Render MathML for mskip and mkern from texified mhchem

Bug: T340024

Change-Id: I2f9e0bbb98f33d6269009248861e4573dc9e6911

src/TexVC/MMLmappings/BaseMappings.php

@@ -483,12 +483,12 @@ class BaseMappings {
 		"qquad" => [ 'spacer', 2 ],
 		"thinspace" => [ 'spacer', MathSpace::THINMATHSPACE ],
 		"negthinspace" => [ 'spacer', MathSpace::NEGATIVETHINMATHSPACE ],
-		"hskip" => 'Hskip',
-		"hspace" => 'Hskip',
-		"kern" => 'Hskip',
-		"mskip" => 'Hskip',
-		"mspace" => 'Hskip',
-		"mkern" => 'Hskip',
+		"hskip" => 'hskip',
+		"hspace" => 'hskip',
+		"kern" => 'hskip',
+		"mskip" => 'hskip',
+		"mspace" => 'hskip',
+		"mkern" => 'hskip',
 		"rule" => 'rule',
 		"Rule" => [ 'Rule' ],
 		"Space" => [ 'Rule', 'blank' ],

src/TexVC/MMLmappings/BaseParsing.php

@@ -346,11 +346,25 @@ class BaseParsing {
 		return $mmlRow->encapsulateRaw( "HLINE TBD" );
 	}
 
-	public static function hskip( $node, $passedArgs, $operatorContent, $name,
-								  $smth1 = null, $smth2 = null, $smth3 = null, $smth4 = null ) {
-		// tbd hskip
-		$mmlRow = new MMLmrow();
-		return $mmlRow->encapsulateRaw( "hskip tbd" );
+	public static function hskip( $node, $passedArgs, $operatorContent, $name ) {
+		if ( $node->getArg() instanceof Curly ) {
+			$unit = MMLutil::squashLitsToUnit( $node->getArg() );
+			if ( !$unit ) {
+				return null;
+			}
+			$em = MMLutil::dimen2em( $unit );
+		} else {
+			// Prevent parsing in unmapped cases
+			return null;
+		}
+		if ( $name == "mskip" || $name == "mkern" ) {
+			$args = [ "width" => $em ];
+		} else {
+			return null;
+		}
+
+		$mspace = new MMLmspace( "", $args );
+		return $mspace->encapsulateRaw( "" );
 	}
 
 	public static function handleOperatorName( $node, $passedArgs, $operatorContent, $name,

src/TexVC/MMLmappings/Util/MMLutil.php

@@ -2,6 +2,8 @@
 namespace MediaWiki\Extension\Math\TexVC\MMLmappings\Util;
 
 use IntlChar;
+use MediaWiki\Extension\Math\TexVC\Nodes\Curly;
+use MediaWiki\Extension\Math\TexVC\Nodes\Literal;
 
 /**
  * Utility Methods for parsing Tex to MathML
@@ -72,6 +74,47 @@ class MMLutil {
 		return preg_replace( "/(\.\d\d\d).+/", '$1', $size ) . "em";
 	}
 
+	/**
+	 * Assumes the input curly contains an TexArray of literals, squashes the TexArray characters to a string.
+	 * @param Curly $node curly containing a TexArray of literals
+	 * @return ?string squashed string in example "2mu", "-3mu" etc. Null if no TexArray inside curly.
+	 */
+	public static function squashLitsToUnit( Curly $node ): ?string {
+		$unit = "";
+		foreach ( $node->getArg()->getArgs() as $literal ) {
+			if ( !$literal instanceof Literal ) {
+				continue;
+			}
+			$unit .= $literal->getArg();
+		}
+
+		return $unit;
+	}
+
+	/**
+	 * Convert a length dimension to em format
+	 * currently supports "mu: math unit and forwards em"
+	 * @param string $dimen input for length dimension  like "-2mu" or "3 em"
+	 * @return string|null converted string i.e. "0.333em"  or null if error
+	 */
+	public static function dimen2em( string $dimen ): ?string {
+		$matches = [];
+		$matched = preg_match( '/([+-]?)(\d*\.*\d+)\s*(mu|em)/', $dimen, $matches );
+
+		if ( !$matched ) {
+			return null;
+		}
+		if ( $matches[3] == "mu" ) {
+			$ret = self::size2em( strval( intval( $matches[2] ) / 18 ) );
+		} elseif ( $matches[3] == "em" ) {
+			$ret = $matches[2] . "em";
+		} else {
+			return null;
+		}
+
+		return ( $matches[1] == "-" ? "-" : "" ) . $ret;
+	}
+
 	/**
 	 * Some common steps of processing an input string before passing it as a key to the mappings.
 	 * @param string $input string to be processed

tests/phpunit/unit/TexVC/Mhchem/MhchemBasicMMLTest.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace MediaWiki\Extension\Math\TexVC\Mhchem;
+
+use MediaWiki\Extension\Math\TexVC\TexVC;
+use MediaWikiUnitTestCase;
+
+/**
+ * Some simple tests for testing MML output of TeXVC for
+ * equations containing mhchem. Test parsing the new TeX-commands introduced
+ * to TexVC for parsing texified mhchem output.
+ *
+ * @covers \MediaWiki\Extension\Math\TexVC\TexVC
+ *
+ */
+final class MhchemBasicMMLTest extends MediaWikiUnitTestCase {
+	public function testMskip() {
+		$input = "\\ce{Cr^{+3}(aq)}";
+		$texVC = new TexVC();
+		$options = [ "usemhchem" => true, "usemhchemtexified" => true ];
+		$warnings = [];
+		$checkRes = $texVC->check( $input, $options, $warnings, true );
+		$this->assertStringContainsString( '<mspace width="0.111em"></mspace>',
+			$checkRes["input"]->renderMML() );
+	}
+
+	public function testMkern() {
+		$input = "\\ce{A, B}";
+		$texVC = new TexVC();
+		$options = [ "usemhchem" => true, "usemhchemtexified" => true ];
+		$warnings = [];
+		$checkRes = $texVC->check( $input, $options, $warnings, true );
+		$this->assertStringContainsString( '<mspace width="0.333em"></mspace>',
+			$checkRes["input"]->renderMML() );
+	}
+}