Package org.gnome.gio

Interface SimpleAction.ChangeStateCallback

All Superinterfaces:

FunctionPointer

Enclosing class:

SimpleAction

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public static interface SimpleAction.ChangeStateCallback
extends FunctionPointer

Functional interface declaration of the ChangeStateCallback callback.

See Also:

• run(org.gnome.glib.Variant)

Method Summary

Modifier and Type	Method	Description
void	run(@Nullable Variant value)	Indicates that the action just received a request to change its state.
default MemorySegment	toCallback(Arena arena)	Creates a native function pointer to the upcall(java.lang.foreign.MemorySegment, java.lang.foreign.MemorySegment) method.
default void	upcall(MemorySegment sourceSimpleAction, MemorySegment value)	The upcall method is called from native code.

Method Details

run

void run(@Nullable
 @Nullable Variant value)

Indicates that the action just received a request to change its state.

value will always be of the correct state type, i.e. the type of the initial state passed to g_simple_action_new_stateful(). If an incorrect type is given when requesting to change the state, this signal is not emitted.

If no handler is connected to this signal then the default behaviour is to call g_simple_action_set_state() to set the state to the requested value. If you connect a signal handler then no default action is taken. If the state should change then you must call g_simple_action_set_state() from the handler.

An example of a 'change-state' handler:

static void
 change_volume_state (GSimpleAction *action,
                      GVariant      *value,
                      gpointer       user_data)
 {
   gint requested;

   requested = g_variant_get_int32 (value);

   // Volume only goes from 0 to 10
   if (0 <= requested && requested <= 10)
     g_simple_action_set_state (action, value);
 }
 

The handler need not set the state to the requested value. It could set it to any value at all, or take some other action.

upcall

default void upcall(MemorySegment sourceSimpleAction,
 MemorySegment value)

The upcall method is called from native code. The parameters are marshaled and run(org.gnome.glib.Variant) is executed.

toCallback

default MemorySegment toCallback(Arena arena)

Creates a native function pointer to the upcall(java.lang.foreign.MemorySegment, java.lang.foreign.MemorySegment) method.

Specified by:

toCallback in interface FunctionPointer

Parameters:

arena - the function pointer will be allocated in this arena

Returns:

the native function pointer