Support \textup and \textmd (#1921)

* Support \textup and \textmd

This PR adds support for `\textup` and `\textmd`, which are the inverses of
`\textit` and `\textbf`.  Unlike bare `\text`, they result in `textup` and
`textmd` classes being applied, but those have no CSS rules, so they act the
same as bare `\text`.

Fixes #1909.

* Add documentation

* Add unsupported font commands

src/Options.js

@@ -36,6 +36,10 @@ const sizeAtStyle = function(size: number, style: StyleInterface): number {
     return style.size < 2 ? size : sizeStyleMap[size - 1][style.size - 1];
 };
 
+// In these types, "" (empty string) means "no change".
+export type FontWeight = "textbf" | "textmd" | "";
+export type FontShape = "textit" | "textup" | "";
+
 export type OptionsData = {
     style: StyleInterface;
     color?: string | void;
@@ -44,8 +48,8 @@ export type OptionsData = {
     phantom?: boolean;
     font?: string;
     fontFamily?: string;
-    fontWeight?: string;
-    fontShape?: string;
+    fontWeight?: FontWeight;
+    fontShape?: FontShape;
     sizeMultiplier?: number;
     maxSize: number;
 };
@@ -68,8 +72,8 @@ class Options {
     // See: https://tex.stackexchange.com/questions/22350/difference-between-textrm-and-mathrm
     font: string;
     fontFamily: string;
-    fontWeight: string;
-    fontShape: string;
+    fontWeight: FontWeight;
+    fontShape: FontShape;
     sizeMultiplier: number;
     maxSize: number;
     _fontMetrics: FontMetrics | void;
@@ -244,7 +248,7 @@ class Options {
     /**
      * Creates a new options object with the given font weight
      */
-    withTextFontWeight(fontWeight: string): Options {
+    withTextFontWeight(fontWeight: FontWeight): Options {
         return this.extend({
             fontWeight,
             font: "",
@@ -254,7 +258,7 @@ class Options {
     /**
      * Creates a new options object with the given font weight
      */
-    withTextFontShape(fontShape: string): Options {
+    withTextFontShape(fontShape: FontShape): Options {
         return this.extend({
             fontShape,
             font: "",

src/functions/text.js

@@ -13,10 +13,12 @@ const textFontFamilies = {
 
 const textFontWeights = {
     "\\textbf": "textbf",
+    "\\textmd": "textmd",
 };
 
 const textFontShapes = {
     "\\textit": "textit",
+    "\\textup": "textup",
 };
 
 const optionsWithFont = (group, options) => {
@@ -39,9 +41,9 @@ defineFunction({
         // Font families
         "\\text", "\\textrm", "\\textsf", "\\texttt", "\\textnormal",
         // Font weights
-        "\\textbf",
+        "\\textbf", "\\textmd",
         // Font Shapes
-        "\\textit",
+        "\\textit", "\\textup",
     ],
     props: {
         numArgs: 1,