content: Handle 'top' property in KaTeX span inline style

Author: rajveermalviya

lib/model/katex.dart

@@ -392,6 +392,7 @@ class _KatexParser {
       if (stylesheet.topLevels case [css_visitor.RuleSet() && final rule]) {
         double? heightEm;
         double? verticalAlignEm;
+        double? topEm;
         double? marginRightEm;
         double? marginLeftEm;
 
@@ -410,6 +411,10 @@ class _KatexParser {
                 verticalAlignEm = _getEm(expression);
                 if (verticalAlignEm != null) continue;
 
+              case 'top':
+                topEm = _getEm(expression);
+                if (topEm != null) continue;
+
               case 'margin-right':
                 marginRightEm = _getEm(expression);
                 if (marginRightEm != null) {
@@ -436,6 +441,7 @@ class _KatexParser {
 
         return KatexSpanStyles(
           heightEm: heightEm,
+          topEm: topEm,
           verticalAlignEm: verticalAlignEm,
           marginRightEm: marginRightEm,
           marginLeftEm: marginLeftEm,
@@ -477,6 +483,8 @@ class KatexSpanStyles {
   final double? heightEm;
   final double? verticalAlignEm;
 
+  final double? topEm;
+
   final double? marginRightEm;
   final double? marginLeftEm;
 
@@ -489,6 +497,7 @@ class KatexSpanStyles {
   const KatexSpanStyles({
     this.heightEm,
     this.verticalAlignEm,
+    this.topEm,
     this.marginRightEm,
     this.marginLeftEm,
     this.fontFamily,
@@ -503,6 +512,7 @@ class KatexSpanStyles {
     'KatexSpanStyles',
     heightEm,
     verticalAlignEm,
+    topEm,
     marginRightEm,
     marginLeftEm,
     fontFamily,
@@ -517,6 +527,7 @@ class KatexSpanStyles {
     return other is KatexSpanStyles &&
       other.heightEm == heightEm &&
       other.verticalAlignEm == verticalAlignEm &&
+      other.topEm == topEm &&
       other.marginRightEm == marginRightEm &&
       other.marginLeftEm == marginLeftEm &&
       other.fontFamily == fontFamily &&
@@ -531,6 +542,7 @@ class KatexSpanStyles {
     final args = <String>[];
     if (heightEm != null) args.add('heightEm: $heightEm');
     if (verticalAlignEm != null) args.add('verticalAlignEm: $verticalAlignEm');
+    if (topEm != null) args.add('topEm: $topEm');
     if (marginRightEm != null) args.add('marginRightEm: $marginRightEm');
     if (marginLeftEm != null) args.add('marginLeftEm: $marginLeftEm');
     if (fontFamily != null) args.add('fontFamily: $fontFamily');
@@ -545,6 +557,7 @@ class KatexSpanStyles {
     return KatexSpanStyles(
       heightEm: other.heightEm ?? heightEm,
       verticalAlignEm: other.verticalAlignEm ?? verticalAlignEm,
+      topEm: other.topEm ?? topEm,
       marginRightEm: other.marginRightEm ?? marginRightEm,
       marginLeftEm: other.marginLeftEm ?? marginLeftEm,
       fontFamily: other.fontFamily ?? fontFamily,

lib/widgets/content.dart

@@ -992,6 +992,9 @@ class _KatexSpan extends StatelessWidget {
       height: styles.heightEm != null
         ? styles.heightEm! * em
         : null,
+      transform: styles.topEm != null
+        ? Matrix4.translationValues(0, styles.topEm! * em, 0)
+        : null,
       child: widget,
     );
   }