Fix tiny svg preview size on hidpi displays

python/gui/symbology-ng/qgssvgselectorwidget.sip

@@ -24,18 +24,20 @@ class QgsSvgSelectorListModel : QAbstractListModel
 %End
   public:
 
-    QgsSvgSelectorListModel( QObject *parent /TransferThis/ );
+    QgsSvgSelectorListModel( QObject *parent /TransferThis/, int iconSize = 30 );
 %Docstring
  Constructor for QgsSvgSelectorListModel. All SVGs in folders from the application SVG
  search paths will be shown.
  \param parent parent object
+ \param iconSize desired size of SVG icons to create
 %End
 
-    QgsSvgSelectorListModel( QObject *parent /TransferThis/, const QString &path );
+    QgsSvgSelectorListModel( QObject *parent /TransferThis/, const QString &path, int iconSize = 30 );
 %Docstring
  Constructor for creating a model for SVG files in a specific path.
  \param parent parent object
  \param path initial path, which is recursively searched
+ \param iconSize desired size of SVG icons to create
 %End
 
     virtual int rowCount( const QModelIndex &parent = QModelIndex() ) const;

src/gui/symbology-ng/qgssvgselectorwidget.cpp

@@ -214,18 +214,20 @@ void QgsSvgGroupLoader::loadGroup( const QString &parentPath )
 // QgsSvgSelectorListModel
 //
 
-QgsSvgSelectorListModel::QgsSvgSelectorListModel( QObject *parent )
+QgsSvgSelectorListModel::QgsSvgSelectorListModel( QObject *parent, int iconSize )
   : QAbstractListModel( parent )
   , mSvgLoader( new QgsSvgSelectorLoader( this ) )
+  , mIconSize( iconSize )
 {
   mSvgLoader->setPath( QString() );
   connect( mSvgLoader, &QgsSvgSelectorLoader::foundSvgs, this, &QgsSvgSelectorListModel::addSvgs );
   mSvgLoader->start();
 }
 
-QgsSvgSelectorListModel::QgsSvgSelectorListModel( QObject *parent, const QString &path )
+QgsSvgSelectorListModel::QgsSvgSelectorListModel( QObject *parent, const QString &path, int iconSize )
   : QAbstractListModel( parent )
   , mSvgLoader( new QgsSvgSelectorLoader( this ) )
+  , mIconSize( iconSize )
 {
   mSvgLoader->setPath( path );
   connect( mSvgLoader, &QgsSvgSelectorLoader::foundSvgs, this, &QgsSvgSelectorListModel::addSvgs );
@@ -263,7 +265,7 @@ QPixmap QgsSvgSelectorListModel::createPreview( const QString &entry ) const
     strokeWidth = 0.2;
 
   bool fitsInCache; // should always fit in cache at these sizes (i.e. under 559 px ^ 2, or half cache size)
-  const QImage &img = QgsApplication::svgCache()->svgAsImage( entry, 30.0, fill, stroke, strokeWidth, 3.5 /*appr. 88 dpi*/, fitsInCache );
+  const QImage &img = QgsApplication::svgCache()->svgAsImage( entry, mIconSize, fill, stroke, strokeWidth, 3.5 /*appr. 88 dpi*/, fitsInCache );
   return QPixmap::fromImage( img );
 }
 
@@ -375,6 +377,9 @@ QgsSvgSelectorWidget::QgsSvgSelectorWidget( QWidget *parent )
   // TODO: in-code gui setup with option to vertically or horizontally stack SVG groups/images widgets
   setupUi( this );
 
+  mIconSize = qMax( 30, qRound( Qgis::UI_SCALE_FACTOR * fontMetrics().width( QStringLiteral( "XXXX" ) ) ) );
+  mImagesListView->setGridSize( QSize( mIconSize * 1.2, mIconSize * 1.2 ) );
+
   mGroupsTreeView->setHeaderHidden( true );
   populateList();
 
@@ -436,7 +441,7 @@ void QgsSvgSelectorWidget::populateIcons( const QModelIndex &idx )
   QString path = idx.data( Qt::UserRole + 1 ).toString();
 
   QAbstractItemModel *oldModel = mImagesListView->model();
-  QgsSvgSelectorListModel *m = new QgsSvgSelectorListModel( mImagesListView, path );
+  QgsSvgSelectorListModel *m = new QgsSvgSelectorListModel( mImagesListView, path, mIconSize );
   mImagesListView->setModel( m );
   delete oldModel; //explicitly delete old model to force any background threads to stop
 

src/gui/symbology-ng/qgssvgselectorwidget.h

@@ -174,14 +174,16 @@ class GUI_EXPORT QgsSvgSelectorListModel : public QAbstractListModel
     /** Constructor for QgsSvgSelectorListModel. All SVGs in folders from the application SVG
      * search paths will be shown.
      * \param parent parent object
+     * \param iconSize desired size of SVG icons to create
      */
-    QgsSvgSelectorListModel( QObject *parent SIP_TRANSFERTHIS );
+    QgsSvgSelectorListModel( QObject *parent SIP_TRANSFERTHIS, int iconSize = 30 );
 
     /** Constructor for creating a model for SVG files in a specific path.
      * \param parent parent object
      * \param path initial path, which is recursively searched
+     * \param iconSize desired size of SVG icons to create
      */
-    QgsSvgSelectorListModel( QObject *parent SIP_TRANSFERTHIS, const QString &path );
+    QgsSvgSelectorListModel( QObject *parent SIP_TRANSFERTHIS, const QString &path, int iconSize = 30 );
 
     int rowCount( const QModelIndex &parent = QModelIndex() ) const override;
     QVariant data( const QModelIndex &index, int role = Qt::DisplayRole ) const override;
@@ -193,6 +195,8 @@ class GUI_EXPORT QgsSvgSelectorListModel : public QAbstractListModel
     QPixmap createPreview( const QString &entry ) const;
     QgsSvgSelectorLoader *mSvgLoader = nullptr;
 
+    int mIconSize = 30;
+
   private slots:
 
     /** Called to add SVG files to the model.
@@ -259,6 +263,9 @@ class GUI_EXPORT QgsSvgSelectorWidget : public QWidget, private Ui::WidgetSvgSel
     void on_mFileLineEdit_textChanged( const QString &text );
 
   private:
+
+    int mIconSize = 30;
+
     QString mCurrentSvgPath; //!< Always stored as absolute path
 
 };

src/gui/symbology-ng/qgssymbollayerwidget.cpp

@@ -1740,6 +1740,9 @@ QgsSvgMarkerSymbolLayerWidget::QgsSvgMarkerSymbolLayerWidget( const QgsVectorLay
   spinOffsetY->setClearValue( 0.0 );
   spinAngle->setClearValue( 0.0 );
 
+  mIconSize = qMax( 30, qRound( Qgis::UI_SCALE_FACTOR * fontMetrics().width( QStringLiteral( "XXXX" ) ) ) );
+  viewImages->setGridSize( QSize( mIconSize * 1.2, mIconSize * 1.2 ) );
+
   populateList();
 
   connect( viewImages->selectionModel(), &QItemSelectionModel::currentChanged, this, &QgsSvgMarkerSymbolLayerWidget::setName );
@@ -1779,7 +1782,7 @@ void QgsSvgMarkerSymbolLayerWidget::populateList()
 
   // Initially load the icons in the List view without any grouping
   oldModel = viewImages->model();
-  QgsSvgSelectorListModel *m = new QgsSvgSelectorListModel( viewImages );
+  QgsSvgSelectorListModel *m = new QgsSvgSelectorListModel( viewImages, mIconSize );
   viewImages->setModel( m );
   delete oldModel;
 }

src/gui/symbology-ng/qgssymbollayerwidget.h

@@ -467,6 +467,7 @@ class GUI_EXPORT QgsSvgMarkerSymbolLayerWidget : public QgsSymbolLayerWidget, pr
   private:
 
     std::shared_ptr< QgsMarkerSymbol > mAssistantPreviewSymbol;
+    int mIconSize = 30;
 
 };