diff --git a/qucs/components/component.cpp b/qucs/components/component.cpp
index 025c56235..e0e48e7bd 100644
--- a/qucs/components/component.cpp
+++ b/qucs/components/component.cpp
@@ -1290,7 +1290,7 @@ int Component::analyseLine(const QString &Row, int numProps) {
         return 1;
     } else if (s == "Text") {  // must be last in order to reuse "s" *********
         if (!getIntegers(Row, &i1, &i2, &i3, 0, &i4)) return -1;
-        Color.setNamedColor(Row.section(' ', 4, 4));
+        Color=misc::ColorFromString(Row.section(' ', 4, 4));
         if (!Color.isValid()) return -1;
 
         s = Row.mid(Row.indexOf('"') + 1);    // Text (can contain " !!!)
@@ -1372,8 +1372,7 @@ bool Component::getPen(const QString &s, QPen &Pen, int i) {
     QString n;
 
     n = s.section(' ', i, i);    // color
-    QColor co;
-    co.setNamedColor(n);
+    QColor co = misc::ColorFromString(n);
     Pen.setColor(co);
     if (!Pen.color().isValid()) return false;
 
@@ -1396,8 +1395,7 @@ bool Component::getBrush(const QString &s, QBrush &Brush, int i) {
     QString n;
 
     n = s.section(' ', i, i);    // fill color
-    QColor co;
-    co.setNamedColor(n);
+    QColor co = misc::ColorFromString(n);
     Brush.setColor(co);
     if (!Brush.color().isValid()) return false;
 
diff --git a/qucs/diagrams/diagram.cpp b/qucs/diagrams/diagram.cpp
index f66d4bb5f..df26249b8 100644
--- a/qucs/diagrams/diagram.cpp
+++ b/qucs/diagrams/diagram.cpp
@@ -1322,8 +1322,7 @@ bool Diagram::load(const QString &Line, QTextStream *stream) {
     hideLines = (c & 2) != 0;
 
     n = s.section(' ', 6, 6);    // color for GridPen
-    QColor co;
-    co.setNamedColor(n);
+    QColor co = misc::ColorFromString(n);
     GridPen.setColor(co);
     if (!GridPen.color().isValid()) return false;
 
diff --git a/qucs/diagrams/graph.cpp b/qucs/diagrams/graph.cpp
index 5e8efa5bd..5b899a1ba 100644
--- a/qucs/diagrams/graph.cpp
+++ b/qucs/diagrams/graph.cpp
@@ -15,6 +15,7 @@
  *                                                                         *
  ***************************************************************************/
 #include "graph.h"
+#include "misc.h"
 
 #include <cstdlib>
 #include <iostream>
@@ -123,7 +124,7 @@ bool Graph::load(const QString& _s)
 
   QString n;
   n  = s.section(' ',1,1);    // Color
-  Color.setNamedColor(n);
+  Color = misc::ColorFromString(n);
   if(!Color.isValid()) return false;
 
   n  = s.section(' ',2,2);    // Thick
diff --git a/qucs/extsimkernels/abstractspicekernel.cpp b/qucs/extsimkernels/abstractspicekernel.cpp
index ee2fca690..066f6d48b 100644
--- a/qucs/extsimkernels/abstractspicekernel.cpp
+++ b/qucs/extsimkernels/abstractspicekernel.cpp
@@ -1331,8 +1331,8 @@ void AbstractSpiceKernel::normalizeVarsNames(QStringList &var_list)
                 QString suffix;
                 if ((*it).startsWith('I')) suffix = ".Ib";
                 else suffix = ".Vb";
-                int idx = it->indexOf('(');
-                int cnt = it->count();
+                auto idx = it->indexOf('(');
+                auto cnt = it->size();
                 *it = it->right(cnt-idx-1);
                 it->remove(')');
                 *it += suffix;
diff --git a/qucs/extsimkernels/qucs2spice.cpp b/qucs/extsimkernels/qucs2spice.cpp
index c6ed2b597..a24b51db6 100644
--- a/qucs/extsimkernels/qucs2spice.cpp
+++ b/qucs/extsimkernels/qucs2spice.cpp
@@ -34,9 +34,9 @@ namespace qucs2spice
    QString convert_rcl(const QString& line);
    QString convert_header(QString line);
    QString convert_diode(QString line,bool xyce=false);
-   QString convert_jfet(QString line, bool xyce=false);
+   QString convert_jfet(const QString& line, bool xyce=false);
    QString convert_mosfet(QString line, bool xyce=false);
-   QString convert_bjt(QString line);
+   QString convert_bjt(const QString& line);
    QString convert_cccs(const QString& line);
    QString convert_ccvs(const QString& line);
    QString convert_ccs(const QString& line, bool voltage);
@@ -131,8 +131,8 @@ QString qucs2spice::convert_rcl(const QString& line)
     s += " " + lst.takeFirst();
     s += " " + lst.takeFirst() + " ";
     s1 = lst.takeFirst().remove("\"");
-    int idx = s1.indexOf('=');
-    s += s1.right(s1.count()-idx-1);
+    auto idx = s1.indexOf('=');
+    s += s1.right(s1.size()-idx-1);
     s += "\n";
     return s;
 }
@@ -153,8 +153,8 @@ QString qucs2spice::convert_diode(QString line,bool xyce)
     QString s="";
     QStringList lst = line.split(" ",qucs::SkipEmptyParts);
     QString name = lst.takeFirst();
-    int idx = name.indexOf(':');
-    name =  name.right(name.count()-idx-1); // name
+    auto idx = name.indexOf(':');
+    name =  name.right(name.size()-idx-1); // name
     QString K = lst.takeFirst();
     QString A = lst.takeFirst();
     s += QString("D%1 %2 %3 DMOD_%4 \n").arg(name).arg(A).arg(K).arg(name);
@@ -170,8 +170,8 @@ QString qucs2spice::convert_mosfet(QString line, bool xyce)
     QString s="";
     QStringList lst = line.split(" ",qucs::SkipEmptyParts);
     QString name = lst.takeFirst();
-    int idx = name.indexOf(':');
-    name =  name.right(name.count()-idx-1); // name
+    auto idx = name.indexOf(':');
+    name =  name.right(name.size()-idx-1); // name
     QString G = lst.takeFirst();
     QString D = lst.takeFirst();
     QString S = lst.takeFirst();
@@ -207,13 +207,13 @@ QString qucs2spice::convert_mosfet(QString line, bool xyce)
     return s;
 }
 
-QString qucs2spice::convert_jfet(QString line, bool xyce)
+QString qucs2spice::convert_jfet(const QString& line, bool xyce)
 {
     QString s="";
     QStringList lst = line.split(" ",qucs::SkipEmptyParts);
     QString name = lst.takeFirst();
-    int idx = name.indexOf(':');
-    name =  name.right(name.count()-idx-1); // name
+    auto idx = name.indexOf(':');
+    name =  name.right(name.size()-idx-1); // name
     QString G = lst.takeFirst();
     QString D = lst.takeFirst();
     QString S = lst.takeFirst();
@@ -221,7 +221,7 @@ QString qucs2spice::convert_jfet(QString line, bool xyce)
     QStringList par_lst;
     par_lst.clear();
     for(int i=0;i<lst.count();i++) {
-        QString s1 = lst.at(i);
+        const QString& s1 = lst.at(i);
         if (s1.startsWith("Type=\"nfet\"")) {
             Typ = "NJF";
         } else if (s1.startsWith("Type=\"pfet\"")) {
@@ -238,13 +238,13 @@ QString qucs2spice::convert_jfet(QString line, bool xyce)
     return s;
 }
 
-QString qucs2spice::convert_bjt(QString line)
+QString qucs2spice::convert_bjt(const QString& line)
 {
     QString s="";
     QStringList lst = line.split(" ",qucs::SkipEmptyParts);
     QString name = lst.takeFirst();
-    int idx = name.indexOf(':');
-    name =  name.right(name.count()-idx-1); // name
+    auto idx = name.indexOf(':');
+    name =  name.right(name.size()-idx-1); // name
     QString B = lst.takeFirst();
     QString C = lst.takeFirst();
     QString E = lst.takeFirst();
@@ -293,8 +293,8 @@ QString qucs2spice::convert_ccs(const QString& line, bool voltage)
 {
     QStringList lst = line.split(" ",qucs::SkipEmptyParts);
     QString name = lst.takeFirst();
-    int idx = name.indexOf(':');
-    name =  name.right(name.count()-idx-1); // name
+    auto idx = name.indexOf(':');
+    name =  name.right(name.size()-idx-1); // name
 
     QString nod0 = lst.takeFirst();
     QString nod1 = lst.takeFirst();
@@ -302,7 +302,7 @@ QString qucs2spice::convert_ccs(const QString& line, bool voltage)
     QString nod3 = lst.takeFirst();
     QString s1 = lst.takeFirst().remove("\"");
     idx = s1.indexOf('=');
-    QString val = s1.right(s1.count()-idx-1);
+    QString val = s1.right(s1.size()-idx-1);
     QString s;
     if (voltage) s="H";
     else s="F";
@@ -325,8 +325,8 @@ QString qucs2spice::convert_vcs(const QString& line,bool voltage)
 {
     QStringList lst = line.split(" ",qucs::SkipEmptyParts);
     QString name = lst.takeFirst();
-    int idx = name.indexOf(':');
-    name =  name.right(name.count()-idx-1); // name
+    auto idx = name.indexOf(':');
+    name =  name.right(name.size()-idx-1); // name
 
     QString nod0 = lst.takeFirst();
     QString nod1 = lst.takeFirst();
@@ -334,7 +334,7 @@ QString qucs2spice::convert_vcs(const QString& line,bool voltage)
     QString nod3 = lst.takeFirst();
     QString s1 = lst.takeFirst().remove("\"");
     idx = s1.indexOf('=');
-    QString val = s1.right(s1.count()-idx-1);
+    QString val = s1.right(s1.size()-idx-1);
 
     QString s;
     if (voltage) s="E";
@@ -352,8 +352,8 @@ QString qucs2spice::convert_dc_src(const QString& line)
     s += " " + lst.takeFirst();
     s += " " + lst.takeFirst() + " ";
     s1 = lst.takeFirst().remove("\"");
-    int idx = s1.indexOf('=');
-    QString val = s1.right(s1.count()-idx-1);
+    auto idx = s1.indexOf('=');
+    QString val = s1.right(s1.size()-idx-1);
     s += "DC " + val + "\n";
     return s;
 }
diff --git a/qucs/extsimkernels/spicecompat.cpp b/qucs/extsimkernels/spicecompat.cpp
index 87bfa3a9b..4a97b020c 100644
--- a/qucs/extsimkernels/spicecompat.cpp
+++ b/qucs/extsimkernels/spicecompat.cpp
@@ -232,8 +232,8 @@ void spicecompat::convertNodeNames(QStringList &tokens, QString &sim)
                 if ((it->endsWith(".Vt"))||(it->endsWith(".It"))) sim = "tran";
                 if ((it->endsWith(".V"))||(it->endsWith(".I"))) sim = "dc";
                 QString suffix = it->section('.',1,1);
-                int idx = it->indexOf('.');
-                int cnt = it->count();
+                auto idx = it->indexOf('.');
+                auto cnt = it->size();
                 it->chop(cnt-idx);
                 if (suffix.toUpper().startsWith("I"))
                     *it = QString("V%1#branch").arg(*it);
diff --git a/qucs/imagewriter.cpp b/qucs/imagewriter.cpp
index 5235fe666..042ce2d4c 100644
--- a/qucs/imagewriter.cpp
+++ b/qucs/imagewriter.cpp
@@ -370,9 +370,10 @@ void ImageWriter::getSelAreaWidthAndHeight(Schematic *sch, int &wsel, int &hsel,
             int x1,y1,x2,y2;
             pd->Bounding(x1,y1,x2,y2);
             updateMinMax(xmin,xmax,ymin,ymax,x1,x2,y1,y2);
-
-            for (auto& pg: qAsConst(pd->Graphs)) {
-                for (auto& pm: qAsConst(pg->Markers)) {
+            auto const graphs = pd->Graphs;
+            for (auto& pg: graphs) {
+                auto const markers = pg->Markers;
+                for (auto& pm: markers) {
                     if (pm->isSelected) {
                         //int x1,y1,x2,y2;
                         pm->Bounding(x1,y1,x2,y2);
diff --git a/qucs/main.cpp b/qucs/main.cpp
index 3c35433ed..f1a579533 100644
--- a/qucs/main.cpp
+++ b/qucs/main.cpp
@@ -92,19 +92,19 @@ bool loadSettings()
     if(settings.contains("LargeFontSize"))QucsSettings.largeFontSize=settings.value("LargeFontSize").toDouble(); // use toDouble() as it can interpret the string according to the current locale
     if(settings.contains("maxUndo"))QucsSettings.maxUndo=settings.value("maxUndo").toInt();
     if(settings.contains("NodeWiring"))QucsSettings.NodeWiring=settings.value("NodeWiring").toInt();
-    if(settings.contains("BGColor"))QucsSettings.BGColor.setNamedColor(settings.value("BGColor").toString());
+    if(settings.contains("BGColor"))QucsSettings.BGColor = misc::ColorFromString(settings.value("BGColor").toString());
     if(settings.contains("Editor"))QucsSettings.Editor=settings.value("Editor").toString();
     if(settings.contains("FileTypes"))QucsSettings.FileTypes=settings.value("FileTypes").toStringList();
     if(settings.contains("Language"))QucsSettings.Language=settings.value("Language").toString();
-    if(settings.contains("Comment"))QucsSettings.Comment.setNamedColor(settings.value("Comment").toString());
-    if(settings.contains("String"))QucsSettings.String.setNamedColor(settings.value("String").toString());
-    if(settings.contains("Integer"))QucsSettings.Integer.setNamedColor(settings.value("Integer").toString());
-    if(settings.contains("Real"))QucsSettings.Real.setNamedColor(settings.value("Real").toString());
-    if(settings.contains("Character"))QucsSettings.Character.setNamedColor(settings.value("Character").toString());
-    if(settings.contains("Type"))QucsSettings.Type.setNamedColor(settings.value("Type").toString());
-    if(settings.contains("Attribute"))QucsSettings.Attribute.setNamedColor(settings.value("Attribute").toString());
-    if(settings.contains("Directive"))QucsSettings.Directive.setNamedColor(settings.value("Directive").toString());
-    if(settings.contains("Task"))QucsSettings.Task.setNamedColor(settings.value("Task").toString());
+    if(settings.contains("Comment"))QucsSettings.Comment=misc::ColorFromString(settings.value("Comment").toString());
+    if(settings.contains("String"))QucsSettings.String=misc::ColorFromString(settings.value("String").toString());
+    if(settings.contains("Integer"))QucsSettings.Integer=misc::ColorFromString(settings.value("Integer").toString());
+    if(settings.contains("Real"))QucsSettings.Real=misc::ColorFromString(settings.value("Real").toString());
+    if(settings.contains("Character"))QucsSettings.Character=misc::ColorFromString(settings.value("Character").toString());
+    if(settings.contains("Type"))QucsSettings.Type=misc::ColorFromString(settings.value("Type").toString());
+    if(settings.contains("Attribute"))QucsSettings.Attribute=misc::ColorFromString(settings.value("Attribute").toString());
+    if(settings.contains("Directive"))QucsSettings.Directive=misc::ColorFromString(settings.value("Directive").toString());
+    if(settings.contains("Task"))QucsSettings.Task=misc::ColorFromString(settings.value("Task").toString());
 
     if (settings.contains("panelIconsTheme")) QucsSettings.panelIconsTheme = settings.value("panelIconsTheme").toInt();
     else QucsSettings.panelIconsTheme = qucs::autoIcons;
@@ -823,8 +823,8 @@ int main(int argc, char *argv[])
   QucsSettings.maxUndo = 20;
   QucsSettings.NodeWiring = 0;
 
-  QApplication::setAttribute(Qt::AA_EnableHighDpiScaling,true);
 #if QT_VERSION < 0x060000
+  QApplication::setAttribute(Qt::AA_EnableHighDpiScaling,true);
   QApplication::setAttribute(Qt::AA_UseHighDpiPixmaps,true);
 #endif
 
@@ -955,7 +955,7 @@ int main(int argc, char *argv[])
     QucsSettings.Task = Qt::darkRed;
 
   QucsSettings.sysDefaultFont = QApplication::font();
-  a.setFont(QucsSettings.appFont);
+  QApplication::setFont(QucsSettings.appFont);
 
   QTranslator tor( 0 );
   QString lang = QucsSettings.Language;
@@ -965,7 +965,7 @@ int main(int argc, char *argv[])
 //    lang = QTextCodec::locale();
   }
   tor.load( QString("qucs_") + lang, QucsSettings.LangDir);
-  a.installTranslator( &tor );
+  QApplication::installTranslator( &tor );
 
   // This seems to be necessary on a few system to make strtod()
   // work properly !???!
diff --git a/qucs/misc.cpp b/qucs/misc.cpp
index 477ffc143..7dbd66585 100644
--- a/qucs/misc.cpp
+++ b/qucs/misc.cpp
@@ -284,6 +284,18 @@ QString misc::num2str(double Num)
   return Str;
 }
 
+QColor misc::ColorFromString(const QString& color)
+{
+#if QT_VERSION >= QT_VERSION_CHECK(6, 4, 0)
+    return QColor::fromString(color);
+#else
+    QColor c;
+    c.setNamedColor(color);
+    return c;
+#endif
+
+}
+
 // #########################################################################
 void misc::convert2Unicode(QString& Text)
 {
diff --git a/qucs/misc.h b/qucs/misc.h
index af14b1e56..c5047c39a 100644
--- a/qucs/misc.h
+++ b/qucs/misc.h
@@ -51,6 +51,7 @@ namespace misc {
   QString StringNum  (double, char form='g', int Precision=3);
   void    str2num    (const QString&, double&, QString&, double&);
   QString num2str    (double);
+  QColor ColorFromString(const QString& color);
   QString StringNiceNum(double);
   void    convert2Unicode(QString&);
   void    convert2ASCII(QString&);
diff --git a/qucs/paintings/arrow.cpp b/qucs/paintings/arrow.cpp
index 3aff065a3..4759a38d6 100644
--- a/qucs/paintings/arrow.cpp
+++ b/qucs/paintings/arrow.cpp
@@ -23,6 +23,7 @@
 #include "arrow.h"
 #include "arrowdialog.h"
 #include "schematic.h"
+#include "misc.h"
 #include <cmath>
 
 #include <QPolygon>
@@ -176,8 +177,7 @@ bool Arrow::load(const QString& s)
   if(!ok) return false;
 
   n  = s.section(' ',7,7);    // color
-  QColor co;
-  co.setNamedColor(n);
+  QColor co = misc::ColorFromString(n);
   Pen.setColor(co);
   if(!Pen.color().isValid()) return false;
 
diff --git a/qucs/paintings/ellipse.cpp b/qucs/paintings/ellipse.cpp
index 027101de2..b253218b1 100644
--- a/qucs/paintings/ellipse.cpp
+++ b/qucs/paintings/ellipse.cpp
@@ -137,8 +137,7 @@ bool qucs::Ellipse::load(const QString& s)
   if(!ok) return false;
 
   n  = s.section(' ',5,5);    // color
-  QColor co;
-  co.setNamedColor(n);
+  QColor co = misc::ColorFromString(n);
   Pen.setColor(co);
   if(!Pen.color().isValid()) return false;
 
@@ -151,7 +150,7 @@ bool qucs::Ellipse::load(const QString& s)
   if(!ok) return false;
 
   n  = s.section(' ',8,8);    // fill color
-  co.setNamedColor(n);
+  co = misc::ColorFromString(n);
   Brush.setColor(co);
   if(!Brush.color().isValid()) return false;
 
diff --git a/qucs/paintings/ellipsearc.cpp b/qucs/paintings/ellipsearc.cpp
index 04409e641..1ed8f4b17 100644
--- a/qucs/paintings/ellipsearc.cpp
+++ b/qucs/paintings/ellipsearc.cpp
@@ -128,8 +128,7 @@ bool EllipseArc::load(const QString& s)
   if(!ok) return false;
 
   n  = s.section(' ',7,7);    // color
-  QColor co;
-  co.setNamedColor(n);
+  QColor co = misc::ColorFromString(n);
   Pen.setColor(co);
   if(!Pen.color().isValid()) return false;
 
diff --git a/qucs/paintings/graphicline.cpp b/qucs/paintings/graphicline.cpp
index 99663ea5d..fb8007763 100644
--- a/qucs/paintings/graphicline.cpp
+++ b/qucs/paintings/graphicline.cpp
@@ -119,8 +119,7 @@ bool GraphicLine::load(const QString& s)
   if(!ok) return false;
 
   n  = s.section(' ',5,5);    // color
-  QColor co;
-  co.setNamedColor(n);
+  QColor co = misc::ColorFromString(n);
   Pen.setColor(co);
   if(!Pen.color().isValid()) return false;
 
diff --git a/qucs/paintings/graphictext.cpp b/qucs/paintings/graphictext.cpp
index 9875a4352..7d0e308a6 100644
--- a/qucs/paintings/graphictext.cpp
+++ b/qucs/paintings/graphictext.cpp
@@ -156,7 +156,7 @@ bool GraphicText::load(const QString& s)
   if(!ok) return false;
 
   n  = s.section(' ',4,4);    // Color
-  Color.setNamedColor(n);
+  Color = misc::ColorFromString(n);
   if(!Color.isValid()) return false;
 
   n  = s.section(' ',5,5);    // Angle
diff --git a/qucs/paintings/rectangle.cpp b/qucs/paintings/rectangle.cpp
index 01468ffc4..443296320 100644
--- a/qucs/paintings/rectangle.cpp
+++ b/qucs/paintings/rectangle.cpp
@@ -136,8 +136,7 @@ bool qucs::Rectangle::load(const QString& s)
   if(!ok) return false;
 
   n  = s.section(' ',5,5);    // color
-  QColor co;
-  co.setNamedColor(n);
+  QColor co = misc::ColorFromString(n);
   Pen.setColor(co);
   if(!Pen.color().isValid()) return false;
 
@@ -150,7 +149,7 @@ bool qucs::Rectangle::load(const QString& s)
   if(!ok) return false;
 
   n  = s.section(' ',8,8);    // fill color
-  co.setNamedColor(n);
+  co = misc::ColorFromString(n);
   Brush.setColor(co);
   if(!Brush.color().isValid()) return false;
 
diff --git a/qucs/symbolwidget.cpp b/qucs/symbolwidget.cpp
index 7b886856c..3b6cc8ca6 100644
--- a/qucs/symbolwidget.cpp
+++ b/qucs/symbolwidget.cpp
@@ -25,6 +25,7 @@
 #include "symbolwidget.h"
 #include "main.h"
 #include "qucslib_common.h"
+#include "misc.h"
 
 /*!
  * \file symbolwidget.cpp
@@ -591,7 +592,7 @@ int SymbolWidget::analyseLine(const QString& Row)
   }
   else if(s == "Text") {  // must be last in order to reuse "s" *********
     if(!getCompLineIntegers(Row, &i1, &i2, &i3))  return -1;
-    Color.setNamedColor(Row.section(' ',4,4));
+    Color=misc::ColorFromString(Row.section(' ',4,4));
     if(!Color.isValid()) return -1;
 
     s = Row.mid(Row.indexOf('"')+1);    // Text (can contain " !!!)
@@ -626,8 +627,7 @@ bool SymbolWidget::getPen(const QString& s, QPen& Pen, int i)
   QString n;
 
   n = s.section(' ',i,i);    // color
-  QColor co;
-  co.setNamedColor(n);
+  QColor co = misc::ColorFromString(n);
   Pen.setColor(co);
   if(!Pen.color().isValid()) return false;
 
@@ -651,8 +651,7 @@ bool SymbolWidget::getBrush(const QString& s, QBrush& Brush, int i)
   QString n;
 
   n = s.section(' ',i,i);    // fill color
-  QColor co;
-  co.setNamedColor(n);
+  QColor co=misc::ColorFromString(n);
   Brush.setColor(co);
   if(!Brush.color().isValid()) return false;
 
diff --git a/qucs/symbolwidget.h b/qucs/symbolwidget.h
index 208e8bd54..b38e418f1 100644
--- a/qucs/symbolwidget.h
+++ b/qucs/symbolwidget.h
@@ -66,7 +66,7 @@ class SymbolWidget : public QWidget  {
 
   int  analyseLine(const QString&);
 
-  bool getPen  (const QString&, QPen&, int);
+  static bool getPen  (const QString&, QPen&, int);
   bool getBrush(const QString&, QBrush&, int);
 
   bool dragNDrop;