From 9b3fede789d234244b0005184aaddae2129ecf70 Mon Sep 17 00:00:00 2001
From: Jean-Marc Lasgouttes <lasgouttes@lyx.org>
Date: Thu, 19 Jul 2018 22:16:40 +0200
Subject: [PATCH] Introduce FontMetrics::xHeight

Use it instead of measuring the height of character 'x'.
---
 src/frontends/FontMetrics.h          | 2 ++
 src/frontends/qt4/GuiFontMetrics.cpp | 7 +++++++
 src/frontends/qt4/GuiFontMetrics.h   | 1 +
 src/insets/InsetSpace.cpp            | 2 +-
 src/insets/InsetSpecialChar.cpp      | 4 ++--
 src/mathed/MathData.cpp              | 4 ++--
 src/mathed/MathData.h                | 3 ++-
 src/mathed/MathSupport.cpp           | 2 +-
 8 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/src/frontends/FontMetrics.h b/src/frontends/FontMetrics.h
index c02606c438..4472aa7008 100644
--- a/src/frontends/FontMetrics.h
+++ b/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
diff --git a/src/frontends/qt4/GuiFontMetrics.cpp b/src/frontends/qt4/GuiFontMetrics.cpp
index c2d4b884e4..1c2421d11b 100644
--- a/src/frontends/qt4/GuiFontMetrics.cpp
+++ b/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();
diff --git a/src/frontends/qt4/GuiFontMetrics.h b/src/frontends/qt4/GuiFontMetrics.h
index 3f50dfe5d2..8a2ebe2525 100644
--- a/src/frontends/qt4/GuiFontMetrics.h
+++ b/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;
diff --git a/src/insets/InsetSpace.cpp b/src/insets/InsetSpace.cpp
index 5e9789c68c..fd8c261d2e 100644
--- a/src/insets/InsetSpace.cpp
+++ b/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;
diff --git a/src/insets/InsetSpecialChar.cpp b/src/insets/InsetSpecialChar.cpp
index e9153cd900..4a46f398eb 100644
--- a/src/insets/InsetSpecialChar.cpp
+++ b/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?
diff --git a/src/mathed/MathData.cpp b/src/mathed/MathData.cpp
index 07decba9e5..87b1820cba 100644
--- a/src/mathed/MathData.cpp
+++ b/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());
diff --git a/src/mathed/MathData.h b/src/mathed/MathData.h
index 7099e64643..cd4d44b4a8 100644
--- a/src/mathed/MathData.h
+++ b/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;
 	///
diff --git a/src/mathed/MathSupport.cpp b/src/mathed/MathSupport.cpp
index ea8309545f..2cf4bd5f26 100644
--- a/src/mathed/MathSupport.cpp
+++ b/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: