fix infobar for histogram images

Author: jcupitt

TODO

@@ -1,10 +1,3 @@
-- try:
-
-	Hist > New > Identity
-	Image A1.value
-
-  infobar shows (x, y), not just x, and value does not display
-
 
 - get judder with rotate and images smaller than the window
 

src/infobar.c

@@ -227,20 +227,15 @@ infobar_get_pixel(void *a, void *b)
 	PixelUpdate *update = (PixelUpdate *) a;
 	VipsImage *image = update->image;
 
-	/* Block outside the image.
+	/* Clip (x, y) to the image dimensions. It might be a histogram, for
+	 * example.
 	 */
-	if (update->image_x >= 0 &&
-		update->image_y >= 0 &&
-		update->image_x < image->Xsize &&
-		update->image_y < image->Ysize)
-		/* Fetch from image, even though this can be very slow.
-		 * This is run in a bg thread, so speed should not matter too much.
-		 */
-		update->result = !vips_getpoint(image,
-				&update->vector, &update->n,
-				update->image_x, update->image_y,
-				"unpack_complex", TRUE,
-				NULL);
+	update->result = !vips_getpoint(image,
+			&update->vector, &update->n,
+			VIPS_CLIP(0, update->image_x, image->Xsize - 1),
+			VIPS_CLIP(0, update->image_y, image->Ysize - 1),
+			"unpack_complex", TRUE,
+			NULL);
 
 	g_idle_add(infobar_update_pixel_idle, update);
 }
@@ -250,25 +245,33 @@ static void
 infobar_update_pixel(Infobar *infobar,
 	Tilesource *tilesource, double image_x, double image_y)
 {
+	/* We need to fetch pixels from base for histograms, from image
+	 * otherwise.
+	 */
+	VipsImage *base = tilesource_get_base_image(tilesource);
+	VipsImage *image = tilesource_get_image(tilesource);
+	VipsImage *selected = base->Type == VIPS_INTERPRETATION_HISTOGRAM ?
+		base : image;
+
 	if (!infobar->updating &&
-		tilesource->image) {
+		selected) {
 		infobar->updating = TRUE;
 
 		PixelUpdate *update = g_new0(PixelUpdate, 1);
 		update->infobar = infobar;
-		update->image = tilesource_get_base_image(tilesource);
-
-		/* Currently in level0 image coordinates ... we will fetch from
-		 * tilesource->image, the current pyr layer.
-		 */
-		int factor = tilesource->image_width / tilesource->image->Xsize;
-		update->image_x = image_x / factor;
-		update->image_y = image_y / factor;
+		update->image = selected;
 
 		// must stay valid until we are done
 		g_object_ref(update->infobar);
 		g_object_ref(update->image);
 
+		/* Currently in level0 image coordinates ... we need to scale for the
+		 * selected image.
+		 */
+		int factor = tilesource->image_width / update->image->Xsize;
+		update->image_x = image_x / factor;
+		update->image_y = image_y / factor;
+
 		if (vips_thread_execute("pixel", infobar_get_pixel, update))
 			// if we can't run a bg task, we must free the update
 			infobar_update_free(update);

src/tilesource.h

@@ -222,9 +222,6 @@ typedef struct _Tilesource {
 
 	/* The base image after the first stage of conversion for display (just
 	 * geometric conversion, no conversion to rgb).
-	 *
-	 * Plus a region to fetch pixel values for the infobar. Except for
-	 * histograms! We need to fetch pixels from base for them.
 	 */
 	VipsImage *image;
 	VipsImage *mask;