cvs-proxy/ui/DARK_MODE_README.md

Dark Mode Implementation

Overview

The CVS Repository Browser now includes a fully functional dark mode with system theme detection and user preference persistence.

Features

1. System Theme Detection

• On first load, the application automatically detects the user's system theme preference using prefers-color-scheme media query
• If the system prefers dark mode, the app starts in dark mode
• If the system prefers light mode, the app starts in light mode
• If no system preference is detected, defaults to dark mode

2. User Preference Persistence

• User's theme choice is saved to browser's localStorage
• On subsequent visits, the saved preference is used instead of system preference
• Users can override system preference by toggling the theme

3. Theme Toggle Button

• Located in the header next to the status indicator
• Shows 🌙 (moon) icon in light mode
• Shows ☀️ (sun) icon in dark mode
• Click to toggle between light and dark themes

4. Comprehensive Dark Mode Styling

• All UI elements are properly styled for both light and dark modes
• Uses CSS custom properties (variables) for easy theme switching
• Maintains excellent contrast ratios for accessibility
• Smooth transitions between themes

Implementation Details

CSS Variables

The application uses CSS custom properties defined in :root and [data-theme="dark"] selectors:

Light Mode (default):

• Background: #f9fafb (light gray)
• Surface: #ffffff (white)
• Text Primary: #111827 (dark gray)
• Text Secondary: #6b7280 (medium gray)
• Border: #e5e7eb (light border)

Dark Mode:

• Background: #1a1a1a (very dark)
• Surface: #2d2d2d (dark gray)
• Text Primary: #f3f4f6 (light gray)
• Text Secondary: #d1d5db (medium light gray)
• Border: #404040 (dark border)

JavaScript Implementation

The UIManager class in ui.js handles theme management:

• initializeTheme(): Initializes theme on page load
• setTheme(theme): Sets the theme and updates localStorage
• toggleTheme(): Toggles between light and dark modes
• updateThemeButton(icon): Updates the toggle button icon

Files Modified

1. styles.css

   • Added [data-theme="dark"] selector with dark mode CSS variables
   • All color references use CSS variables for dynamic theming

2. index.html

   • Added theme toggle button in header: <button id="themeToggleBtn" class="btn-icon">🌙</button>

3. ui.js

   • Added initializeTheme() method to detect and apply system theme
   • Added setTheme() method to apply theme and save preference
   • Added toggleTheme() method to switch between themes
   • Added updateThemeButton() method to update button icon
   • Added theme toggle button event listener

Usage

For Users

1. The app automatically uses your system theme preference on first visit
2. Click the moon/sun icon in the header to toggle between light and dark modes
3. Your preference is saved and will be remembered on future visits

For Developers

To modify the dark mode colors, edit the CSS variables in styles.css:

[data-theme="dark"] {
    --primary-color: #3b82f6;
    --primary-hover: #2563eb;
    --secondary-color: #9ca3af;
    /* ... other variables ... */
}

Browser Compatibility

• Works in all modern browsers that support:
  • CSS Custom Properties (CSS Variables)
  • prefers-color-scheme media query
  • localStorage API
  • ES6 JavaScript

Testing

A test file test-dark-mode.html is included for testing the dark mode functionality independently.

To test:

1. Open test-dark-mode.html in a browser
2. Click the moon/sun button to toggle themes
3. Refresh the page to verify persistence
4. Check browser DevTools to see localStorage values