wayland fallback on X11-Ogre

When running on wayland with Ogre without wayland support,
explicitly force Qt to use the XCB protocol running
through Xwayland.

Backported with adaptations from ros2/rviz#847 .

Author: v4hn

src/rviz/main.cpp

@@ -28,11 +28,32 @@
  */
 
 #include <QApplication>
+#include <QProcessEnvironment>
 
 #include <rviz/visualizer_app.h>
 
 int main(int argc, char** argv)
 {
+#if !OGRE_USE_WAYLAND
+  // If Ogre does not support wayland, but we are running on wayland,
+  // explicitly force the xcb platform in Qt unless the user set it
+  std::vector<char*> args;
+  for (int i = 0; i < argc; ++i)
+  {
+    args.push_back(argv[i]);
+  }
+  auto env = QProcessEnvironment::systemEnvironment();
+  if (env.value("XDG_SESSION_TYPE") == "wayland" &&
+      args.end() == std::find(args.begin(), args.end(), "-platform") && !env.contains("QT_QPA_PLATFORM"))
+  {
+    static const char* xcb_platform_args[] = {"-platform", "xcb"};
+    args.push_back(const_cast<char*>(xcb_platform_args[0]));
+    args.push_back(const_cast<char*>(xcb_platform_args[1]));
+  }
+  argc = static_cast<int>(args.size());
+  argv = args.data();
+#endif
+
   QApplication qapp(argc, argv);
 
   rviz::VisualizerApp vapp;