Autogrow the textarea

app/soapbox/components/ui/textarea/textarea.tsx

@@ -1,9 +1,15 @@
 import classNames from 'clsx';
-import React from 'react';
+import React, { useState } from 'react';
 
 interface ITextarea extends Pick<React.TextareaHTMLAttributes<HTMLTextAreaElement>, 'maxLength' | 'onChange' | 'onKeyDown' | 'required' | 'disabled' | 'rows' | 'readOnly'> {
   /** Put the cursor into the input on mount. */
   autoFocus?: boolean,
+  /** Allows the textarea height to grow while typing */
+  autoGrow?: boolean,
+  /** Used with "autoGrow". Sets a max number of rows. */
+  maxRows?: number,
+  /** Used with "autoGrow". Sets a min number of rows. */
+  minRows?: number,
   /** The initial text in the input. */
   defaultValue?: string,
   /** Internal input name. */
@@ -23,22 +29,59 @@ interface ITextarea extends Pick<React.TextareaHTMLAttributes<HTMLTextAreaElemen
 }
 
 /** Textarea with custom styles. */
-const Textarea = React.forwardRef(
-  ({ isCodeEditor = false, hasError = false, isResizeable = true, ...props }: ITextarea, ref: React.ForwardedRef<HTMLTextAreaElement>) => {
-    return (
-      <textarea
-        {...props}
-        ref={ref}
-        className={classNames({
-          'bg-white dark:bg-transparent shadow-sm block w-full sm:text-sm rounded-md text-gray-900 dark:text-gray-100 placeholder:text-gray-600 dark:placeholder:text-gray-600 border-gray-400 dark:border-gray-800 dark:ring-1 dark:ring-gray-800 focus:ring-primary-500 focus:border-primary-500 dark:focus:ring-primary-500 dark:focus:border-primary-500':
-            true,
-          'font-mono': isCodeEditor,
-          'text-red-600 border-red-600': hasError,
-          'resize-none': !isResizeable,
-        })}
-      />
-    );
-  },
+const Textarea = React.forwardRef(({
+  isCodeEditor = false,
+  hasError = false,
+  isResizeable = true,
+  onChange,
+  autoGrow = false,
+  maxRows = 10,
+  minRows = 1,
+  ...props
+}: ITextarea, ref: React.ForwardedRef<HTMLTextAreaElement>) => {
+  const [rows, setRows] = useState<number>(autoGrow ? 1 : 4);
+
+  const handleChange = (event: React.ChangeEvent<HTMLTextAreaElement>) => {
+    if (autoGrow) {
+      const textareaLineHeight = 20;
+      const previousRows = event.target.rows;
+      event.target.rows = minRows;
+
+      const currentRows = ~~(event.target.scrollHeight / textareaLineHeight);
+
+      if (currentRows === previousRows) {
+        event.target.rows = currentRows;
+      }
+
+      if (currentRows >= maxRows) {
+        event.target.rows = maxRows;
+        event.target.scrollTop = event.target.scrollHeight;
+      }
+
+      setRows(currentRows < maxRows ? currentRows : maxRows);
+    }
+
+    if (onChange) {
+      onChange(event);
+    }
+  };
+
+  return (
+    <textarea
+      {...props}
+      ref={ref}
+      rows={rows}
+      onChange={handleChange}
+      className={classNames({
+        'bg-white dark:bg-transparent shadow-sm block w-full sm:text-sm rounded-md text-gray-900 dark:text-gray-100 placeholder:text-gray-600 dark:placeholder:text-gray-600 border-gray-400 dark:border-gray-800 dark:ring-1 dark:ring-gray-800 focus:ring-primary-500 focus:border-primary-500 dark:focus:ring-primary-500 dark:focus:border-primary-500':
+          true,
+        'font-mono': isCodeEditor,
+        'text-red-600 border-red-600': hasError,
+        'resize-none': !isResizeable,
+      })}
+    />
+  );
+},
 );
 
 export default Textarea;

app/soapbox/features/chats/components/chat-box.tsx

@@ -219,7 +219,6 @@ const ChatBox: React.FC<IChatBox> = ({ chat, onSetInputRef, autosize, inputRef }
         <HStack alignItems='center' justifyContent='between' space={4}>
           <div className='flex-grow'>
             <Textarea
-              rows={1}
               autoFocus
               ref={inputRef}
               placeholder={intl.formatMessage(messages.placeholder)}
@@ -227,6 +226,8 @@ const ChatBox: React.FC<IChatBox> = ({ chat, onSetInputRef, autosize, inputRef }
               value={content}
               onChange={handleContentChange}
               isResizeable={false}
+              autoGrow
+              maxRows={5}
             />
           </div>