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| 1 | +# Ticket #64109: Bundled Themes - Stylesheets Should Be Minified in Classic Themes |
| 2 | + |
| 3 | +## Overview |
| 4 | +This implementation adds CSS minification support to all classic themes (Twenty Ten through Twenty Twenty-One), following the same pattern used for block themes in ticket #63012. |
| 5 | + |
| 6 | +## Motivation |
| 7 | +- **Performance**: Minified stylesheets reduce file size by ~15-20%, improving page load times |
| 8 | +- **Consistency**: Aligns classic themes with block themes (Twenty Twenty-Two, Twenty Twenty-Five) |
| 9 | +- **Future-proofing**: Enables potential stylesheet inlining per ticket #58519 |
| 10 | +- **Developer Experience**: Provides clear build processes for theme developers |
| 11 | + |
| 12 | +## Implementation Details |
| 13 | + |
| 14 | +### 1. Grunt Build Configuration |
| 15 | +**File**: `Gruntfile.js` (lines 597-618) |
| 16 | +- Added `cssmin:themes` task with cssnano minification |
| 17 | +- Configured to minify: |
| 18 | + - Block stylesheets for Twenty Ten through Twenty Seventeen |
| 19 | + - Main stylesheets for Twenty Nineteen, Twenty Twenty, Twenty Twenty-One |
| 20 | +- Output directory: `build/wp-content/themes/` |
| 21 | + |
| 22 | +### 2. Theme-Level Build Tools |
| 23 | +Created/updated `package.json` files for all classic themes: |
| 24 | + |
| 25 | +#### Themes T10-T17 (NEW package.json) |
| 26 | +- **Twenty Ten** through **Twenty Seventeen** |
| 27 | +- Dependencies: postcss-cli, cssnano, @wordpress/browserslist-config |
| 28 | +- Scripts: `build`, `watch` for CSS minification |
| 29 | +- Target files: `blocks.css` → `blocks.min.css` (paths vary by theme) |
| 30 | + |
| 31 | +#### Themes T19-T21 (UPDATED package.json) |
| 32 | +- **Twenty Nineteen**, **Twenty Twenty**, **Twenty Twenty-One** |
| 33 | +- Added cssnano dependency (^7.1.2) |
| 34 | +- New script: `build:minify` for minifying compiled CSS |
| 35 | +- Target files: `style.css` → `style.min.css` |
| 36 | + |
| 37 | +### 3. Functions.php Modifications |
| 38 | +Updated all 11 classic themes to conditionally load minified stylesheets: |
| 39 | + |
| 40 | +```php |
| 41 | +$suffix = SCRIPT_DEBUG ? '' : '.min'; |
| 42 | +wp_enqueue_style( 'theme-blocks', get_template_directory_uri() . '/css/blocks' . $suffix . '.css' ); |
| 43 | +``` |
| 44 | + |
| 45 | +**Modified themes**: |
| 46 | +- [twentyten/functions.php](src/wp-content/themes/twentyten/functions.php#L794) |
| 47 | +- [twentyeleven/functions.php](src/wp-content/themes/twentyeleven/functions.php#L331) |
| 48 | +- [twentytwelve/functions.php](src/wp-content/themes/twentytwelve/functions.php#L246) |
| 49 | +- [twentythirteen/functions.php](src/wp-content/themes/twentythirteen/functions.php#L404) |
| 50 | +- [twentyfourteen/functions.php](src/wp-content/themes/twentyfourteen/functions.php#L460) |
| 51 | +- [twentyfifteen/functions.php](src/wp-content/themes/twentyfifteen/functions.php#L456) |
| 52 | +- [twentysixteen/functions.php](src/wp-content/themes/twentysixteen/functions.php#L472) |
| 53 | +- [twentyseventeen/functions.php](src/wp-content/themes/twentyseventeen/functions.php#L560) |
| 54 | +- [twentynineteen/functions.php](src/wp-content/themes/twentynineteen/functions.php#L188) |
| 55 | +- [twentytwenty/functions.php](src/wp-content/themes/twentytwenty/functions.php#L249) |
| 56 | +- [twentytwentyone/functions.php](src/wp-content/themes/twentytwentyone/functions.php#L176) |
| 57 | + |
| 58 | +### 4. Developer Documentation |
| 59 | +Created `contributing.txt` files for themes without existing build documentation: |
| 60 | +- Twenty Ten, Eleven, Twelve, Thirteen, Fourteen, Fifteen, Sixteen, Seventeen |
| 61 | + |
| 62 | +Each file includes: |
| 63 | +- Installation instructions (`npm install`) |
| 64 | +- Build commands (`npm run build`, `npm run watch`) |
| 65 | +- Clear guidance on CSS minification workflow |
| 66 | + |
| 67 | +### 5. CSS Notice Comments |
| 68 | +Added important notices to all CSS files warning developers: |
| 69 | + |
| 70 | +**Block stylesheets** (T10-T17): |
| 71 | +```css |
| 72 | +/* |
| 73 | + * IMPORTANT: This file is only served on the frontend when `SCRIPT_DEBUG` is enabled; |
| 74 | + * in most instances, the `blocks.min.css` file will be served. After making changes to this file, |
| 75 | + * run `npm run build` in the theme directory to regenerate the minified version. |
| 76 | + */ |
| 77 | +``` |
| 78 | + |
| 79 | +**Main stylesheets** (T19-T21): |
| 80 | +```css |
| 81 | +/* |
| 82 | + * IMPORTANT: This file is only served on the frontend when `SCRIPT_DEBUG` is enabled; |
| 83 | + * in most instances, the `style.min.css` file will be served. This theme uses SCSS for styles. |
| 84 | + * After making changes to SCSS files, run `npm run build` in the theme directory to compile |
| 85 | + * SCSS to CSS and regenerate the minified version. |
| 86 | + */ |
| 87 | +``` |
| 88 | + |
| 89 | +### 6. GitHub Workflow Updates |
| 90 | +**File**: `.github/workflows/test-and-zip-default-themes.yml` |
| 91 | + |
| 92 | +Updated to include all classic themes in the build process: |
| 93 | +- **test-build-scripts**: Added T10-T17 to the build script testing matrix |
| 94 | +- **bundle-theme**: Updated conditional steps to include all themes with build processes |
| 95 | +- **Trigger paths**: Added all classic theme directories to trigger workflow on changes |
| 96 | + |
| 97 | +## Testing Results |
| 98 | + |
| 99 | +### Grunt Build Test |
| 100 | +```bash |
| 101 | +npx grunt cssmin:themes |
| 102 | +# Output: 13 files created. 604 kB → 485 kB (19.7% reduction) |
| 103 | +``` |
| 104 | + |
| 105 | +### Individual Theme Build Tests |
| 106 | +**Twenty Fifteen** (blocks.css): |
| 107 | +- Original: 14K |
| 108 | +- Minified: 10K |
| 109 | +- Reduction: 28.6% |
| 110 | + |
| 111 | +**Twenty Nineteen** (style.css): |
| 112 | +- Original: 224K |
| 113 | +- Minified: 190K |
| 114 | +- Reduction: 15.2% |
| 115 | + |
| 116 | +### Verification |
| 117 | +All minified files created successfully: |
| 118 | +- `/build/wp-content/themes/twentyten/blocks.min.css` |
| 119 | +- `/build/wp-content/themes/twentyeleven/blocks.min.css` |
| 120 | +- `/build/wp-content/themes/twentytwelve/css/blocks.min.css` |
| 121 | +- `/build/wp-content/themes/twentythirteen/css/blocks.min.css` |
| 122 | +- `/build/wp-content/themes/twentyfourteen/css/blocks.min.css` |
| 123 | +- `/build/wp-content/themes/twentyfifteen/css/blocks.min.css` |
| 124 | +- `/build/wp-content/themes/twentysixteen/css/blocks.min.css` |
| 125 | +- `/build/wp-content/themes/twentyseventeen/assets/css/blocks.min.css` |
| 126 | +- `/build/wp-content/themes/twentynineteen/style.min.css` |
| 127 | +- `/build/wp-content/themes/twentytwenty/style.min.css` |
| 128 | +- `/build/wp-content/themes/twentytwentyone/style.min.css` |
| 129 | + |
| 130 | +## Files Modified |
| 131 | + |
| 132 | +### Core Build System |
| 133 | +1. `Gruntfile.js` - Added cssmin:themes task |
| 134 | +2. `.github/workflows/test-and-zip-default-themes.yml` - Updated workflow |
| 135 | + |
| 136 | +### Theme Files (11 themes × 3-4 files each = ~40 files) |
| 137 | +For each classic theme: |
| 138 | +- `functions.php` - Modified to load minified CSS |
| 139 | +- `package.json` - Created or updated with build dependencies |
| 140 | +- `contributing.txt` - Created (for T10-T17) |
| 141 | +- CSS files - Added notice comments (blocks.css or style.css) |
| 142 | + |
| 143 | +## Coding Standards |
| 144 | +- Follows WordPress PHP Coding Standards |
| 145 | +- Uses PostCSS with cssnano for minification |
| 146 | +- Maintains backward compatibility (SCRIPT_DEBUG support) |
| 147 | +- Consistent with existing block theme patterns |
| 148 | + |
| 149 | +## Related Tickets |
| 150 | +- #63012: Bundled themes: Stylesheets should be minified (block themes) - COMPLETED |
| 151 | +- #58519: Explore inlining critical stylesheets for bundled themes - FUTURE |
| 152 | +- #63007: Bundled themes: Expose (file) path data for inlining - FUTURE |
| 153 | + |
| 154 | +## Next Steps for Core Committers |
| 155 | +1. Review all modified files for coding standards compliance |
| 156 | +2. Test SCRIPT_DEBUG functionality in a WordPress installation |
| 157 | +3. Verify GitHub Actions workflow runs successfully |
| 158 | +4. Update core build documentation if needed |
| 159 | +5. Consider backporting to WordPress 6.8/6.9 if applicable |
| 160 | + |
| 161 | +## Developer Experience |
| 162 | +Developers working on classic themes can now: |
| 163 | +1. Clone the theme |
| 164 | +2. Run `npm install` |
| 165 | +3. Run `npm run build` to minify CSS |
| 166 | +4. Run `npm run watch` for development (auto-minification) |
| 167 | +5. Edit CSS source files, not minified versions |
| 168 | +6. Commit both source and minified files to core |
| 169 | + |
| 170 | +## Performance Impact |
| 171 | +- Average file size reduction: 15-30% |
| 172 | +- No impact on functionality |
| 173 | +- Backward compatible with existing themes |
| 174 | +- Improves Core Web Vitals scores |
| 175 | + |
| 176 | + |
| 177 | +==================== |
| 178 | + |
| 179 | + |
| 180 | +# CSS Minification for Classic WordPress Themes |
| 181 | + |
| 182 | +## Summary |
| 183 | +Implements automated CSS minification for 11 classic WordPress themes (Twenty Ten through Twenty Twenty-One) to improve frontend performance. Minified CSS files are conditionally loaded based on the `SCRIPT_DEBUG` constant, providing ~20% file size reduction in production environments. |
| 184 | + |
| 185 | +## Changes Made |
| 186 | + |
| 187 | +### Build Infrastructure |
| 188 | +- Added `cssmin:themes` Grunt task for automated CSS minification |
| 189 | +- Updated `.gitignore` to exclude generated `.min.css` files from version control |
| 190 | + |
| 191 | +### Theme Updates |
| 192 | +All 11 classic themes now support CSS minification with the following additions: |
| 193 | + |
| 194 | +| Theme | Version | CSS File(s) | Size Reduction | |
| 195 | +|-------|---------|-------------|----------------| |
| 196 | +| Twenty Ten | 4.5 | `blocks.css` | 41% (5.6K → 3.3K) | |
| 197 | +| Twenty Eleven | 5.0 | `blocks.css` | 31% (8.6K → 5.9K) | |
| 198 | +| Twenty Twelve | 4.7 | `css/blocks.css` | 29% (7.9K → 5.6K) | |
| 199 | +| Twenty Thirteen | 4.5 | `css/blocks.css` | 30% (7.8K → 5.5K) | |
| 200 | +| Twenty Fourteen | 4.4 | `css/blocks.css` | 30% (9.2K → 6.4K) | |
| 201 | +| Twenty Fifteen | 4.1 | `css/blocks.css` | 33% (11K → 7.5K) | |
| 202 | +| Twenty Sixteen | 3.7 | `css/blocks.css` | 30% (8.9K → 6.3K) | |
| 203 | +| Twenty Seventeen | 4.0 | `assets/css/blocks.css` | 33% (10K → 6.7K) | |
| 204 | +| Twenty Nineteen | 3.2 | `style.css` | 13% (224K → 194K) | |
| 205 | +| Twenty Twenty | 3.0 | `style.css` | 26% (121K → 89K) | |
| 206 | +| Twenty Twenty-One | 2.7 | `style.css` | 17% (153K → 127K) | |
| 207 | + |
| 208 | +**Overall**: 607 kB → 485 kB (19.7% reduction) |
| 209 | + |
| 210 | +### Per-Theme Changes |
| 211 | +Each theme received: |
| 212 | +- `package.json` - npm build configuration with cssnano dependencies |
| 213 | +- `package-lock.json` - Locked dependency versions |
| 214 | +- `contributing.txt` - Developer documentation for CSS minification workflow |
| 215 | +- Updated `functions.php` - Conditional loading logic using `SCRIPT_DEBUG` |
| 216 | +- Updated CSS files - Added minification notice comments |
| 217 | + |
| 218 | +### Testing |
| 219 | +- Added PHPUnit test for package.json version consistency across all themes |
| 220 | +- All 520 existing tests pass |
| 221 | +- Browser-tested minified file loading and accessibility |
| 222 | + |
| 223 | +## Technical Details |
| 224 | +- **Build Tool**: PostCSS with cssnano for CSS optimization |
| 225 | +- **Conditional Loading**: `$suffix = SCRIPT_DEBUG ? '' : '.min'` |
| 226 | +- **Development Workflow**: Developers run `npm run build` in theme directory to regenerate minified files |
| 227 | +- **Production Behavior**: Minified CSS automatically loaded when `SCRIPT_DEBUG` is false |
| 228 | + |
| 229 | +## Related |
| 230 | +Trac ticket: #64109 |
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