Update infobar in a background thread

Thius stops a lot of nasty hitching. It needs libvips 8.15.

Author: jcupitt

src/imagewindow.c

@@ -60,6 +60,9 @@ struct _ImageWindow
 	gint64 last_frame_time;
 
 	GSettings *settings;
+
+	// use for any bg threads we need
+	VipsThreadset *threadset;
 };
 
 G_DEFINE_TYPE( ImageWindow, image_window, GTK_TYPE_APPLICATION_WINDOW );
@@ -83,6 +86,7 @@ image_window_dispose( GObject *object )
 	printf( "image_window_dispose:\n" ); 
 #endif /*DEBUG*/
 
+	VIPS_FREEF( vips_threadset_free, win->threadset );
 	VIPS_UNREF( win->tile_source );
 	VIPS_UNREF( win->tile_cache );
 	VIPS_FREEF( gtk_widget_unparent, win->right_click_menu );
@@ -1364,6 +1368,8 @@ image_window_init( ImageWindow *win )
 	win->last_progress_time = -1;
 	win->scale_rate = 1.0;
 	win->settings = g_settings_new( APPLICATION_ID );
+	// only need a couple of threads
+	win->threadset = vips_threadset_new( 2 );
 
 	gtk_widget_init_template( GTK_WIDGET( win ) );
 
@@ -1611,3 +1617,9 @@ image_window_get_mouse_position( ImageWindow *win,
 	imagedisplay_gtk_to_image( VIPSDISP_IMAGEDISPLAY( win->imagedisplay ), 
 		win->last_x_gtk, win->last_y_gtk, x_image, y_image );
 }
+
+VipsThreadset *
+image_window_get_threadset( ImageWindow *win )
+{
+	return( win->threadset );
+}

src/imagewindow.h

@@ -13,6 +13,7 @@ TileSource *image_window_get_tile_source( ImageWindow *win );
 void image_window_set_tile_source( ImageWindow *win, TileSource *tile_source );
 void image_window_get_mouse_position( ImageWindow *win, 
 	double *image_x, double *image_y );
+VipsThreadset *image_window_get_threadset( ImageWindow *win );
 
 #endif /* __IMAGE_WINDOW_H */
 

src/infobar.c

@@ -19,6 +19,9 @@ struct _Infobar {
 	GtkWidget *mag;
 
 	GSList *value_widgets;
+
+	// a background pixel value fetch is in progress
+	gboolean updating;
 };
 
 G_DEFINE_TYPE( Infobar, infobar, GTK_TYPE_WIDGET );
@@ -137,18 +140,97 @@ infobar_status_value_set_array( Infobar *infobar, double *d )
 	}
 }
 
+/* Asynchronous update of the pixel value ... we need this off the main thread
+ * or we get awful hitching for some formats.
+ */
+typedef struct _PixelUpdate {
+	// what we update, where we get the pixel data
+	Infobar *infobar;
+	TileSource *tile_source;
+
+	// fetch params
+	int image_x;
+	int image_y;
+	double *vector;
+	int n;
+	gboolean result;
+} PixelUpdate;
+
+static void
+infobar_update_free( PixelUpdate *update )
+{
+	update->infobar->updating = FALSE;
+
+	VIPS_UNREF( update->infobar );
+	VIPS_UNREF( update->tile_source );
+	VIPS_FREE( update->vector );
+	VIPS_FREE( update );
+}
+
+// runs back in the main thread again ... update the screen
+static gboolean
+infobar_update_pixel_cb( void *a )
+{
+	PixelUpdate *update = (PixelUpdate *) a;
+
+	if( update->result )
+		infobar_status_value_set_array( update->infobar, update->vector );
+
+	infobar_update_free( update );
+
+	return( FALSE );
+}
+
+// runs in a bg thread
+static void
+infobar_get_pixel( void *a, void *b )
+{
+	PixelUpdate *update = (PixelUpdate *) a;
+
+	update->result = tile_source_get_pixel( update->tile_source, 
+		update->image_x, update->image_y, &update->vector, &update->n ); 
+
+	g_idle_add( infobar_update_pixel_cb, update );
+}
+
+// fetch the mouse position pixel and update the screen in a bg thread
+static void
+infobar_update_pixel( Infobar *infobar )
+{
+	if( !infobar->updating ) {
+		ImageWindow *win = infobar->win;
+		PixelUpdate *update = g_new0( PixelUpdate, 1 );
+
+		double x_image;
+		double y_image;
+
+		update->infobar = infobar;
+		update->tile_source = image_window_get_tile_source( win );
+		image_window_get_mouse_position( infobar->win, &x_image, &y_image );
+		update->image_x = (int) x_image;
+		update->image_y = (int) y_image;
+		infobar->updating = TRUE;
+
+		// must stay valid until we are done
+		g_object_ref( update->infobar );
+		g_object_ref( update->tile_source );
+
+		if( vips_threadset_run(image_window_get_threadset( win ), "pixel", 
+			infobar_get_pixel, update ) )
+			// if we can't run a bg task, we must free the update
+			infobar_update_free( update );
+	}
+}
+
 void
 infobar_status_update( Infobar *infobar )
 {
-	TileSource *tile_source = image_window_get_tile_source( infobar->win );
 	double scale = image_window_get_scale( infobar->win );
 
 	char str[64];
 	VipsBuf buf = VIPS_BUF_STATIC( str );
 	double image_x;
 	double image_y;
-	double *vector;
-	int n;
 
 #ifdef DEBUG
 	printf( "infobar_status_update:\n" ); 
@@ -166,13 +248,6 @@ infobar_status_update( Infobar *infobar )
 		vips_buf_all( &buf ) ); 
 	vips_buf_rewind( &buf ); 
 
-	if( tile_source_get_pixel( tile_source, &vector, &n, 
-		image_x, image_y ) ) {
-		infobar_status_value_set_array( infobar, vector );
-		g_free( vector );
-	}
-
-	vips_buf_rewind( &buf ); 
 	vips_buf_appendf( &buf, "Magnification " );
 	if( scale >= 1.0 )
 		vips_buf_appendf( &buf, "%d:1", (int) scale );
@@ -181,6 +256,8 @@ infobar_status_update( Infobar *infobar )
 	gtk_label_set_text( GTK_LABEL( infobar->mag ), 
 		vips_buf_all( &buf ) ); 
 
+	// queue bg update of pixel value
+	infobar_update_pixel( infobar );
 }
 
 static void

src/tilesource.c

@@ -1873,8 +1873,8 @@ tile_source_get_base_image( TileSource *tile_source )
 }
 
 gboolean
-tile_source_get_pixel( TileSource *tile_source, 
-	double **vector, int *n, int x, int y )
+tile_source_get_pixel( TileSource *tile_source, int image_x, int image_y,
+	double **vector, int *n )
 {
 	if( !tile_source->loaded ||
 		!tile_source->image )
@@ -1883,21 +1883,22 @@ tile_source_get_pixel( TileSource *tile_source,
 	/* x and y are in base image coordinates, so we need to scale by the
 	 * current z.
 	 */
-	x /= 1 << tile_source->current_z;
-	y /= 1 << tile_source->current_z;
+	image_x /= 1 << tile_source->current_z;
+	image_y /= 1 << tile_source->current_z;
 
 	/* Block outside the image.
 	 */
-	if( x < 0 || 
-		y < 0 || 
-		x >= tile_source->display->Xsize ||
-		y >= tile_source->display->Ysize )
+	if( image_x < 0 || 
+		image_y < 0 || 
+		image_x >= tile_source->display->Xsize ||
+		image_y >= tile_source->display->Ysize )
 		return( FALSE );
 
 	/* The ->display image is cached in a sink screen, so this will be 
 	 * reasonably quick, even for things like svg and pdf.
 	 */
-	if( vips_getpoint( tile_source->display, vector, n, x, y, NULL ) )
+	if( vips_getpoint( tile_source->display, 
+		vector, n, image_x, image_y, NULL ) )
 		return( FALSE );
 
 	return( TRUE );

src/tilesource.h

@@ -235,8 +235,8 @@ GFile *tile_source_get_file( TileSource *tile_source );
 
 VipsImage *tile_source_get_image( TileSource *tile_source );
 VipsImage *tile_source_get_base_image( TileSource *tile_source );
-gboolean tile_source_get_pixel( TileSource *tile_source,
-	double **vector, int *n, int x, int y );
+gboolean tile_source_get_pixel( TileSource *tile_source, 
+	int image_x, int image_y, double **vector, int *n );
 TileSource *tile_source_duplicate( TileSource *tile_source );
 
 #endif /*__TILE_SOURCE_H*/