Sets the modifiers that will be considered significant for keyboard accelerators. The default mod mask depends on the GDK backend in use, but will typically include #GDK_CONTROL_MASK | #GDK_SHIFT_MASK |

GDK_MOD1_MASK | #GDK_SUPER_MASK | #GDK_HYPER_MASK | #GDK_META_MASK.

In other words, Control, Shift, Alt, Super, Hyper and Meta. Other modifiers will by default be ignored by GtkAccelGroup.

You must include at least the three modifiers Control, Shift and Alt in any value you pass to this function.

The default mod mask should be changed on application startup, before using any accelerator groups.