Fix RHS reply input focus issues (#33965) (#34099)

Automatic Merge

webapp/channels/src/components/advanced_text_editor/advanced_text_editor.test.tsx

@@ -236,7 +236,9 @@ describe('components/avanced_text_editor/advanced_text_editor', () => {
             expect(textbox).not.toHaveFocus();
 
             // save is called with a short delayed after pressing escape key
-            jest.advanceTimersByTime(Constants.SAVE_DRAFT_TIMEOUT + 50);
+            act(() => {
+                jest.advanceTimersByTime(Constants.SAVE_DRAFT_TIMEOUT + 50);
+            });
             expect(mockedRemoveDraft).toHaveBeenCalled();
             expect(mockedUpdateDraft).not.toHaveBeenCalled();
         });

webapp/channels/src/components/advanced_text_editor/use_textbox_focus.tsx

@@ -33,11 +33,20 @@ const useTextboxFocus = (
     const focusTextbox = useCallback((keepFocus = false) => {
         const postTextboxDisabled = !canPost;
         if (textboxRef.current && postTextboxDisabled) {
-            textboxRef.current.blur(); // Fixes Firefox bug which causes keyboard shortcuts to be ignored (MM-22482)
+            // Fixes Firefox bug which causes keyboard shortcuts to be ignored (MM-22482)
+            requestAnimationFrame(() => {
+                textboxRef.current?.blur();
+            });
             return;
         }
         if (textboxRef.current && (keepFocus || !UserAgent.isMobile())) {
-            textboxRef.current.focus();
+            // Focus immediately, so we capture any typed text.
+            textboxRef.current?.focus();
+
+            // Also re-focus after the next animation frame, to work around issues where the RHS is "opening".
+            requestAnimationFrame(() => {
+                textboxRef.current?.focus();
+            });
         }
     }, [canPost, textboxRef]);