Replace tribute with text-expander-element for textarea (#23985)

The completion popup now behaves now much more as expected than before
for the raw textarea:
- You can press <kbd>Tab</kbd> or <kbd>Enter</kbd> once the completion
popup is open to accept the selected item
- The menu does not close automatically when moving the cursor
- When you delete text, previously correct suggestions are shown again
- If you delete all text until the opening char (`@` or `:`) after
applying a suggestion, the popup reappears again
- Menu UI has been improved

<img width="278" alt="Screenshot 2023-04-07 at 19 43 42"
src="https://user-images.githubusercontent.com/115237/230653601-d6517b9f-0988-445e-aa57-5ebfaf5039f3.png">

6 files changed, 172 insertions, 5 deletions

diff --git a/package-lock.json b/package-lock.json
index fa096811ea..3d565d7864 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -13,6 +13,7 @@
         "@citation-js/plugin-software-formats": "0.6.1",
         "@claviska/jquery-minicolors": "2.3.6",
         "@github/markdown-toolbar-element": "2.1.1",
+        "@github/text-expander-element": "2.3.0",
         "@mcaptcha/vanilla-glue": "0.1.0-alpha-3",
         "@primer/octicons": "18.3.0",
         "@vue/compiler-sfc": "3.2.47",
@@ -840,11 +841,24 @@
         "node": "^12.22.0 || ^14.17.0 || >=16.0.0"
       }
     },
+    "node_modules/@github/combobox-nav": {
+      "version": "2.1.7",
+      "resolved": "https://registry.npmjs.org/@github/combobox-nav/-/combobox-nav-2.1.7.tgz",
+      "integrity": "sha512-Webx0W5iTpkk5Chy9dB/1BEUORQ0qrwui8HaaVBiy75W2VOJg96WTuKj1rXENAJ3XTMhdEF53bn0LYfvP0EKvg=="
+    },
     "node_modules/@github/markdown-toolbar-element": {
       "version": "2.1.1",
       "resolved": "https://registry.npmjs.org/@github/markdown-toolbar-element/-/markdown-toolbar-element-2.1.1.tgz",
       "integrity": "sha512-J++rpd5H9baztabJQB82h26jtueOeBRSTqetk9Cri+Lj/s28ndu6Tovn0uHQaOKtBWDobFunk9b5pP5vcqt7cA=="
     },
+    "node_modules/@github/text-expander-element": {
+      "version": "2.3.0",
+      "resolved": "https://registry.npmjs.org/@github/text-expander-element/-/text-expander-element-2.3.0.tgz",
+      "integrity": "sha512-E1KCxTOA/7Y4dP5g7vXbfRDFU6/SjU0TuJxx6JMwvxzI/NlBrXyXsx/fjFskD2T/un6i6CNKnXu1ZwExDLjcqw==",
+      "dependencies": {
+        "@github/combobox-nav": "^2.0.2"
+      }
+    },
     "node_modules/@humanwhocodes/config-array": {
       "version": "0.11.8",
       "resolved": "https://registry.npmjs.org/@humanwhocodes/config-array/-/config-array-0.11.8.tgz",
diff --git a/package.json b/package.json
index bc9f8676bb..829b9f4ad0 100644
--- a/package.json
+++ b/package.json
@@ -13,6 +13,7 @@
     "@citation-js/plugin-software-formats": "0.6.1",
     "@claviska/jquery-minicolors": "2.3.6",
     "@github/markdown-toolbar-element": "2.1.1",
+    "@github/text-expander-element": "2.3.0",
     "@mcaptcha/vanilla-glue": "0.1.0-alpha-3",
     "@primer/octicons": "18.3.0",
     "@vue/compiler-sfc": "3.2.47",
diff --git a/templates/shared/combomarkdowneditor.tmpl b/templates/shared/combomarkdowneditor.tmpl
index 0027ce8427..887673e40e 100644
--- a/templates/shared/combomarkdowneditor.tmpl
+++ b/templates/shared/combomarkdowneditor.tmpl
@@ -39,7 +39,9 @@ Template Attributes:
 				<span class="markdown-toolbar-button markdown-switch-easymde">{{svg "octicon-arrow-switch"}}</span>
 			</div>
 		</markdown-toolbar>
-		<textarea class="markdown-text-editor js-quick-submit" name="{{.TextareaName}}" placeholder="{{.TextareaPlaceholder}}">{{.TextareaContent}}</textarea>
+		<text-expander keys=": @">
+			<textarea class="markdown-text-editor js-quick-submit" name="{{.TextareaName}}" placeholder="{{.TextareaPlaceholder}}">{{.TextareaContent}}</textarea>
+		</text-expander>
 	</div>
 	<div class="ui tab markup" data-tab-panel="markdown-previewer">
 		{{.locale.Tr "loading"}}
diff --git a/web_src/css/editor-markdown.css b/web_src/css/editor-markdown.css
index da64164aec..1a09b5d596 100644
--- a/web_src/css/editor-markdown.css
+++ b/web_src/css/editor-markdown.css
@@ -30,3 +30,66 @@
 .combo-markdown-editor .CodeMirror-scroll {
   max-height: calc(100vh - 200px);
 }
+
+text-expander {
+  display: block;
+  position: relative;
+}
+
+text-expander .suggestions {
+  position: absolute;
+  min-width: 180px;
+  padding: 0;
+  margin-top: 24px;
+  list-style: none;
+  background: var(--color-box-body);
+  border-radius: 5px;
+  border: 1px solid var(--color-secondary);
+  box-shadow: 0 .5rem 1rem var(--color-shadow);
+}
+
+text-expander .suggestions li {
+  display: flex;
+  align-items: center;
+  cursor: pointer;
+  padding: 4px 8px;
+  font-weight: 500;
+}
+
+text-expander .suggestions li + li {
+  border-top: 1px solid var(--color-secondary-alpha-40);
+}
+
+text-expander .suggestions li:first-child {
+  border-radius: 4px 4px 0 0;
+}
+
+text-expander .suggestions li:last-child {
+  border-radius: 0 0 4px 4px;
+}
+
+text-expander .suggestions li:only-child {
+  border-radius: 4px;
+}
+
+text-expander .suggestions li:hover {
+  background: var(--color-hover);
+}
+
+text-expander .suggestions .fullname {
+  font-weight: normal;
+  margin-left: 4px;
+  color: var(--color-text-light-1);
+}
+
+text-expander .suggestions li[aria-selected="true"],
+text-expander .suggestions li[aria-selected="true"] span {
+  background: var(--color-primary);
+  color: var(--color-primary-contrast);
+}
+
+text-expander .suggestions img {
+  width: 24px;
+  height: 24px;
+  margin-right: 8px;
+}
diff --git a/web_src/css/form.css b/web_src/css/form.css
index ffcf5794b9..85d1136de8 100644
--- a/web_src/css/form.css
+++ b/web_src/css/form.css
@@ -1,3 +1,20 @@
+.ui.input textarea,
+.ui.form textarea,
+.ui.form input:not([type]),
+.ui.form input[type="date"],
+.ui.form input[type="datetime-local"],
+.ui.form input[type="email"],
+.ui.form input[type="number"],
+.ui.form input[type="password"],
+.ui.form input[type="search"],
+.ui.form input[type="tel"],
+.ui.form input[type="time"],
+.ui.form input[type="text"],
+.ui.form input[type="file"],
+.ui.form input[type="url"] {
+  transition: none;
+}
+
 input,
 textarea,
 .ui.input > input,
diff --git a/web_src/js/features/comp/ComboMarkdownEditor.js b/web_src/js/features/comp/ComboMarkdownEditor.js
index c1607a1da8..13b28da828 100644
--- a/web_src/js/features/comp/ComboMarkdownEditor.js
+++ b/web_src/js/features/comp/ComboMarkdownEditor.js
@@ -1,4 +1,5 @@
 import '@github/markdown-toolbar-element';
+import '@github/text-expander-element';
 import $ from 'jquery';
 import {attachTribute} from '../tribute.js';
 import {hideElem, showElem, autosize} from '../../utils/dom.js';
@@ -6,8 +7,10 @@ import {initEasyMDEImagePaste, initTextareaImagePaste} from './ImagePaste.js';
 import {initMarkupContent} from '../../markup/content.js';
 import {handleGlobalEnterQuickSubmit} from './QuickSubmit.js';
 import {attachRefIssueContextPopup} from '../contextpopup.js';
+import {emojiKeys, emojiString} from '../emoji.js';
 
 let elementIdCounter = 0;
+const maxExpanderMatches = 6;
 
 /**
  * validate if the given textarea is non-empty.
@@ -40,13 +43,10 @@ class ComboMarkdownEditor {
 
   async init() {
     this.prepareEasyMDEToolbarActions();
-
     this.setupTab();
     this.setupDropzone();
-
     this.setupTextarea();
-
-    await attachTribute(this.textarea, {mentions: true, emoji: true});
+    this.setupExpander();
 
     if (this.userPreferredEditor === 'easymde') {
       await this.switchToEasyMDE();
@@ -83,6 +83,76 @@ class ComboMarkdownEditor {
     }
   }
 
+  setupExpander() {
+    const expander = this.container.querySelector('text-expander');
+    expander?.addEventListener('text-expander-change', ({detail: {key, provide, text}}) => {
+      if (key === ':') {
+        const matches = [];
+        for (const name of emojiKeys) {
+          if (name.includes(text)) {
+            matches.push(name);
+            if (matches.length >= maxExpanderMatches) break;
+          }
+        }
+        if (!matches.length) return provide({matched: false});
+
+        const ul = document.createElement('ul');
+        ul.classList.add('suggestions');
+        for (const name of matches) {
+          const emoji = emojiString(name);
+          const li = document.createElement('li');
+          li.setAttribute('role', 'option');
+          li.setAttribute('data-value', emoji);
+          li.textContent = `${emoji} ${name}`;
+          ul.append(li);
+        }
+
+        provide({matched: true, fragment: ul});
+      } else if (key === '@') {
+        const matches = [];
+        for (const obj of window.config.tributeValues) {
+          if (obj.key.includes(text)) {
+            matches.push(obj);
+            if (matches.length >= maxExpanderMatches) break;
+          }
+        }
+        if (!matches.length) return provide({matched: false});
+
+        const ul = document.createElement('ul');
+        ul.classList.add('suggestions');
+        for (const {value, name, fullname, avatar} of matches) {
+          const li = document.createElement('li');
+          li.setAttribute('role', 'option');
+          li.setAttribute('data-value', `${key}${value}`);
+
+          const img = document.createElement('img');
+          img.src = avatar;
+          li.append(img);
+
+          const nameSpan = document.createElement('span');
+          nameSpan.textContent = name;
+          li.append(nameSpan);
+
+          if (fullname && fullname.toLowerCase() !== name) {
+            const fullnameSpan = document.createElement('span');
+            fullnameSpan.classList.add('fullname');
+            fullnameSpan.textContent = fullname;
+            li.append(fullnameSpan);
+          }
+
+          ul.append(li);
+        }
+
+        provide({matched: true, fragment: ul});
+      }
+    });
+    expander?.addEventListener('text-expander-value', ({detail}) => {
+      if (detail?.item) {
+        detail.value = detail.item.getAttribute('data-value');
+      }
+    });
+  }
+
   setupDropzone() {
     const dropzoneParentContainer = this.container.getAttribute('data-dropzone-parent-container');
     if (dropzoneParentContainer) {