From 80f94a9398ef1843d2592e87bd71d1cd2b40703c Mon Sep 17 00:00:00 2001
From: Enrico Forestieri <forenr@lyx.org>
Date: Sat, 29 Aug 2020 20:10:26 +0200
Subject: [PATCH] Use correct width for \fint

Both QTextLine::naturalTextWidth() and QTextLine::horizontalAdvance()
return the same value for \fint. However, examining esint10.ttf with
fontforge does not reveal any issue with the metrics. The fact that
\fint seems to be the only affected symbol might be due to its code
point, which corresponds to a space, so that maybe Qt makes some
assumptions on the metrics.

As QTextLine::naturalTextWidth() returns the width of the line that is
occupied by text, in the case of a single symbol we can obtain the
same value by using the width of the rectangle bounding the symbol.
---
 src/frontends/qt/GuiFontMetrics.cpp | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/frontends/qt/GuiFontMetrics.cpp b/src/frontends/qt/GuiFontMetrics.cpp
index 9ff027eb08..361125056e 100644
--- a/src/frontends/qt/GuiFontMetrics.cpp
+++ b/src/frontends/qt/GuiFontMetrics.cpp
@@ -245,18 +245,18 @@ int GuiFontMetrics::width(docstring const & s) const
 #else
 	bool const math_char = s.length() == 1;
 #endif
-	// keep value 0 for math chars with width 0
-	if (!math_char || metrics_.width(toqstr(s)) != 0) {
+	if (math_char) {
+		// keep value 0 for math chars with width 0
+		if (metrics_.width(toqstr(s)) != 0)
+			w = metrics_.boundingRect(toqstr(s)).width();
+	} else {
 		QTextLayout tl;
 		tl.setText(toqstr(s));
 		tl.setFont(font_);
 		tl.beginLayout();
 		QTextLine line = tl.createLine();
 		tl.endLayout();
-		if (math_char)
-			w = iround(line.naturalTextWidth());
-		else
-			w = iround(line.horizontalAdvance());
+		w = iround(line.horizontalAdvance());
 	}
 	strwidth_cache_.insert(s, w, s.size() * sizeof(char_type));
 	return w;