Merge pull request #5820 from elpaso/colorramp-hidpi

Adjust colorramp height on HiDPI screens

src/gui/qgscolorrampbutton.cpp

@@ -67,9 +67,10 @@ QSize QgsColorRampButton::sizeHint() const
 {
   //make sure height of button looks good under different platforms
 #ifdef Q_OS_WIN
-  return QSize( 120, 22 );
+  return QSize( 120, static_cast<int>( std::max( Qgis::UI_SCALE_FACTOR * fontMetrics().height( ), 22.0 ) ) );
 #else
-  return QSize( 120, 28 );
+  // Adjust height for HiDPI screens
+  return QSize( 120, static_cast<int>( std::max( Qgis::UI_SCALE_FACTOR * fontMetrics().height( ) * 1.4, 28.0 ) ) );
 #endif
 }
 

src/gui/symbology/qgscategorizedsymbolrendererwidget.cpp

@@ -64,9 +64,12 @@ void QgsCategorizedSymbolRendererModel::setRenderer( QgsCategorizedSymbolRendere
   }
   if ( renderer )
   {
-    beginInsertRows( QModelIndex(), 0, renderer->categories().size() - 1 );
     mRenderer = renderer;
-    endInsertRows();
+    if ( renderer->categories().size() > 0 )
+    {
+      beginInsertRows( QModelIndex(), 0, renderer->categories().size() - 1 );
+      endInsertRows();
+    }
   }
 }