Use true fullscreen mode, display just the background image on all but one screen

CMakeLists.txt

@@ -27,6 +27,8 @@ set(PROJECT_SOURCES
     src/installerprompt.cpp
     src/installerprompt.h
     src/installerprompt.ui
+    src/backgroundscreen.h
+    src/backgroundscreen.cpp
     src/resource.qrc
 )
 

src/backgroundscreen.cpp

@@ -0,0 +1,27 @@
+#include "backgroundscreen.h"
+
+#include <QMessageBox>
+#include <QGuiApplication>
+#include <QScreen>
+
+BackgroundScreen::BackgroundScreen(QWidget *parent)
+    : QWidget(parent) {
+    // Set the background image and scale it
+    QPixmap bg(":/background");
+    if (bg.isNull()) {
+        // the user will see the warning message that the InstallerPrompt object pops up, no need to bombard them with one message per screen
+        return;
+    }
+
+    QScreen *screen = QGuiApplication::primaryScreen();
+    QRect screenGeometry = screen->geometry();
+    bg = bg.scaled(screenGeometry.size(), Qt::IgnoreAspectRatio);
+
+    QPalette palette;
+    palette.setBrush(QPalette::Window, bg);
+    this->setPalette(palette);
+}
+
+BackgroundScreen::~BackgroundScreen()
+{
+}

src/backgroundscreen.h

@@ -0,0 +1,14 @@
+#ifndef BACKGROUNDSCREEN_H
+#define BACKGROUNDSCREEN_H
+
+#include <QWidget>
+
+class BackgroundScreen : public QWidget {
+    Q_OBJECT
+
+public:
+    explicit BackgroundScreen(QWidget *parent = nullptr);
+    virtual ~BackgroundScreen();
+};
+
+#endif // BACKGROUNDSCREEN_H

src/main.cpp

@@ -14,6 +14,7 @@
  */
 
 #include "installerprompt.h"
+#include "backgroundscreen.h"
 #include <QApplication>
 #include <QScreen>
 #include <QTranslator>
@@ -32,23 +33,20 @@ int main(int argc, char *argv[])
         }
     }
 
-    QList<InstallerPrompt*> ws;
+    InstallerPrompt* w;
+    QList<BackgroundScreen *> bss;
 
     // Iterate through all available screens
     for (QScreen *screen : QApplication::screens()) {
-        InstallerPrompt *w = new InstallerPrompt();
-        w->setGeometry(screen->geometry());
-        w->show();
-        ws.append(w);
-    }
-
-    for (InstallerPrompt *w : ws) {
-        for (InstallerPrompt *otherWindow : ws) {
-            if (w != otherWindow) {
-                // Connect signals and slots for synchronization
-                // Example: connect(ws.last(), &InstallerPrompt::someSignal, otherWindow, &InstallerPrompt::someSlot);
-            }
+        if (screen == QApplication::primaryScreen()) {
+            w = new InstallerPrompt();
+            w->showFullScreen();
+            continue;
         }
+        BackgroundScreen *backscreen = new BackgroundScreen();
+        backscreen->setGeometry(screen->geometry());
+        backscreen->showFullScreen();
+        bss.append(backscreen);
     }
 
     return app.exec();