Definition collapsing when overflowing (#1575)

* Add double-down-chevron.svg

* Add options

* Update dictionary importers

* Update settings

* Add support for collapsible definitions

* Improve case when there is a very small amount of overflow

* Fix incorrect enabled state of newly imported dictionaries

2 files changed, 135 insertions, 0 deletions

diff --git a/ext/js/display/display.js b/ext/js/display/display.js
index ee2448d6..b17a6168 100644
--- a/ext/js/display/display.js
+++ b/ext/js/display/display.js
@@ -23,6 +23,7 @@
  * DisplayHistory
  * DisplayNotification
  * DocumentUtil
+ * ElementOverflowController
  * FrameEndpoint
  * Frontend
  * HotkeyHelpController
@@ -114,6 +115,7 @@ class Display extends EventDispatcher {
         this._ankiNoteNotificationEventListeners = null;
         this._queryPostProcessor = null;
         this._optionToggleHotkeyHandler = new OptionToggleHotkeyHandler(this);
+        this._elementOverflowController = new ElementOverflowController();
 
         this._hotkeyHandler.registerActions([
             ['close',             () => { this._onHotkeyClose(); }],
@@ -305,6 +307,7 @@ class Display extends EventDispatcher {
         this._hotkeyHelpController.setOptions(options);
         this._displayGenerator.updateHotkeys();
         this._hotkeyHelpController.setupNode(document.documentElement);
+        this._elementOverflowController.setOptions(options);
 
         this._queryParser.setOptions({
             selectedParser: options.parsing.selectedParser,
@@ -535,6 +538,7 @@ class Display extends EventDispatcher {
             this._hideAnkiNoteErrors(false);
             this._definitions = [];
             this._definitionNodes = [];
+            this._elementOverflowController.clearElements();
 
             // Prepare
             const urlSearchParams = new URLSearchParams(location.search);
@@ -966,6 +970,8 @@ class Display extends EventDispatcher {
             if (focusEntry === i) {
                 this._focusEntry(i, false);
             }
+
+            this._elementOverflowController.addElements(entry);
         }
 
         if (typeof scrollX === 'number' || typeof scrollY === 'number') {
diff --git a/ext/js/display/element-overflow-controller.js b/ext/js/display/element-overflow-controller.js
new file mode 100644
index 00000000..ccea1417
--- /dev/null
+++ b/ext/js/display/element-overflow-controller.js
@@ -0,0 +1,129 @@
+/*
+ * Copyright (C) 2021  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/>.
+ */
+
+class ElementOverflowController {
+    constructor() {
+        this._elements = [];
+        this._checkTimer = null;
+        this._eventListeners = new EventListenerCollection();
+        this._windowEventListeners = new EventListenerCollection();
+        this._dictionaries = new Map();
+        this._updateBind = this._update.bind(this);
+        this._onWindowResizeBind = this._onWindowResize.bind(this);
+        this._onToggleButtonClickBind = this._onToggleButtonClick.bind(this);
+    }
+
+    setOptions(options) {
+        this._dictionaries.clear();
+        for (const [dictionary, {definitionsCollapsible}] of Object.entries(options.dictionaries)) {
+            let collapsible = false;
+            let collapsed = false;
+            switch (definitionsCollapsible) {
+                case 'expanded':
+                    collapsible = true;
+                    break;
+                case 'collapsed':
+                    collapsible = true;
+                    collapsed = true;
+                    break;
+            }
+            if (!collapsible) { continue; }
+            this._dictionaries.set(dictionary, {collapsed});
+        }
+    }
+
+    addElements(entry) {
+        if (this._dictionaries.size === 0) { return; }
+
+        const elements = entry.querySelectorAll('.definition-item-inner');
+        let any = false;
+        for (const element of elements) {
+            const {dictionary} = element.parentNode.dataset;
+            const dictionaryInfo = this._dictionaries.get(dictionary);
+            if (typeof dictionaryInfo === 'undefined') { continue; }
+
+            this._updateElement(element);
+            this._elements.push(element);
+
+            if (dictionaryInfo.collapsed) {
+                element.classList.add('collapsed');
+            }
+
+            const button = element.querySelector('.definition-item-expansion-button');
+            if (button !== null) {
+                this._eventListeners.addEventListener(button, 'click', this._onToggleButtonClickBind, false);
+            }
+
+            any = true;
+        }
+
+        if (any && this._windowEventListeners.size === 0) {
+            this._windowEventListeners.addEventListener(window, 'resize', this._onWindowResizeBind, false);
+        }
+    }
+
+    clearElements() {
+        if (this._elements.length === 0) { return; }
+        this._elements = [];
+        this._windowEventListeners.removeAllEventListeners();
+    }
+
+    // Private
+
+    _onWindowResize() {
+        if (this._checkTimer !== null) {
+            this._cancelIdleCallback(this._checkTimer);
+        }
+        this._checkTimer = this._requestIdleCallback(this._updateBind, 100);
+    }
+
+    _onToggleButtonClick(e) {
+        const container = e.currentTarget.closest('.definition-item-inner');
+        if (container === null) { return; }
+        container.classList.toggle('collapsed');
+    }
+
+    _update() {
+        for (const element of this._elements) {
+            this._updateElement(element);
+        }
+    }
+
+    _updateElement(element) {
+        const {classList} = element;
+        classList.add('collapse-test');
+        const collapsible = element.scrollHeight > element.clientHeight || element.scrollWidth > element.clientWidth;
+        classList.toggle('collapsible', collapsible);
+        classList.remove('collapse-test');
+    }
+
+    _requestIdleCallback(callback, timeout) {
+        if (typeof requestIdleCallback === 'function') {
+            return requestIdleCallback(callback, {timeout});
+        } else {
+            return setTimeout(callback, timeout);
+        }
+    }
+
+    _cancelIdleCallback(handle) {
+        if (typeof cancelIdleCallback === 'function') {
+            cancelIdleCallback(handle);
+        } else {
+            clearTimeout(handle);
+        }
+    }
+}