Introduce FontMetrics::xHeight

Use it instead of measuring the height of character 'x'.

src/frontends/FontMetrics.h

@@ -65,6 +65,8 @@ public:
 	virtual Dimension const defaultDimension() const = 0;
 	/// return the em size
 	virtual int em() const = 0;
+	/// return the x height
+	virtual int xHeight() const = 0;
 	/// return the width of a line for underlining
 	virtual int lineWidth() const = 0;
 	/// return the distance from the base line to where an underline

src/frontends/qt4/GuiFontMetrics.cpp

@@ -117,6 +117,13 @@ int GuiFontMetrics::em() const
 }
 
 
+int GuiFontMetrics::xHeight() const
+{
+//	LATTEST(metrics_.xHeight() == ascent('x'));
+	return metrics_.xHeight();
+}
+
+
 int GuiFontMetrics::lineWidth() const
 {
 	return metrics_.lineWidth();

src/frontends/qt4/GuiFontMetrics.h

@@ -38,6 +38,7 @@ public:
 	virtual int maxDescent() const;
 	virtual Dimension const defaultDimension() const;
 	virtual int em() const;
+	virtual int xHeight() const;
 	virtual int lineWidth() const;
 	virtual int underlinePos() const;
 	virtual int strikeoutPos() const;

src/insets/InsetSpace.cpp

@@ -352,7 +352,7 @@ void InsetSpace::draw(PainterInfo & pi, int x, int y) const
 	}
 
 	int const w = dim.wid;
-	int const h = theFontMetrics(pi.base.font).ascent('x');
+	int const h = theFontMetrics(pi.base.font).xHeight();
 	int xp[4], yp[4];
 
 	xp[0] = x;

src/insets/InsetSpecialChar.cpp

@@ -202,7 +202,7 @@ void drawLogo(PainterInfo & pi, int & x, int const y, InsetSpecialChar::Kind kin
 		/** Reference macro:
 		 *  \def\TeX{T\kern-.1667em\lower.5ex\hbox{E}\kern-.125emX\@}
 		 */
-		int const ex = theFontMetrics(font).ascent('x');
+		int const ex = theFontMetrics(font).xHeight();
 		drawChar(pi, x, y, 'T');
 		x -= em / 6;
 		drawChar(pi, x, y + ex / 2, 'E');
@@ -265,7 +265,7 @@ void InsetSpecialChar::draw(PainterInfo & pi, int x, int y) const
 	case ALLOWBREAK:
 	{
 		// A small vertical line
-		int const asc = theFontMetrics(pi.base.font).ascent('x');
+		int const asc = theFontMetrics(pi.base.font).xHeight();
 		int const desc = theFontMetrics(pi.base.font).descent('g');
 		int const x0 = x; // x + 1; // FIXME: incline,
 		int const x1 = x; // x - 1; // similar to LibreOffice?

src/mathed/MathData.cpp

@@ -271,7 +271,7 @@ void MathData::metrics(MetricsInfo & mi, Dimension & dim, bool tight) const
 	frontend::FontMetrics const & fm = theFontMetrics(mi.base.font);
 	BufferView * bv = mi.base.bv;
 	int const Iascent = fm.dimension('I').ascent();
-	int xascent = fm.dimension('x').ascent();
+	int xascent = fm.xHeight();
 	if (xascent >= Iascent)
 		xascent = (2 * Iascent) / 3;
 	minasc_ = xascent;
@@ -288,7 +288,7 @@ void MathData::metrics(MetricsInfo & mi, Dimension & dim, bool tight) const
 	if (tight)
 		// FIXME: this is the minimal ascent seen empirically, check
 		// what the TeXbook says.
-		dim.asc = max(dim.asc, fm.ascent('x'));
+		dim.asc = max(dim.asc, fm.xHeight());
 	else {
 		dim.asc = max(dim.asc, fm.maxAscent());
 		dim.des = max(dim.des, fm.maxDescent());

src/mathed/MathData.h

@@ -129,7 +129,8 @@ public:
 
 	/// rebuild cached metrics information
 	/** When \c tight is true, the height of the cell will be at least
-	 *  that of 'x'. Otherwise, it will be the max height of the font.
+	 *  the x height of the font. Otherwise, it will be the max height
+	 *  of the font.
 	 */
 	void metrics(MetricsInfo & mi, Dimension & dim, bool tight = true) const;
 	///

src/mathed/MathSupport.cpp

@@ -520,7 +520,7 @@ int mathed_font_em(FontInfo const & font)
 
 int mathed_font_x_height(FontInfo const & font)
 {
-	return theFontMetrics(font).ascent('x');
+	return theFontMetrics(font).xHeight();
 }
 
 /* The math units. Quoting TeX by Topic, p.205: