INSTALL

@@ -59,10 +59,10 @@ LyX makes great use of the C++ Standard Library. This means that gcc
 users will have to install the relevant libstdc++ library to be able
 to compile this version of LyX.
 
-LyX requires Qt 5.12 and higher. It is also possible to compile
-against Qt 6. The only special point to make is that you must ensure
-that both LyX and the Qt libraries are compiled with the same C++
-compiler.
+For full LyX usability we suggest to use Qt 5.6 and higher, or at the
+very least Qt 5.4. It is also possible to compile against Qt 6. The
+only special point to make is that you must ensure that both LyX and
+the Qt libraries are compiled with the same C++ compiler.
 
 To build LyX with spell checking capabilities included you have to
 install at least one of the development packages of the spell checker

README

@@ -90,8 +90,8 @@ What do I need to compile LyX from the source distribution?
       but clang and MSVC are known to work too. As of LyX 2.5.0, you
       need at least gcc 8.0.
 
-    * The Qt library, at least version 5.12. It is also possible to
-      compile with Qt 6.x.
+    * The Qt library, at least version 5.2 (5.6 recommended). It is
+      also possible to compile with Qt 6.x.
 
     Read the file "INSTALL" for more information on compiling.
 

configure.ac

@@ -147,7 +147,7 @@ AC_CHECK_HEADERS(magic.h,
 ### setup the qt frontend.
 dnl The code below is not in a macro, because this would cause big
 dnl problems with the AC_REQUIRE contained in QT_DO_IT_ALL.
-QT_DO_IT_ALL([5.12.0])
+QT_DO_IT_ALL([5.0.0])
 AC_SUBST([FRONTENDS_SUBDIRS], [qt])
 FRONTEND_INFO="${FRONTEND_INFO}\
   Qt Frontend:\n\

src/convert/lyxconvert.cpp

@@ -28,7 +28,9 @@
 #include <QImage>
 #include <QFile>
 #include <QPainter>
+#if (QT_VERSION >= 0x050300)
 #include <QPdfWriter>
+#endif
 
 
 const char * basename(const char * name)
@@ -141,6 +143,7 @@ int main(int argc, char **argv)
 		std::cerr << myname << ": Conversion of images to format '" << oformat << "' is not supported" << std::endl;
 		return 4;
 	} else if (NULL != oformat && !strcmp(oformat, "pdf")) {
+#if (QT_VERSION >= 0x050300)
 		QSize size = img.size();
 		QPdfWriter pdfwriter(QString::fromLocal8Bit(outfile));
 		int dpi = pdfwriter.logicalDpiX();
@@ -151,6 +154,10 @@ int main(int argc, char **argv)
 		QPainter painter(&pdfwriter);
 		painter.drawImage(0, 0, img);
 		painter.end();
+#else
+		std::cerr << myname << ": Conversion of images to format '" << oformat << "' is not supported" << std::endl;
+		return 4;
+#endif
 	} else if (!img.save(QString::fromLocal8Bit(outfile), oformat)) {
 		std::cerr << myname << ": Cannot save converted image to '" << outfile << "'" << std::endl;
 		return 5;

src/frontends/qt/CategorizedCombo.cpp

@@ -287,7 +287,11 @@ void CategorizedCombo::Private::setFilter(QString const & s)
 		lastSel_ = filterModel_->mapToSource(filterModel_->index(sel, 0)).row();
 
 	filter_ = s;
+#if QT_VERSION < QT_VERSION_CHECK(5, 12, 0)
+	filterModel_->setFilterRegExp(charFilterRegExp(filter_));
+#else
 	filterModel_->setFilterRegularExpression(charFilterRegExp(filter_));
+#endif
 	countCategories();
 
 	// restore old selection

src/frontends/qt/GuiAbout.cpp

@@ -59,7 +59,7 @@ static QString credits()
 			out << qt_("Please install correctly to estimate the great\namount of work other people have done for the LyX project.");
 		} else {
 			QTextStream ts(&file);
-#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+#if QT_VERSION < 0x060000
 			ts.setCodec("UTF-8");
 #endif
 			QString line;
@@ -103,7 +103,7 @@ static QString release_notes()
 			out << qt_("Please install correctly to see what has changed\nfor this version of LyX.");
 		} else {
 			QTextStream ts(&file);
-#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+#if QT_VERSION < 0x060000
 			ts.setCodec("UTF-8");
 #endif
 			QString line;
@@ -295,12 +295,14 @@ static QString version(bool const plain = false)
 		out << '\n';
 	else
 		out << "</p><p>";
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 4, 0))
 	out << toqstr(bformat(_("OS Version (run-time): %1$s"),
 		qstring_to_ucs4(QSysInfo::prettyProductName())));
 	if (plain)
 		out << '\n';
 	else
 		out << "</p><p>";
+#endif
 	out << toqstr(bformat(_("Python detected: %1$s"), from_utf8(os::python_info())));
 	if (plain)
 		out << '\n';

src/frontends/qt/GuiApplication.cpp

@@ -106,7 +106,9 @@
 #include <QObject>
 #include <QPainter>
 #include <QPixmap>
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 10, 0))
 #include <QRandomGenerator>
+#endif
 #include <QScreen>
 #include <QSessionManager>
 #include <QSettings>
@@ -126,33 +128,35 @@
 #endif
 #endif
 
+#if (QT_VERSION >= 0x050400)
 #if defined(Q_OS_WIN) || defined(Q_CYGWIN_WIN)
-#  if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0))
-#    if (QT_VERSION >= QT_VERSION_CHECK(6, 5, 0))
-#      include <QtGui/QWindowsMimeConverter>
-#      define QWINDOWSMIME QWindowsMimeConverter
-#      define QVARIANTTYPE QMetaType
-#    else
-#      include <QtGui/private/qguiapplication_p.h>
-#      include <QtGui/private/qwindowsmime_p.h>
-#      include <QtGui/qpa/qplatformintegration.h>
-#      define QWINDOWSMIME QWindowsMime
-#      define QVARIANTTYPE QMetaType
+#if (QT_VERSION >= 0x060000)
+#if (QT_VERSION >= 0x060500)
+#include <QtGui/QWindowsMimeConverter>
+#define QWINDOWSMIME QWindowsMimeConverter
+#define QVARIANTTYPE QMetaType
+#else
+#include <QtGui/private/qguiapplication_p.h>
+#include <QtGui/private/qwindowsmime_p.h>
+#include <QtGui/qpa/qplatformintegration.h>
+#define QWINDOWSMIME QWindowsMime
+#define QVARIANTTYPE QMetaType
 using QWindowsMime = QNativeInterface::Private::QWindowsMime;
 using QWindowsApplication = QNativeInterface::Private::QWindowsApplication;
-#    endif
-#  else
-#    include <QWinMime>
-#    define QWINDOWSMIME QWinMime
-#    define QVARIANTTYPE QVariant::Type
-#  endif
-#  ifdef Q_CC_GNU
-#    include <wtypes.h>
-#  endif
-#  include <objidl.h>
+#endif
+#else
+#include <QWinMime>
+#define QWINDOWSMIME QWinMime
+#define QVARIANTTYPE QVariant::Type
+#endif
+#ifdef Q_CC_GNU
+#include <wtypes.h>
+#endif
+#include <objidl.h>
+#endif
 #endif
 
-#if defined(Q_OS_MAC) && (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
+#if defined(Q_OS_MAC) && (QT_VERSION < 0x060000)
 #include <QMacPasteboardMime>
 #endif // Q_OS_MAC
 
@@ -191,10 +195,12 @@ frontend::Application * createApplication(int & argc, char * argv[])
 // Setup high DPI handling. This is a bit complicated, but will be default in Qt6.
 // macOS does it by itself.
 #if QT_VERSION < QT_VERSION_CHECK(6, 0, 0) && !defined(Q_OS_MAC)
+#if QT_VERSION >= QT_VERSION_CHECK(5, 6, 0)
     // Attribute Qt::AA_EnableHighDpiScaling must be set before QCoreApplication is created
     if (getEnv("QT_ENABLE_HIGHDPI_SCALING").empty()
 		&& getEnv("QT_AUTO_SCREEN_SCALE_FACTOR").empty())
         QApplication::setAttribute(Qt::AA_EnableHighDpiScaling, true);
+#endif
 
 #if QT_VERSION >= QT_VERSION_CHECK(5, 14, 0)
     // HighDPI scale factor policy must be set before QGuiApplication is created
@@ -785,7 +791,7 @@ public:
 //
 ////////////////////////////////////////////////////////////////////////
 
-#if defined(Q_OS_MAC) && (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
+#if defined(Q_OS_MAC) && (QT_VERSION < 0x060000)
 // QMacPasteboardMimeGraphics can only be compiled on Mac.
 
 class QMacPasteboardMimeGraphics : public QMacPasteboardMime
@@ -845,6 +851,7 @@ public:
 ////////////////////////////////////////////////////////////////////////
 // Windows specific stuff goes here...
 
+#if (QT_VERSION >= 0x050400)
 #if defined(Q_OS_WIN) || defined(Q_CYGWIN_WIN)
 // QWindowsMimeMetafile can only be compiled on Windows.
 
@@ -943,6 +950,7 @@ public:
 };
 
 #endif
+#endif
 
 
 /// Allows to check whether ESC was pressed during a long operation
@@ -1006,19 +1014,21 @@ struct GuiApplication::Private
 	Private(): language_model_(nullptr), meta_fake_bit(NoModifier),
 		global_menubar_(nullptr), last_state_(Qt::ApplicationInactive)
 	{
+	#if (QT_VERSION >= 0x050400)
 	#if defined(Q_OS_WIN) || defined(Q_CYGWIN_WIN)
 		/// WMF Mime handler for Windows clipboard.
 		wmf_mime_ = new QWindowsMimeMetafile;
-	#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0) && QT_VERSION < QT_VERSION_CHECK(6, 5, 0))
+	#if (QT_VERSION >= 0x060000 && QT_VERSION < 0x060500)
 		win_app_ = dynamic_cast<QWindowsApplication *>
 			(QGuiApplicationPrivate::platformIntegration());
 		win_app_->registerMime(wmf_mime_);
 	#endif
+	#endif
 	#endif
 		initKeySequences(&theTopLevelKeymap());
 	}
 
-	#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0) && QT_VERSION < QT_VERSION_CHECK(6, 5, 0))
+	#if (QT_VERSION >= 0x060000 && QT_VERSION < 0x060500)
 	#if defined(Q_OS_WIN) || defined(Q_CYGWIN_WIN)
 	~Private()
 	{
@@ -1093,17 +1103,19 @@ struct GuiApplication::Private
 	/// Holds previous application state on Mac
 	Qt::ApplicationState last_state_;
 
-#if defined(Q_OS_MAC) && (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
+#if defined(Q_OS_MAC) && (QT_VERSION < 0x060000)
 	/// Linkback mime handler for MacOSX.
 	QMacPasteboardMimeGraphics mac_pasteboard_mime_;
 #endif
 
+#if (QT_VERSION >= 0x050400)
 #if defined(Q_OS_WIN) || defined(Q_CYGWIN_WIN)
 	/// WMF Mime handler for Windows clipboard.
 	QWindowsMimeMetafile * wmf_mime_;
-#if (QT_VERSION >= QT_VERSION_CHECK(6, 0, 0) && QT_VERSION < QT_VERSION_CHECK(6, 5, 0))
+#if (QT_VERSION >= 0x060000 && QT_VERSION < 0x060500)
 	QWindowsApplication * win_app_;
 #endif
+#endif
 #endif
 
 	/// Allows to check whether ESC was pressed during a long operation
@@ -1130,12 +1142,19 @@ GuiApplication::GuiApplication(int & argc, char ** argv)
 	QCoreApplication::setOrganizationName(app_name);
 	QCoreApplication::setOrganizationDomain("lyx.org");
 	QCoreApplication::setApplicationName(lyx_package);
-#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+#if QT_VERSION < 0x060000
 	QCoreApplication::setAttribute(Qt::AA_UseHighDpiPixmaps);
 #endif
 
+#if QT_VERSION >= 0x050700
 	setDesktopFileName(lyx_package);
+#endif
+
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 10, 0))
 	QRandomGenerator(QDateTime::currentDateTime().toSecsSinceEpoch());
+#else
+	qsrand(QDateTime::currentDateTime().toTime_t());
+#endif
 
 	// Install LyX translator for missing Qt translations
 	installTranslator(&d->gui_trans_);
@@ -2817,7 +2836,7 @@ void GuiApplication::execBatchCommands()
 
 #ifdef Q_OS_MAC
 	setAttribute(Qt::AA_MacDontSwapCtrlAndMeta,lyxrc.mac_dontswap_ctrl_meta);
-#  if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+#  if QT_VERSION < 0x060000
 	setAttribute(Qt::AA_UseHighDpiPixmaps,true);
 #  endif
 	// Create the global default menubar which is shown for the dialogs

src/frontends/qt/GuiApplication.h

@@ -122,7 +122,7 @@ public:
 	bool notify(QObject * receiver, QEvent * event) override;
 	void commitData(QSessionManager & sm);
 #if defined(HAVE_XCB_XCB_H) && defined(HAVE_LIBXCB)
-#if (QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
+#if (QT_VERSION < 0x060000)
 #define QINTPTR long
 #else
 #define QINTPTR qintptr

src/frontends/qt/GuiChanges.cpp

@@ -70,9 +70,15 @@ void GuiChanges::updateContents()
 			text += inserted ? qt_("Inserted by %1").arg(author)
 					 : qt_("Deleted by %1").arg(author);
 
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 8, 0))
 		QString const date =
 			QLocale().toString(QDateTime::fromSecsSinceEpoch(c.changetime),
 					QLocale::LongFormat);
+#else
+		QString const date =
+			QLocale().toString(QDateTime::fromTime_t(c.changetime),
+					QLocale::LongFormat);
+#endif
 		if (!date.isEmpty()) {
 			if (!author.isEmpty())
 				text += qt_(" on[[date]] %1").arg(date);

src/frontends/qt/GuiClipboard.cpp

@@ -361,7 +361,7 @@ QString tidyHtml(QString const & input)
 	// clutter.
 	QTextDocument converter;
 	converter.setHtml(input);
-#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+#if QT_VERSION < 0x060000
 	return converter.toHtml("utf-8");
 #else
 	return converter.toHtml();

src/frontends/qt/GuiDocument.cpp

@@ -494,7 +494,13 @@ PreambleModule::PreambleModule(QWidget * parent)
 	checkFindButton();
 	int const tabStop = 4;
 	QFontMetrics metrics(preambleTE->currentFont());
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 11, 0))
+	// horizontalAdvance() is available starting in 5.11.0
+	// setTabStopDistance() is available starting in 5.10.0
 	preambleTE->setTabStopDistance(tabStop * metrics.horizontalAdvance(' '));
+#else
+	preambleTE->setTabStopWidth(tabStop * metrics.width(' '));
+#endif
 }
 
 
@@ -640,7 +646,13 @@ LocalLayout::LocalLayout(QWidget * parent)
 	connect(editPB, SIGNAL(clicked()), this, SLOT(editExternal()));
 	int const tabStop = 4;
 	QFontMetrics metrics(locallayoutTE->currentFont());
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 11, 0))
+	// horizontalAdvance() is available starting in 5.11.0
+	// setTabStopDistance() is available starting in 5.10.0
 	locallayoutTE->setTabStopDistance(tabStop * metrics.horizontalAdvance(' '));
+#else
+	locallayoutTE->setTabStopWidth(tabStop * metrics.width(' '));
+#endif
 }
 
 
@@ -2510,7 +2522,11 @@ void GuiDocument::updateQuoteStyles(bool const set)
 	for (int i = 0; i < langModule->quoteStyleCO->count(); ++i) {
 		langModule->quoteStyleCO->setItemData(i, QVariant(comboFont), Qt::FontRole);
 		QString str = langModule->quoteStyleCO->itemText(i);
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 11, 0))
 		qswidth = max(qswidth, fm.horizontalAdvance(str));
+#else
+		qswidth = max(qswidth, fm.width(str));
+#endif
 	}
 	// add scrollbar width and margin to width
 	qswidth += langModule->quoteStyleCO->style()->pixelMetric(QStyle::PM_ScrollBarExtent);
@@ -2896,7 +2912,7 @@ void GuiDocument::updateFontlist()
 		fontModule->fontsMathCO->addItem(qt_("Class Default (TeX Fonts)"), QString("auto"));
 		fontModule->fontsMathCO->addItem(unimath, QString("default"));
 
-#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+#if QT_VERSION >= 0x060000
 		const QStringList families(QFontDatabase::families());
 #else
 		QFontDatabase fontdb;

src/frontends/qt/GuiFontMetrics.cpp

@@ -284,7 +284,11 @@ int GuiFontMetrics::width(docstring const & s) const
 	if (math_char) {
 		QString const qs = toqstr(s);
 		int br_width = rbearing(s[0]);
+#if QT_VERSION >= 0x050b00
 		int s_width = metrics_.horizontalAdvance(qs);
+#else
+		int s_width = metrics_.width(qs);
+#endif
 		// keep value 0 for math chars with width 0
 		if (s_width != 0)
 			w = max(br_width, s_width);
@@ -664,10 +668,17 @@ int GuiFontMetrics::width(char_type c) const
 	if (value != outOfLimitMetric)
 		return value;
 
+#if QT_VERSION >= 0x050b00
 	if (is_utf16(c))
 		value = metrics_.horizontalAdvance(ucs4_to_qchar(c));
 	else
 		value = metrics_.horizontalAdvance(toqstr(docstring(1, c)));
+#else
+	if (is_utf16(c))
+		value = metrics_.width(ucs4_to_qchar(c));
+	else
+		value = metrics_.width(toqstr(docstring(1, c)));
+#endif
 
 	width_cache_.insert(c, value);
 

src/frontends/qt/GuiHSpace.cpp

@@ -56,7 +56,7 @@ GuiHSpace::GuiHSpace(bool math_mode, QWidget * parent)
 		spacingCO->addItem(qt_("Visible Space"), "visible");
 	spacingCO->addItem(qt_("Custom"), "custom");
 
-#if QT_VERSION < QT_VERSION_CHECK(5, 15, 0)
+#if QT_VERSION < 0x050e00
 	connect(spacingCO, SIGNAL(highlighted(QString)),
 		this, SLOT(changedSlot()));
 #else

src/frontends/qt/GuiKeySymbol.cpp

@@ -845,15 +845,25 @@ bool KeySymbol::operator==(KeySymbol const & ks) const
 KeyModifier q_key_state(Qt::KeyboardModifiers state)
 {
 	KeyModifier k = NoModifier;
+#if defined(Q_OS_MAC) && (QT_VERSION < QT_VERSION_CHECK(5, 12, 0))
+	/// Additional check for Control and Meta modifier swap state.
+	/// Starting with Qt 5 the modifiers aren't reported correctly.
+	/// Until this is fixed a correction is required.
+	/// AFAIK it is fixed at least with Qt 5.12.0
+	const bool dontSwapCtrlAndMeta =
+		frontend::theGuiApp()->testAttribute(Qt::AA_MacDontSwapCtrlAndMeta);
+#else
+	const bool dontSwapCtrlAndMeta = false;
+#endif
 
-	if (state & Qt::ControlModifier)
+	if (state & (dontSwapCtrlAndMeta ? Qt::MetaModifier : Qt::ControlModifier))
 		k |= ControlModifier;
 	if (state & Qt::ShiftModifier)
 		k |= ShiftModifier;
 	if (state & Qt::AltModifier)
 		k |= AltModifier;
 #if defined(USE_MACOSX_PACKAGING) || defined(USE_META_KEYBINDING)
-	if (state & Qt::MetaModifier)
+	if (state & (dontSwapCtrlAndMeta ? Qt::ControlModifier : Qt::MetaModifier))
 		k |= MetaModifier;
 #else
 	if (state & Qt::MetaModifier)

src/frontends/qt/GuiPrefs.cpp

@@ -802,7 +802,7 @@ PrefScreenFonts::PrefScreenFonts(GuiPreferences * form)
 {
 	setupUi(this);
 
-#if QT_VERSION < QT_VERSION_CHECK(5, 15, 0)
+#if QT_VERSION < 0x050e00
 	connect(screenRomanCO, SIGNAL(activated(QString)),
 		this, SLOT(selectRoman(QString)));
 	connect(screenSansCO, SIGNAL(activated(QString)),
@@ -818,7 +818,7 @@ PrefScreenFonts::PrefScreenFonts(GuiPreferences * form)
 		this, SLOT(selectTypewriter(QString)));
 #endif
 
-#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+#if QT_VERSION >= 0x060000
 	const QStringList families(QFontDatabase::families());
 #else
 	QFontDatabase fontdb;
@@ -829,7 +829,7 @@ PrefScreenFonts::PrefScreenFonts(GuiPreferences * form)
 		screenSansCO->addItem(family);
 		screenTypewriterCO->addItem(family);
 	}
-#if QT_VERSION < QT_VERSION_CHECK(5, 15, 0)
+#if QT_VERSION < 0x050e00
 	connect(screenRomanCO, SIGNAL(activated(QString)),
 		this, SIGNAL(changed()));
 	connect(screenSansCO, SIGNAL(activated(QString)),
@@ -1563,7 +1563,7 @@ PrefConverters::PrefConverters(GuiPreferences * form)
 		this, SLOT(updateConverter()));
 	connect(convertersLW, SIGNAL(currentRowChanged(int)),
 		this, SLOT(switchConverter()));
-#if QT_VERSION < QT_VERSION_CHECK(5, 15, 0)
+#if QT_VERSION < 0x050e00
 	connect(converterFromCO, SIGNAL(activated(QString)),
 		this, SLOT(changeConverter()));
 	connect(converterToCO, SIGNAL(activated(QString)),
@@ -1934,7 +1934,7 @@ PrefFileformats::PrefFileformats(GuiPreferences * form)
 		this, SLOT(updatePrettyname()));
 	connect(formatsCB->lineEdit(), SIGNAL(textEdited(QString)),
 		this, SIGNAL(changed()));
-#if QT_VERSION < QT_VERSION_CHECK(5, 15, 0)
+#if QT_VERSION < 0x050e00
 	connect(defaultFormatCB, SIGNAL(activated(QString)),
 		this, SIGNAL(changed()));
 	connect(defaultOTFFormatCB, SIGNAL(activated(QString)),

src/frontends/qt/GuiSearch.cpp

@@ -603,7 +603,7 @@ GuiSearch::GuiSearch(GuiView & parent, Qt::DockWidgetArea area, Qt::WindowFlags
 void GuiSearch::mousePressEvent(QMouseEvent * event)
 {
 	if (isFloating() && event->button() == Qt::LeftButton) {
-#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+#if QT_VERSION >= 0x060000
 		dragPosition = event->globalPosition().toPoint() - frameGeometry().topLeft();
 #else
 		dragPosition = event->globalPos() - frameGeometry().topLeft();
@@ -617,7 +617,7 @@ void GuiSearch::mousePressEvent(QMouseEvent * event)
 void GuiSearch::mouseMoveEvent(QMouseEvent * event)
 {
 	if (isFloating() && event->buttons() & Qt::LeftButton) {
-#if QT_VERSION >= QT_VERSION_CHECK(6, 0, 0)
+#if QT_VERSION >= 0x060000
 		move(event->globalPosition().toPoint() - dragPosition);
 #else
 		move(event->globalPos() - dragPosition);

src/frontends/qt/GuiView.cpp

@@ -261,7 +261,7 @@ private:
 
 	/// Current ratio between physical pixels and device-independent pixels
 	double pixelRatio() const {
-#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 6, 0) && QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
 		return devicePixelRatioF();
 #else
 		return devicePixelRatio();
@@ -665,7 +665,11 @@ GuiView::GuiView(int id)
 	connect(stat_counts_, SIGNAL(clicked()), this, SLOT(statsPressed()));
 
 	zoom_slider_ = new QSlider(Qt::Horizontal, statusBar());
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 11, 0))
 	zoom_slider_->setFixedWidth(fm.horizontalAdvance('x') * 15);
+#else
+	zoom_slider_->setFixedWidth(fm.width('x') * 15);
+#endif
 	// Make the defaultZoom center
 	zoom_slider_->setRange(10, (lyxrc.defaultZoom * 2) - 10);
 	// Initialize proper zoom value
@@ -678,7 +682,11 @@ GuiView::GuiView(int id)
 	zoom_slider_->setToolTip(qt_("Workarea zoom level. Drag, use Ctrl-+/- or Shift-Mousewheel to adjust."));
 
 	// Buttons to change zoom stepwise
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 11, 0))
 	QSize s(fm.horizontalAdvance('+'), fm.height());
+#else
+	QSize s(fm.width('+'), fm.height());
+#endif
 	zoom_in_ = new GuiClickableLabel(statusBar());
 	zoom_in_->setText("+");
 	zoom_in_->setFixedSize(s);
@@ -718,7 +726,11 @@ GuiView::GuiView(int id)
 	// zoom_value_->setPalette(palette);
 	zoom_value_->setForegroundRole(statusBar()->foregroundRole());
 	zoom_value_->setFixedHeight(fm.height());
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 11, 0))
 	zoom_value_->setMinimumWidth(fm.horizontalAdvance("444\%"));
+#else
+	zoom_value_->setMinimumWidth(fm.width("444\%"));
+#endif
 	zoom_value_->setAlignment(Qt::AlignCenter);
 	zoom_value_->setText(toqstr(bformat(_("[[ZOOM]]%1$d%"), zoom)));
 	statusBar()->addPermanentWidget(zoom_value_);
@@ -1694,8 +1706,10 @@ bool GuiView::event(QEvent * e)
 			}
 			for (int i = 0; i != d.splitter_->count(); ++i)
 				d.tabWorkArea(i)->setFullScreen(true);
-			// Safe area measures won't allow us to go negative in margins
+#if QT_VERSION > 0x050903
+			//Qt's 5.9.4 ba44cdae38406c safe area measures won't allow us to go negative in margins
 			setAttribute(Qt::WA_ContentsMarginsRespectsSafeArea, false);
+#endif
 			setContentsMargins(-2, -2, -2, -2);
 			// bug 5274
 			hideDialogs("prefs", nullptr);
@@ -1714,7 +1728,9 @@ bool GuiView::event(QEvent * e)
 			}
 			for (int i = 0; i != d.splitter_->count(); ++i)
 				d.tabWorkArea(i)->setFullScreen(false);
+#if QT_VERSION > 0x050903
 			setAttribute(Qt::WA_ContentsMarginsRespectsSafeArea, true);
+#endif
 			setContentsMargins(0, 0, 0, 0);
 		}
 		return result;
@@ -1856,7 +1872,7 @@ void GuiView::resetCommandExecute()
 
 double GuiView::pixelRatio() const
 {
-#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 6, 0) && QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
 	return devicePixelRatioF();
 #else
 	return devicePixelRatio();
@@ -5173,10 +5189,14 @@ bool GuiView::lfunUiToggle(string const & ui_component)
 		//are the frames in default state?
 		d.current_work_area_->setFrameStyle(QFrame::NoFrame);
 		if (l == 0) {
+#if QT_VERSION >  0x050903
 			setAttribute(Qt::WA_ContentsMarginsRespectsSafeArea, false);
+#endif
 			setContentsMargins(-2, -2, -2, -2);
 		} else {
+#if QT_VERSION >  0x050903
 			setAttribute(Qt::WA_ContentsMarginsRespectsSafeArea, true);
+#endif
 			setContentsMargins(0, 0, 0, 0);
 		}
 	} else

src/frontends/qt/GuiWorkArea.cpp

@@ -178,7 +178,7 @@ GuiWorkArea::GuiWorkArea(Buffer & buffer, GuiView & gv)
 
 double GuiWorkArea::pixelRatio() const
 {
-#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 6, 0) && QT_VERSION < QT_VERSION_CHECK(6, 0, 0))
 	return devicePixelRatioF();
 #else
 	return devicePixelRatio();
@@ -774,7 +774,8 @@ void GuiWorkArea::mouseReleaseEvent(QMouseEvent * e)
 	FuncRequest const cmd(LFUN_MOUSE_RELEASE, e->x(), e->y(),
 #endif
 			q_button_state(e->button()), q_key_state(e->modifiers()));
-#if QT_VERSION < QT_VERSION_CHECK(5,15,1)
+#if (QT_VERSION > QT_VERSION_CHECK(5,10,1) && \
+	QT_VERSION < QT_VERSION_CHECK(5,15,1))
 	d->synthetic_mouse_event_.cmd = cmd; // QtBug QAbstractScrollArea::mouseMoveEvent
 #endif
 	d->dispatch(cmd);
@@ -784,7 +785,8 @@ void GuiWorkArea::mouseReleaseEvent(QMouseEvent * e)
 
 void GuiWorkArea::mouseMoveEvent(QMouseEvent * e)
 {
-#if QT_VERSION < QT_VERSION_CHECK(5,15,1)
+#if (QT_VERSION > QT_VERSION_CHECK(5,10,1) && \
+	QT_VERSION < QT_VERSION_CHECK(5,15,1))
 	// cancel the event if the coordinates didn't change, this is due to QtBug
 	// QAbstractScrollArea::mouseMoveEvent, the event is triggered falsely when quickly
 	// double tapping a touchpad. To test: try to select a word by quickly double tapping
@@ -1595,10 +1597,12 @@ QVariant GuiWorkArea::inputMethodQuery(Qt::InputMethodQuery query) const
 		return QVariant(d->im_cursor_rect_);
 		break;
 	}
+#if QT_VERSION >= QT_VERSION_CHECK(5, 7, 0)
 	case Qt::ImAnchorRectangle: {
 		return QVariant(d->im_anchor_rect_);
 		break;
 	}
+#endif
 	default:
 		return QWidget::inputMethodQuery(query);
 	}

src/frontends/qt/IconPalette.cpp

@@ -50,7 +50,7 @@ void TearOff::mouseReleaseEvent(QMouseEvent * /*event*/)
 }
 
 
-#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+#if QT_VERSION < 0x060000
 void TearOff::enterEvent(QEvent * event)
 #else
 void TearOff::enterEvent(QEnterEvent * event)
@@ -81,7 +81,7 @@ void TearOff::paintEvent(QPaintEvent * /*event*/)
 	menuOpt.checkType = QStyleOptionMenuItem::NotCheckable;
 	menuOpt.menuRect = rect();
 	menuOpt.maxIconWidth = 0;
-#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+#if QT_VERSION < 0x060000
 	menuOpt.tabWidth = 0;
 #endif
 	menuOpt.menuItemType = QStyleOptionMenuItem::TearOff;
@@ -103,7 +103,7 @@ IconPalette::IconPalette(QWidget * parent)
 	v->setSpacing(0);
 	layout_ = new QGridLayout;
 	layout_->setSpacing(0);
-#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+#if QT_VERSION < 0x060000
 	const int fw = style()->pixelMetric(QStyle::PM_MenuPanelWidth, 0, this);
 	layout_->setMargin(fw);
 #else

src/frontends/qt/IconPalette.h

@@ -27,7 +27,7 @@ class TearOff : public QWidget {
 	Q_OBJECT
 public:
 	TearOff(QWidget * parent);
-#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
+#if QT_VERSION < 0x060000
 	void enterEvent(QEvent *) override;
 #else
 	void enterEvent(QEnterEvent *) override;

src/frontends/qt/LayoutBox.cpp

@@ -320,7 +320,11 @@ void LayoutBox::Private::setFilter(QString const & s)
 		lastSel_ = filterModel_->mapToSource(filterModel_->index(sel, 0)).row();
 
 	filter_ = s;
+#if QT_VERSION < QT_VERSION_CHECK(5, 12, 0)
 	filterModel_->setFilterRegExp(charFilterRegExp(filter_));
+#else
+	filterModel_->setFilterRegularExpression(charFilterRegExp(filter_));
+#endif
 	countCategories();
 
 	// restore old selection

src/frontends/qt/qt_helpers.cpp

@@ -766,7 +766,11 @@ QString formatToolTip(QString text, int width)
 		text = Qt::convertFromPlainText(text, Qt::WhiteSpaceNormal);
 	// Compute desired width in pixels
 	QFont const font = QToolTip::font();
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 11, 0))
 	int const px_width = width * QFontMetrics(font).horizontalAdvance("M");
+#else
+	int const px_width = width * QFontMetrics(font).width("M");
+#endif
 	// Determine the ideal width of the tooltip
 	QTextDocument td("");
 	td.setHtml(text);

src/frontends/qt/qt_helpers.h

@@ -179,6 +179,24 @@ QString changeExtension(QString const & oldname, QString const & ext);
 QString formatToolTip(QString text, int width = 30);
 
 
+#if QT_VERSION < 0x050300
+// Very partial implementation of QSignalBlocker for archaic qt versions.
+class QSignalBlocker {
+public:
+	explicit QSignalBlocker(QObject * o)
+		: obj(o), init_state(obj && obj->blockSignals(true)) {}
+
+	~QSignalBlocker() {
+		if (obj)
+			obj->blockSignals(init_state);
+	}
+private:
+	QObject * obj;
+	bool init_state;
+};
+#endif
+
+
 // Check if text is understood as rich text (Qt HTML) and if so, produce a
 // rendering in plain text.
 QString qtHtmlToPlainText(QString const & text);

src/insets/InsetInfo.cpp

@@ -303,7 +303,11 @@ vector<pair<string,docstring>> InsetInfoParams::getArguments(Buffer const * buf,
 		string const dt = split(name, '@');
 		QDate date;
 		if (itype == "moddate")
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 8, 0))
 			date = QDateTime::fromSecsSinceEpoch(buf->fileName().lastModified()).date();
+#else
+			date = QDateTime::fromTime_t(buf->fileName().lastModified()).date();
+#endif
 		else if (itype == "fixdate" && !dt.empty()) {
 			QDate const gdate = QDate::fromString(toqstr(dt), Qt::ISODate);
 			date = (gdate.isValid()) ? gdate : QDate::currentDate();
@@ -330,7 +334,11 @@ vector<pair<string,docstring>> InsetInfoParams::getArguments(Buffer const * buf,
 		string const tt = split(name, '@');
 		QTime time;
 		if (itype == "modtime")
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 8, 0))
 			time = QDateTime::fromSecsSinceEpoch(buf->fileName().lastModified()).time();
+#else
+			time = QDateTime::fromTime_t(buf->fileName().lastModified()).time();
+#endif
 		else if (itype == "fixtime" && !tt.empty()) {
 			QTime const gtime = QTime::fromString(toqstr(tt), Qt::ISODate);
 			time = (gtime.isValid()) ? gtime : QTime::currentTime();
@@ -1222,7 +1230,11 @@ void InsetInfo::build()
 				? split(params_.name, date_format, '@') : string();
 		QDate date;
 		if (params_.type == InsetInfoParams::MODDATE_INFO)
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 8, 0))
 			date = QDateTime::fromSecsSinceEpoch(buffer().fileName().lastModified()).date();
+#else
+			date = QDateTime::fromTime_t(buffer().fileName().lastModified()).date();
+#endif
 		else if (params_.type == InsetInfoParams::FIXDATE_INFO && !date_specifier.empty())
 			date = QDate::fromString(toqstr(date_specifier), Qt::ISODate);
 		else
@@ -1240,7 +1252,11 @@ void InsetInfo::build()
 				? split(params_.name, time_format, '@') : string();
 		QTime time;
 		if (params_.type == InsetInfoParams::MODTIME_INFO)
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 8, 0))
 			time = QDateTime::fromSecsSinceEpoch(buffer().fileName().lastModified()).time();
+#else
+			time = QDateTime::fromTime_t(buffer().fileName().lastModified()).time();
+#endif
 		else if (params_.type == InsetInfoParams::FIXTIME_INFO && !time_specifier.empty())
 			time = QTime::fromString(toqstr(time_specifier), Qt::ISODate);
 		else
@@ -1287,7 +1303,11 @@ std::pair<QDate, std::string> parseDate(Buffer const & buffer, const InsetInfoPa
 
 	QDate date;
 	if (params.type == InsetInfoParams::MODDATE_INFO)
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 8, 0))
 		date = QDateTime::fromSecsSinceEpoch(buffer.fileName().lastModified()).date();
+#else
+		date = QDateTime::fromTime_t(buffer.fileName().lastModified()).date();
+#endif
 	else if (params.type == InsetInfoParams::FIXDATE_INFO && !date_specifier.empty()) {
 		QDate date = QDate::fromString(toqstr(date_specifier), Qt::ISODate);
 		date = (date.isValid()) ? date : QDate::currentDate();
@@ -1308,7 +1328,11 @@ std::pair<QTime, std::string> parseTime(Buffer const & buffer, const InsetInfoPa
 
 	QTime time;
 	if (params.type == InsetInfoParams::MODTIME_INFO)
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 8, 0))
 		time = QDateTime::fromSecsSinceEpoch(buffer.fileName().lastModified()).time();
+#else
+		time = QDateTime::fromTime_t(buffer.fileName().lastModified()).time();
+#endif
 	else if (params.type == InsetInfoParams::FIXTIME_INFO && !date_specifier.empty()) {
 		time = QTime::fromString(toqstr(date_specifier), Qt::ISODate);
 		time = (time.isValid()) ? time : QTime::currentTime();

src/support/ConsoleApplicationPrivate.h

@@ -16,7 +16,9 @@
 #include <QCoreApplication>
 #include <QDateTime>
 #include <QTimer>
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 10, 0))
 #include <QRandomGenerator>
+#endif
 
 #include <string>
 
@@ -39,7 +41,11 @@ public:
 		setOrganizationDomain("lyx.org");
 		setApplicationName(toqstr(app));
 
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 10, 0))
 		QRandomGenerator(QDateTime::currentDateTime().toSecsSinceEpoch());
+#else
+		qsrand(QDateTime::currentDateTime().toTime_t());
+#endif
 	}
 	int execute()
 	{

src/support/FileName.cpp

@@ -518,7 +518,12 @@ time_t FileName::lastModified() const
 	// been touched between the object creation and now, we refresh the file
 	// information.
 	d->refresh();
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 8, 0))
 	return d->fi.lastModified().toSecsSinceEpoch();
+#else
+	return d->fi.lastModified().toTime_t();
+#endif
+	
 }
 
 

src/support/Systemcall.cpp

@@ -369,7 +369,11 @@ SystemcallPrivate::SystemcallPrivate(std::string const & sf, std::string const &
 
 	connect(process_, SIGNAL(readyReadStandardOutput()), SLOT(stdOut()));
 	connect(process_, SIGNAL(readyReadStandardError()), SLOT(stdErr()));
+#if QT_VERSION >= 0x050600
 	connect(process_, SIGNAL(errorOccurred(QProcess::ProcessError)), SLOT(processError(QProcess::ProcessError)));
+#else
+	connect(process_, SIGNAL(error(QProcess::ProcessError)), SLOT(processError(QProcess::ProcessError)));
+#endif
 	connect(process_, SIGNAL(started()), this, SLOT(processStarted()));
 	connect(process_, SIGNAL(finished(int, QProcess::ExitStatus)), SLOT(processFinished(int, QProcess::ExitStatus)));
 }

src/support/lyxtime.cpp

@@ -37,12 +37,20 @@ time_t current_time()
 docstring formatted_datetime(time_t t, string const & fmt)
 {
 	QString qres;
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 8, 0))
 	if (fmt.empty())
 		qres = QLocale().toString(QDateTime::fromSecsSinceEpoch(t),
 		                          QLocale::ShortFormat);
 	else
 		qres = QLocale().toString(QDateTime::fromSecsSinceEpoch(t),
 					  toqstr(fmt));
+#else
+	if (fmt.empty())
+		qres = QLocale().toString(QDateTime::fromTime_t(t),
+		                          QLocale::ShortFormat);
+	else
+		qres = QLocale().toString(QDateTime::fromTime_t(t), toqstr(fmt));
+#endif
 	return qstring_to_ucs4(qres);
 }
 
@@ -69,7 +77,11 @@ time_t from_asctime_utc(string t)
 #else
 	loc_dt.setTimeSpec(Qt::UTC);
 #endif
+#if (QT_VERSION >= QT_VERSION_CHECK(5, 8, 0))
 	return loc_dt.toSecsSinceEpoch();
+#else
+	return loc_dt.toTime_t();
+#endif
 }
 
 } // namespace support