Try to make sure the wizard looks the same on all platforms

This should also avoid problems with the stylesheet (such as overlapping widgets etc.), since it has been developed against Fusion.

src/gui/newwizard/setupwizardwindow.cpp

@@ -7,6 +7,7 @@
 #include "theme.h"
 
 #include <QLabel>
+#include <QStyleFactory>
 
 using namespace std::chrono_literals;
 
@@ -55,6 +56,17 @@ SetupWizardWindow::SetupWizardWindow(QWidget *parent)
 
     resize(ocApp()->gui()->settingsDialog()->sizeHintForChild());
 
+    // different styles (e.g., 'Windows', 'Fusion') may require different approaches in the stylesheet
+    // therefore we want to force a standard style on all platforms
+    // this further makes sure the wizard (well, its contents) looks exactly the same on all platforms
+    // Fusion should be available everywhere
+    auto fusionStyle = QStyleFactory::create(QStringLiteral("Fusion"));
+    if (OC_ENSURE(fusionStyle != nullptr)) {
+        _ui->contentWidget->setStyle(fusionStyle);
+    } else {
+        qDebug() << "Could not set up default style, wizard contents will be shown using default style";
+    }
+
     loadStylesheet();
 
     _ui->transitionProgressIndicator->setFixedSize(32, 32);