn't focusable after all.
+            NS_ADDREF(*aResultContent = aOriginalStartContent);
+            return NS_OK;
+          }
         }
         // There is no next tabbable content in currentTopLevelScopeOwner's
         // scope. We should continue the loop in order to skip all contents that
-        // is in currentTopLevelScopeOwner's scope. Unless we've wrapped around
-        // already.
-        if (aOriginalStartContent &&
-            currentTopLevelScopeOwner ==
-                GetTopLevelScopeOwner(aOriginalStartContent)) {
-          // FIXME: Shouldn't this return null instead?  aOriginalStartContent
-          // isn't focusable after all.
-          NS_ADDREF(*aResultContent = aOriginalStartContent);
-          return NS_OK;
-        }
+        // is in currentTopLevelScopeOwner's scope.
         continue;
       }
 

dom/tests/mochitest/chrome/chrome.ini

@@ -20,6 +20,7 @@ support-files =
   file_subscript_bindings.js
   focus_frameset.html
   focus_window2.xhtml
+  focus_dialog.xhtml
   fullscreen.xhtml
   queryCaretRectUnix.html
   queryCaretRectWin.html
@@ -57,6 +58,7 @@ skip-if = os != 'mac' || os_version == '10.14' # 10.14 due to bug 1558642
 [test_elements_proto.xhtml]
 [test_focus.xhtml]
 skip-if = os == 'linux' # bug 1296622, Bug 1605253
+[test_focus_dialog.xhtml]
 [test_focus_docnav.xhtml]
 [test_focused_link_scroll.xhtml]
 [test_fullscreen.xhtml]

dom/tests/mochitest/chrome/focus_dialog.xhtml

@@ -0,0 +1,71 @@
+<?xml version="1.0"?>
+<?xml-stylesheet href="chrome://global/skin" type="text/css"?>
+
+<window id="other-document"
+        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+<dialog buttons="accept">
+
+<script src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"></script>
+
+<button id="button-1" label="Something"/>
+<button id="button-2" label="Something else"/>
+
+<script>
+<![CDATA[
+
+window.is = window.arguments[0].is;
+window.isnot = window.arguments[0].isnot;
+window.ok = window.arguments[0].ok;
+window.SimpleTest = window.arguments[0].SimpleTest;
+
+(async function() {
+  await new Promise(resolve => {
+    window.onload = resolve;
+  });
+
+  await new Promise(resolve => SimpleTest.waitForFocus(resolve, window));
+
+  let dialog = document.querySelector("dialog");
+  let shadow = dialog.shadowRoot;
+
+  let button = document.getElementById("button-1");
+  let button2 = document.getElementById("button-2");
+  let forwardSequence = [];
+
+  button.focus();
+
+  is(document.activeElement, button, "Should've focused the button");
+  forwardSequence.push(button);
+
+  synthesizeKey("KEY_Tab");
+
+  is(document.activeElement, button2, "Should've moved to the second button");
+  forwardSequence.push(button2);
+
+  synthesizeKey("KEY_Tab");
+
+  isnot(shadow.activeElement, null, "Should've focused the shadow root button");
+  is(document.activeElement, dialog, "document.focusedElement should be the dialog because retargeting");
+  forwardSequence.push(shadow.activeElement);
+
+  synthesizeKey("KEY_Tab");
+
+  is(document.activeElement, button, "Should properly wrap around going forward");
+
+  while (forwardSequence.length) {
+    synthesizeKey("KEY_Tab", { shiftKey: true });
+    is(
+      shadow.activeElement || document.activeElement,
+      forwardSequence.pop(),
+      "Should travel backwards correctly: " + forwardSequence.length
+    );
+  }
+
+  window.close();
+  SimpleTest.finish();
+}());
+
+]]>
+</script>
+</dialog>
+</window>

dom/tests/mochitest/chrome/test_focus_dialog.xhtml

@@ -0,0 +1,33 @@
+<?xml version="1.0"?>
+<?xml-stylesheet href="chrome://global/skin" type="text/css"?>
+<?xml-stylesheet href="chrome://mochikit/content/tests/SimpleTest/test.css" type="text/css"?>
+
+<window title="Focus Tests"
+  onload="setTimeout(runTest, 0);"
+  xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+
+  <script src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"/>
+
+<script>
+if (navigator.platform.startsWith("Win")) {
+  SimpleTest.expectAssertions(0, 1);
+}
+
+SimpleTest.waitForExplicitFinish();
+async function runTest() {
+  // Enable full tab focus model on mac.
+  await SpecialPowers.pushPrefEnv({ set: [["accessibility.tabfocus", 7]] });
+  window.openDialog("focus_dialog.xhtml", "_blank", "chrome,modal,noopener", window);
+}
+</script>
+
+<body xmlns="http://www.w3.org/1999/xhtml">
+<p id="display">
+</p>
+<div id="content" style="display: none">
+</div>
+<pre id="test">
+</pre>
+</body>
+
+</window>