Implement \colon as amsmath does (#1410)

* Implement \colon as amsmath does

* Remove \colon from symbols.js

* Update screenshots

* Pick up comments

* Replace screenshots

src/macros.js

@@ -289,6 +289,11 @@ defineMacro("\\varPhi", "\\mathit{\\Phi}");
 defineMacro("\\varPsi", "\\mathit{\\Psi}");
 defineMacro("\\varOmega", "\\mathit{\\Omega}");
 
+// \renewcommand{\colon}{\nobreak\mskip2mu\mathpunct{}\nonscript
+// \mkern-\thinmuskip{:}\mskip6muplus1mu\relax}
+defineMacro("\\colon", "\\nobreak\\mskip2mu\\mathpunct{}" +
+    "\\mathchoice{\\mkern-3mu}{\\mkern-3mu}{}{}{:}\\mskip6mu");
+
 // \newcommand{\boxed}[1]{\fbox{\m@th$\displaystyle#1$}}
 defineMacro("\\boxed", "\\fbox{\\displaystyle{#1}}");
 

src/symbols.js

@@ -592,7 +592,6 @@ defineSymbol(math, main, spacing, null, "\\nobreak");
 defineSymbol(math, main, spacing, null, "\\allowbreak");
 defineSymbol(math, main, punct, ",", ",");
 defineSymbol(math, main, punct, ";", ";");
-defineSymbol(math, main, punct, ":", "\\colon");
 defineSymbol(math, ams, bin, "\u22bc", "\\barwedge", true);
 defineSymbol(math, ams, bin, "\u22bb", "\\veebar", true);
 defineSymbol(math, main, bin, "\u2299", "\\odot", true);

test/katex-spec.js

@@ -99,7 +99,7 @@ describe("A rel parser", function() {
 });
 
 describe("A punct parser", function() {
-    const expression = ",;\\colon";
+    const expression = ",;";
 
     it("should not fail", function() {
         expect(expression).toParse(strictSettings);

test/screenshotter/ss_data.yaml

@@ -289,6 +289,7 @@ Spacing: |
         ^3+[-1][1-1]1=1(=1)\lvert a\rvert~b \\
         \scriptstyle{^3+[-1][1-1]1=1(=1)\lvert a\rvert~b} \\
         \scriptscriptstyle{^3+[-1][1-1]1=1(=1)\lvert a\rvert~b} \\
+        a : a \colon a \\
     \end{matrix}
 Sqrt: |
     \sqrt{\sqrt{\sqrt{x}}}_{\sqrt{\sqrt{x}}}^{\sqrt{\sqrt{\sqrt{x}}}