Api update

Small API update + get the main window as a raw pointer like the main document and the main document view. May throw a logic_error if no main window is present, i.e. the application is not in its main loop, you should not catch it and let Vivy crash...

src/VivyApplication.cc

@@ -57,8 +57,8 @@ VivyApplication::exec() noexcept
     setCursorFlashTime(0);
 
     // Show the main window
-    MainWindow mainWindow;
-    mainWindow.show();
+    mainWindowPtr = std::make_unique<MainWindow>();
+    mainWindowPtr->show();
 
     // Main loop
     return QApplication::exec();
@@ -83,3 +83,11 @@ VivyApplication::getApplicationFont(Font id) const noexcept
     // Let the program crash
     qFatal("UNREACHABLE");
 }
+
+MainWindow *
+VivyApplication::getMainWindow() const
+{
+    if (!mainWindowPtr)
+        throw std::logic_error("No main window in the graphic VivyApplication");
+    return mainWindowPtr.get();
+}