Fixes for the layer legend

app/layer/layerdetaildata.cpp

@@ -13,6 +13,8 @@
 #include "qgslegendsettings.h"
 #include "qgslayertreemodel.h"
 
+#include "mmstyle.h"
+
 LayerDetailData::LayerDetailData( QObject *parent )
   : QObject{parent}
 {
@@ -100,6 +102,14 @@ void LayerDetailData::setLayerTreeNode( QgsLayerTreeNode *newLayerTreeNode )
   // setup render context for legend
   QgsLegendSettings legendSettings;
 
+  QgsTextFormat textFormat = legendSettings.rstyle( QgsLegendStyle::Style::SymbolLabel ).textFormat();
+  textFormat.setSize( 14 ); // 14 is the pixel size of MMStyle::p5, used in form widgets
+  textFormat.setSizeUnit( Qgis::RenderUnit::Pixels );
+  textFormat.setColor( MMStyle::nightColor() );
+  legendSettings.rstyle( QgsLegendStyle::Style::SymbolLabel ).setTextFormat( textFormat );
+  legendSettings.rstyle( QgsLegendStyle::Style::SymbolLabel ).setMargin( 4 ); // match the top and left total margin of the legend
+  legendSettings.rstyle( QgsLegendStyle::Style::Title ).setMargin( 0 ); // Our empty Title still adds some margins, so we set those to zero
+
   mLayerTreeNode->setCustomProperty( QStringLiteral( "legend/title-style" ), QStringLiteral( "hidden" ) );
 
   QgsLayerTree *tree = new QgsLayerTree();

app/layer/layerdetaillegendimageprovider.cpp

@@ -47,31 +47,36 @@ QImage LayerDetailLegendImageProvider::requestImage( const QString &, QSize *siz
   // it by dpr.
 
   QScreen *screen = QGuiApplication::screens().at( 0 );
-  qreal pdpi = screen->physicalDotsPerInch() * screen->devicePixelRatio();
-  qreal dpm = pdpi / 25.4;
+  const qreal ldpi = screen->logicalDotsPerInch();
+  const qreal dpr = screen->devicePixelRatio();
 
-  QSize desiredSize( requestedSize );
-  if ( desiredSize.isEmpty() )
-  {
-    // fallback size
-    desiredSize = QSize( 60, 60 );
-  }
+  const qreal dpmm = ldpi * dpr / 25.4;
+
+  // 60 is fallback size, not sure how it came to be
+  const int width = requestedSize.isEmpty() ? static_cast<int>( 60 * dpr ) : static_cast<int>( requestedSize.width() * dpr );
+  const int height = static_cast<int>( minimumSize.height() * dpmm );
 
-  QImage legend = QImage( desiredSize.width(), minimumSize.height() * dpm, QImage::Format_ARGB32_Premultiplied );
+  QImage legend = QImage( width, height, QImage::Format_ARGB32_Premultiplied );
 
-  QPainter painter( &legend );
-  painter.setRenderHint( QPainter::Antialiasing );
+  {
+    QPainter painter( &legend );
+    painter.setRenderHint( QPainter::Antialiasing );
+
+    QgsRenderContext context = QgsRenderContext::fromQPainter( &painter );
 
-  QgsRenderContext context = QgsRenderContext::fromQPainter( &painter );
+    painter.scale( dpmm, dpmm );
 
-  painter.scale( dpm, dpm );
+    legend.fill( Qt::transparent );
 
-  legend.fill( Qt::transparent );
+    renderer->drawLegend( context );
+  }
 
-  renderer->drawLegend( context );
+  // Tag with DPR only after painting so QPainter does not auto-scale the
+  // coordinate system by dpr (which would otherwise double-apply the factor).
+  legend.setDevicePixelRatio( dpr );
 
-  size->setHeight( desiredSize.height() );
-  size->setWidth( desiredSize.width() );
+  size->setWidth( static_cast<int>( width / dpr ) );
+  size->setHeight( static_cast<int>( height / dpr ) );
 
   return legend;
 }