Improved fix for #9966

* provide GuiApplication::typewriterSystemFont() to get a fixed font consistently
* enlarge fixed font on Mac because of the too small default Qt system font
* use it in source pane, progress view, log view and document preamble editor

src/frontends/qt4/GuiApplication.cpp

@@ -82,6 +82,7 @@
 
 #include <queue>
 
+#include <QFontDatabase>
 #include <QByteArray>
 #include <QClipboard>
 #include <QDateTime>
@@ -2557,11 +2558,41 @@ QString const GuiApplication::sansFontName()
 
 QString const GuiApplication::typewriterFontName()
 {
-	QFont font;
-	font.setStyleHint(QFont::TypeWriter);
-	font.setFamily("monospace");
+	return QFontInfo(typewriterSystemFont()).family();
+}
 
-	return QFontInfo(font).family();
+
+namespace {
+	// We cannot use QFont::fixedPitch() because it doesn't
+	// return the fact but only if it is requested.
+	static bool isFixedPitch(const QFont & font) {
+		const QFontInfo fi(font);
+		return fi.fixedPitch();
+	}
+}
+
+
+QFont const GuiApplication::typewriterSystemFont()
+{
+#if QT_VERSION >= 0x050200
+	QFont font = QFontDatabase::systemFont(QFontDatabase::FixedFont);
+#else
+	QFont font("monospace");
+#endif
+	if (!isFixedPitch(font)) {
+		// try to enforce a real monospaced font
+		font.setStyleHint(QFont::Monospace);
+		if (!isFixedPitch(font)) {
+			font.setStyleHint(QFont::TypeWriter);
+			if (!isFixedPitch(font)) font.setFamily("courier");
+		}
+	}
+#ifdef Q_OS_MAC
+	// On a Mac the result is too small and it's not practical to
+	// rely on Qtconfig utility to change the system settings of Qt.
+	font.setPointSize(12);
+#endif
+	return font;
 }
 
 

src/frontends/qt4/GuiApplication.h

@@ -25,6 +25,7 @@
 class QAbstractItemModel;
 class QIcon;
 class QSessionManager;
+class QFont;
 
 namespace lyx {
 
@@ -145,6 +146,8 @@ public:
 
 	/// return a suitable monospaced font name.
 	QString const typewriterFontName();
+	QFont const typewriterSystemFont();
+
 	///
 	void unregisterView(GuiView * gv);
 	///

src/frontends/qt4/GuiDocument.cpp

@@ -453,10 +453,7 @@ PreambleModule::PreambleModule() : current_id_(0)
 	// This is not a memory leak. The object will be destroyed
 	// with this.
 	(void) new LaTeXHighlighter(preambleTE->document());
-	QFont font(guiApp->typewriterFontName());
-	font.setFixedPitch(true);
-	font.setStyleHint(QFont::TypeWriter);
-	preambleTE->setFont(font);
+	preambleTE->setFont(guiApp->typewriterSystemFont());
 	preambleTE->setWordWrapMode(QTextOption::NoWrap);
 	setFocusProxy(preambleTE);
 	connect(preambleTE, SIGNAL(textChanged()), this, SIGNAL(changed()));

src/frontends/qt4/GuiLog.cpp

@@ -133,10 +133,7 @@ GuiLog::GuiLog(GuiView & lv)
 	highlighter = new LogHighlighter(logTB->document());
 
 	logTB->setReadOnly(true);
-	QFont font(guiApp->typewriterFontName());
-	font.setFixedPitch(true);
-	font.setStyleHint(QFont::TypeWriter);
-	logTB->setFont(font);
+	logTB->setFont(guiApp->typewriterSystemFont());
 }
 
 

src/frontends/qt4/GuiProgressView.cpp

@@ -71,10 +71,7 @@ GuiProgressView::GuiProgressView(GuiView & parent, Qt::DockWidgetArea area,
 	widget_->adjustSize();
 	setWidget(widget_);
 
-	QFont font(guiApp->typewriterFontName());
-	font.setFixedPitch(true);
-	font.setStyleHint(QFont::TypeWriter);
-	widget_->outTE->setFont(font);
+	widget_->outTE->setFont(guiApp->typewriterSystemFont());
 	widget_->tabWidget->widget(0)->setContentsMargins(-5, -7, 0, -7);
 
 	connect(widget_->debugNoneRB, SIGNAL(clicked()),

src/frontends/qt4/GuiViewSource.cpp

@@ -86,10 +86,7 @@ ViewSourceWidget::ViewSourceWidget()
 	viewSourceTV->setReadOnly(true);
 	///dialog_->viewSourceTV->setAcceptRichText(false);
 	// this is personal. I think source code should be in fixed-size font
-	QFont font(guiApp->typewriterFontName());
-	font.setFixedPitch(true);
-	font.setStyleHint(QFont::TypeWriter);
-	viewSourceTV->setFont(font);
+	viewSourceTV->setFont(guiApp->typewriterSystemFont());
 	// again, personal taste
 	viewSourceTV->setWordWrapMode(QTextOption::NoWrap);
 }