diff --git a/src/mathed/InsetMathFrac.cpp b/src/mathed/InsetMathFrac.cpp
index 5662923b7b..42cc3a2f58 100644
--- a/src/mathed/InsetMathFrac.cpp
+++ b/src/mathed/InsetMathFrac.cpp
@@ -152,62 +152,71 @@ void InsetMathFrac::metrics(MetricsInfo & mi, Dimension & dim) const
 {
 	Dimension dim0, dim1, dim2;
 
-	// This could be simplified, including avoiding useless recalculation of
-	// cell metrics
-	if (kind_ == UNIT || (kind_ == UNITFRAC && nargs() == 3)) {
-		if (nargs() == 1) {
-			Changer dummy = mi.base.font.changeShape(UP_SHAPE);
-			cell(0).metrics(mi, dim0);
-			dim.wid = dim0.width()+ 3;
-			dim.asc = dim0.asc;
-			dim.des = dim0.des;
-		} else if (nargs() == 2) {
-			cell(0).metrics(mi, dim0);
-			Changer dummy = mi.base.font.changeShape(UP_SHAPE);
-			cell(1).metrics(mi, dim1);
-			dim.wid = dim0.width() + dim1.wid + 5;
-			dim.asc = max(dim0.asc, dim1.asc);
-			dim.des = max(dim0.des, dim1.des);
-		} else {
-			cell(2).metrics(mi, dim2);
-			Changer dummy = mi.base.font.changeShape(UP_SHAPE);
-			Changer dummy2 = mi.base.changeFrac();
-			cell(0).metrics(mi, dim0);
-			cell(1).metrics(mi, dim1);
-			dim.wid = dim0.width() + dim1.wid + dim2.wid + 10;
-			dim.asc = max(dim2.asc, dim0.height() + 5);
-			dim.des = max(dim2.des, dim1.height() - 5);
+	switch (kind_) {
+	case UNIT: {
+		// \unitone, \unittwo
+		dim.wid = 0;
+		int unit_cell = 0;
+		// is there an extra cell holding the value being given a dimension?
+		// (this is \unittwo)
+		if (nargs() == 2) {
+			cell(0).metrics(mi, dim1);
+			dim.wid += dim1.wid + 4;
+			unit_cell = 1;
 		}
-	} else {
-		// general cell metrics used for \frac
-		Changer dummy = mi.base.changeFrac();
-		// FIXME: Exponential blowup
+		Changer dummy = mi.base.font.changeShape(UP_SHAPE);
+		cell(unit_cell).metrics(mi, dim0);
+		dim.wid += dim0.width() + 1;
+		dim.asc = max(dim0.asc, dim1.asc);
+		dim.des = max(dim0.des, dim1.des);
+	}
+		break;
+
+	case UNITFRAC:
+	case NICEFRAC: {
+		// \unitfrac, \unitfracthree, \nicefrac
+		dim.wid = 0;
+		// is there an extra cell holding the value being given a dimension?
+		// (this is \unitfracthree)
+		if (kind_ == UNITFRAC && nargs() == 3) {
+			cell(2).metrics(mi, dim2);
+			dim.wid += dim2.wid + 4;
+		}
+		Changer dummy = mi.base.font.changeShape(UP_SHAPE, kind_ == UNITFRAC);
+		Changer dummy2 = mi.base.changeScript();
 		cell(0).metrics(mi, dim0);
 		cell(1).metrics(mi, dim1);
-		if (nargs() == 3)
-			cell(2).metrics(mi, dim2);
-		// metrics for special fraction types
-		if (kind_ == NICEFRAC || kind_ == UNITFRAC) {
-			Changer dummy2 = mi.base.font.changeShape(UP_SHAPE, kind_ == UNITFRAC);
-			dim.wid = dim0.width() + dim1.wid + 5;
-			dim.asc = dim0.height() + 5;
-			dim.des = dim1.height() - 5;
-		} else {
-			if (kind_ == CFRAC || kind_ == CFRACLEFT || kind_ == CFRACRIGHT
-			    || kind_ == DFRAC || kind_ == TFRAC) {
-				// \cfrac and \dfrac are always in display size
-				// \tfrac is in always in text size
-				Changer dummy2 = mi.base.font.changeStyle((kind_ == TFRAC)
-				                                          ? LM_ST_SCRIPT
-				                                          : LM_ST_DISPLAY);
-				cell(0).metrics(mi, dim0);
-				cell(1).metrics(mi, dim1);
-			}
-			dim.wid = max(dim0.wid, dim1.wid) + 2;
-			dim.asc = dim0.height() + 2 + 5;
-			dim.des = dim1.height() + 2 - 5;
-		}
+		dim.wid += dim0.wid + dim1.wid + 5;
+		dim.asc = max(dim2.asc, dim0.height() + 5);
+		dim.des = max(dim2.des, dim1.height() - 5);
 	}
+		break;
+
+	case FRAC:
+	case CFRAC:
+	case CFRACLEFT:
+	case CFRACRIGHT:
+	case DFRAC:
+	case TFRAC:
+	case OVER:
+	case ATOP: {
+		Changer dummy =
+			// \tfrac is always in text size
+			(kind_ == TFRAC) ? mi.base.font.changeStyle(LM_ST_SCRIPT) :
+			// \cfrac and \dfrac are always in display size
+			(kind_ == CFRAC
+			 || kind_ == CFRACLEFT
+			 || kind_ == CFRACRIGHT
+			 || kind_ == DFRAC) ? mi.base.font.changeStyle(LM_ST_DISPLAY) :
+			// all others
+			                      mi.base.changeFrac();
+		cell(0).metrics(mi, dim0);
+		cell(1).metrics(mi, dim1);
+		dim.wid = max(dim0.wid, dim1.wid) + 2;
+		dim.asc = dim0.height() + 2 + 5;
+		dim.des = dim1.height() + 2 - 5;
+	}
+	} //switch (kind_)
 	metricsMarkers(mi, dim);
 }
 
@@ -217,74 +226,89 @@ void InsetMathFrac::draw(PainterInfo & pi, int x, int y) const
 	setPosCache(pi, x, y);
 	Dimension const dim = dimension(*pi.base.bv);
 	Dimension const dim0 = cell(0).dimension(*pi.base.bv);
-	if (kind_ == UNIT || (kind_ == UNITFRAC && nargs() == 3)) {
-		if (nargs() == 1) {
-			Changer dummy = pi.base.font.changeShape(UP_SHAPE);
+	switch (kind_) {
+	case UNIT: {
+		// \unitone, \unittwo
+		int xx = x;
+		int unit_cell = 0;
+		// is there an extra cell holding the value being given a dimension?
+		// (this is \unittwo)
+		if (nargs() == 2) {
 			cell(0).draw(pi, x + 1, y);
-		} else if (nargs() == 2) {
-			cell(0).draw(pi, x + 1, y);
-			Changer dummy = pi.base.font.changeShape(UP_SHAPE);
-			cell(1).draw(pi, x + dim0.width() + 5, y);
-		} else {
-			cell(2).draw(pi, x + 1, y);
-			Changer dummy = pi.base.font.changeShape(UP_SHAPE);
-			Changer dummy2 = pi.base.changeFrac();
-			Dimension const dim1 = cell(1).dimension(*pi.base.bv);
-			Dimension const dim2 = cell(2).dimension(*pi.base.bv);
-			int xx = x + dim2.wid + 5;
-			cell(0).draw(pi, xx + 2, 
-					 y - dim0.des - 5);
-			cell(1).draw(pi, xx  + dim0.width() + 5, 
-					 y + dim1.asc / 2);
+			xx += dim0.wid + 4;
+			unit_cell = 1;
 		}
-	} else {
-		Changer dummy = pi.base.changeFrac();
+		Changer dummy = pi.base.font.changeShape(UP_SHAPE);
+		cell(unit_cell).draw(pi, xx + 1, y);
+	}
+		break;
+
+	case UNITFRAC:
+	case NICEFRAC: {
+		// \unitfrac, \unitfracthree, \nicefrac
+		int xx = x;
+		// is there an extra cell holding the value being given a dimension?
+		// (this is \unitfracthree)
+		if (kind_ == UNITFRAC && nargs() == 3) {
+			cell(2).draw(pi, x + 1, y);
+			xx += cell(2).dimension(*pi.base.bv).wid + 4;
+		}
+		Changer dummy = pi.base.font.changeShape(UP_SHAPE, kind_ == UNITFRAC);
+		// nice fraction
+		// FIXME:
+		// * the solidus should be \kern-2mu/\kern-1mu.
+		// * the vertical offset of the first cell should be such that the
+		//   top of M in the first cell matches the one of the
+		//   surrounding text.
+		Changer dummy2 = pi.base.changeScript();
+		cell(0).draw(pi, xx + 2, y - dim0.des - 5);
+		Dimension const dim1 = cell(1).dimension(*pi.base.bv);
+		cell(1).draw(pi, xx + dim0.wid + 5, y + dim1.asc / 2);
+		// Diag line:
+		pi.pain.line(xx + dim0.wid + 1, y + dim.des - 2,
+		             xx + dim0.wid + 6, y - dim.asc + 2,
+		             pi.base.font.color());
+	}
+		break;
+
+	case FRAC:
+	case CFRAC:
+	case CFRACLEFT:
+	case CFRACRIGHT:
+	case DFRAC:
+	case TFRAC:
+	case OVER:
+	case ATOP: {
+		Changer dummy =
+			// \tfrac is always in text size
+			(kind_ == TFRAC) ? pi.base.font.changeStyle(LM_ST_SCRIPT) :
+			// \cfrac and \dfrac are always in display size
+			(kind_ == CFRAC
+			 || kind_ == CFRACLEFT
+			 || kind_ == CFRACRIGHT
+			 || kind_ == DFRAC) ? pi.base.font.changeStyle(LM_ST_DISPLAY) :
+			// all others
+			                      pi.base.changeFrac();
 		Dimension const dim1 = cell(1).dimension(*pi.base.bv);
 		int m = x + dim.wid / 2;
-		if (kind_ == NICEFRAC) {
-			cell(0).draw(pi, x + 2,
-					y - dim0.des - 5);
-			cell(1).draw(pi, x + dim0.width() + 5,
-					y + dim1.asc / 2);
-		} else if (kind_ == UNITFRAC) {
-			Changer dummy2 = pi.base.font.changeShape(UP_SHAPE);
-			cell(0).draw(pi, x + 2,	y - dim0.des - 5);
-			cell(1).draw(pi, x + dim0.width() + 5, y + dim1.asc / 2);
-		} else if (kind_ == FRAC || kind_ == ATOP || kind_ == OVER
-		           || kind_ == TFRAC) {
-			// tfrac is in always in text size
-			Changer dummy2 = pi.base.font.changeStyle(LM_ST_SCRIPT,
-			                                          kind_ == TFRAC);
-			cell(0).draw(pi, m - dim0.wid / 2, y - dim0.des - 2 - 5);
-			cell(1).draw(pi, m - dim1.wid / 2, y + dim1.asc + 2 - 5);
-		} else {
-			// \cfrac and \dfrac are always in display size
-			Changer dummy2 = pi.base.font.changeStyle(LM_ST_DISPLAY);
-			if (kind_ == CFRAC || kind_ == DFRAC)
-				cell(0).draw(pi, m - dim0.wid / 2, y - dim0.des - 2 - 5);
-			else if (kind_ == CFRACLEFT)
-				cell(0).draw(pi, x + 2, y - dim0.des - 2 - 5);
-			else if (kind_ == CFRACRIGHT)
-				cell(0).draw(pi, x + dim.wid - dim0.wid - 2,
-					y - dim0.des - 2 - 5);
-			cell(1).draw(pi, m - dim1.wid / 2, y + dim1.asc + 2 - 5);
-		}
+		int xx =
+			// align left
+			(kind_ == CFRACLEFT) ? x + 2 :
+			// align right
+			(kind_ == CFRACRIGHT) ? x + dim.wid - dim0.wid - 2 :
+			// center
+			                        m - dim0.wid / 2;
+		// FIXME: vertical offset should be based on ex
+		//int dy = theFontMetrics(pi.base.font).ex() / 2;
+		cell(0).draw(pi, xx, y - dim0.des - 2 - 5);
+		// center
+		cell(1).draw(pi, m - dim1.wid / 2, y + dim1.asc + 2 - 5);
+		// horizontal line
+		if (kind_ != ATOP)
+			pi.pain.line(x + 1, y - 5,
+			             x + dim.wid - 2, y - 5, pi.base.font.color());
 	}
-	if (kind_ == NICEFRAC || kind_ == UNITFRAC) {
-		// Diag line:
-		int xx = x;
-		if (nargs() == 3)
-			xx += cell(2).dimension(*pi.base.bv).wid + 5;
-		pi.pain.line(xx + dim0.wid,
-				y + dim.des - 2,
-				xx + dim0.wid + 5,
-				y - dim.asc + 2, pi.base.font.color());
-	}
-	if (kind_ == FRAC || kind_ == CFRAC || kind_ == CFRACLEFT
-		|| kind_ == CFRACRIGHT || kind_ == DFRAC
-		|| kind_ == TFRAC || kind_ == OVER)
-		pi.pain.line(x + 1, y - 5,
-				x + dim.wid - 2, y - 5, pi.base.font.color());
+	} //switch (kind_)
 	drawMarkers(pi, x, y);
 }