GdkDisplayManager

The purpose of the GdkDisplayManager singleton object is to offer notification when displays appear or disappear or the default display changes.

You can use gdk_display_manager_get() to obtain the GdkDisplayManager singleton, but that should be rarely necessary. Typically, initializing GTK+ opens a display that you can work with without ever accessing the GdkDisplayManager.

The GDK library can be built with support for multiple backends. The GdkDisplayManager object determines which backend is used at runtime.

When writing backend-specific code that is supposed to work with multiple GDK backends, you have to consider both compile time and runtime. At compile time, use the #GDK_WINDOWING_X11, #GDK_WINDOWING_WIN32 macros, etc. to find out which backends are present in the GDK library you are building your application against. At runtime, use type-check macros like GDK_IS_X11_DISPLAY() to find out which backend is in use:

Backend-specific code ## {#backend-specific}

#ifdef GDK_WINDOWING_X11
  if (GDK_IS_X11_DISPLAY (display))
    {
      // make X11-specific calls here
    }
  else
#endif
#ifdef GDK_WINDOWING_QUARTZ
  if (GDK_IS_QUARTZ_DISPLAY (display))
    {
      // make Quartz-specific calls here
    }
  else
#endif
  g_error ("Unsupported GDK backend");