jetpack / modules / latex.php

latex.php in Jetpack – WP Security, Backup, Speed, & Growth 15.9, at modules/latex.php

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1	<?php
2	/**
3	* Module Name: Beautiful Math
4	* Module Description: Add beautifully formatted math equations to your posts and pages using LaTeX.
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	if ( ! defined( 'ABSPATH' ) ) {
17	exit( 0 );
18	}
19
20	/**
21	* LaTeX support.
22	*
23	* Backward compatibility requires support for both "[latex][/latex]", and
24	* "$latex $" shortcodes.
25	*
26	* $latex e^{\i \pi} + 1 = 0$ -> [latex]e^{\i \pi} + 1 = 0[/latex]
27	* $latex [a, b]$ -> [latex][a, b][/latex]
28	*/
29
30	/**
31	* Markup LaTeX content.
32	*
33	* @param string $content Post or comment contents to markup.
34	*/
35	function latex_markup( $content ) {
36	$textarr = wp_html_split( $content );
37
38	$regex = '%
39	\$latex(?:=\s*\|\s+)
40	((?:
41	[^$]+ # Not a dollar
42	\|
43	(?<=(?<!\\\\)\\\\)\$ # Dollar preceded by exactly one slash
44	)+)
45	(?<!\\\\)\$ # Dollar preceded by zero slashes
46	%ix';
47
48	foreach ( $textarr as &$element ) {
49	if ( '' === $element \|\| '<' === $element[0] ) {
50	continue;
51	}
52
53	if ( false === stripos( $element, '$latex' ) ) {
54	continue;
55	}
56
57	$element = preg_replace_callback( $regex, 'latex_src', $element );
58	}
59
60	return implode( '', $textarr );
61	}
62
63	/**
64	* Process LaTeX string to rendered image.
65	*
66	* @param array $matches Matched regex results.
67	*/
68	function latex_src( $matches ) {
69	$latex = $matches[1];
70
71	$bg = latex_get_default_color( 'bg' );
72	$fg = latex_get_default_color( 'text', '000' );
73	$s = 0;
74
75	$latex = latex_entity_decode( $latex );
76	if ( preg_match( '/.+(&fg=[0-9a-f]{6}).*/i', $latex, $fg_matches ) ) {
77	$fg = substr( $fg_matches[1], 4 );
78	$latex = str_replace( $fg_matches[1], '', $latex );
79	}
80	if ( preg_match( '/.+(&bg=[0-9a-f]{6}).*/i', $latex, $bg_matches ) ) {
81	$bg = substr( $bg_matches[1], 4 );
82	$latex = str_replace( $bg_matches[1], '', $latex );
83	}
84	if ( preg_match( '/.+(&s=[0-9-]{1,2}).*/i', $latex, $s_matches ) ) {
85	$s = (int) substr( $s_matches[1], 3 );
86	$latex = str_replace( $s_matches[1], '', $latex );
87	}
88
89	return latex_render( $latex, $fg, $bg, $s );
90	}
91
92	/**
93	* Get the default color for an attribute.
94	*
95	* @param string $color Attribute to color (e.g. bg).
96	* @param string $default_color Default fallback color to use.
97	*/
98	function latex_get_default_color( $color, $default_color = 'ffffff' ) {
99	global $themecolors;
100	return $themecolors[ $color ] ?? $default_color;
101	}
102
103	/**
104	* Decode special characters in a LaTeX string.
105	*
106	* @param string $latex Character encoded content.
107	*/
108	function latex_entity_decode( $latex ) {
109	return str_replace( array( '<', '>', '"', ''', '&', '&', "\n", "\r" ), array( '<', '>', '"', "'", '&', '&', ' ', ' ' ), $latex );
110	}
111
112	/**
113	* Returns the URL for the server-side rendered image of LaTeX.
114	*
115	* @param string $latex LaTeX string.
116	* @param string $fg Foreground color.
117	* @param string $bg Background color.
118	* @param int $s Matches.
119	*
120	* @return string Image URL for the rendered LaTeX.
121	*/
122	function latex_render( $latex, $fg, $bg, $s = 0 ) {
123	$url = add_query_arg(
124	urlencode_deep(
125	array(
126	'latex' => $latex,
127	'bg' => $bg,
128	'fg' => $fg,
129	's' => $s,
130	'c' => '20201002', // cache buster. Added 2020-10-02 after server migration caused faulty rendering.
131	)
132	),
133	( is_ssl() ? 'https://' : 'http://' ) . 's0.wp.com/latex.php'
134	);
135
136	$alt = str_replace( '\\', '\', esc_attr( $latex ) );
137
138	return sprintf(
139	'<img src="%1$s" alt="%2$s" class="latex" />',
140	esc_url( $url ),
141	$alt
142	);
143	}
144
145	/**
146	* The shortcode way. The attributes are the same as the old ones - 'fg' and 'bg', instead of foreground
147	* and background, and 's' is for the font size.
148	*
149	* Example: [latex s=4 bg=00f fg=ff0]\LaTeX[/latex]
150	*
151	* @param array $atts Shortcode attributes.
152	* @param string $content Content to format.
153	*/
154	function latex_shortcode( $atts, $content = '' ) {
155	$attr = shortcode_atts(
156	array(
157	's' => 0,
158	'bg' => latex_get_default_color( 'bg' ),
159	'fg' => latex_get_default_color( 'text', '000' ),
160	),
161	$atts,
162	'latex'
163	);
164
165	return latex_render( latex_entity_decode( $content ), $attr['fg'], $attr['bg'], $attr['s'] );
166	}
167
168	/**
169	* LaTeX needs to be untexturized.
170	*
171	* @param array $shortcodes Array of shortcodes not to texturize.
172	*/
173	function latex_no_texturize( $shortcodes ) {
174	$shortcodes[] = 'latex';
175	return $shortcodes;
176	}
177	add_filter( 'no_texturize_shortcodes', 'latex_no_texturize' );
178
179	add_filter( 'the_content', 'latex_markup', 9 ); // Before wptexturize.
180	add_filter( 'comment_text', 'latex_markup', 9 ); // Before wptexturize.
181	add_shortcode( 'latex', 'latex_shortcode' );
182