katex [nfc]: Join the CSS-class switch statements into one

Conveniently, the two redundant rules say the exact same thing
when they apply.  So the first one has no effect, and we can
ignore it.

Author: gnprice

lib/model/katex.dart

@@ -141,7 +141,7 @@ class _KatexParser {
     // Aggregate the CSS styles that apply, in the same order as the CSS
     // classes specified for this span, mimicking the behaviour on web.
     //
-    // Each case in the switch blocks below is a separate CSS class definition
+    // Each case in the switch block below is a separate CSS class definition
     // in the same order as in katex.scss :
     //   https://github.com/KaTeX/KaTeX/blob/2fe1941b/src/styles/katex.scss
     // A copy of class definition (where possible) is accompanied in a comment
@@ -178,10 +178,10 @@ class _KatexParser {
           styles.fontFamily = 'KaTeX_Main';
           classFound = true;
 
-        case 'textsf':
-          // .textsf { font-family: KaTeX_SansSerif; }
-          styles.fontFamily = 'KaTeX_SansSerif';
-          classFound = true;
+        // case 'textsf':
+        //   // .textsf { font-family: KaTeX_SansSerif; }
+        // This CSS rule has no effect, because the other `.textsf` rule below
+        // has the exact same list of declarations.  Handle it there instead.
 
         case 'texttt':
           // .texttt { font-family: KaTeX_Typewriter; }
@@ -261,13 +261,7 @@ class _KatexParser {
           // .textscr { font-family: KaTeX_Script; }
           styles.fontFamily = 'KaTeX_Script';
           classFound = true;
-      }
 
-      // We can't add the case for the next class (.mathsf, .textsf) in the
-      // above switch block, because there is already a case for .textsf above.
-      // So start a new block, to keep the order of the cases here same as the
-      // CSS class definitions in katex.scss .
-      switch (spanClass) {
         case 'mathsf':
         case 'textsf':
           // .mathsf,
@@ -378,13 +372,11 @@ class _KatexParser {
           throw KatexHtmlParseError();
 
         // TODO handle more classes from katex.scss
-      }
 
-      // Ignore these classes because they don't have a CSS definition
-      // in katex.scss, but we encounter them in the generated HTML.
-      switch (spanClass) {
         case 'mord':
         case 'mopen':
+          // Ignore these classes because they don't have a CSS definition
+          // in katex.scss, but we encounter them in the generated HTML.
           classFound = true;
       }