demo: Fix startup delay

examples/dockwidgets/MyMainWindow.cpp

@@ -88,7 +88,13 @@ MyMainWindow::MyMainWindow(KDDockWidgets::MainWindowOptions options, QWidget *pa
         saver.restoreFromDisk();
     });
 
+    createDockWidgets();
+}
+
+void MyMainWindow::createDockWidgets()
+{
     KDDockWidgets::DockWidget::List dockwidgets;
+    // Create 9 KDDockWidget::DockWidget and the respective widgets they're hosting (MyWidget instances)
     for (int i = 0; i < 9; i++)
         dockwidgets << newDockWidget();
 

examples/dockwidgets/MyMainWindow.h

@@ -27,6 +27,7 @@ public:
     explicit MyMainWindow(KDDockWidgets::MainWindowOptions options, QWidget *parent = nullptr);
 
 private:
+    void createDockWidgets();
     KDDockWidgets::DockWidgetBase* newDockWidget();
     QMenu *m_toggleMenu = nullptr;
 };

examples/dockwidgets/MyWidget.cpp

@@ -24,14 +24,24 @@
 #include <QDebug>
 #include <QFile>
 
+static QHash<QString, QImage> s_images;
+
 MyWidget::MyWidget(const QString &backgroundFile, const QString &logoFile, QWidget *parent)
     : QWidget(parent)
 {
-    if (!backgroundFile.isEmpty())
-        m_background = QImage(backgroundFile);
+    if (!backgroundFile.isEmpty()) {
+        auto it = s_images.find(backgroundFile);
+        if (it == s_images.end())
+            it = s_images.insert(backgroundFile, QImage(backgroundFile));
+        m_background = it.value();
+    }
 
-    if (!logoFile.isEmpty())
-        m_logo = QImage(logoFile);
+    if (!logoFile.isEmpty()) {
+        auto it = s_images.find(logoFile);
+        if (it == s_images.end())
+            it = s_images.insert(logoFile, QImage(logoFile));
+        m_logo = it.value();
+    }
 }
 
 MyWidget::~MyWidget()