1 files changed, 103 insertions, 0 deletions
diff --git a/ext/js/dom/panel-element.js b/ext/js/dom/panel-element.js
new file mode 100644
index 00000000..1ef61d6f
--- /dev/null
+++ b/ext/js/dom/panel-element.js
@@ -0,0 +1,103 @@
+/*
+ * Copyright (C) 2020-2021  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 PanelElement extends EventDispatcher {
+    constructor({node, closingAnimationDuration}) {
+        super();
+        this._node = node;
+        this._closingAnimationDuration = closingAnimationDuration;
+        this._hiddenAnimatingClass = 'hidden-animating';
+        this._mutationObserver = null;
+        this._visible = false;
+        this._closeTimer = null;
+    }
+
+    get node() {
+        return this._node;
+    }
+
+    isVisible() {
+        return !this._node.hidden;
+    }
+
+    setVisible(value, animate=true) {
+        value = !!value;
+        if (this.isVisible() === value) { return; }
+
+        if (this._closeTimer !== null) {
+            clearTimeout(this._closeTimer);
+            this._completeClose(true);
+        }
+
+        const node = this._node;
+        const {classList} = node;
+        if (value) {
+            if (animate) { classList.add(this._hiddenAnimatingClass); }
+            getComputedStyle(node).getPropertyValue('display'); // Force update of CSS display property, allowing animation
+            classList.remove(this._hiddenAnimatingClass);
+            node.hidden = false;
+            node.focus();
+        } else {
+            if (animate) { classList.add(this._hiddenAnimatingClass); }
+            node.hidden = true;
+            if (animate) {
+                this._closeTimer = setTimeout(() => this._completeClose(false), this._closingAnimationDuration);
+            }
+        }
+    }
+
+    on(eventName, callback) {
+        if (eventName === 'visibilityChanged') {
+            if (this._mutationObserver === null) {
+                this._visible = this.isVisible();
+                this._mutationObserver = new MutationObserver(this._onMutation.bind(this));
+                this._mutationObserver.observe(this._node, {
+                    attributes: true,
+                    attributeFilter: ['hidden'],
+                    attributeOldValue: true
+                });
+            }
+        }
+        return super.on(eventName, callback);
+    }
+
+    off(eventName, callback) {
+        const result = super.off(eventName, callback);
+        if (eventName === 'visibilityChanged' && !this.hasListeners(eventName)) {
+            if (this._mutationObserver !== null) {
+                this._mutationObserver.disconnect();
+                this._mutationObserver = null;
+            }
+        }
+        return result;
+    }
+
+    // Private
+
+    _onMutation() {
+        const visible = this.isVisible();
+        if (this._visible === visible) { return; }
+        this._visible = visible;
+        this.trigger('visibilityChanged', {visible});
+    }
+
+    _completeClose(reopening) {
+        this._closeTimer = null;
+        this._node.classList.remove(this._hiddenAnimatingClass);
+        this.trigger('closeCompleted', {reopening});
+    }
+}