Improve spacing of BOX elements

Tweak the algorithm so that a BOX math row element can have some
spacing. To this end, MathRow::before/after do not look at the type of
an element for deciding when to skip it, but rather to its math class.

In the new setting, the spacing algorithm works on all elements, but
skips the MC_UNKNOWN elements as if they were not present. As a
consequence, the two element types BEGIN and END have been replaced by
a single DUMMY (they can be recognized from their class).

To simply the code, add a new `mclass' argument to the
MathRow::Element constructor (default is MC_UNKNOWN).

src/mathed/InsetMath.cpp

@@ -60,9 +60,8 @@ MathClass InsetMath::mathClass() const
 
 bool InsetMath::addToMathRow(MathRow & mrow, MetricsInfo & ) const
 {
-	MathRow::Element e(MathRow::INSET);
+	MathRow::Element e(MathRow::INSET, mathClass());
 	e.inset = this;
-	e.mclass = mathClass();
 	mrow.push_back(e);
 	return true;
 }

src/mathed/MathMacro.cpp

@@ -96,7 +96,8 @@ public:
 		// if there was no contents, and the contents is editable,
 		// then we insert a box instead.
 		if (!has_contents && mathMacro_->nesting() == 1) {
-			MathRow::Element e(MathRow::BOX);
+			// mathclass is ord because it should be spaced as a normal atom
+			MathRow::Element e(MathRow::BOX, MC_ORD);
 			e.color = Color_mathline;
 			mrow.push_back(e);
 			has_contents = true;
@@ -310,6 +311,7 @@ bool MathMacro::addToMathRow(MathRow & mrow, MetricsInfo & mi) const
 	// if there was no contents and the array is editable, then we
 	// insert a grey box instead.
 	if (!has_contents && mi.base.macro_nesting == 1) {
+		// mathclass is unknown because it is irrelevant for spacing
 		MathRow::Element e(MathRow::BOX);
 		e.color = Color_mathmacroblend;
 		mrow.push_back(e);

src/mathed/MathRow.cpp

@@ -36,8 +36,8 @@ using namespace std;
 namespace lyx {
 
 
-MathRow::Element::Element(Type t)
+MathRow::Element::Element(Type t, MathClass mc)
-	: type(t), inset(0), mclass(MC_ORD), before(0), after(0),
+	: type(t), mclass(mc), before(0), after(0), inset(0),
 	  compl_unique_to(0), macro(0), color(Color_red)
 {}
 
@@ -45,8 +45,7 @@ MathRow::Element::Element(Type t)
 MathRow::MathRow(MetricsInfo & mi, MathData const * ar)
 {
 	// First there is a dummy element of type "open"
-	push_back(Element(BEGIN));
+	push_back(Element(DUMMY, MC_OPEN));
-	back().mclass = MC_OPEN;
 
 	// Then insert the MathData argument
 	bool const has_contents = ar->addToMathRow(*this, mi);
@@ -54,14 +53,13 @@ MathRow::MathRow(MetricsInfo & mi, MathData const * ar)
 	// empty arrays are visible when they are editable
 	// we reserve the necessary space anyway (even if nothing gets drawn)
 	if (!has_contents) {
-		Element e(BOX);
+		Element e(BOX, MC_ORD);
 		e.color = mi.base.macro_nesting == 0 ? Color_mathline : Color_none;
 		push_back(e);
 	}
 
 	// Finally there is a dummy element of type "close"
-	push_back(Element(END));
+	push_back(Element(DUMMY, MC_CLOSE));
-	back().mclass = MC_CLOSE;
 
 	/* Do spacing only in math mode. This test is a bit clumsy,
 	 * but it is used in other places for guessing the current mode.
@@ -71,7 +69,7 @@ MathRow::MathRow(MetricsInfo & mi, MathData const * ar)
 
 	// update classes
 	for (int i = 1 ; i != static_cast<int>(elements_.size()) - 1 ; ++i) {
-		if (elements_[i].type != INSET)
+		if (elements_[i].mclass == MC_UNKNOWN)
 			continue;
 		update_class(elements_[i].mclass, elements_[before(i)].mclass,
 		             elements_[after(i)].mclass);
@@ -80,7 +78,7 @@ MathRow::MathRow(MetricsInfo & mi, MathData const * ar)
 	// set spacing
 	// We go to the end to handle spacing at the end of equation
 	for (int i = 1 ; i != static_cast<int>(elements_.size()) ; ++i) {
-		if (elements_[i].type != INSET)
+		if (elements_[i].mclass == MC_UNKNOWN)
 			continue;
 		Element & bef = elements_[before(i)];
 		int spc = class_spacing(bef.mclass, elements_[i].mclass, mi.base);
@@ -100,8 +98,7 @@ int MathRow::before(int i) const
 {
 	do
 		--i;
-	while (elements_[i].type != BEGIN
+	while (elements_[i].mclass == MC_UNKNOWN);
-		   && elements_[i].type != INSET);
 
 	return i;
 }
@@ -111,8 +108,7 @@ int MathRow::after(int i) const
 {
 	do
 		++i;
-	while (elements_[i].type != END
+	while (elements_[i].mclass == MC_UNKNOWN);
-		   && elements_[i].type != INSET);
 
 	return i;
 }
@@ -134,8 +130,7 @@ void MathRow::metrics(MetricsInfo & mi, Dimension & dim) const
 		mi.base.macro_nesting = macro_nesting.back();
 		Dimension d;
 		switch (e.type) {
-		case BEGIN:
+		case DUMMY:
-		case END:
 			break;
 		case INSET:
 			e.inset->metrics(mi, d);
@@ -239,11 +234,10 @@ void MathRow::draw(PainterInfo & pi, int x, int const y) const
 			if (e.color != Color_none)
 				pi.pain.rectangle(x + e.before, y - d.ascent(),
 				                  d.width(), d.height(), e.color);
-			x += d.wid;
+			x += d.wid + e.before + e.after;
 			break;
 		}
-		case BEGIN:
+		case DUMMY:
-		case END:
 		case END_MACRO:
 			break;
 		}
@@ -285,11 +279,8 @@ int MathRow::kerning(BufferView const * bv) const
 ostream & operator<<(ostream & os, MathRow::Element const & e)
 {
 	switch (e.type) {
-	case MathRow::BEGIN:
+	case MathRow::DUMMY:
-		os << "{";
+		os << (e.mclass == MC_OPEN ? "{" : "}");
-		break;
-	case MathRow::END:
-		os << "}";
 		break;
 	case MathRow::INSET:
 		os << "<" << e.before << "-"
@@ -310,7 +301,7 @@ ostream & operator<<(ostream & os, MathRow::Element const & e)
 		os << ")";
 		break;
 	case MathRow::BOX:
-		os << "@";
+		os << "<" << e.before << "-[]-" << e.after << ">";
 		break;
 	}
 	return os;

src/mathed/MathRow.h

@@ -47,31 +47,30 @@ public:
 	// What row elements can be
 	enum Type {
 		INSET, // this element is a plain inset
+		BOX, // an empty box
 		BEG_MACRO, // a macro begins here
 		END_MACRO, // a macro ends here
 		BEG_ARG, // a macro argument begins here
 		END_ARG, // a macro argument ends here
-		BEGIN, // dummy element before row
+		DUMMY // a dummy element (used before or after row)
-		END, // dummy element after row
-		BOX // an empty box
 	};
 
 	// An elements, together with its spacing
 	struct Element
 	{
 		///
-		Element(Type t);
+		Element(Type t, MathClass mc = MC_UNKNOWN);
 
 		/// Classifies the contents of the object
 		Type type;
+		/// the class of the element
+		MathClass mclass;
+		/// the spacing around the element
+		int before, after;
 
 		/// When type is INSET
 		/// the math inset
 		InsetMath const * inset;
-		/// the class of the inset
-		MathClass mclass;
-		/// the spacing around the inset
-		int before, after;
 		// Non empty when there is a completion to draw
 		docstring compl_text;
 		// the number of characters forming the unique part.