Re-instate support for Qt 5.9.4

It was a bit overkill to require support for Qt 5.12 at 6ba2b5c5 and
c39d5b76. Revert partly these commits.

INSTALL

@@ -59,7 +59,7 @@ 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
+LyX requires Qt 5.9.4 or 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.

README

@@ -90,7 +90,7 @@ 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
+    * The Qt library, at least version 5.9.4. 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([5.9.4])
 AC_SUBST([FRONTENDS_SUBDIRS], [qt])
 FRONTEND_INFO="${FRONTEND_INFO}\
   Qt Frontend:\n\

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/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>
@@ -1136,7 +1138,12 @@ GuiApplication::GuiApplication(int & argc, char ** argv)
 #endif
 
 	setDesktopFileName(lyx_package);
+
+#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_);

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
 }
 
 
@@ -2512,7 +2524,11 @@ 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);

src/frontends/qt/GuiFontMetrics.cpp

@@ -283,7 +283,11 @@ int GuiFontMetrics::width(docstring const & s) const
 	if (math_char) {
 		QString const qs = toqstr(s);
 		int br_width = rbearing(s[0]);
+#if QT_VERSION >= QT_VERSION_CHECK(5, 11, 0)
 		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);
@@ -663,10 +667,17 @@ int GuiFontMetrics::width(char_type c) const
 	if (value != outOfLimitMetric)
 		return value;
 
+#if QT_VERSION >= QT_VERSION_CHECK(5, 11, 0)
 	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/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/GuiView.cpp

@@ -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_);

src/frontends/qt/GuiWorkArea.cpp

@@ -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

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

@@ -769,7 +769,11 @@ 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/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()
 	{