Changes between Version 7 and Version 22 of Ticket #46370
- Timestamp:
- 12/13/2019 11:49:52 AM (4 years ago)
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Ticket #46370
- Property Focuses privacy added
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Ticket #46370 – Description
v7 v22 2 2 Loading custom fonts in a sub-optimal manner can cause significant performance and privacy issues. Anecdotally, inefficient font loading is frequently one of the biggest performance bottlenecks in many WordPress themes/sites. 3 3 4 This is, in part, because there hasn’t been a ‘best practice’ approach; there’s no ‘standard’ way of adding a font to a theme, and ensuring that it’s loaded in a performance-friendly manner. 5 6 Loading resources from Google Fonts has been the generally-accepted workaround to this, but that’s come with privacy concerns, and, poor implementations (no DNS prefetching, multiple requests, loading unneeded localisations/weights, etc). 7 8 Even our own sites and setups ([https://wordpress.org/ wordpress.org], the WordPress admin area, Gutenberg, and some of our [https://wp-themes.com/twentyseventeen/ core themes]) fall afoul of these issues. 9 10 If we’re serious about WordPress becoming a fast platform, we can’t rely on theme developers to add and manage fonts without providing a framework to support them. 4 This is, in part, because there hasn’t been a ‘best practice’ approach; there’s no ‘standard’ way of adding a font to a theme and ensuring that it’s loaded in a performance- and privacy-friendly manner. 5 6 In almost all cases, theme/plugin developers either enqueue a third-party stylesheet (e.g., Google Fonts), or, bundle and enqueue the CSS for a local font. Both approaches cause problems. In particular: 7 8 - Loading third-party resources can raise privacy concerns. 9 10 - Loading fonts from external sources means that WordPress is often unable to optimize those fonts (no DNS prefetching, no intelligent browser prioritisation, no de-duplication, etc). 11 12 - Bundling/enqueuing local fonts puts a strong reliance on the theme/plugin author understanding the complex nuances of efficient font-loading. 13 14 Even our own sites and setups ([https://wordpress.org/ wordpress.org], the WordPress admin area, Gutenberg, and some of our [https://wp-themes.com/twentyseventeen/ core themes]) fall afoul of these issues. They're slow, and they have privacy problems. 15 16 If we’re serious about WordPress becoming a fast, privacy-friendly platform, we can’t rely on theme developers to add and manage fonts without providing a framework to support them. 11 17 12 18 == Why now? … … 16 22 - Best practices for defining and loading fonts via CSS are now well-established, stable, and see broad usage elsewhere. 17 23 18 - The increasing adoption of of HTTP/2 means that localising assets can (in many cases) be faster than loading them from remote sources. 19 20 - Specifically, [https://developers.google.com/web/fundamentals/performance/optimizing-content-efficiency/webfont-optimization Google's Web Fundamentals documentation] (which much of this spec is directly lifted and adapted from) describes a stable, compatible, and plug-and-play approach to loading fonts. 24 - The increasing adoption of HTTP/2 means that localising assets can (in many cases) be faster than loading them from remote sources. 25 26 - There is increasing discomfort with WordPress 'passively endorsing' Google Fonts, which 'leaks' private information (IP addresses). 27 28 Now, standards like [https://developers.google.com/web/fundamentals/performance/optimizing-content-efficiency/webfont-optimization Google's Web Fundamentals documentation] (which much of this spec is directly lifted and adapted from) describe a stable, compatible, and plug-and-play approach to loading fonts. 29 30 There are well-defied, standardised approaches to loading fonts, which we can implement into WordPress core. This will allow theme and plugin developers to bypass all of these pitfalls. 21 31 22 32 == The vision … … 27 37 A move to an enqueue-based approach may also provide plugin developers with hooks to intercept the default behaviours, and to modify the output. E.g., to utilise the [https://developers.google.com/web/fundamentals/performance/optimizing-content-efficiency/webfont-optimization#the_font_loading_api font loading API] rather than outputting CSS. This provides a huge opportunity for caching and performance-optimising plugins to speed up WordPress sites/themes. 28 38 39 In its simplest form, `wp_enqueue_font()` provides a thin abstraction over existing WP mechanisms (`wp_enqueue_style()`), `wp_add_inline_style()`, etc), and simply enforces a performant, privacy-friendly implementation. 40 29 41 = The ‘Web Fundamentals’ approach 30 42 The [https://developers.google.com/web/fundamentals/performance/optimizing-content-efficiency/webfont-optimization Web Fundamentals documentation] provides an example of an optimal CSS structure for loading fonts. E.g., … … 35 47 font-style: normal; 36 48 font-weight: 400; 49 font-display: auto; 37 50 src: local('Awesome Font'), 38 51 url('/fonts/awesome-l.woff2') format('woff2'), … … 40 53 url('/fonts/awesome-l.ttf') format('truetype'), 41 54 url('/fonts/awesome-l.eot') format('embedded-opentype'); 42 unicode-range: U+000-5FF; /* Latin glyphs */55 unicode-range: U+000-5FF; 43 56 } 44 57 … … 47 60 font-style: normal; 48 61 font-weight: 700; 62 font-display: auto; 49 63 src: local('Awesome Font'), 50 64 url('/fonts/awesome-l-700.woff2') format('woff2'), … … 52 66 url('/fonts/awesome-l-700.ttf') format('truetype'), 53 67 url('/fonts/awesome-l-700.eot') format('embedded-opentype'); 54 unicode-range: U+000-5FF; /* Latin glyphs */68 unicode-range: U+000-5FF; 55 69 } 56 70 }}} … … 60 74 In addition to using an optimal CSS approach, the documentation recommends using a `<link rel="preload">` directive (or equivalents JavaScript-based approaches). This prevents the browser from having to wait until the render tree is complete before downloading font resources. 61 75 62 Our aim is to enable all themes/plugins to achieve this approach and to output this code (theCSS, paired with a preload directive) without requiring developers to explicitly craft and maintain this code.76 Our aim is to enable all themes/plugins to achieve this type of approach and to output this approach (the optimized CSS, paired with a preload directive) without requiring developers to explicitly craft and maintain this code. 63 77 64 78 = A spec … … 72 86 * Enqueue font. 73 87 * 74 * @param string $ handle The name of the font.88 * @param string $family The name of the font family. 75 89 * @param string|array|bool $src The source(s) of the font files. 76 90 * @param array $params { 77 91 * Params. 78 92 * 79 * @type string $style The style of the font. 80 * @type int $weight The weight of the font. 81 * @type string $display Display/swap behaviour. 82 * @type string $range A unicode range value. 83 * @type string|bool $external Externalise the CSS file/code. 84 * @type bool $preload Should the resource be preloaded. 85 * @type bool $in_footer Output the CSS/file in the footer. 93 * @type string $style The style of the font. 94 * @type int $weight The weight of the font. 95 * @type string $display Display/swap behaviour. 96 * @type string|array $variation Variation settings. 97 * @type string $range A unicode range value. 98 * @type string|bool $external Externalise the CSS file/code. 99 * @type bool $preload Should the resource be preloaded. 100 * @type bool $in_footer Output the CSS/file in the footer. 101 * @type string|bool $media Apply a media query to the output. 86 102 * } 87 103 */ 88 function wp_enqueue_font( $ handle, $src = false, $params = array() ) {104 function wp_enqueue_font( $family, $src = false, $params = array() ) { 89 105 $params = wp_parse_args( 90 106 $params, 91 107 array( 92 'style' => 'normal', 93 'weight' => 400, 94 'display' => 'auto', 95 'range' => false, 96 'external' => false, 97 'preload' => true, 98 'in_footer' => false, 108 'style' => 'normal', 109 'weight' => 400, 110 'display' => 'auto', 111 'font-variation-settings' => normal, 112 'range' => false, 113 'external' => false, 114 'preload' => true, 115 'in_footer' => false, 116 'media' => false 99 117 ) 100 118 ); … … 103 121 }}} 104 122 105 Note that the args after `$src` are in an associative array to avoid having to supply positional params with default values and to make it easier to easily identify the parameters. Something similar could be done for `wp_register_script()` and `wp_register_style()`.123 Note that the args after `$src` are in an associative array to avoid having to supply positional params with default values and to make it easier to easily identify the parameters. It's worth considering that something similar could be done for `wp_register_script()` and `wp_register_style()`. 106 124 107 125 == Starting from simplicity … … 111 129 <?php 112 130 wp_enqueue_font( 113 'Awesome Font', 131 'Awesome Font', 114 132 '/fonts/awesome-font-400.woff2' 115 133 ); 116 134 }}} 117 135 118 In this example, we’ve only specified the bare minimum information required to enqueue a font - a nameand a location. But there’s enough here that we can generate the following CSS:136 In this example, we’ve specified the bare minimum information required to enqueue a font - a family and a location. But there’s enough here that we can generate the following CSS: 119 137 120 138 {{{#!css … … 128 146 }}} 129 147 130 - ''NOTE: If no `$src` value is defined, only a local font should be referenced (via `$handle`).'' 131 132 == Supporting font registration 133 As with scripts and styles, we should allow for registration and enqueuing as separate processes. I.e., `wp_register_font` should accept the same arguments as `wp_enqueue_font`, and then, `wp_enqueue_font` can simply reference a registered `$handle`. 148 We can simplify even further, though. If no `$src` value is defined, then a local src can still be referenced via the `$family`. Note that this will only work if the user's system has the font installed locally. E.g.: 149 150 {{{#!php 151 wp_enqueue_font('Awesome Font'); 152 }}} 153 154 Produces the following: 155 156 {{{#!css 157 @font-face { 158 font-family: 'Awesome Font'; 159 font-style: normal; 160 font-weight: 400; 161 src: local('Awesome Font'); 162 } 163 }}} 164 165 == Registering and Enqueue'ing 166 As with scripts and styles, we should allow for registration and enqueuing as separate processes. 167 168 I.e., `wp_register_font()` should accept the same parameters as `wp_enqueue_font()`. Filters/hooks should be introduced to enable theme/plugin authors to manipulate the behaviour of fonts between these stages. 169 170 Behind the scenes, there's some additional complexity here. Scripts and styles use a `$handle` to identify them uniquely. Fonts don't have an equivalent concept (multiple font variations may share the same family namespace), so we need to synthesize one. This will allow us to pass gracefully wrap functions like `wp_enqueue_style()`. 171 172 To achieve this, we should combine the (sanitized) `$family`, `$style`, `$weight` and `$media` strings to create a unique representation; e.g., `base64encode($family.$style.$weight.$media)`. 173 174 If multiple fonts are registered with the same handle, the last-enqueued version should take priority (overwriting previous enqueues). 175 176 === De-regestering and de-queue'ing 177 178 As we've highlighted, the `$handle` is sometimes insufficient to represent a unique font (for the purposes of identification, registration, and conflict management). 179 180 This means that `wp_dequeue_font()` and `wp_deregister_font()` should accept an optional array of values in addition to the handle. E.g., 181 182 {{{#!php 183 /** 184 * Dequeue font. 185 * 186 * @param string $family The family of the font. 187 * @param array|false $params { 188 * Params. 189 * 190 * @type string $style The style of the font. 191 * @type string $weight The weight of the font. 192 * @type string $media The media query for the font. 193 * } 194 */ 195 }}} 196 197 If only a string is passed, ''all'' fonts matching that `$family` name should be removed. If an array is passed, then only fonts matching the family ''and'' the passed params should be dequeued/deregistered. 198 134 199 135 200 == Definitions 201 Some of the properties we're using here are lifted directly from `wp_enqueue_style()`, and should be treated identically and passed directly through to that function (e.g., `$in_footer`, `$media`). Some are fairly self-descriptive, and shouldn't need any special consideration (e.g., `$range`). 202 203 The unique and more complex remaining properties are explored below. 204 136 205 === $src 137 206 Whilst our `$src` variable can accept a simple string, more advanced usage should specify multiple versions and their formats. That looks like this (maintaining the rest of our ‘simplest implementation’ approach): … … 140 209 <?php 141 210 wp_enqueue_font( 142 'Awesome Font', 211 'Awesome Font', 143 212 array( 144 213 'woff2' => '/fonts/awesome-font-400.woff2', … … 154 223 - ''NOTE: Data URLs (e.g., `data:application/font-woff2;charset=utf-8;base64[...]`) may be provided instead of file paths.'' 155 224 225 The source values may be either a local or absolute URL (including remote URLs). However, this spec assumes (and prefers) that plugins and themes should generally store their font files locally; e.g., `/wp-content/themes/{{theme_name}}/fonts/` or `/wp-content/plugins/{{plugin_name}}/fonts/`. 226 227 === $variation 228 There's a maturing standard around 'variable fonts', which adds a 'font-variation-settings' property. This accepts a string of key/value pairs, which define attributes like the font's weight, slant, or other variations. 229 230 The `$variation` property accepts either a string (`normal`), or, an array of key/value pairs (e.g., `["wght" => 637, "wdth" => 100]`), and returns a string of these values (e.g., `wght 637, wdth 100`). 231 156 232 === $external 157 233 When the `$external` flag is false (which is the default behaviour), the generated CSS should be output in the <head>, via `wp_add_inline_style()` (unless `$in_footer` is set to `true`, in which case, the code should be output in a generated `<style>` tag hooked into `wp_footer`). 158 234 159 When set to `true`, we should wrap `wp_enqueue_style` and call a procedurally generated CSS file containing the relevant CSS (with a filename of `font-$handle-$style-$weight.css`).160 161 Alternatively, the value may be a string which represents a filepath, where the CSS ‘file’ should be accessible from (via a rewrite rule).162 163 - ''NOTE: When `$external` is true, we should check that the composite handle for the font can be converted to a unique stylesheet handle. If such a stylesheet handle already exists, we should de-enqueue the existing stylesheet and enqueue the new one.'' 164 - ''NOTE: Default location of generated CSS file TBD.'' 165 - ''NOTE: Invalid string values should fall back to the default behaviour.'' 235 When `$external` is set to `true`, we should use `wp_register_style()` and `wp_enqueue_style()` to reference a procedurally generated CSS file containing the relevant CSS at `/wp-content/fonts/$handle.css`. 236 237 Because we can't rely on having write permission to that folder (or know that it even exists), we should _not_ try to create a physical file, but rather, utilise a URL rewrite similar to the approach used in `do_robots()` to serve `/robots.txt`. 238 239 Note that this assumes the standardisation of /wp-content/fonts/ as a protected space. New WordPress installations should generate this (empty) folder. 240 241 When `$external` is set to a string, we should use the string value as the endpoint to reference (e.g., `/wp-content/plugins/{{some-plugin}}/fonts/custom-endpoint.css`). 166 242 167 243 === $preload 168 When the `$preload` flag is true (which is the default behaviour), `wp_resource_hints`* should be filtered to add a `<link rel="preload">` directive for the most modern format font file in the $src array (usually woff2). 244 When the `$preload` flag is true (which is the default behaviour), `wp_resource_hints`* should be filtered to add a `<link rel="preload">` directive for the most modern format font file in the $src array (usually woff2). 169 245 170 246 If `$external` is set to true, the associated CSS file should also be preloaded. … … 172 248 - ''NOTE: The preload tag is currently unsupported by `wp_resource_hints`, and it's expected that another (similar) function may be introduced to support this. Discussion [https://core.trac.wordpress.org/ticket/42438 here].'' 173 249 174 = Other considerations 175 == Unique handles 176 Unlike a style/script, the `$handle` is insufficient to represent a unique font (for the purposes of identification, registration, and conflict management). For fonts, we should consider the combination of the `$handle`, `$style` and `$weight` to represent a unique instance. 177 178 - ''NOTE: If there are non-unique instances of a font, the last-enqueued version should take priority.'' 250 = Other considerations 179 251 180 252 == Invalid values & minimum requirements … … 183 255 Invalid or malformed values for parameters without constrained values (e.g., `$range`, `$src`) should be ignored. 184 256 185 If this validation results in there being no values for `$handle` and `$src` (which represents the bare minimum requirements), no CSS should be generated/output. 257 If this validation results in there being no values for `$family` and `$src` (which represents the bare minimum requirements), no CSS should be generated/output. 258 259 = Hooks & filters 260 261 Filters/hooks should be introduced to enable theme/plugin authors to manipulate the behaviour of fonts between each of the stages we've defined - registration, enqueuing, and output (in various formats/locations). 262 263 These will need to be defined. 186 264 187 265 = Next steps 188 There are lots of moving parts on this one, but I’m hoping that most of it is fairly straightforward. I’d love some feedback on (any gaps in / issues with) the spec. 266 There are lots of moving parts on this one, but I’m hoping that most of it is fairly straightforward. I’d love some feedback on (any gaps in / issues with) the spec. 189 267 190 268 I’m anticipating that we'll need a bunch of discussion, iteration, exploration and definition before it makes sense to start authoring any code on this one, but that said, it’d be super to see some of this start to take shape.