Remove calls to wave_set_callback_is_output_enabled.

These calls are used to pre-emptively exit when writing audio
data. This is also handled within dispatch_audio. The difference
is that this callback could allow espeak to cancel quicker. In
practice it does not make much difference.

src/libespeak-ng/speech.c

 					return -1;
 				}
 #ifdef USE_ASYNC
-				if ((my_mode & ENOUTPUT_MODE_SYNCHRONOUS) == 0) {
-					wave_set_callback_is_output_enabled(fifo_is_command_enabled);
+				if ((my_mode & ENOUTPUT_MODE_SYNCHRONOUS) == 0)
 					event_init();
-				}
 #endif
 			}
 		}

src/libespeak-ng/wave.c

 int wave_port_is_busy(void *theHandler);
 void wave_port_terminate();
 void wave_port_flush(void *theHandler);
-void wave_port_set_callback_is_output_enabled(t_wave_callback *cb);
 void *wave_port_test_get_write_buffer();
 
 // wave_pulse.cpp
 int wave_pulse_is_busy(void *theHandler);
 void wave_pulse_terminate();
 void wave_pulse_flush(void *theHandler);
-void wave_pulse_set_callback_is_output_enabled(t_wave_callback *cb);
 void *wave_pulse_test_get_write_buffer();
 
 // wrappers
 		wave_port_flush(theHandler);
 }
 
-void wave_set_callback_is_output_enabled(t_wave_callback *cb)
-{
-	if (pulse_running)
-		wave_pulse_set_callback_is_output_enabled(cb);
-	else
-		wave_port_set_callback_is_output_enabled(cb);
-}
-
 // rename functions to be wrapped
 #define wave_open wave_port_open
 #define wave_write wave_port_write
 #define wave_is_busy wave_port_is_busy
 #define wave_terminate wave_port_terminate
 #define wave_flush wave_port_flush
-#define wave_set_callback_is_output_enabled wave_port_set_callback_is_output_enabled
 
 #endif
 
-static t_wave_callback *my_callback_is_output_enabled = NULL;
-
 #define MAX_SAMPLE_RATE 22050
 #define FRAMES_PER_BUFFER 512
 #define BUFFER_LENGTH (MAX_SAMPLE_RATE*2*sizeof(uint16_t))
 	return selectedDeviceInfo;
 }
 
-void wave_set_callback_is_output_enabled(t_wave_callback *cb)
-{
-	my_callback_is_output_enabled = cb;
-}
-
 void *wave_open(int srate, const char *device)
 {
 	PaError err;
 	char *aRead;
 
 	while (1) {
-		if (my_callback_is_output_enabled && (0 == my_callback_is_output_enabled()))
-			return 0;
-
 		aRead = myRead;
 
 		// write pointer is before read pointer?
 	(void)theHandler; // unused
 }
 
-void wave_set_callback_is_output_enabled(t_wave_callback *cb)
-{
-	(void)cb; // unused
-}
-
 #endif

src/libespeak-ng/wave.h

 extern int wave_is_busy(void *theHandler);
 extern void wave_terminate();
 
-// set the callback which informs if the output is still enabled.
-// Helpful if a new sample is waiting for free space whereas sound must be stopped.
-typedef int (t_wave_callback)(void);
-extern void wave_set_callback_is_output_enabled(t_wave_callback *cb);
-
 // general functions
 extern void clock_gettime2(struct timespec *ts);
 extern void add_time_in_ms(struct timespec *ts, int time_in_ms);

src/libespeak-ng/wave_pulse.c

 
 #ifdef USE_PULSEAUDIO
 
-static t_wave_callback *my_callback_is_output_enabled = NULL;
-
 #define SAMPLE_RATE 22050
 #define ESPEAK_FORMAT PA_SAMPLE_S16LE
 #define ESPEAK_CHANNEL 1
 #define wave_is_busy wave_pulse_is_busy
 #define wave_terminate wave_pulse_terminate
 #define wave_flush wave_pulse_flush
-#define wave_set_callback_is_output_enabled wave_pulse_set_callback_is_output_enabled
 
 // check whether we can connect to PulseAudio
 #include <pulse/simple.h>
 	(void)theHandler; // unused
 }
 
-void wave_set_callback_is_output_enabled(t_wave_callback *cb)
-{
-	my_callback_is_output_enabled = cb;
-}
-
 void *wave_open(int srate, const char *device)
 {
 	stream = NULL;
 	pthread_mutex_lock(&pulse_mutex);
 
 	while (1) {
-		if (my_callback_is_output_enabled
-		    && (0 == my_callback_is_output_enabled())) {
-			theSize = 0;
-			goto terminate;
-		}
-
 		aTotalFreeMem = pulse_free();
 		if (aTotalFreeMem >= bytes_to_write)
 			break;

src/libespeak-ng/wave_sada.c

 
 #ifdef USE_SADA
 
-static t_wave_callback *my_callback_is_output_enabled = NULL;
-
 static const char *sun_audio_device = "/dev/audio";
 static int sun_audio_fd = -1;
 
                   size_t theSize)
 {
 	size_t num;
-	if (my_callback_is_output_enabled && (0 == my_callback_is_output_enabled()))
-		return 0;
 
 #if defined(BYTE_ORDER) && BYTE_ORDER == BIG_ENDIAN
 	// BIG-ENDIAN, swap the order of bytes in each sound sample
 	(void)theHandler; // unused
 }
 
-// wave_set_callback_is_output_enabled
-//
-// DESCRIPTION:
-//
-// Sets the callback to call from wave_write before it sends data to
-// be played.  It helps wave_write determine if the data should be
-// thrown away or not.
-//
-// PARAMETERS:
-//
-// cb: the callback to call from wave_write
-//
-void wave_set_callback_is_output_enabled(t_wave_callback *cb)
-{
-	my_callback_is_output_enabled = cb;
-}
-
 // wave_get_remaining_time
 //
 // DESCRIPTION: