Design Rich Text Editor
Last Updated: July 16, 2025
Design a Rich Text Editor that supports text formatting, undo/redo operations, and content management.
A Rich Text Editor is a software component that allows users to create and edit text with formatting features such as bold, italics, underline, font styles, colors, lists, headings, and alignment. Some editors also support embedding media, hyperlinks, and tables.
Rich text editors are commonly found in applications like Google Docs, Microsoft Word, and modern content management systems.
In this chapter, we will explore the low-level design of a simplified rich text editor.
Let's start by clarifying the requirements:
1. Clarifying Requirements
Before starting the design, it's important to ask thoughtful questions to uncover hidden assumptions, clarify ambiguities, and define the system's scope more precisely.
Here is an example of how a conversation between the candidate and the interviewer might unfold:
Candidate: What formatting options should the editor support?
Interviewer: It should support basic formatting such as bold, italic, underline,, font size, and font color.
Candidate: What types of editing operations should the system support?
Interviewer: Just text insertion and deletion for now.
Candidate: Should we support undo and redo functionality? If yes, to what depth?
Interviewer: Yes, the editor should support multi-level undo and redo for both content and formatting changes.
Candidate: Do we need to persist the document state to disk or a server, or can we assume the system runs entirely in-memory?
Interviewer: You can assume an in-memory implementation. No need for persistence in this version.
Candidate: How should we simulate user input?
Interviewer: A demo class with hardcoded input commands is sufficient.
After gathering the details, we can summarize the key system requirements.
1.1 Functional Requirements
- Support basic text formatting options: bold, italic, underline, font size, and font color
- Support core editing operations: insert and delete.
- Support multi-level undo and redo functionality for both content and formatting changes.
- Allow printing the current state of the document.
- Provide a simple interface (e.g., demo method) to perform editing and formatting operations.
1.2 Non-Functional Requirements
- Modularity: The system should follow clean, object-oriented design principles with well-defined responsibilities.
- Extensibility: The architecture should allow future support for advanced features.
- Maintainability: The codebase should be clean, easy to test and extend.