riscos: Ensure the mouse focus is set when creating the window

src/video/riscos/SDL_riscoswindow.c

@@ -25,6 +25,8 @@
 #include "SDL_version.h"
 #include "SDL_syswm.h"
 #include "../SDL_sysvideo.h"
+#include "../../events/SDL_mouse_c.h"
+
 
 #include "SDL_riscosvideo.h"
 #include "SDL_riscoswindow.h"
@@ -42,6 +44,8 @@ RISCOS_CreateWindow(_THIS, SDL_Window * window)
 
     window->flags |= SDL_WINDOW_FULLSCREEN;
 
+    SDL_SetMouseFocus(window);
+
     /* All done! */
     window->driverdata = driverdata;
     return 0;