fix "scale" in displaybar

Author: jcupitt

TODO

@@ -1,41 +1,38 @@
-- try:
-
-	nip4 k2.jpg
-	alt-R
-	segv in infobar_status_update()
-
-
 - try:
 
 	nip4 ~/pics/S000_t000002_V000_R0000_X000_Y000_C02_I1_D0_P00101.tif
 
-  incredibly slow, in fact does not draw at all, and it's not clear why
-
-  this takes under 2s to draw the image:
+	switch to multipage, go to page 72, enable falsecolour, set scale 6,
+	close window
 
-image = pyvips.Image.new_from_file(sys.argv[1], n=-1);
+  thumbnail gets falsecolour and scale, but not multipage or page number
 
-	page_width = image.width
-	page_height = image.get("page-height")
+- "reset" in display bar resets the position of scale/offset widgets, but does
+  not reset the menu items (eg. tick on falsecolour)
 
-	pages = [image.crop(0, y * page_height, page_width, page_height)
-		 for y in range(3)]
+	I forget how menu items are linked to actions, reread this
 
-	rgb = pages[0].bandjoin(pages[1:])
+	gaction bound to a gsetting? do we need to add to the settings
+	schema?
 
-	rgb = rgb.copy(interpretation="rgb16")
+  likewise, load ws with locked tab, rightclick menu on locked tab does not
+  have tick selected
 
-	rgb.write_to_file(sys.argv[2])
+- the "new tab" icon is still broken in the windows build
 
+- change "Merge into ..."
 
+	split to "Merge from file ..." and "Merge column >" with a
+	pullright listing all columns
 
+	Same for merge in tab menu, except "Merge tab >"
 
+	Just does save/load for you
 
-- alt-L and R for a while, coredump
+# menu redesign
 
 - maxpos, then create mark from coordinate should be two clicks
 
-
 - try:
 
 	minpair image constant
@@ -57,30 +54,6 @@ image = pyvips.Image.new_from_file(sys.argv[1], n=-1);
 
   we'll need to do constant expansion in minpair
 
-- the "new tab" icon is still broken in the windows build
-
-- "reset" in display bar resets the position of scale/offset widgets, but does
-  not reset the menu items (eg. tick on falsecolour)
-
-	I forget how menu items are linked to actions, reread this
-
-	gaction bound to a gsetting? do we need to add to the settings
-	schema?
-
-  likewise, load ws with locked tab, rightclick menu on locked tab does not
-  have tick selected
-
-- change "Merge into ..."
-
-	split to "Merge from file ..." and "Merge column >" with a
-	pullright listing all columns
-
-	Same for merge in tab menu, except "Merge tab >"
-
-	Just does save/load for you
-
-# menu redesign
-
 - implement Menuseparator?
 
 	we've implemented #separator

src/imageui.c

@@ -888,21 +888,30 @@ imageui_scale(Imageui *imageui)
 	VipsImage *image;
 
 	if ((image = tilesource_get_image(imageui->tilesource))) {
-		double image_zoom;
+		/* Get the view rect in level0 coordinates.
+		 */
+		double image_zoom = imageui_get_zoom(imageui);
 		int left, top, width, height;
-		double scale, offset;
-
-		image_zoom = imageui_get_zoom(imageui);
 		imageui_get_position(imageui, &left, &top, &width, &height);
+
 		left /= image_zoom;
 		top /= image_zoom;
 		width /= image_zoom;
 		height /= image_zoom;
 
+		/* image is scaled down by current_z, so we must scale the rect by
+		 * that.
+		 */
+		left /= 1 << imageui->tilesource->current_z;
+		top /= 1 << imageui->tilesource->current_z;
+		width /= 1 << imageui->tilesource->current_z;
+		height /= 1 << imageui->tilesource->current_z;
+
 		/* FIXME ... this will be incredibly slow, esp. for large
 		 * images. Instead, it would be better to just search the
 		 * cached tiles we have.
 		 */
+		double scale, offset;
 		if (imageui_find_scale(image,
 				left, top, width, height, &scale, &offset))
 			return FALSE;