Fix k=1 should appear under sum in displaystyle

* In test MathNativeTests: "\sum_{k=1}^N k^2"
* also verify that textstyle variant works correctly

Bug: T315978
Change-Id: I8f6cd5ef1e4539616439542184cb7d9dc5cf2363

Author: Hyper-Node

src/TexVC/Nodes/FQ.php

@@ -6,6 +6,7 @@
 
 use MediaWiki\Extension\Math\TexVC\MMLmappings\BaseParsing;
 use MediaWiki\Extension\Math\TexVC\MMLnodes\MMLmrow;
+use MediaWiki\Extension\Math\TexVC\MMLnodes\MMLmstyle;
 use MediaWiki\Extension\Math\TexVC\MMLnodes\MMLmsubsup;
 use MediaWiki\Extension\Math\TexVC\MMLnodes\MMLmunderover;
 
@@ -84,10 +85,18 @@ public function renderMML( $arguments = [], $state = [] ) {
 			$emptyMrow = $mrow->getEmpty();
 		}
 		// This seems to be the common case
-		return $melement->encapsulateRaw(
+		$inner = $melement->encapsulateRaw(
 			$emptyMrow .
 			$this->getBase()->renderMML( [], $state ) .
 			$mrow->encapsulateRaw( $this->getDown()->renderMML( [], $state ) ) .
 			$mrow->encapsulateRaw( $this->getUp()->renderMML( [], $state ) ) );
+
+		if ( $melement instanceof MMLmunderover ) {
+			$args = $state['styleargs'] ?? [ "displaystyle" => "true", "scriptlevel" => 0 ];
+			$style = new MMLmstyle( "", $args );
+			return $style->encapsulateRaw( $inner );
+		}
+
+		return $inner;
 	}
 }

tests/phpunit/unit/TexVC/MMLRenderTest.php

@@ -14,13 +14,26 @@
  * @covers \MediaWiki\Extension\Math\TexVC\TexVC
  */
 class MMLRenderTest extends MediaWikiUnitTestCase {
-	public function testUnderbrace() {
-		$input = "\underbrace{ a+b+\cdots+z }_{26}";
+
+	public function testUnder() {
+		$input = "\\underbrace{ a+b+\\cdots+z }_{26}";
 		$mathMLtexVC = $this->generateMML( $input );
 		$this->assertStringContainsString( "<munder>",  $mathMLtexVC );
 		$this->assertStringNotContainsString( "<msub>",  $mathMLtexVC );
 	}
 
+	public function testSumDisplaystyle() {
+		$input = "\sum_{k=1}^N k^2";
+		$mathMLtexVC = $this->generateMML( $input );
+		$this->assertStringContainsString( "<mstyle displaystyle=\"true\" scriptlevel=\"0\">", $mathMLtexVC );
+	}
+
+	public function testSumTextstyle() {
+		$input = "\\textstyle \sum_{k=1}^N k^2";
+		$mathMLtexVC = $this->generateMML( $input );
+		$this->assertStringContainsString( "<mstyle displaystyle=\"false\" scriptlevel=\"0\">", $mathMLtexVC );
+	}
+
 	public function testPilcrow() {
 		$input = "\P";
 		$mathMLtexVC = $this->generateMML( $input );