Ignore model font style and color in embed layers dialog

And always show layers in standard font and colors. Otherwise
they inherit the styling of the standard layer tree model,
which means unchecked layers show in a "disabled" looking
style, which is misleading (and meaningless) for the embedded
layer choice.

src/app/qgsprojectlayergroupdialog.cpp

@@ -26,6 +26,24 @@
 #include <QFileInfo>
 #include <QMessageBox>
 
+
+
+
+QgsEmbeddedLayerTreeModel::QgsEmbeddedLayerTreeModel( QgsLayerTree *rootNode, QObject *parent )
+  : QgsLayerTreeModel( rootNode, parent )
+{
+}
+
+QVariant QgsEmbeddedLayerTreeModel::data( const QModelIndex &index, int role ) const
+{
+  if ( role == Qt::ForegroundRole || role == Qt::FontRole )
+    return QVariant();
+
+  return QgsLayerTreeModel::data( index, role );
+}
+
+
+
 QgsProjectLayerGroupDialog::QgsProjectLayerGroupDialog( QWidget *parent, const QString &projectFile, Qt::WindowFlags f )
   : QDialog( parent, f )
   , mRootGroup( new QgsLayerTree )
@@ -180,7 +198,7 @@ void QgsProjectLayerGroupDialog::changeProjectFile()
   if ( !mShowEmbeddedContent )
     removeEmbeddedNodes( mRootGroup );
 
-  QgsLayerTreeModel *model = new QgsLayerTreeModel( mRootGroup, this );
+  QgsEmbeddedLayerTreeModel *model = new QgsEmbeddedLayerTreeModel( mRootGroup, this );
   mTreeView->setModel( model );
 
   connect( mTreeView->selectionModel(), &QItemSelectionModel::selectionChanged, this, &QgsProjectLayerGroupDialog::onTreeViewSelectionChanged );

src/app/qgsprojectlayergroupdialog.h

@@ -18,12 +18,31 @@
 #include "QDialog"
 #include "ui_qgsprojectlayergroupdialogbase.h"
 #include "qgshelp.h"
+#include "qgslayertreemodel.h"
 #include "qgis_app.h"
 
 class QDomElement;
 
 class QgsLayerTree;
 
+/**
+ * Subclass of QgsLayerTreeModel which overrides font styling
+ * from base model.
+ */
+class QgsEmbeddedLayerTreeModel : public QgsLayerTreeModel
+{
+    Q_OBJECT
+  public:
+
+    /**
+     * Construct a new tree model with given layer tree (root node must not be null pointer).
+     * The root node is not transferred by the model.
+     */
+    explicit QgsEmbeddedLayerTreeModel( QgsLayerTree *rootNode, QObject *parent = nullptr );
+
+    QVariant data( const QModelIndex &index, int role = Qt::DisplayRole ) const override;
+};
+
 //! A dialog to select layers and groups from a qgs project
 class APP_EXPORT QgsProjectLayerGroupDialog: public QDialog, private Ui::QgsProjectLayerGroupDialogBase
 {