Bug 1628476: Add keyboard navigation pref to allow focus mode changes on macOS r=Jamie,fluent-reviewers,settings-reviewers,flod,mconley

Differential Revision: https://phabricator.services.mozilla.com/D182266

browser/components/preferences/main.inc.xhtml

@@ -724,6 +724,11 @@
   <checkbox id="useCursorNavigation"
             data-l10n-id="browsing-use-cursor-navigation"
             preference="accessibility.browsewithcaret"/>
+#ifdef XP_MACOSX
+  <checkbox id="useFullKeyboardNavigation"
+            data-l10n-id="browsing-use-full-keyboard-navigation"
+            preference="accessibility.tabfocus" />
+#endif
   <checkbox id="searchStartTyping"
             data-l10n-id="browsing-search-on-start-typing"
             preference="accessibility.typeaheadfind"/>

browser/components/preferences/main.js

@@ -129,6 +129,7 @@ Preferences.addAll([
   { id: "general.smoothScroll", type: "bool" },
   { id: "widget.gtk.overlay-scrollbars.enabled", type: "bool", inverted: true },
   { id: "layout.spellcheckDefault", type: "int" },
+  { id: "accessibility.tabfocus", type: "int" },
 
   {
     id: "browser.preferences.defaultPerformanceSettings.enabled",
@@ -725,6 +726,14 @@ var gMainPane = {
       document.getElementById("defaultFont"),
       element => FontBuilder.readFontSelection(element)
     );
+    Preferences.addSyncFromPrefListener(
+      document.getElementById("useFullKeyboardNavigation"),
+      () => this.readUseFullKeyboardNavigation()
+    );
+    Preferences.addSyncToPrefListener(
+      document.getElementById("useFullKeyboardNavigation"),
+      () => this.writeUseFullKeyboardNavigation()
+    );
     Preferences.addSyncFromPrefListener(
       document.getElementById("checkSpelling"),
       () => this.readCheckSpelling()
@@ -2181,6 +2190,50 @@ var gMainPane = {
     migrationWizardDialog.showModal();
   },
 
+  /**
+   * Stores the original value of the tabfocus preference to enable proper
+   * restoration if unchanged (since we're mapping an int pref onto a checkbox).
+   */
+  _storedFullKeyboardNavigation: Preferences.get("accessibility.tabfocus"),
+
+  /**
+   * Returns true if any full keyboard nav is enabled and false otherwise, caching
+   * the current value to enable proper pref restoration if the checkbox is
+   * never changed.
+   *
+   * accessibility.tabfocus
+   * - an integer controlling the focusability of:
+   *     1  text controls
+   *     2  form elements
+   *     4  links
+   *     7  all of the above
+   */
+  readUseFullKeyboardNavigation() {
+    var pref = Preferences.get("accessibility.tabfocus");
+    this._storedFullKeyboardNavigation = pref.value;
+
+    return pref.value == 7;
+  },
+
+  /**
+   * Returns the value of the full keyboard nav preference represented by UI,
+   * preserving the preference's "hidden" value if the preference is
+   * unchanged and represents a value not strictly allowed in UI.
+   */
+  writeUseFullKeyboardNavigation() {
+    var checkbox = document.getElementById("useFullKeyboardNavigation");
+    if (checkbox.checked) {
+      return 7;
+    }
+    if (this._storedFullKeyboardNavigation != 7) {
+      // 1/2/4 values set via about:config should persist
+      return this._storedFullKeyboardNavigation;
+    }
+    // When the checkbox is unchecked, this pref shouldn't exist
+    // at all.
+    return undefined;
+  },
+
   /**
    * Stores the original value of the spellchecking preference to enable proper
    * restoration if unchanged (since we're mapping a tristate onto a checkbox).

browser/components/preferences/tests/browser.ini

@@ -71,6 +71,8 @@ https_first_disabled = true
 [browser_https_only_exceptions.js]
 [browser_https_only_section.js]
 [browser_ignore_invalid_capability.js]
+[browser_keyboardfocus.js]
+skip-if = os != "mac"
 [browser_languages_subdialog.js]
 [browser_layersacceleration.js]
 [browser_localSearchShortcuts.js]

browser/components/preferences/tests/browser_keyboardfocus.js

@@ -0,0 +1,80 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+async function launchPreferences() {
+  let prefs = await openPreferencesViaOpenPreferencesAPI("paneGeneral", {
+    leaveOpen: true,
+  });
+  Assert.equal(prefs.selectedPane, "paneGeneral", "General pane was selected");
+}
+
+add_task(async function () {
+  await launchPreferences();
+  let checkbox = gBrowser.contentDocument.querySelector(
+    "#useFullKeyboardNavigation"
+  );
+  Assert.ok(
+    !Services.prefs.getIntPref("accessibility.tabfocus", undefined),
+    "no pref value should exist"
+  );
+  Assert.ok(
+    !checkbox.checked,
+    "checkbox should be unchecked before clicking on checkbox"
+  );
+
+  checkbox.click();
+
+  Assert.equal(
+    Services.prefs.getIntPref("accessibility.tabfocus"),
+    7,
+    "Prefstore should reflect checkbox's associated numeric value"
+  );
+  Assert.ok(
+    checkbox.checked,
+    "checkbox should be checked after clicking on checkbox"
+  );
+
+  checkbox.click();
+
+  Assert.ok(
+    !checkbox.checked,
+    "checkbox should be unchecked after clicking on checkbox"
+  );
+  Assert.ok(
+    !Services.prefs.getIntPref("accessibility.tabfocus", undefined),
+    "No pref value should exist"
+  );
+
+  BrowserTestUtils.removeTab(gBrowser.selectedTab);
+  SpecialPowers.pushPrefEnv({ set: [["accessibility.tabfocus", 4]] });
+  await launchPreferences();
+  checkbox = gBrowser.contentDocument.querySelector(
+    "#useFullKeyboardNavigation"
+  );
+
+  Assert.ok(
+    !checkbox.checked,
+    "checkbox should stay unchecked after setting non-7 pref value"
+  );
+  Assert.equal(
+    Services.prefs.getIntPref("accessibility.tabfocus", 0),
+    4,
+    "pref should have value in store"
+  );
+
+  BrowserTestUtils.removeTab(gBrowser.selectedTab);
+  SpecialPowers.pushPrefEnv({ set: [["accessibility.tabfocus", 7]] });
+  await launchPreferences();
+  checkbox = gBrowser.contentDocument.querySelector(
+    "#useFullKeyboardNavigation"
+  );
+
+  Assert.equal(
+    Services.prefs.getIntPref("accessibility.tabfocus", 0),
+    7,
+    "Pref value should update after modification"
+  );
+  Assert.ok(checkbox.checked, "checkbox should be checked");
+
+  BrowserTestUtils.removeTab(gBrowser.selectedTab);
+});

browser/locales/en-US/browser/preferences/preferences.ftl

@@ -583,6 +583,10 @@ browsing-use-cursor-navigation =
     .label = Always use the cursor keys to navigate within pages
     .accesskey = k
 
+browsing-use-full-keyboard-navigation =
+    .label = Use the tab key to move focus between form controls and links
+    .accesskey = t
+
 browsing-search-on-start-typing =
     .label = Search for text when you start typing
     .accesskey = x