SFML Text Editor (Name TBD)

A simple text editor built with C++ and SFML.
I made this project to learn more about text rendering, cursor movement, and input handling using SFML.

Features

Core Editing

• Text input (typing, backspace)
• Movable cursor with blinking animation
• Keyboard navigation (Left, Right, Up, Down with auto-repeat)
• Mouse click to position cursor anywhere in text
• Click and drag text selection with visual highlighting
• Vertical navigation that keeps the cursor aligned using a preferred X position
• Automatic word wrapping that adjusts to window size

File Operations

• Save files with native file dialog (Ctrl+S / Cmd+S)
• Load files with native file dialog (Ctrl+O / Cmd+O)
• Automatic .txt extension on save

UI & Interaction

• Resizable window with responsive UI elements
• Scrollbar with multiple interaction modes:
  • Click and drag the scrollbar thumb
  • Click anywhere on the track to jump to that position
  • Mouse wheel scrolling support
• Auto-scroll to keep cursor visible
• Dynamic font size adjustment (Ctrl+Plus / Ctrl+Minus)
• Font size display (anchored to top-right corner)
• Clean header bar with Save and Load buttons

Visual Polish

• Blinking cursor (500ms interval)
• Semi-transparent blue selection highlighting
• Smooth scrolling animations
• Proportional scrollbar thumb (size reflects document length)
• Responsive layout that adapts to window resizing

Controls

Keyboard Shortcuts

• Type to insert text
• Backspace to delete character before cursor
• Arrow keys to move the cursor (hold for auto-repeat)
• Ctrl/Cmd + O to open a file
• Ctrl/Cmd + S to save the file
• Ctrl/Cmd + = (Plus) to increase font size
• Ctrl/Cmd + - (Minus) to decrease font size (minimum 6pt)

Mouse Controls

• Left click to position cursor in text
• Click and drag to select text
• Mouse wheel to scroll through document
• Click scrollbar thumb and drag to scroll
• Click scrollbar track to jump to that position
• Save/Load buttons in top-left corner

How It Works

This program uses a gap buffer for efficient text editing and a modular architecture for maintainability.

Gap Buffer

All text lives in a single buffer with a gap at the cursor position.

• Typing inserts characters directly into the gap
• Deleting text expands the gap
• Moving the cursor shifts the gap instead of copying text

This keeps common edits fast, even as the file grows.

Modular Architecture

The codebase is organized into focused, reusable components:

• GapBuffer (src/GapBuffer.h/cpp): Efficient text storage and manipulation
• UI (src/UI.h/cpp): Button creation and cursor management
• Scrollbar (src/Scrollbar.h/cpp): Complete scrollbar with mouse interaction
• TextRenderer (src/TextRenderer.h/cpp): Text wrapping, cursor movement, and selection rendering
• FileOperations (src/FileOperations.h/cpp): Save and load dialogs
• InputHandler (src/InputHandler.h/cpp): Mouse click processing and coordinate mapping

This separation makes the code easier to:

• Read and understand (each file has one clear purpose)
• Maintain and debug (changes are localized)
• Test (components can be tested independently)
• Extend (new features have clear homes)

Cursor & Rendering

• Cursor movement is tracked logically, separate from rendering
• Vertical movement preserves a preferred X position across lines
• Each frame, the gap buffer is converted to a string and rendered with SFML
• The cursor is drawn based on glyph positions in the rendered text

Input

• Keyboard input edits the gap buffer
• Mouse clicks map screen positions to text indices
• Loading a file replaces the buffer and resets cursor state

Project Structure

text-editor/
├── main_refactored.cpp          # Main application entry point (~330 lines)
├── CMakeLists.txt               # Build configuration
├── fonts/
│   └── Roboto.ttf              # Default font
├── src/
│   ├── GapBuffer.h/cpp         # Text buffer implementation
│   ├── UI.h/cpp                # UI components
│   ├── Scrollbar.h/cpp         # Scrollbar system
│   ├── TextRenderer.h/cpp      # Text display and wrapping
│   ├── FileOperations.h/cpp    # File I/O
│   └── InputHandler.h/cpp      # Mouse and keyboard input
└── libs/
    └── nativefiledialog/       # Native file dialogs

Requirements

• C++17 or newer
• SFML 3
• A font file (currently uses fonts/Roboto.ttf)

Build & Run

Make sure SFML is installed and linked correctly.

If using CMake:

mkdir build
cd build
cmake ..
make
./text_editor

Future Features

• Ability to upload and change fonts
• Different themes
• More GUI elements

Learning Outcomes

This project demonstrates:

• Data structures: Gap buffer for efficient text editing
• Event-driven programming: SFML event loop and input handling
• Software architecture: Modular design with separation of concerns
• Graphics programming: Text rendering, scrolling, and UI elements
• File I/O: Native dialogs and file operations
• State management: Cursor, selection, and scroll positions
• Coordinate systems: Screen space, world space, and text positions
• Performance optimization: Efficient rendering and input processing