3 files changed, 56 insertions, 0 deletions
diff --git a/web_src/js/utils/dom.ts b/web_src/js/utils/dom.ts
index 83a0d9c8df..8b540cebb1 100644
--- a/web_src/js/utils/dom.ts
+++ b/web_src/js/utils/dom.ts
@@ -161,6 +161,7 @@ export function autosize(textarea: HTMLTextAreaElement, {viewportMarginBottom =
   function resizeToFit() {
     if (isUserResized) return;
     if (textarea.offsetWidth <= 0 && textarea.offsetHeight <= 0) return;
+    const previousMargin = textarea.style.marginBottom;
 
     try {
       const {top, bottom} = overflowOffset();
@@ -176,6 +177,9 @@ export function autosize(textarea: HTMLTextAreaElement, {viewportMarginBottom =
       const curHeight = parseFloat(computedStyle.height);
       const maxHeight = curHeight + bottom - adjustedViewportMarginBottom;
 
+      // In Firefox, setting auto height momentarily may cause the page to scroll up
+      // unexpectedly, prevent this by setting a temporary margin.
+      textarea.style.marginBottom = `${textarea.clientHeight}px`;
       textarea.style.height = 'auto';
       let newHeight = textarea.scrollHeight + borderAddOn;
 
@@ -196,6 +200,12 @@ export function autosize(textarea: HTMLTextAreaElement, {viewportMarginBottom =
       textarea.style.height = `${newHeight}px`;
       lastStyleHeight = textarea.style.height;
     } finally {
+      // restore previous margin
+      if (previousMargin) {
+        textarea.style.marginBottom = previousMargin;
+      } else {
+        textarea.style.removeProperty('margin-bottom');
+      }
       // ensure that the textarea is fully scrolled to the end, when the cursor
       // is at the end during an input event
       if (textarea.selectionStart === textarea.selectionEnd &&
@@ -304,6 +314,7 @@ export function replaceTextareaSelection(textarea: HTMLTextAreaElement, text: st
 export function createElementFromHTML<T extends HTMLElement>(htmlString: string): T {
   htmlString = htmlString.trim();
   // some tags like "tr" are special, it must use a correct parent container to create
+  // eslint-disable-next-line github/unescaped-html-literal -- FIXME: maybe we need to use other approaches to create elements from HTML, e.g. using DOMParser
   if (htmlString.startsWith('<tr')) {
     const container = document.createElement('table');
     container.innerHTML = htmlString;
@@ -359,3 +370,8 @@ export function addDelegatedEventListener<T extends HTMLElement, E extends Event
     listener(elem as T, e as E);
   }, options);
 }
+
+/** Returns whether a click event is a left-click without any modifiers held */
+export function isPlainClick(e: MouseEvent) {
+  return e.button === 0 && !e.ctrlKey && !e.metaKey && !e.altKey && !e.shiftKey;
+}
diff --git a/web_src/js/utils/html.test.ts b/web_src/js/utils/html.test.ts
new file mode 100644
index 0000000000..3028b7bb0a
--- /dev/null
+++ b/web_src/js/utils/html.test.ts
@@ -0,0 +1,8 @@
+import {html, htmlEscape, htmlRaw} from './html.ts';
+
+test('html', async () => {
+  expect(html`<a>${'<>&\'"'}</a>`).toBe(`<a>&lt;&gt;&amp;&#39;&quot;</a>`);
+  expect(html`<a>${htmlRaw('<img>')}</a>`).toBe(`<a><img></a>`);
+  expect(html`<a>${htmlRaw`<img ${'&'}>`}</a>`).toBe(`<a><img &amp;></a>`);
+  expect(htmlEscape(`<a></a>`)).toBe(`&lt;a&gt;&lt;/a&gt;`);
+});
diff --git a/web_src/js/utils/html.ts b/web_src/js/utils/html.ts
new file mode 100644
index 0000000000..22e5703c34
--- /dev/null
+++ b/web_src/js/utils/html.ts
@@ -0,0 +1,32 @@
+export function htmlEscape(s: string, ...args: Array<any>): string {
+  if (args.length !== 0) throw new Error('use html or htmlRaw instead of htmlEscape'); // check legacy usages
+  return s.replace(/&/g, '&amp;')
+    .replace(/"/g, '&quot;')
+    .replace(/'/g, '&#39;')
+    .replace(/</g, '&lt;')
+    .replace(/>/g, '&gt;');
+}
+
+class rawObject {
+  private readonly value: string;
+  constructor(v: string) { this.value = v }
+  toString(): string { return this.value }
+}
+
+export function html(tmpl: TemplateStringsArray, ...parts: Array<any>): string {
+  let output = tmpl[0];
+  for (let i = 0; i < parts.length; i++) {
+    const value = parts[i];
+    const valueEscaped = (value instanceof rawObject) ? value.toString() : htmlEscape(String(parts[i]));
+    output = output + valueEscaped + tmpl[i + 1];
+  }
+  return output;
+}
+
+export function htmlRaw(s: string|TemplateStringsArray, ...tmplParts: Array<any>): rawObject {
+  if (typeof s === 'string') {
+    if (tmplParts.length !== 0) throw new Error("either htmlRaw('str') or htmlRaw`tmpl`");
+    return new rawObject(s);
+  }
+  return new rawObject(html(s, ...tmplParts));
+}