Fix SVG Scaling; Allow SVGs to be rendered at sizes other than their natural size. (LMMS#7769)

Allow embed.cpp to load SVG assets at screen DPI by leveraging QPixmap::setDevicePixelRatio

---------

Co-authored-by: Tres Finocchiaro <tres.finocchiaro@gmail.com>
Co-authored-by: Fawn <rubiefawn@gmail.com>

Author: 3 people

src/gui/embed.cpp

@@ -24,22 +24,74 @@
 
 #include "embed.h"
 
-#include <QDebug>
 #include <QDir>
+#include <QGuiApplication>
 #include <QImageReader>
+#include <QPainter>
 #include <QPixmapCache>
 #include <QResource>
+#include <QScreen>
+#include <QSvgRenderer>
 
 namespace lmms::embed {
 
 namespace {
 
+// QPixmapCache and HiDPI compatible SVG-->QPixmap wrapper
+auto loadSvgPixmap(const QString& resourceName, int width, int height) -> QPixmap
+{
+	// QFile requires the file extension to be present, unlike QImageReader
+	QString fileName = resourceName;
+	if (!fileName.endsWith(".svg", Qt::CaseInsensitive)) { fileName += ".svg"; }
+
+	QFile file(fileName);
+	if (!file.open(QIODevice::ReadOnly))
+	{
+		qWarning() << "Failed to open resource for SVG: " << resourceName;
+		return QPixmap{1, 1};
+	}
+
+	QSvgRenderer renderer(file.readAll());
+	if (!renderer.isValid())
+	{
+		qWarning() << "Error loading SVG file: " << resourceName;
+		return QPixmap{1, 1};
+	}
+
+	// Get the default size of the SVG (without scaling)
+	QSize svgSize = renderer.defaultSize();
+
+	// If width/height are provided, use them
+	if (width > 0 && height > 0) { svgSize.scale(width, height, Qt::IgnoreAspectRatio); }
+
+	// Scale the svg
+	qreal devicePixelRatio = QGuiApplication::primaryScreen()->devicePixelRatio();
+	svgSize *= devicePixelRatio;
+
+	QImage image(svgSize, QImage::Format_ARGB32);
+	image.fill(Qt::transparent);
+	QPainter painter(&image);
+	renderer.render(&painter);
+	painter.end();
+
+	auto pixmap = QPixmap::fromImage(image);
+	pixmap.setDevicePixelRatio(devicePixelRatio);
+
+	return pixmap;
+}
+
 auto loadPixmap(const QString& name, int width, int height, const char* const* xpm) -> QPixmap
 {
 	if (xpm) { return QPixmap{xpm}; }
 
 	const auto resourceName = QDir::isAbsolutePath(name) ? name : "artwork:" + name;
 	auto reader = QImageReader{resourceName};
+
+	if (reader.format().toLower() == "svg")
+	{
+		return loadSvgPixmap(resourceName, width, height);
+	}
+
 	if (width > 0 && height > 0) { reader.setScaledSize(QSize{width, height}); }
 
 	const auto pixmap = QPixmap::fromImageReader(&reader);

src/gui/tracks/TrackOperationsWidget.cpp

@@ -108,17 +108,16 @@ TrackOperationsWidget::TrackOperationsWidget( TrackView * parent ) :
 		const auto activePixmap = embed::getIconPixmap(activeGraphic);
 		const auto inactivePixmap = embed::getIconPixmap(inactiveGraphic);
 
-		auto necessarySize = activePixmap.size().expandedTo(inactivePixmap.size());
-
 		auto wrapperWidget = new QWidget(parent);
-		wrapperWidget->setFixedSize(necessarySize);
 
 		auto button = new PixmapButton(wrapperWidget, toolTip);
 		button->setCheckable(true);
 		button->setActiveGraphic(activePixmap);
 		button->setInactiveGraphic(inactivePixmap);
 		button->setToolTip(toolTip);
 
+		wrapperWidget->setFixedSize(button->minimumSizeHint());
+
 		pixmapButton = button;
 
 		return wrapperWidget;

src/gui/widgets/PixmapButton.cpp

@@ -107,7 +107,7 @@ void PixmapButton::mouseDoubleClickEvent( QMouseEvent * _me )
 void PixmapButton::setActiveGraphic( const QPixmap & _pm )
 {
 	m_activePixmap = _pm;
-	resize( m_activePixmap.width(), m_activePixmap.height() );
+	resize(m_activePixmap.size() / m_activePixmap.devicePixelRatio());
 }
 
 
@@ -129,7 +129,9 @@ QSize PixmapButton::sizeHint() const
 
 QSize PixmapButton::minimumSizeHint() const
 {
-	return m_activePixmap.size().expandedTo(m_inactivePixmap.size());
+	const auto activeSize = m_activePixmap.size() / m_activePixmap.devicePixelRatio();
+	const auto inactiveSize = m_inactivePixmap.size() / m_inactivePixmap.devicePixelRatio();
+	return activeSize.expandedTo(inactiveSize);
 }
 
 bool PixmapButton::isActive() const