Scale the pixel sizes in the stylesheet according to GUI font size

data/gui/normalStyle.css

@@ -409,15 +409,22 @@ QCheckBox:disabled {
 }
 
 QCheckBox::indicator,
-QListWidget::indicator,
-QListView::indicator,
 QGroupBox::indicator {
 	width: 16px;
 	height: 16px;
 	margin: 0;
 	background: none;
 }
 
+/* FIXME: these should configured the same way as QCheckBox and QGroupBox
+ * indicators, but there's a problem with spacing discussed at
+ * https://stackoverflow.com/q/77422984 */
+QListWidget::indicator,
+QListView::indicator {
+	margin: 0;
+	background: none;
+}
+
 QCheckBox::indicator:checked,
 QListWidget::indicator:checked,
 QListView::indicator:checked,

src/gui/StelGui.cpp

@@ -66,6 +66,28 @@
 #include <QAction>
 #include <QKeySequence>
 
+static QString applyScaleToCSS(const QString& css, const double scale)
+{
+	auto out = css;
+	const QRegularExpression pat("\\b([0-9.]+)px\\b");
+	QRegularExpressionMatch match;
+	int pos = 0;
+	while((pos = out.indexOf(pat, pos, &match)) >= 0)
+	{
+		const auto numStr = match.captured(1);
+		bool ok = false;
+		const auto num = numStr.toDouble(&ok);
+		assert(ok);
+		const auto scaled = num * scale;
+		const bool hasDot = numStr.contains(QLatin1Char('.'));
+		const auto newNumStr = hasDot ? QString::number(scaled,'f',3)
+		                              : QString::number(int(scaled));
+		out.replace(pos, numStr.size(), newNumStr);
+		pos += newNumStr.size() + 2; // skip the whole resulting pattern
+	}
+	return out;
+}
+
 StelGui::StelGui()
 	: topLevelGraphicsWidget(nullptr)
 	, skyGui(nullptr)
@@ -189,6 +211,11 @@ StelGui::~StelGui()
 	}
 }
 
+void StelGui::updateStelStyle()
+{
+	setStelStyle(StelApp::getInstance().getCurrentStelStyle());
+}
+
 void StelGui::init(QGraphicsWidget *atopLevelGraphicsWidget)
 {
 	qDebug() << "Creating GUI ...";
@@ -384,7 +411,8 @@ void StelGui::init(QGraphicsWidget *atopLevelGraphicsWidget)
 	l->addItem(skyGui, 0, 0);
 	atopLevelGraphicsWidget->setLayout(l);
 
-	setStelStyle(StelApp::getInstance().getCurrentStelStyle());
+	connect(&StelApp::getInstance(), &StelApp::guiFontSizeChanged, this, &StelGui::updateStelStyle);
+	updateStelStyle();
 
 	int margin = conf->value("gui/space_between_groups", 5).toInt();
 	skyGui->bottomBar->setGroupMargin("020-gridsGroup", margin, 0);
@@ -484,6 +512,8 @@ void StelGui::setStelStyle(const QString& style)
 	else
 		qDebug().noquote() << "Cannot find HTML style file:" << htmlStyleFileName;
 
+	const auto scale = double(StelApp::getInstance().getGuiFontSize()) / StelApp::getDefaultGuiFontSize();
+	currentStelStyle.qtStyleSheet = applyScaleToCSS(currentStelStyle.qtStyleSheet, scale);
 	emit guiStyleChanged(currentStelStyle.qtStyleSheet);
 	emit htmlStyleChanged(currentStelStyle.htmlStyleSheet);
 }

src/gui/StelGui.hpp

@@ -312,6 +312,7 @@ private slots:
 	void copySelectedObjectInfo(void);
 
 private:
+	void updateStelStyle();
 	//! convenience method to find an action in the StelActionMgr.
 	StelAction* getAction(const QString& actionName) const;