Here's the changelog comparing the two versions of the UPX_GUI.py file:

### Changelog: UPX EXE Compressor GUI v1.3 → v1.8

#### Major Improvements:
1. **Threaded Compression**:
   - Added `CompressionThread` class to handle compression in a background thread
   - Prevents UI freezing during compression operations

2. **Enhanced Settings Management**:
   - Replaced simple config file with `QSettings` for better cross-platform support
   - Added window geometry persistence
   - Added recent files list with menu integration (stores up to 5 recent files)

3. **Improved UI/UX**:
   - Added progress bar for compression operations
   - Added file information display showing file size
   - Better font handling with default to Segoe UI
   - Added tooltips for various controls
   - Increased minimum window size (650x550 → 800x700)

4. **New Features**:
   - Added "Test UPX" functionality
   - Added UPX CLI help dialog
   - Added advanced options (backup original file, auto-overwrite)
   - Enhanced about dialog with UPX version info and credits
   - Added menu bar with File, Edit, View, and Help menus
   - Added keyboard shortcuts for common actions

5. **Robust Error Handling**:
   - Better input validation and error scenarios handling
   - Improved file overwrite handling with multiple options
   - Better CFG protection detection and warnings

#### Code Structure Improvements:
1. **Refactored Compression Logic**:
   - Split compression process into separate handler methods
   - Better separation of concerns with dedicated methods for different scenarios

2. **Enhanced UI State Management**:
   - Added `set_ui_enabled()` method to disable UI during operations
   - Better visual feedback during operations

3. **New Utility Methods**:
   - `update_file_info()` - shows file size information
   - `get_upx_version()` - retrieves UPX version
   - `reset_all()` - clears all fields

#### Bug Fixes:
1. Fixed potential issues with file paths containing spaces
2. Improved handling of UPX executable detection
3. Better handling of file overwrite scenarios
4. Fixed potential race conditions during compression

#### Visual Changes:
1. Improved status display with monospace font
2. Better button styling with disabled state handling
3. Added separators and better spacing in dialogs
4. More professional about dialog with credits section

#### Backward Compatibility:
- Old config file (`upx_gui_config.txt`) will be replaced with registry/QSettings storage
- All existing functionality remains working with additional improvements

This update represents a significant improvement in both functionality and code quality, making the application more robust and user-friendly while maintaining all existing features.