handle messageboxes inside qt's thread

src/qt/qt_main.cpp

@@ -77,15 +77,14 @@ int main(int argc, char* argv[]) {
     QApplication app(argc, argv);
     elapsed_timer.start();
 
+    main_window = new MainWindow();
+    main_window->show();
+
     pc_init(argc, argv);
     if (! pc_init_modules()) {
         ui_msgbox_header(MBX_FATAL, VC(L"No ROMs found."), VC(L"86Box could not find any usable ROM images.\n\nPlease download a ROM set and extract it into the \"roms\" directory."));
         return 6;
     }
-
-    main_window = new MainWindow();
-    main_window->show();
-
     pc_reset_hard_init();
 
     /* Set the PAUSE mode depending on the renderer. */

src/qt/qt_mainwindow.cpp

@@ -3,8 +3,6 @@
 
 extern "C" {
 #include <86box/86box.h>
-//#include <86box/keyboard.h>
-//#include <86box/mouse.h>
 #include <86box/config.h>
 #include <86box/plat.h>
 
@@ -15,6 +13,7 @@ extern "C" {
 #include <QDebug>
 #include <QTimer>
 #include <QKeyEvent>
+#include <QMessageBox>
 
 #include "qt_settings.hpp"
 
@@ -26,6 +25,11 @@ MainWindow::MainWindow(QWidget *parent) :
 
     ui->setupUi(this);
 
+    connect(this, &MainWindow::showMessage, this, [this](const QString& header, const QString& message) {
+        QMessageBox box(QMessageBox::Warning, header, message, QMessageBox::NoButton, this);
+        box.exec();
+    }, Qt::BlockingQueuedConnection);
+
     connect(this, &MainWindow::pollMouse, this, [] {
         sdl_mouse_poll();
     });

src/qt/qt_mainwindow.hpp

@@ -25,6 +25,7 @@ signals:
 
     void setFullscreen(bool state);
     void setMouseCapture(bool state);
+    void showMessage(const QString& header, const QString& message);
 
 private slots:
     void on_actionFullscreen_triggered();

src/qt/qt_ui.cpp

@@ -2,7 +2,6 @@
 
 #include <QDebug>
 #include <QThread>
-#include <QMessageBox>
 
 #include <QStatusBar>
 
@@ -57,16 +56,14 @@ void plat_mouse_capture(int on) {
     main_window->setMouseCapture(on > 0 ? true : false);
 }
 
-int	ui_msgbox_header(int flags, void *header, void* message)
-{
+int	ui_msgbox_header(int flags, void *header, void* message) {
     if (header <= (void*)7168) header = plat_get_string(reinterpret_cast<long>(header));
     if (message <= (void*)7168) message = plat_get_string(reinterpret_cast<long>(message));
 
     auto hdr = QString::fromWCharArray(reinterpret_cast<const wchar_t*>(header));
     auto msg = QString::fromWCharArray(reinterpret_cast<const wchar_t*>(message));
 
-    QMessageBox box(QMessageBox::Warning, hdr, msg);
-    box.exec();
+    main_window->showMessage(hdr, msg);
     return 0;
 }