+ make PropertyEditor class ready to be customized with Qt style sheet

src/Gui/propertyeditor/PropertyEditor.cpp

@@ -49,6 +49,10 @@ PropertyEditor::PropertyEditor(QWidget *parent)
 
     setAlternatingRowColors(true);
     setRootIsDecorated(true);
+
+    QStyleOptionViewItem opt = viewOptions();
+    this->background = opt.palette.dark();
+    this->groupColor = opt.palette.color(QPalette::BrightText);
 }
 
 PropertyEditor::~PropertyEditor()
@@ -65,6 +69,26 @@ bool PropertyEditor::isAutomaticDocumentUpdate(bool) const
     return autoupdate;
 }
 
+QBrush PropertyEditor::groupBackground() const
+{
+    return this->background;
+}
+
+void PropertyEditor::setGroupBackground(const QBrush& c)
+{
+    this->background = c;
+}
+
+QColor PropertyEditor::groupTextColor() const
+{
+    return this->groupColor;
+}
+
+void PropertyEditor::setGroupTextColor(const QColor& c)
+{
+    this->groupColor = c;
+}
+
 QStyleOptionViewItem PropertyEditor::viewOptions() const
 {
     QStyleOptionViewItem option = QTreeView::viewOptions();
@@ -114,7 +138,7 @@ void PropertyEditor::drawBranches(QPainter *painter, const QRect &rect, const QM
     QStyleOptionViewItem opt = viewOptions();
     PropertyItem *property = static_cast<PropertyItem*>(index.internalPointer());
     if (property && property->isSeparator()) {
-        painter->fillRect(rect, opt.palette.dark());
+        painter->fillRect(rect, this->background);
     //} else if (selectionModel()->isSelected(index)) {
     //    painter->fillRect(rect, opt.palette.brush(QPalette::Highlight));
     }

src/Gui/propertyeditor/PropertyEditor.h

@@ -41,10 +41,26 @@ namespace Gui {
 namespace PropertyEditor {
 
 class PropertyModel;
+/*!
+ Put this into the .qss file after Gui--PropertyEditor--PropertyEditor
+ 
+ Gui--PropertyEditor--PropertyEditor
+ {
+    qproperty-groupBackground: gray;
+    qproperty-groupTextColor: white;
+ }
+
+ See also: https://man42.net/blog/2011/09/qt-4-7-modify-a-custom-q_property-with-a-qt-style-sheet/
+
+*/
+
 class PropertyEditor : public QTreeView
 {
     Q_OBJECT
 
+    Q_PROPERTY(QBrush groupBackground READ groupBackground WRITE setGroupBackground DESIGNABLE true SCRIPTABLE true)
+    Q_PROPERTY(QColor groupTextColor READ groupTextColor WRITE setGroupTextColor DESIGNABLE true SCRIPTABLE true)
+
 public:
     PropertyEditor(QWidget *parent = 0);
     ~PropertyEditor();
@@ -57,6 +73,11 @@ public:
     void setAutomaticDocumentUpdate(bool);
     bool isAutomaticDocumentUpdate(bool) const;
 
+    QBrush groupBackground() const;
+    void setGroupBackground(const QBrush& c);
+    QColor groupTextColor() const;
+    void setGroupTextColor(const QColor& c);
+
 protected:
     virtual void closeEditor (QWidget * editor, QAbstractItemDelegate::EndEditHint hint);
     virtual void commitData (QWidget * editor);
@@ -72,6 +93,8 @@ private:
     bool autoupdate;
     bool committing;
     bool delaybuild;
+    QColor groupColor;
+    QBrush background;
 };
 
 } //namespace PropertyEditor

src/Gui/propertyeditor/PropertyItemDelegate.cpp

@@ -58,7 +58,14 @@ void PropertyItemDelegate::paint(QPainter *painter, const QStyleOptionViewItem &
     PropertyItem *property = static_cast<PropertyItem*>(index.internalPointer());
 
     if (property && property->isSeparator()) {
-        option.palette.setColor(QPalette::Text, option.palette.color(QPalette::BrightText));
+        QColor color = option.palette.color(QPalette::BrightText);
+        QObject* par = parent();
+        if (par) {
+            QVariant value = par->property("groupTextColor");
+            if (value.canConvert<QColor>())
+                color = value.value<QColor>();
+        }
+        option.palette.setColor(QPalette::Text, color);
         option.font.setBold(true);
         option.state &= ~QStyle::State_Selected;
     }
@@ -70,8 +77,14 @@ void PropertyItemDelegate::paint(QPainter *painter, const QStyleOptionViewItem &
     option.state &= ~QStyle::State_HasFocus;
 
     if (property && property->isSeparator()) {
-        QBrush bg = option.palette.dark();
-        painter->fillRect(option.rect, bg);
+        QBrush brush = option.palette.dark();
+        QObject* par = parent();
+        if (par) {
+            QVariant value = par->property("groupBackground");
+            if (value.canConvert<QBrush>())
+                brush = value.value<QBrush>();
+        }
+        painter->fillRect(option.rect, brush);
     }
 
     QPen savedPen = painter->pen();