Define mathClass of MathMacro

Enables intelligent splitting for math macros.

Crucially improves the detection of math words for the new Ctrl-Arrow movement.

src/mathed/MathData.cpp

@@ -889,6 +889,20 @@ int MathData::yo(BufferView const & bv) const
 }
 
 
+MathClass MathData::mathClass() const
+{
+	MathClass res = MC_UNKNOWN;
+	for (MathAtom const & at : *this) {
+		MathClass mc = at->mathClass();
+		if (res == MC_UNKNOWN)
+			res = mc;
+		else if (mc != MC_UNKNOWN && res != mc)
+			return MC_ORD;
+	}
+	return res == MC_UNKNOWN ? MC_ORD : res;
+}
+
+
 ostream & operator<<(ostream & os, MathData const & ar)
 {
 	odocstringstream oss;

src/mathed/MathData.h

@@ -137,6 +137,8 @@ public:
 	void drawT(TextPainter & pi, int x, int y) const;
 	/// mark cell for re-drawing
 	void touch() const;
+	/// approximate the math class of the data
+	MathClass mathClass() const;
 
 	/// access to cached x coordinate of last drawing
 	int xo(BufferView const & bv) const;

src/mathed/MathMacro.cpp

@@ -140,6 +140,15 @@ public:
 	void htmlize(HtmlStream & ms) const { ms << mathMacro_->cell(idx_); }
 	///
 	void octave(OctaveStream & os) const { os << mathMacro_->cell(idx_); }
+	///
+	MathClass mathClass() const
+	{
+		return MC_UNKNOWN;
+		// This can be refined once the pointer issues are fixed. I did not
+		// notice any immediate crash with the following code, but it is risky
+		// nevertheless:
+		//return mathMacro_->cell(idx_).mathClass();
+	}
 
 private:
 	///
@@ -823,16 +832,21 @@ size_t MathMacro::appetite() const
 
 MathClass MathMacro::mathClass() const
 {
-	// this only affects intelligent splitting since global macros are always
+	// This can be just a heuristic, since it is only considered for display
-	// linearised.
+	// when the macro is not linearised. Therefore it affects:
+	// * The spacing of the inset while being edited,
+	// * Intelligent splitting
+	// * Cursor word movement (Ctrl-Arrow).
 	if (MacroData const * m = macroBackup()) {
+		// If it is a global macro and is defined explicitly
 		if (m->symbol()) {
 			MathClass mc = string_to_class(d->macroBackup_.symbol()->extra);
 			if (mc != MC_UNKNOWN)
 				return mc;
 		}
 	}
-	return MC_ORD;
+	// Otherwise guess from the expanded macro
+	return d->expanded_.mathClass();
 }