Use tippy.js for context popup (#20393)

By appending the tooltips to `document.body`, we can avoid any stacking context issues caused by surrounding element's CSS.

This uses [tippy.js](https://github.com/atomiks/tippyjs) instead of Fomantic popups. We should aim to replace all Fomantic popups with this eventually and then get rid of the Fomantic `popup` module completely.

web_src/js/features/contextpopup.js

@@ -2,6 +2,7 @@ import $ from 'jquery';
 import Vue from 'vue';
 import ContextPopup from '../components/ContextPopup.vue';
 import {parseIssueHref} from '../utils.js';
+import {createTippy} from '../modules/tippy.js';
 
 export default function initContextPopups() {
   const refIssues = $('.ref-issue');
@@ -16,7 +17,6 @@ export default function initContextPopups() {
     if (!owner) return;
 
     const el = document.createElement('div');
-    el.className = 'ui custom popup hidden';
     el.innerHTML = '<div></div>';
     this.parentNode.insertBefore(el, this.nextSibling);
 
@@ -33,17 +33,12 @@ export default function initContextPopups() {
       el.textContent = 'ContextPopup failed to load';
     }
 
-    $(this).popup({
-      variation: 'wide',
-      delay: {
-        show: 250
-      },
+    createTippy(this, {
+      content: el,
+      interactive: true,
       onShow: () => {
-        view.$emit('load-context-popup', {owner, repo, index}, () => {
-          $(this).popup('reposition');
-        });
-      },
-      popup: $(el),
+        view.$emit('load-context-popup', {owner, repo, index});
+      }
     });
   });
 }

web_src/js/modules/tippy.js

@@ -0,0 +1,12 @@
+import tippy from 'tippy.js';
+
+export function createTippy(target, opts) {
+  return tippy(target, {
+    appendTo: document.body,
+    placement: 'top-start',
+    animation: false,
+    allowHTML: true,
+    arrow: `<svg width="16" height="7"><path d="m0 7 8-7 8 7Z" class="tippy-svg-arrow-outer"/><path d="m0 8 8-7 8 7Z" class="tippy-svg-arrow-inner"/></svg>`,
+    ...opts,
+  });
+}

web_src/less/index.less

@@ -9,6 +9,7 @@
 @import "./features/imagediff.less";
 @import "./features/codeeditor.less";
 @import "./features/projects.less";
+@import "./modules/tippy.less";
 @import "./markup/content.less";
 @import "./markup/codecopy.less";
 @import "./code/linebutton.less";

web_src/less/modules/tippy.less

@@ -0,0 +1,84 @@
+/* styles are based on node_modules/tippy.js/dist/tippy.css */
+
+.tippy-box[data-animation="fade"][data-state="hidden"] {
+  opacity: 0;
+}
+
+[data-tippy-root] {
+  max-width: calc(100vw - 10px);
+}
+
+.tippy-box {
+  position: relative;
+  background-color: var(--color-body);
+  color: var(--color-secondary-dark-6);
+  border: 1px solid var(--color-secondary);
+  border-radius: var(--border-radius);
+  font-size: 1rem;
+  transition-property: transform, visibility, opacity;
+}
+
+.tippy-content {
+  position: relative;
+  padding: 1rem;
+  z-index: 1;
+}
+
+.tippy-box[data-placement^="top"] > .tippy-svg-arrow {
+  bottom: 0;
+}
+
+.tippy-box[data-placement^="top"] > .tippy-svg-arrow::after,
+.tippy-box[data-placement^="top"] > .tippy-svg-arrow > svg {
+  top: 16px;
+  transform: rotate(180deg);
+}
+
+.tippy-box[data-placement^="bottom"] > .tippy-svg-arrow {
+  top: 0;
+}
+
+.tippy-box[data-placement^="bottom"] > .tippy-svg-arrow > svg {
+  bottom: 16px;
+}
+
+.tippy-box[data-placement^="left"] > .tippy-svg-arrow {
+  right: 0;
+}
+
+.tippy-box[data-placement^="left"] > .tippy-svg-arrow::after,
+.tippy-box[data-placement^="left"] > .tippy-svg-arrow > svg {
+  transform: rotate(90deg);
+  top: calc(50% - 3px);
+  left: 11px;
+}
+
+.tippy-box[data-placement^="right"] > .tippy-svg-arrow {
+  left: 0;
+}
+
+.tippy-box[data-placement^="right"] > .tippy-svg-arrow::after,
+.tippy-box[data-placement^="right"] > .tippy-svg-arrow > svg {
+  transform: rotate(-90deg);
+  top: calc(50% - 3px);
+  right: 11px;
+}
+
+.tippy-svg-arrow {
+  width: 16px;
+  height: 16px;
+  text-align: initial;
+}
+
+.tippy-svg-arrow,
+.tippy-svg-arrow > svg {
+  position: absolute;
+}
+
+.tippy-svg-arrow-outer {
+  fill: var(--color-secondary);
+}
+
+.tippy-svg-arrow-inner {
+  fill: var(--color-body);
+}