diff --git a/ChangeLog b/ChangeLog
index 1d07792f..882c0b7c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -2,6 +2,7 @@
 - version bump for new dev cycle
 - im_subtract(), im_avg() redone as classes
 - added VIPS_ARGUMENT_APPEND to help control arg ordering
+- generate has a 'stop' param to signal successful early termination
 
 10/8/11 started 7.26.3
 - don't use G_VALUE_COLLECT_INIT(), many platforms do not have a glib this
diff --git a/libvips/arithmetic/binary.c b/libvips/arithmetic/binary.c
index b18b3751..b29a2b29 100644
--- a/libvips/arithmetic/binary.c
+++ b/libvips/arithmetic/binary.c
@@ -258,7 +258,8 @@ vips__bandalike( const char *domain,
  */
 
 static int
-vips_binary_process_region( VipsRegion *or, void *seq, void *a, void *b )
+vips_binary_process_region( VipsRegion *or, 
+	void *seq, void *a, void *b, gboolean *stop )
 {
 	VipsRegion **ir = (VipsRegion **) seq;
 	VipsBinary *binary = VIPS_BINARY( b ); 
diff --git a/libvips/arithmetic/im_deviate.c b/libvips/arithmetic/im_deviate.c
index 6868882d..bddc3e3f 100644
--- a/libvips/arithmetic/im_deviate.c
+++ b/libvips/arithmetic/im_deviate.c
@@ -99,7 +99,7 @@ wrapscan_stop( void *seq, void *a, void *b )
 }
 
 static int
-wrapscan_scan( REGION *reg, void *seq, void *a, void *b )
+wrapscan_scan( REGION *reg, void *seq, void *a, void *b, gboolean *stop )
 {
 	Wrapscan *wrapscan = (Wrapscan *) a;
 	Rect *r = &reg->valid;
@@ -124,7 +124,7 @@ wrapscan_scan( REGION *reg, void *seq, void *a, void *b )
  */
 int
 im__wrapscan( VipsImage *in, 
-	VipsStart start, im__wrapscan_fn scan, VipsStop stop,
+	VipsStartFn start, im__wrapscan_fn scan, VipsStopFn stop,
 	void *a, void *b )
 {
 	Wrapscan wrapscan;
diff --git a/libvips/arithmetic/im_maxpos.c b/libvips/arithmetic/im_maxpos.c
index d6b7ee3d..1125aa7b 100644
--- a/libvips/arithmetic/im_maxpos.c
+++ b/libvips/arithmetic/im_maxpos.c
@@ -161,7 +161,7 @@ maxpos_stop( void *seq, void *a, void *b )
 /* Loop over region, adding to seq.
  */
 static int
-maxpos_scan( REGION *reg, void *seq, void *a, void *b )
+maxpos_scan( REGION *reg, void *seq, void *a, void *b, gboolean *stop )
 {
 	const Rect *r = &reg->valid;
 	const int sz = IM_REGION_N_ELEMENTS( reg );
diff --git a/libvips/arithmetic/im_maxpos_avg.c b/libvips/arithmetic/im_maxpos_avg.c
index 28a44abe..ad3346f9 100644
--- a/libvips/arithmetic/im_maxpos_avg.c
+++ b/libvips/arithmetic/im_maxpos_avg.c
@@ -158,7 +158,7 @@ maxposavg_stop( void *seq, void *a, void *b )
 /* Loop over region, adding to seq.
  */
 static int
-maxposavg_scan( REGION *reg, void *seq, void *a, void *b )
+maxposavg_scan( REGION *reg, void *seq, void *a, void *b, gboolean *stop )
 {
 	const Rect *r = &reg->valid;
 	const int sz = IM_REGION_N_ELEMENTS( reg );
diff --git a/libvips/arithmetic/im_maxpos_vec.c b/libvips/arithmetic/im_maxpos_vec.c
index 3bf63786..d3f7b30f 100644
--- a/libvips/arithmetic/im_maxpos_vec.c
+++ b/libvips/arithmetic/im_maxpos_vec.c
@@ -74,13 +74,13 @@ static void           maxpos_list_free( maxpos_list *list );
 
 static void           maxpos_list_init( maxpos_list *list, int n );
 static void          *maxpos_vec_start( IMAGE *unrequired, void *, void * );
-static int            maxpos_vec_scan( REGION *reg, void *seq, void *, void * );
+static int            maxpos_vec_scan( REGION *reg, void *seq, void *, void *, gboolean * );
 static void           add_to_maxpos_list( maxpos_list *list, int x, int y, double val );
 static int            maxpos_vec_stop( void *seq, void *, void * );
 
 static void           minpos_list_init( maxpos_list *list, int n );
 static void          *minpos_vec_start( IMAGE *unrequired, void *, void * );
-static int            minpos_vec_scan( REGION *reg, void *seq, void *, void * );
+static int            minpos_vec_scan( REGION *reg, void *seq, void *, void *, gboolean * );
 static void           add_to_minpos_list( maxpos_list *list, int x, int y, double val );
 static int            minpos_vec_stop( void *seq, void *, void * );
 
@@ -275,7 +275,7 @@ static void *maxpos_vec_start( IMAGE *unrequired, void *a, void *b ){
   return list;
 }
 
-static int maxpos_vec_scan( REGION *reg, void *seq, void *a, void *b ){
+static int maxpos_vec_scan( REGION *reg, void *seq, void *a, void *b, gboolean *stop ){
   
   maxpos_list *list = (maxpos_list *) seq;
 
@@ -399,7 +399,7 @@ static void *minpos_vec_start( IMAGE *unrequired, void *a, void *b ){
   return list;
 }
 
-static int minpos_vec_scan( REGION *reg, void *seq, void *a, void *b ){
+static int minpos_vec_scan( REGION *reg, void *seq, void *a, void *b, gboolean *stop ){
   
   maxpos_list *list = (maxpos_list *) seq;
 
diff --git a/libvips/arithmetic/im_minpos.c b/libvips/arithmetic/im_minpos.c
index 30380041..82ce27d5 100644
--- a/libvips/arithmetic/im_minpos.c
+++ b/libvips/arithmetic/im_minpos.c
@@ -145,7 +145,7 @@ minpos_stop( void *seq, void *a, void *b )
 /* Loop over region, adding to seq.
  */
 static int
-minpos_scan( REGION *reg, void *seq, void *a, void *b )
+minpos_scan( REGION *reg, void *seq, void *a, void *b, gboolean *stop )
 {
 	const Rect *r = &reg->valid;
 	const int sz = IM_REGION_N_ELEMENTS( reg );
diff --git a/libvips/arithmetic/statistic.c b/libvips/arithmetic/statistic.c
index bb6eb2f9..c616bd95 100644
--- a/libvips/arithmetic/statistic.c
+++ b/libvips/arithmetic/statistic.c
@@ -74,7 +74,8 @@ vips_statistic_scan_start( VipsImage *in, void *a, void *b )
 }
 
 static int
-vips_statistic_scan( VipsRegion *region, void *seq, void *a, void *b )
+vips_statistic_scan( VipsRegion *region, 
+	void *seq, void *a, void *b, gboolean *stop )
 {
 	VipsStatistic *statistic = VIPS_STATISTIC( a );
 	VipsStatisticClass *class = VIPS_STATISTIC_GET_CLASS( statistic );
diff --git a/libvips/deprecated/rename.c b/libvips/deprecated/rename.c
index e7b3128a..bd2c2bb0 100644
--- a/libvips/deprecated/rename.c
+++ b/libvips/deprecated/rename.c
@@ -405,7 +405,7 @@ im_iterate( IMAGE *im,
 	im_start_fn start, im_generate_fn generate, im_stop_fn stop,
 	void *b, void *c )
 {
-	return( vips_sink( im, start, generate, stop, b, c ) );
+	return( vips_sink( im, start, (VipsGenerateFn) generate, stop, b, c ) );
 }
 
 int
diff --git a/libvips/deprecated/vips7compat.c b/libvips/deprecated/vips7compat.c
index 9e62af5c..3ff2130d 100644
--- a/libvips/deprecated/vips7compat.c
+++ b/libvips/deprecated/vips7compat.c
@@ -506,7 +506,8 @@ im_wrapmany( IMAGE **in, IMAGE *out, im_wrapmany_fn fn, void *a, void *b )
 	/* Generate!
 	 */
 	if( vips_image_generate( out,
-		vips_start_many, process_region, vips_stop_many, in, bun ) )
+		vips_start_many, (VipsGenerateFn) process_region, 
+		vips_stop_many, in, bun ) )
 		return( -1 );
 
 	return( 0 );
@@ -954,3 +955,11 @@ im_avg( IMAGE *in, double *out )
 {
 	return( vips_avg( in, out, NULL ) ); 
 }
+
+int im_generate( VipsImage *im,
+	im_start_fn start, im_generate_fn generate, im_stop_fn stop,
+	void *a, void *b )
+{
+	return( vips_image_generate( im, 
+		start, (VipsGenerateFn) generate, stop, a, b ) );
+}
diff --git a/libvips/format/im_vips2tiff.c b/libvips/format/im_vips2tiff.c
index 5a1cb5bc..15f84be1 100644
--- a/libvips/format/im_vips2tiff.c
+++ b/libvips/format/im_vips2tiff.c
@@ -1020,7 +1020,7 @@ new_tile( PyramidLayer *layer, REGION *tile, Rect *area )
  * generated.
  */
 static int
-write_tif_tile( REGION *out, void *seq, void *a, void *b )
+write_tif_tile( REGION *out, void *seq, void *a, void *b, gboolean *stop )
 {
 	TiffWrite *tw = (TiffWrite *) a;
 
diff --git a/libvips/histograms_lut/im_histgr.c b/libvips/histograms_lut/im_histgr.c
index 20922742..faf2c0bf 100644
--- a/libvips/histograms_lut/im_histgr.c
+++ b/libvips/histograms_lut/im_histgr.c
@@ -138,7 +138,7 @@ merge_subhist( void *seq, void *a, void *b )
 /* Histogram of all bands of a uchar image.
  */
 static int
-find_uchar_hist( REGION *reg, void *seq, void *a, void *b )
+find_uchar_hist( REGION *reg, void *seq, void *a, void *b, gboolean *stop )
 {
 	Histogram *hist = (Histogram *) seq;
 	Rect *r = &reg->valid;
@@ -170,7 +170,8 @@ find_uchar_hist( REGION *reg, void *seq, void *a, void *b )
 /* Histogram of a selected band of a uchar image.
  */
 static int
-find_uchar_hist_extract( REGION *reg, void *seq, void *a, void *b )
+find_uchar_hist_extract( REGION *reg, 
+	void *seq, void *a, void *b, gboolean *stop )
 {
 	Histogram *hist = (Histogram *) seq;
 	Rect *r = &reg->valid;
@@ -202,7 +203,7 @@ find_uchar_hist_extract( REGION *reg, void *seq, void *a, void *b )
 /* Histogram of all bands of a ushort image.
  */
 static int
-find_ushort_hist( REGION *reg, void *seq, void *a, void *b )
+find_ushort_hist( REGION *reg, void *seq, void *a, void *b, gboolean *stop )
 {
 	Histogram *hist = (Histogram *) seq;
 	Rect *r = &reg->valid;
@@ -244,7 +245,8 @@ find_ushort_hist( REGION *reg, void *seq, void *a, void *b )
 /* Histogram of all bands of a ushort image.
  */
 static int
-find_ushort_hist_extract( REGION *reg, void *seq, void *a, void *b )
+find_ushort_hist_extract( REGION *reg, 
+	void *seq, void *a, void *b, gboolean *stop )
 {
 	Histogram *hist = (Histogram *) seq;
 	Rect *r = &reg->valid;
@@ -305,7 +307,7 @@ im_histgr( IMAGE *in, IMAGE *out, int bandno )
 	int size;		/* Length of hist */
 	int bands;		/* Number of bands in output */
 	Histogram *mhist;
-	im_generate_fn scanfn;
+	VipsGenerateFn scanfn;
 	int i, j;
 	unsigned int *obuffer, *q;
 
diff --git a/libvips/histograms_lut/im_histindexed.c b/libvips/histograms_lut/im_histindexed.c
index d08e71eb..c46d3375 100644
--- a/libvips/histograms_lut/im_histindexed.c
+++ b/libvips/histograms_lut/im_histindexed.c
@@ -155,7 +155,7 @@ hist_stop( void *seq, void *a, void *b )
 /* A uchar index image.
  */
 static int
-hist_scan_uchar( REGION *reg, void *seq, void *a, void *b )
+hist_scan_uchar( REGION *reg, void *seq, void *a, void *b, gboolean *stop )
 {
 	Histogram *hist = (Histogram *) seq;
 	Rect *r = &reg->valid;
@@ -230,7 +230,7 @@ hist_scan_uchar( REGION *reg, void *seq, void *a, void *b )
 /* A ushort index image.
  */
 static int
-hist_scan_ushort( REGION *reg, void *seq, void *a, void *b )
+hist_scan_ushort( REGION *reg, void *seq, void *a, void *b, gboolean *stop )
 {
 	Histogram *hist = (Histogram *) seq;
 	Rect *r = &reg->valid;
@@ -327,7 +327,7 @@ im_hist_indexed( IMAGE *index, IMAGE *value, IMAGE *out )
 {
 	int size;		/* Length of hist */
 	Histogram *mhist;
-	im_generate_fn scanfn;
+	VipsGenerateFn scanfn;
 
 	/* Check images. PIO from in, WIO to out.
 	 */
diff --git a/libvips/histograms_lut/im_histnD.c b/libvips/histograms_lut/im_histnD.c
index 8fbcb5e9..d8e24131 100644
--- a/libvips/histograms_lut/im_histnD.c
+++ b/libvips/histograms_lut/im_histnD.c
@@ -154,7 +154,7 @@ merge_subhist( void *seq, void *a, void *b )
 }
 
 static int
-find_hist( REGION *reg, void *seq, void *a, void *b )
+find_hist( REGION *reg, void *seq, void *a, void *b, gboolean *stop )
 {
 	Histogram *hist = (Histogram *) seq;
 	Rect *r = &reg->valid;
diff --git a/libvips/histograms_lut/im_project.c b/libvips/histograms_lut/im_project.c
index b3c69cc8..daad9ac3 100644
--- a/libvips/histograms_lut/im_project.c
+++ b/libvips/histograms_lut/im_project.c
@@ -189,7 +189,7 @@ project_merge( void *seq, void *a, void *b )
 /* Add a region to a project.
  */
 static int
-project_scan( REGION *reg, void *seq, void *a, void *b )
+project_scan( REGION *reg, void *seq, void *a, void *b, gboolean *stop )
 {
 	Project *project = (Project *) seq;
 	Rect *r = &reg->valid;
diff --git a/libvips/include/vips/almostdeprecated.h b/libvips/include/vips/almostdeprecated.h
index 57103157..ed329c2d 100644
--- a/libvips/include/vips/almostdeprecated.h
+++ b/libvips/include/vips/almostdeprecated.h
@@ -131,7 +131,7 @@ void im_warning( const char *fmt, ... )
 	__attribute__((format(printf, 1, 2)));
 
 int im_iterate( VipsImage *im,
-	VipsStartFn start, VipsGenerateFn generate, VipsStopFn stop,
+	VipsStartFn start, im_generate_fn generate, VipsStopFn stop,
 	void *a, void *b
 );
 
diff --git a/libvips/include/vips/generate.h b/libvips/include/vips/generate.h
index b11f9a04..35babfe9 100644
--- a/libvips/include/vips/generate.h
+++ b/libvips/include/vips/generate.h
@@ -1,4 +1,4 @@
-/* Definitions for partial image regions.
+/* Generate pixels.
  *
  * J.Cupitt, 8/4/93
  */
@@ -36,9 +36,30 @@
 extern "C" {
 #endif /*__cplusplus*/
 
+typedef int (*VipsRegionWrite)( VipsRegion *region, VipsRect *area, void *a );
+int vips_sink_disc( VipsImage *im, VipsRegionWrite write_fn, void *a );
+
 typedef void *(*VipsStartFn)( VipsImage *out, void *a, void *b );
-typedef int (*VipsGenerateFn)( VipsRegion *out, void *seq, void *a, void *b );
+typedef int (*VipsGenerateFn)( VipsRegion *out, 
+	void *seq, void *a, void *b, gboolean *stop );
 typedef int (*VipsStopFn)( void *seq, void *a, void *b );
+int vips_sink( VipsImage *im, 
+	VipsStartFn start, VipsGenerateFn generate, VipsStopFn stop,
+	void *a, void *b );
+int vips_sink_tile( VipsImage *im, 
+	int tile_width, int tile_height,
+	VipsStartFn start, VipsGenerateFn generate, VipsStopFn stop,
+	void *a, void *b );
+
+typedef void (*VipsSinkNotify)( VipsImage *im, VipsRect *rect, void *a );
+int vips_sink_screen( VipsImage *in, VipsImage *out, VipsImage *mask,
+	int tile_width, int tile_height, int max_tiles,
+	int priority,
+	VipsSinkNotify notify, void *a );
+int vips_image_cache( VipsImage *in, VipsImage *out, 
+	int width, int height, int max );
+
+int vips_sink_memory( VipsImage *im );
 
 void *vips_start_one( VipsImage *out, void *a, void *b );
 int vips_stop_one( void *seq, void *a, void *b );
diff --git a/libvips/include/vips/threadpool.h b/libvips/include/vips/threadpool.h
index 024ac9b3..a4fd67a5 100644
--- a/libvips/include/vips/threadpool.h
+++ b/libvips/include/vips/threadpool.h
@@ -98,58 +98,34 @@ VipsThreadState *vips_thread_state_new( VipsImage *im, void *a );
 
 /* Constructor for per-thread state.
  */
-typedef VipsThreadState *(*VipsThreadStart)( VipsImage *im, void *a );
+typedef VipsThreadState *(*VipsThreadStartFn)( VipsImage *im, void *a );
 
 /* A work allocate function. This is run single-threaded by a worker to
  * set up a new work unit. 
  * Return non-zero for errors. Set *stop for "no more work to do"
  */
-typedef int (*VipsThreadpoolAllocate)( VipsThreadState *state,
+typedef int (*VipsThreadpoolAllocateFn)( VipsThreadState *state,
 	void *a, gboolean *stop );
 
 /* A work function. This does a unit of work (eg. processing a tile or
  * whatever). Return non-zero for errors. 
  */
-typedef int (*VipsThreadpoolWork)( VipsThreadState *state, void *a );
+typedef int (*VipsThreadpoolWorkFn)( VipsThreadState *state, void *a );
 
 /* A progress function. This is run by the main thread once for every
  * allocation. Return an error to kill computation early.
  */
-typedef int (*VipsThreadpoolProgress)( void *a );
+typedef int (*VipsThreadpoolProgressFn)( void *a );
 
 int vips_threadpool_run( VipsImage *im, 
-	VipsThreadStart start, 
-	VipsThreadpoolAllocate allocate, 
-	VipsThreadpoolWork work,
-	VipsThreadpoolProgress progress,
+	VipsThreadStartFn start, 
+	VipsThreadpoolAllocateFn allocate, 
+	VipsThreadpoolWorkFn work,
+	VipsThreadpoolProgressFn progress,
 	void *a );
 void vips_get_tile_size( VipsImage *im, 
 	int *tile_width, int *tile_height, int *nlines );
 
-typedef int (*VipsRegionWrite)( VipsRegion *region, VipsRect *area, void *a );
-int vips_sink_disc( VipsImage *im, VipsRegionWrite write_fn, void *a );
-
-typedef void *(*VipsStart)( VipsImage *out, void *a, void *b );
-typedef int (*VipsGenerate)( VipsRegion *out, void *seq, void *a, void *b );
-typedef int (*VipsStop)( void *seq, void *a, void *b );
-int vips_sink( VipsImage *im, 
-	VipsStart start, VipsGenerate generate, VipsStop stop,
-	void *a, void *b );
-int vips_sink_tile( VipsImage *im, 
-	int tile_width, int tile_height,
-	VipsStart start, VipsGenerate generate, VipsStop stop,
-	void *a, void *b );
-
-typedef void (*VipsSinkNotify)( VipsImage *im, VipsRect *rect, void *a );
-int vips_sink_screen( VipsImage *in, VipsImage *out, VipsImage *mask,
-	int tile_width, int tile_height, int max_tiles,
-	int priority,
-	VipsSinkNotify notify, void *a );
-int vips_image_cache( VipsImage *in, VipsImage *out, 
-	int width, int height, int max );
-
-int vips_sink_memory( VipsImage *im );
-
 void vips__print_renders( void );
 
 void vips_concurrency_set( int concurrency );
diff --git a/libvips/include/vips/vips7compat.h b/libvips/include/vips/vips7compat.h
index afd63ec7..12421d1e 100644
--- a/libvips/include/vips/vips7compat.h
+++ b/libvips/include/vips/vips7compat.h
@@ -275,9 +275,11 @@ VipsDemandStyle im_char2dhint( const char *str );
 #define im_stop_many vips_stop_many
 #define im_allocate_input_array vips_allocate_input_array
 #define im_start_fn VipsStartFn
-#define im_generate_fn VipsGenerateFn
+typedef int (*im_generate_fn)( VipsRegion *out, void *seq, void *a, void *b );
 #define im_stop_fn VipsStopFn
-#define im_generate vips_image_generate
+int im_generate( VipsImage *im,
+	im_start_fn start, im_generate_fn generate, im_stop_fn stop,
+	void *a, void *b );
 
 #define im__mmap vips__mmap
 #define im__munmap vips__munmap
diff --git a/libvips/iofuncs/image.c b/libvips/iofuncs/image.c
index 3a0aff70..9eaf9306 100644
--- a/libvips/iofuncs/image.c
+++ b/libvips/iofuncs/image.c
@@ -640,7 +640,8 @@ open_lazy_start( VipsImage *out, void *a, void *dummy )
 /* Just copy.
  */
 static int
-open_lazy_generate( VipsRegion *or, void *seq, void *a, void *b )
+open_lazy_generate( VipsRegion *or, 
+	void *seq, void *a, void *b, gboolean *stop )
 {
 	VipsRegion *ir = (VipsRegion *) seq;
 
diff --git a/libvips/iofuncs/sink.c b/libvips/iofuncs/sink.c
index 81741231..979a60e6 100644
--- a/libvips/iofuncs/sink.c
+++ b/libvips/iofuncs/sink.c
@@ -85,6 +85,10 @@ typedef struct _SinkThreadState {
 	 * parent_object.reg, it's defined on the outer image.
 	 */
 	VipsRegion *reg;
+
+	/* Set this in work to get the allocate to signal stop.
+	 */
+	gboolean stop;
 } SinkThreadState;
 
 typedef struct _SinkThreadStateClass {
@@ -184,6 +188,7 @@ sink_thread_state_init( SinkThreadState *state )
 {
 	state->seq = NULL;
 	state->reg = NULL;
+	state->stop = FALSE;
 }
 
 static VipsThreadState *
@@ -246,10 +251,19 @@ sink_init( Sink *sink,
 int 
 vips_sink_base_allocate( VipsThreadState *state, void *a, gboolean *stop )
 {
+	SinkThreadState *sstate = (SinkThreadState *) state;
 	SinkBase *sink_base = (SinkBase *) a;
 
 	VipsRect image, tile;
 
+	/* Has work requested early termination?
+	 */
+	if( sstate->stop ) {
+		*stop = TRUE;
+
+		return( 0 );
+	}
+
 	/* Is the state x/y OK? New line or maybe all done.
 	 */
 	if( sink_base->x >= sink_base->im->Xsize ) {
@@ -289,7 +303,8 @@ sink_work( VipsThreadState *state, void *a )
 	Sink *sink = (Sink *) a;
 
 	if( vips_region_prepare( sstate->reg, &state->pos ) ||
-		sink->generate( sstate->reg, sstate->seq, sink->a, sink->b ) ) 
+		sink->generate( sstate->reg, sstate->seq, 
+			sink->a, sink->b, &sstate->stop ) ) 
 		return( -1 );
 
 	return( 0 );
@@ -327,8 +342,6 @@ vips_sink_base_progress( void *a )
  *
  * Loops over an image. @generate is called for every pixel in the image, with
  * the @reg argument being a region of pixels for processing. 
- * vips_sink_tile() is
- * used to implement operations like im_avg() which have no image output.
  *
  * Each set of
  * pixels is @tile_width by @tile_height pixels (less at the image edges). 
@@ -343,7 +356,7 @@ vips_sink_base_progress( void *a )
 int
 vips_sink_tile( VipsImage *im, 
 	int tile_width, int tile_height,
-	VipsStart start, VipsGenerate generate, VipsStop stop,
+	VipsStartFn start, VipsGenerateFn generate, VipsStopFn stop,
 	void *a, void *b )
 {
 	Sink sink;
@@ -394,7 +407,7 @@ vips_sink_tile( VipsImage *im,
  *
  * Loops over an image. @generate is called for every pixel in the image, with
  * the @reg argument being a region of pixels for processing. vips_sink() is
- * used to implement operations like im_avg() which have no image output.
+ * used to implement operations like #VipsAvg which have no image output.
  *
  * Each set of pixels is sized according to the requirements of the image
  * pipeline that generated @im.
@@ -405,7 +418,7 @@ vips_sink_tile( VipsImage *im,
  */
 int
 vips_sink( VipsImage *im, 
-	VipsStart start, VipsGenerate generate, VipsStop stop,
+	VipsStartFn start, VipsGenerateFn generate, VipsStopFn stop,
 	void *a, void *b )
 {
 	return( vips_sink_tile( im, -1, -1, start, generate, stop, a, b ) );
diff --git a/libvips/iofuncs/sinkscreen.c b/libvips/iofuncs/sinkscreen.c
index 88522890..d46e2df2 100644
--- a/libvips/iofuncs/sinkscreen.c
+++ b/libvips/iofuncs/sinkscreen.c
@@ -910,7 +910,7 @@ image_start( IMAGE *out, void *a, void *b )
 /* Loop over the output region, filling with data from cache.
  */
 static int
-image_fill( VipsRegion *out, void *seq, void *a, void *b )
+image_fill( VipsRegion *out, void *seq, void *a, void *b, gboolean *stop )
 {
 	Render *render = (Render *) a;
 	VipsRegion *reg = (VipsRegion *) seq;
@@ -970,7 +970,7 @@ image_stop( void *seq, void *a, void *b )
 /* The mask image is 255 / 0 for the state of painted for each tile.
  */
 static int
-mask_fill( VipsRegion *out, void *seq, void *a, void *b )
+mask_fill( VipsRegion *out, void *seq, void *a, void *b, gboolean *stop )
 {
 #ifdef HAVE_THREADS
 	Render *render = (Render *) a;
diff --git a/libvips/iofuncs/threadpool.c b/libvips/iofuncs/threadpool.c
index 4939c549..41a81e77 100644
--- a/libvips/iofuncs/threadpool.c
+++ b/libvips/iofuncs/threadpool.c
@@ -356,9 +356,9 @@ typedef struct _VipsThreadpool {
 	 * a unit of work (serial). Plus the mutex we use to serialize work 
 	 * allocation.
 	 */
-	VipsThreadStart start; 
-	VipsThreadpoolAllocate allocate;
-	VipsThreadpoolWork work;
+	VipsThreadStartFn start; 
+	VipsThreadpoolAllocateFn allocate;
+	VipsThreadpoolWorkFn work;
 	GMutex *allocate_lock;
         void *a; 		/* User argument to start / allocate / etc. */
 
@@ -715,7 +715,7 @@ vips_threadpool_create_threads( VipsThreadpool *pool )
 }
 
 /**
- * VipsThreadpoolStart:
+ * VipsThreadpoolStartFn:
  * @a: client data
  * @b: client data
  * @c: client data
@@ -733,7 +733,7 @@ vips_threadpool_create_threads( VipsThreadpool *pool )
  */
 
 /**
- * _VipsThreadpoolAllocate:
+ * VipsThreadpoolAllocateFn:
  * @state: per-thread state
  * @a: client data
  * @b: client data
@@ -756,7 +756,7 @@ vips_threadpool_create_threads( VipsThreadpool *pool )
  */
 
 /**
- * _VipsThreadpoolWork:
+ * VipsThreadpoolWorkFn:
  * @state: per-thread state
  * @a: client data
  * @b: client data
@@ -775,7 +775,7 @@ vips_threadpool_create_threads( VipsThreadpool *pool )
  */
 
 /**
- * _VipsThreadpoolProgress:
+ * VipsThreadpoolProgressFn:
  * @a: client data
  * @b: client data
  * @c: client data
@@ -819,10 +819,10 @@ vips_threadpool_create_threads( VipsThreadpool *pool )
  */
 int
 vips_threadpool_run( VipsImage *im, 
-	VipsThreadStart start, 
-	VipsThreadpoolAllocate allocate, 
-	VipsThreadpoolWork work,
-	VipsThreadpoolProgress progress, 
+	VipsThreadStartFn start, 
+	VipsThreadpoolAllocateFn allocate, 
+	VipsThreadpoolWorkFn work,
+	VipsThreadpoolProgressFn progress, 
 	void *a )
 {
 	VipsThreadpool *pool;