- backport fix for bug #10466

Handle the command \multicolumn correctly in math macros

src/mathed/InsetMathAMSArray.h

@@ -54,6 +54,9 @@ public:
 	char const * name_left() const;
 	///
 	char const * name_right() const;
+	/// 
+	bool handlesMulticolumn() const { return true; } //override 
+
 private:
 	virtual Inset * clone() const;
 	///

src/mathed/InsetMathArray.h

@@ -51,6 +51,9 @@ public:
 	void validate(LaTeXFeatures & features) const;
 	///
 	InsetCode lyxCode() const { return MATH_ARRAY_CODE; }
+	/// 
+	bool handlesMulticolumn() const { return true; } //override 
+
 private:
 	virtual Inset * clone() const;
 	///

src/mathed/InsetMathCases.h

@@ -54,6 +54,9 @@ public:
 	InsetCode lyxCode() const { return MATH_CASES_CODE; }
 	///
 	int displayColSpace(col_type) const;
+	/// see e.g. https://tex.stackexchange.com/a/133283/87201 
+	bool handlesMulticolumn() const { return true; } //override
+
 private:
 	virtual Inset * clone() const;
 };

src/mathed/InsetMathGrid.h

@@ -221,6 +221,8 @@ public:
 	virtual int vlinesep() const;
 	///
 	virtual int border() const;
+	/// 
+	virtual bool handlesMulticolumn() const { return false; }
 
 	///
 	void write(WriteStream & os) const;

src/mathed/InsetMathHull.cpp

@@ -15,7 +15,6 @@
 #include "InsetMathChar.h"
 #include "InsetMathColor.h"
 #include "InsetMathFrac.h"
-#include "InsetMathGrid.h"
 #include "InsetMathNest.h"
 #include "InsetMathScript.h"
 #include "MathExtern.h"

src/mathed/InsetMathMatrix.h

@@ -47,6 +47,8 @@ public:
 	void octave(OctaveStream &) const;
 	///
 	InsetCode lyxCode() const { return MATH_MATRIX_CODE; }
+	/// 
+	bool handlesMulticolumn() const { return true; } //override
 
 private:
 	virtual Inset * clone() const;

src/mathed/InsetMathSplit.cpp

@@ -48,11 +48,6 @@ Inset * InsetMathSplit::clone() const
 }
 
 
-// FIXME: InsetMathGrid should be changed to let the real column alignment be
-// given by a virtual method like displayColAlign, because the values produced
-// by defaultColAlign can be invalidated by lfuns such as add-column. I suspect
-// that for the moment the values produced by defaultColAlign are not used,
-// notably because alignment is not implemented in the LyXHTML output.
 char InsetMathSplit::defaultColAlign(col_type col)
 {
 	if (name_ == "gathered")

src/mathed/InsetMathTabular.h

@@ -47,6 +47,8 @@ public:
 	void maple(MapleStream &) const;
 	///
 	InsetCode lyxCode() const { return MATH_TABULAR_CODE; }
+	/// 
+	bool handlesMulticolumn() const { return true; } //override
 
 private:
 	Inset * clone() const;

src/mathed/MathParser.cpp

@@ -1361,36 +1361,39 @@ bool Parser::parse1(InsetMathGrid & grid, unsigned flags,
 			}
 		}
 
-		else if (t.cs() == "multicolumn") {
-			// extract column count and insert dummy cells
+		else if (t.cs() == "multicolumn" && grid.handlesMulticolumn()) {
+			// if the columns are specified numerically,
+			// extract column count and insert dummy cells,
+			// otherwise parse it as an user macro
 			MathData count;
 			parse(count, FLAG_ITEM, mode);
-			int cols = 1;
-			if (!extractNumber(count, cols)) {
-				success_ = false;
-				error("can't extract number of multicolumn cells");
-			}
-			// resize the table if necessary
-			size_t first = grid.index(cellrow, cellcol);
-			for (int i = 1; i < cols; ++i) {
-				if (addCol(grid, cellcol)) {
-					size_t const idx = grid.index(cellrow, cellcol);
-					grid.cellinfo(idx).multi_ =
-						InsetMathGrid::CELL_PART_OF_MULTICOLUMN;
+			int cols;
+			if (extractNumber(count, cols)) {
+				// resize the table if necessary
+				size_t first = grid.index(cellrow, cellcol);
+				for (int i = 1; i < cols; ++i) {
+					if (addCol(grid, cellcol)) {
+						size_t const idx = grid.index(cellrow, cellcol);
+						grid.cellinfo(idx).multi_ = 
+							InsetMathGrid::CELL_PART_OF_MULTICOLUMN;
+					}
 				}
+
+				// the first cell is the real thing, not a dummy 
+				cell = &grid.cell(first); 
+				grid.cellinfo(first).multi_ =
+					InsetMathGrid::CELL_BEGIN_OF_MULTICOLUMN; 
+				// read special alignment 
+				MathData align; 
+				parse(align, FLAG_ITEM, mode); 
+				grid.cellinfo(first).align_ = asString(align); 
+				// parse the remaining contents into the "real" cell
+				parse(*cell, FLAG_ITEM, mode); 
+			} else {
+				MathAtom at = MathAtom(new MathMacro(buf, t.cs()));
+				cell->push_back(at);
+				cell->push_back(MathAtom(new InsetMathBrace(count)));
 			}
-
-			// the first cell is the real thing, not a dummy
-			cell = &grid.cell(first);
-			grid.cellinfo(first).multi_ = InsetMathGrid::CELL_BEGIN_OF_MULTICOLUMN;
-
-			// read special alignment
-			MathData align;
-			parse(align, FLAG_ITEM, mode);
-			grid.cellinfo(first).align_ = asString(align);
-
-			// parse the remaining contents into the "real" cell
-			parse(*cell, FLAG_ITEM, mode);
 		}
 
 		else if (t.cs() == "limits" || t.cs() == "nolimits") {

status.22x

@@ -160,7 +160,7 @@ What's new
 
 - Do not convert "--" to "\twohyphens" in formula macros.
 
-- Fix bug in the reversion of colored boxes with special frame settings.
+- Fix bugs in the reversion of colored boxes with special frame settings.
 
 
 * USER INTERFACE
@@ -219,6 +219,8 @@ What's new
 - Fix display and output of math macros with optional arguments appearing
   in the optional argument of another macro.
 
+- Handle the command \multicolumn correctly in math macros (bug 10466).
+
 - Do not prematurely cut selected text when inserting a Hyperref (bug 10306).
 
 - Consider the argument of the hyperref-insert function even if there is a