Improve document focus control (#1167)

* Improve styles for #content-scroll-focus

* Create new class to manage and control document focus

* Use new focus class

* Add a check to prevent redundant .blur calls

19 files changed, 179 insertions, 34 deletions

diff --git a/ext/bg/css/settings2.css b/ext/bg/css/settings2.css
index 80217d9b..0933019f 100644
--- a/ext/bg/css/settings2.css
+++ b/ext/bg/css/settings2.css
@@ -361,8 +361,16 @@ h3 {
     opacity: 0;
     margin: 0;
     padding: 0;
+    outline: none;
     background-color: transparent;
     display: inline;
+    width: 0;
+    height: 0;
+    line-height: 0;
+    user-select: none;
+}
+#content-scroll-focus::-moz-focus-inner {
+    border: 0;
 }
 .content-dimmer {
     display: block;
diff --git a/ext/bg/info.html b/ext/bg/info.html
index 99f595d1..cc69ed1c 100644
--- a/ext/bg/info.html
+++ b/ext/bg/info.html
@@ -62,6 +62,7 @@
 <script src="/mixed/js/comm.js"></script>
 <script src="/mixed/js/api.js"></script>
 
+<script src="/mixed/js/document-focus-controller.js"></script>
 <script src="/mixed/js/html-template-collection.js"></script>
 <script src="/bg/js/settings/settings-controller.js"></script>
 <script src="/bg/js/settings/backup-controller.js"></script>
diff --git a/ext/bg/js/generic-page-main.js b/ext/bg/js/generic-page-main.js
index 8e1b3c76..29fcf63d 100644
--- a/ext/bg/js/generic-page-main.js
+++ b/ext/bg/js/generic-page-main.js
@@ -15,13 +15,18 @@
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  */
 
+/* global
+ * DocumentFocusController
+ */
+
 function setupEnvironmentInfo() {
     const {manifest_version: manifestVersion} = chrome.runtime.getManifest();
     document.documentElement.dataset.manifestVersion = `${manifestVersion}`;
 }
 
 (() => {
-    document.querySelector('#content-scroll-focus').focus();
+    const documentFocusController = new DocumentFocusController();
+    documentFocusController.prepare();
     document.documentElement.dataset.loaded = 'true';
     setupEnvironmentInfo();
 })();
diff --git a/ext/bg/js/info-main.js b/ext/bg/js/info-main.js
index 58e9d3b7..71cfdbd8 100644
--- a/ext/bg/js/info-main.js
+++ b/ext/bg/js/info-main.js
@@ -17,6 +17,7 @@
 
 /* global
  * BackupController
+ * DocumentFocusController
  * SettingsController
  * api
  */
@@ -47,7 +48,8 @@ function getOperatingSystemDisplayName(os) {
 
 (async () => {
     try {
-        document.querySelector('#content-scroll-focus').focus();
+        const documentFocusController = new DocumentFocusController();
+        documentFocusController.prepare();
 
         const manifest = chrome.runtime.getManifest();
         const language = chrome.i18n.getUILanguage();
diff --git a/ext/bg/js/permissions-main.js b/ext/bg/js/permissions-main.js
index a464f40e..b1c0430e 100644
--- a/ext/bg/js/permissions-main.js
+++ b/ext/bg/js/permissions-main.js
@@ -16,6 +16,7 @@
  */
 
 /* global
+ * DocumentFocusController
  * api
  */
 
@@ -52,7 +53,9 @@ async function setPermissionsGranted(permissions, shouldHave) {
 
 (async () => {
     try {
-        document.querySelector('#content-scroll-focus').focus();
+        const documentFocusController = new DocumentFocusController();
+        documentFocusController.prepare();
+
         document.querySelector('#extension-id-example').textContent = chrome.runtime.getURL('/');
 
         api.forwardLogsToBackend();
diff --git a/ext/bg/js/search-main.js b/ext/bg/js/search-main.js
index f98028b3..4bcf14e8 100644
--- a/ext/bg/js/search-main.js
+++ b/ext/bg/js/search-main.js
@@ -17,6 +17,7 @@
 
 /* global
  * DisplaySearch
+ * DocumentFocusController
  * JapaneseUtil
  * api
  * wanakana
@@ -24,11 +25,14 @@
 
 (async () => {
     try {
+        const documentFocusController = new DocumentFocusController();
+        documentFocusController.prepare();
+
         api.forwardLogsToBackend();
         await yomichan.backendReady();
 
         const japaneseUtil = new JapaneseUtil(wanakana);
-        const displaySearch = new DisplaySearch(japaneseUtil);
+        const displaySearch = new DisplaySearch(japaneseUtil, documentFocusController);
         await displaySearch.prepare();
 
         document.documentElement.dataset.loaded = 'true';
diff --git a/ext/bg/js/search.js b/ext/bg/js/search.js
index 884ab33c..fb8757eb 100644
--- a/ext/bg/js/search.js
+++ b/ext/bg/js/search.js
@@ -24,8 +24,8 @@
  */
 
 class DisplaySearch extends Display {
-    constructor(japaneseUtil) {
-        super('search', japaneseUtil);
+    constructor(japaneseUtil, documentFocusController) {
+        super('search', japaneseUtil, documentFocusController);
         this._searchButton = document.querySelector('#search-button');
         this._queryInput = document.querySelector('#search-textbox');
         this._introElement = document.querySelector('#intro');
diff --git a/ext/bg/js/settings2/settings-main.js b/ext/bg/js/settings2/settings-main.js
index 6e6186e5..162ed3cd 100644
--- a/ext/bg/js/settings2/settings-main.js
+++ b/ext/bg/js/settings2/settings-main.js
@@ -23,6 +23,7 @@
  * ClipboardPopupsController
  * DictionaryController
  * DictionaryImportController
+ * DocumentFocusController
  * GenericSettingController
  * ModalController
  * NestedPopupsController
@@ -53,7 +54,8 @@ async function setupGenericSettingsController(genericSettingController) {
 
 (async () => {
     try {
-        document.querySelector('#content-scroll-focus').focus();
+        const documentFocusController = new DocumentFocusController();
+        documentFocusController.prepare();
 
         const statusFooter = new StatusFooter(document.querySelector('.status-footer-container'));
         statusFooter.prepare();
diff --git a/ext/bg/js/welcome-main.js b/ext/bg/js/welcome-main.js
index 8d43fdb0..cbc7e2f8 100644
--- a/ext/bg/js/welcome-main.js
+++ b/ext/bg/js/welcome-main.js
@@ -18,6 +18,7 @@
 /* global
  * DictionaryController
  * DictionaryImportController
+ * DocumentFocusController
  * GenericSettingController
  * ModalController
  * ScanInputsSimpleController
@@ -42,7 +43,8 @@ async function setupGenericSettingsController(genericSettingController) {
 
 (async () => {
     try {
-        document.querySelector('#content-scroll-focus').focus();
+        const documentFocusController = new DocumentFocusController();
+        documentFocusController.prepare();
 
         const statusFooter = new StatusFooter(document.querySelector('.status-footer-container'));
         statusFooter.prepare();
diff --git a/ext/bg/legal.html b/ext/bg/legal.html
index cda3dcc7..7aca19bc 100644
--- a/ext/bg/legal.html
+++ b/ext/bg/legal.html
@@ -224,6 +224,8 @@ THE SOFTWARE.
 </div></div>
 
 <!-- Scripts -->
+<script src="/mixed/js/document-focus-controller.js"></script>
+
 <script src="/bg/js/generic-page-main.js"></script>
 
 </body>
diff --git a/ext/bg/permissions.html b/ext/bg/permissions.html
index a1138aee..596f038a 100644
--- a/ext/bg/permissions.html
+++ b/ext/bg/permissions.html
@@ -138,6 +138,8 @@
 <script src="/mixed/js/comm.js"></script>
 <script src="/mixed/js/api.js"></script>
 
+<script src="/mixed/js/document-focus-controller.js"></script>
+
 <script src="/bg/js/permissions-main.js"></script>
 
 </body>
diff --git a/ext/bg/search.html b/ext/bg/search.html
index bcc02578..f0333ab2 100644
--- a/ext/bg/search.html
+++ b/ext/bg/search.html
@@ -79,6 +79,7 @@
 <script src="/mixed/js/japanese.js"></script>
 
 <script src="/mixed/js/cache-map.js"></script>
+<script src="/mixed/js/document-focus-controller.js"></script>
 <script src="/mixed/js/document-util.js"></script>
 <script src="/fg/js/dom-text-scanner.js"></script>
 <script src="/fg/js/text-source-range.js"></script>
diff --git a/ext/bg/settings2.html b/ext/bg/settings2.html
index 850b6794..120f4ba3 100644
--- a/ext/bg/settings2.html
+++ b/ext/bg/settings2.html
@@ -2555,6 +2555,7 @@
 <script src="/mixed/js/audio-system.js"></script>
 <script src="/mixed/js/cache-map.js"></script>
 <script src="/mixed/js/dictionary-data-util.js"></script>
+<script src="/mixed/js/document-focus-controller.js"></script>
 <script src="/mixed/js/document-util.js"></script>
 <script src="/mixed/js/dom-data-binder.js"></script>
 <script src="/mixed/js/html-template-collection.js"></script>
diff --git a/ext/bg/welcome.html b/ext/bg/welcome.html
index f3a8c63f..6aebb356 100644
--- a/ext/bg/welcome.html
+++ b/ext/bg/welcome.html
@@ -334,6 +334,7 @@
 <script src="/mixed/js/api.js"></script>
 
 <script src="/mixed/js/cache-map.js"></script>
+<script src="/mixed/js/document-focus-controller.js"></script>
 <script src="/mixed/js/document-util.js"></script>
 <script src="/mixed/js/dom-data-binder.js"></script>
 <script src="/mixed/js/html-template-collection.js"></script>
diff --git a/ext/fg/float.html b/ext/fg/float.html
index 4dc0696e..2064e8ed 100644
--- a/ext/fg/float.html
+++ b/ext/fg/float.html
@@ -95,6 +95,7 @@
 <script src="/mixed/js/display-generator.js"></script>
 <script src="/mixed/js/display-history.js"></script>
 <script src="/mixed/js/display-notification.js"></script>
+<script src="/mixed/js/document-focus-controller.js"></script>
 <script src="/mixed/js/dynamic-loader.js"></script>
 <script src="/mixed/js/frame-endpoint.js"></script>
 <script src="/mixed/js/media-loader.js"></script>
diff --git a/ext/fg/js/float-main.js b/ext/fg/js/float-main.js
index a8554867..aee736a2 100644
--- a/ext/fg/js/float-main.js
+++ b/ext/fg/js/float-main.js
@@ -17,17 +17,21 @@
 
 /* global
  * Display
+ * DocumentFocusController
  * JapaneseUtil
  * api
  */
 
 (async () => {
     try {
+        const documentFocusController = new DocumentFocusController();
+        documentFocusController.prepare();
+
         api.forwardLogsToBackend();
         await yomichan.backendReady();
 
         const japaneseUtil = new JapaneseUtil(null);
-        const display = new Display('popup', japaneseUtil);
+        const display = new Display('popup', japaneseUtil, documentFocusController);
         await display.prepare();
         display.initializeState();
 
diff --git a/ext/mixed/css/display.css b/ext/mixed/css/display.css
index a6ca2810..f0f39d07 100644
--- a/ext/mixed/css/display.css
+++ b/ext/mixed/css/display.css
@@ -244,6 +244,24 @@ a {
 }
 
 
+/* Selection */
+#content-scroll-focus {
+    opacity: 0;
+    margin: 0;
+    padding: 0;
+    outline: none;
+    background-color: transparent;
+    display: inline;
+    width: 0;
+    height: 0;
+    line-height: 0;
+    user-select: none;
+}
+#content-scroll-focus::-moz-focus-inner {
+    border: 0;
+}
+
+
 /* Scrollbars */
 :root:not([data-theme=default]) .scrollbar {
     scrollbar-color: var(--scrollbar-thumb-color) var(--scrollbar-track-color);
diff --git a/ext/mixed/js/display.js b/ext/mixed/js/display.js
index 7491cd60..b9ea3802 100644
--- a/ext/mixed/js/display.js
+++ b/ext/mixed/js/display.js
@@ -35,10 +35,11 @@
  */
 
 class Display extends EventDispatcher {
-    constructor(pageType, japaneseUtil) {
+    constructor(pageType, japaneseUtil, documentFocusController) {
         super();
         this._pageType = pageType;
         this._japaneseUtil = japaneseUtil;
+        this._documentFocusController = documentFocusController;
         this._container = document.querySelector('#definitions');
         this._definitions = [];
         this._optionsContext = {depth: 0, url: window.location.href};
@@ -95,7 +96,6 @@ class Display extends EventDispatcher {
         this._updateAdderButtonsPromise = Promise.resolve();
         this._contentScrollElement = document.querySelector('#content-scroll');
         this._contentScrollBodyElement = document.querySelector('#content-body');
-        this._contentScrollFocusElement = document.querySelector('#content-scroll-focus');
         this._windowScroll = new WindowScroll(this._contentScrollElement);
         this._contentSidebar = document.querySelector('#content-sidebar');
         this._closeButton = document.querySelector('#close-button');
@@ -218,7 +218,6 @@ class Display extends EventDispatcher {
             ['popupMessage', {async: 'dynamic', handler: this._onDirectMessage.bind(this)}]
         ]);
         window.addEventListener('message', this._onWindowMessage.bind(this), false);
-        window.addEventListener('focus', this._onWindowFocus.bind(this), false);
 
         if (this._pageType === 'popup' && documentElement !== null) {
             documentElement.addEventListener('mouseup', this._onDocumentElementMouseUp.bind(this), false);
@@ -241,9 +240,6 @@ class Display extends EventDispatcher {
         if (this._frameResizeHandle !== null) {
             this._frameResizeHandle.addEventListener('mousedown', this._onFrameResizerMouseDown.bind(this), false);
         }
-
-        // Final preparation
-        this._updateFocusedElement();
     }
 
     initializeState() {
@@ -457,8 +453,7 @@ class Display extends EventDispatcher {
     }
 
     blurElement(element) {
-        element.blur();
-        this._updateFocusedElement();
+        this._documentFocusController.blurElement(element);
     }
 
     searchLast() {
@@ -711,10 +706,6 @@ class Display extends EventDispatcher {
         }
     }
 
-    _onWindowFocus() {
-        this._updateFocusedElement();
-    }
-
     async _onKanjiLookup(e) {
         try {
             e.preventDefault();
@@ -1633,19 +1624,6 @@ class Display extends EventDispatcher {
         await this.setOptionsContext(optionsContext);
     }
 
-    _updateFocusedElement() {
-        const target = this._contentScrollFocusElement;
-        if (target === null) { return; }
-        const {activeElement} = document;
-        if (
-            activeElement === null ||
-            activeElement === document.documentElement ||
-            activeElement === document.body
-        ) {
-            target.focus({preventScroll: true});
-        }
-    }
-
     _setContentScale(scale) {
         const body = document.body;
         if (body === null) { return; }
diff --git a/ext/mixed/js/document-focus-controller.js b/ext/mixed/js/document-focus-controller.js
new file mode 100644
index 00000000..985e9f5a
--- /dev/null
+++ b/ext/mixed/js/document-focus-controller.js
@@ -0,0 +1,110 @@
+/*
+ * Copyright (C) 2020  Yomichan Authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+/**
+ * This class is used to control the document focus when a non-body element contains the main scrollbar.
+ * Web browsers will not automatically focus a custom element with the scrollbar on load, which results in
+ * keyboard shortcuts (e.g. arrow keys) not controlling page scroll. Instead, this class will manually
+ * focus a dummy element inside the main content, which gives keyboard scroll focus to that element.
+ */
+class DocumentFocusController {
+    constructor() {
+        this._contentScrollFocusElement = document.querySelector('#content-scroll-focus');
+    }
+
+    prepare() {
+        window.addEventListener('focus', this._onWindowFocus.bind(this), false);
+        this._updateFocusedElement(false);
+    }
+
+    blurElement(element) {
+        if (document.activeElement !== element) { return; }
+        element.blur();
+        this._updateFocusedElement(false);
+    }
+
+    // Private
+
+    _onWindowFocus() {
+        this._updateFocusedElement(false);
+    }
+
+    _updateFocusedElement(force) {
+        const target = this._contentScrollFocusElement;
+        if (target === null) { return; }
+
+        const {activeElement} = document;
+        if (
+            force ||
+            activeElement === null ||
+            activeElement === document.documentElement ||
+            activeElement === document.body
+        ) {
+            // Get selection
+            const selection = window.getSelection();
+            const selectionRanges1 = this._getSelectionRanges(selection);
+
+            // Note: This function will cause any selected text to be deselected on Firefox.
+            target.focus({preventScroll: true});
+
+            // Restore selection
+            const selectionRanges2 = this._getSelectionRanges(selection);
+            if (!this._areRangesSame(selectionRanges1, selectionRanges2)) {
+                this._setSelectionRanges(selection, selectionRanges1);
+            }
+        }
+    }
+
+    _getSelectionRanges(selection) {
+        const ranges = [];
+        for (let i = 0, ii = selection.rangeCount; i < ii; ++i) {
+            ranges.push(selection.getRangeAt(i));
+        }
+        return ranges;
+    }
+
+    _setSelectionRanges(selection, ranges) {
+        selection.removeAllRanges();
+        for (const range of ranges) {
+            selection.addRange(range);
+        }
+    }
+
+    _areRangesSame(ranges1, ranges2) {
+        const ii = ranges1.length;
+        if (ii !== ranges2.length) {
+            return false;
+        }
+
+        for (let i = 0; i < ii; ++i) {
+            const range1 = ranges1[i];
+            const range2 = ranges2[i];
+            try {
+                if (
+                    range1.compareBoundaryPoints(Range.START_TO_START, range2) !== 0 ||
+                    range1.compareBoundaryPoints(Range.END_TO_END, range2) !== 0
+                ) {
+                    return false;
+                }
+            } catch (e) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}