Compatibility with older Qt 6

Author: VioletGiraffe

plugins/viewer/textviewer/src/ctextviewerwindow.cpp

@@ -33,7 +33,8 @@ CTextViewerWindow::CTextViewerWindow(QWidget* parent) noexcept :
 
 	{
 		QFont fixedFont = QFontDatabase::systemFont(QFontDatabase::FixedFont);
-		const qreal sizeReatio = (qreal)QFontMetrics{qApp->font()}.height() / (qreal)QFontMetrics{fixedFont}.height();
+		QFontMetrics fm{fixedFont};
+		const qreal sizeReatio = fm.height() > 0 ? ((qreal)QFontMetrics{qApp->font()}.height() / (qreal)fm.height()) : 1.0;
 		fixedFont.setPointSizeF(fixedFont.pointSizeF() * sizeReatio);
 		_textBrowser->setFont(fixedFont);
 	}

qt-app/src/main.cpp

@@ -40,9 +40,11 @@ int main(int argc, char *argv[])
 	// Init style and color scheme, if specified
 	{
 		CSettings s;
+#if QT_VERSION >= QT_VERSION_CHECK(6,8,0)
 		const int colorScheme = s.value(KEY_INTERFACE_COLOR_SCHEME, -1).toInt();
 		if (colorScheme != -1)
 			QApplication::styleHints()->setColorScheme(static_cast<Qt::ColorScheme>(colorScheme));
+#endif
 
 		const QString styleName = s.value(KEY_INTERFACE_STYLE).toString();
 		if (!styleName.isEmpty())

qt-app/src/settings/csettingspageinterface.cpp

@@ -67,6 +67,7 @@ CSettingsPageInterface::CSettingsPageInterface(QWidget *parent) :
 	colorSchemeGroup->addButton(ui->_rbColorSchemeLight);
 	colorSchemeGroup->addButton(ui->_rbColorSchemeDark);
 
+#if QT_VERSION >= QT_VERSION_CHECK(6,8,0)
 	if (const auto colorScheme = QApplication::styleHints()->colorScheme(); colorScheme == Qt::ColorScheme::Dark)
 		ui->_rbColorSchemeDark->setChecked(true);
 	else if (colorScheme == Qt::ColorScheme::Light)
@@ -82,6 +83,7 @@ CSettingsPageInterface::CSettingsPageInterface(QWidget *parent) :
 			_colorSchemeChanged = true;
 		}
 	});
+#endif
 
 	const auto settingsDialog = dynamic_cast<QDialog*>(parent);
 	connect(settingsDialog, &QDialog::finished, this, [this] {
@@ -118,10 +120,14 @@ void CSettingsPageInterface::updateFontInfoLabel()
 
 int CSettingsPageInterface::colorSchemeFromButton(QAbstractButton* btn)
 {
+#if QT_VERSION >= QT_VERSION_CHECK(6,8,0)
 	if (btn == ui->_rbColorSchemeDark)
 		return static_cast<int>(Qt::ColorScheme::Dark);
 	else if (btn == ui->_rbColorSchemeLight)
 		return static_cast<int>(Qt::ColorScheme::Light);
 	else
 		return static_cast<int>(Qt::ColorScheme::Unknown);
+#else
+	return 0;
+#endif
 }