latex.php
| 1 | <?php |
| 2 | /** |
| 3 | * Module Name: Beautiful Math |
| 4 | * Module Description: Use the LaTeX markup language to write mathematical equations and formulas |
| 5 | * Sort Order: 12 |
| 6 | * First Introduced: 1.1 |
| 7 | * Requires Connection: No |
| 8 | * Auto Activate: No |
| 9 | * Module Tags: Writing |
| 10 | * Feature: Writing |
| 11 | * Additional Search Queries: latex, math, equation, equations, formula, code |
| 12 | * |
| 13 | * @package automattic/jetpack |
| 14 | */ |
| 15 | |
| 16 | /** |
| 17 | * LaTeX support. |
| 18 | * |
| 19 | * Backward compatibility requires support for both "[latex][/latex]", and |
| 20 | * "$latex $" shortcodes. |
| 21 | * |
| 22 | * $latex e^{\i \pi} + 1 = 0$ -> [latex]e^{\i \pi} + 1 = 0[/latex] |
| 23 | * $latex [a, b]$ -> [latex][a, b][/latex] |
| 24 | */ |
| 25 | |
| 26 | /** |
| 27 | * Markup LaTeX content. |
| 28 | * |
| 29 | * @param string $content Post or comment contents to markup. |
| 30 | */ |
| 31 | function latex_markup( $content ) { |
| 32 | $textarr = wp_html_split( $content ); |
| 33 | |
| 34 | $regex = '% |
| 35 | \$latex(?:=\s*|\s+) |
| 36 | ((?: |
| 37 | [^$]+ # Not a dollar |
| 38 | | |
| 39 | (?<=(?<!\\\\)\\\\)\$ # Dollar preceded by exactly one slash |
| 40 | )+) |
| 41 | (?<!\\\\)\$ # Dollar preceded by zero slashes |
| 42 | %ix'; |
| 43 | |
| 44 | foreach ( $textarr as &$element ) { |
| 45 | if ( '' === $element || '<' === $element[0] ) { |
| 46 | continue; |
| 47 | } |
| 48 | |
| 49 | if ( false === stripos( $element, '$latex' ) ) { |
| 50 | continue; |
| 51 | } |
| 52 | |
| 53 | $element = preg_replace_callback( $regex, 'latex_src', $element ); |
| 54 | } |
| 55 | |
| 56 | return implode( '', $textarr ); |
| 57 | } |
| 58 | |
| 59 | /** |
| 60 | * Process LaTeX string to rendered image. |
| 61 | * |
| 62 | * @param array $matches Matched regex results. |
| 63 | */ |
| 64 | function latex_src( $matches ) { |
| 65 | $latex = $matches[1]; |
| 66 | |
| 67 | $bg = latex_get_default_color( 'bg' ); |
| 68 | $fg = latex_get_default_color( 'text', '000' ); |
| 69 | $s = 0; |
| 70 | |
| 71 | $latex = latex_entity_decode( $latex ); |
| 72 | if ( preg_match( '/.+(&fg=[0-9a-f]{6}).*/i', $latex, $fg_matches ) ) { |
| 73 | $fg = substr( $fg_matches[1], 4 ); |
| 74 | $latex = str_replace( $fg_matches[1], '', $latex ); |
| 75 | } |
| 76 | if ( preg_match( '/.+(&bg=[0-9a-f]{6}).*/i', $latex, $bg_matches ) ) { |
| 77 | $bg = substr( $bg_matches[1], 4 ); |
| 78 | $latex = str_replace( $bg_matches[1], '', $latex ); |
| 79 | } |
| 80 | if ( preg_match( '/.+(&s=[0-9-]{1,2}).*/i', $latex, $s_matches ) ) { |
| 81 | $s = (int) substr( $s_matches[1], 3 ); |
| 82 | $latex = str_replace( $s_matches[1], '', $latex ); |
| 83 | } |
| 84 | |
| 85 | return latex_render( $latex, $fg, $bg, $s ); |
| 86 | } |
| 87 | |
| 88 | /** |
| 89 | * Get the default color for an attribute. |
| 90 | * |
| 91 | * @param string $color Attribute to color (e.g. bg). |
| 92 | * @param string $default_color Default fallback color to use. |
| 93 | */ |
| 94 | function latex_get_default_color( $color, $default_color = 'ffffff' ) { |
| 95 | global $themecolors; |
| 96 | return isset( $themecolors[ $color ] ) ? $themecolors[ $color ] : $default_color; |
| 97 | } |
| 98 | |
| 99 | /** |
| 100 | * Decode special characters in a LaTeX string. |
| 101 | * |
| 102 | * @param string $latex Character encoded content. |
| 103 | */ |
| 104 | function latex_entity_decode( $latex ) { |
| 105 | return str_replace( array( '<', '>', '"', ''', '&', '&', "\n", "\r" ), array( '<', '>', '"', "'", '&', '&', ' ', ' ' ), $latex ); |
| 106 | } |
| 107 | |
| 108 | /** |
| 109 | * Returns the URL for the server-side rendered image of LaTeX. |
| 110 | * |
| 111 | * @param string $latex LaTeX string. |
| 112 | * @param string $fg Foreground color. |
| 113 | * @param string $bg Background color. |
| 114 | * @param int $s Matches. |
| 115 | * |
| 116 | * @return string Image URL for the rendered LaTeX. |
| 117 | */ |
| 118 | function latex_render( $latex, $fg, $bg, $s = 0 ) { |
| 119 | $url = add_query_arg( |
| 120 | urlencode_deep( |
| 121 | array( |
| 122 | 'latex' => $latex, |
| 123 | 'bg' => $bg, |
| 124 | 'fg' => $fg, |
| 125 | 's' => $s, |
| 126 | 'c' => '20201002', // cache buster. Added 2020-10-02 after server migration caused faulty rendering. |
| 127 | ) |
| 128 | ), |
| 129 | ( is_ssl() ? 'https://' : 'http://' ) . 's0.wp.com/latex.php' |
| 130 | ); |
| 131 | |
| 132 | $alt = str_replace( '\\', '\', esc_attr( $latex ) ); |
| 133 | |
| 134 | return sprintf( |
| 135 | '<img src="%1$s" alt="%2$s" class="latex" />', |
| 136 | esc_url( $url ), |
| 137 | $alt |
| 138 | ); |
| 139 | } |
| 140 | |
| 141 | /** |
| 142 | * The shortcode way. The attributes are the same as the old ones - 'fg' and 'bg', instead of foreground |
| 143 | * and background, and 's' is for the font size. |
| 144 | * |
| 145 | * Example: [latex s=4 bg=00f fg=ff0]\LaTeX[/latex] |
| 146 | * |
| 147 | * @param array $atts Shortcode attributes. |
| 148 | * @param string $content Content to format. |
| 149 | */ |
| 150 | function latex_shortcode( $atts, $content = '' ) { |
| 151 | $attr = shortcode_atts( |
| 152 | array( |
| 153 | 's' => 0, |
| 154 | 'bg' => latex_get_default_color( 'bg' ), |
| 155 | 'fg' => latex_get_default_color( 'text', '000' ), |
| 156 | ), |
| 157 | $atts, |
| 158 | 'latex' |
| 159 | ); |
| 160 | |
| 161 | return latex_render( latex_entity_decode( $content ), $attr['fg'], $attr['bg'], $attr['s'] ); |
| 162 | } |
| 163 | |
| 164 | /** |
| 165 | * LaTeX needs to be untexturized. |
| 166 | * |
| 167 | * @param array $shortcodes Array of shortcodes not to texturize. |
| 168 | */ |
| 169 | function latex_no_texturize( $shortcodes ) { |
| 170 | $shortcodes[] = 'latex'; |
| 171 | return $shortcodes; |
| 172 | } |
| 173 | add_filter( 'no_texturize_shortcodes', 'latex_no_texturize' ); |
| 174 | |
| 175 | add_filter( 'the_content', 'latex_markup', 9 ); // Before wptexturize. |
| 176 | add_filter( 'comment_text', 'latex_markup', 9 ); // Before wptexturize. |
| 177 | add_shortcode( 'latex', 'latex_shortcode' ); |
| 178 |