untransform_dpi rect before send to pixbuf

source/gui/detail/drawer.cpp

@@ -15,6 +15,7 @@
 #include <nana/config.hpp>
 #include <nana/gui/detail/bedrock.hpp>
 #include <nana/gui/detail/drawer.hpp>
+#include "../../detail/platform_abstraction.hpp"
 
 #if defined(NANA_X11)
 	#include "../../detail/posix/platform_spec.hpp"
@@ -625,6 +626,11 @@ namespace nana
 					(good_r.right() > visual.right()) || (good_r.bottom() > visual.bottom()))
 				{
 					auto graph = wd->root_graph;
+
+					// untransform r and good_r to the System-side dpi before creating a pixel buffer
+					platform_abstraction::untransform_dpi(r     , graph->get_dpi());
+					platform_abstraction::untransform_dpi(good_r, graph->get_dpi());
+
 					nana::paint::pixel_buffer pixbuf(graph->handle(), r);
 
 					pixel_argb_t px0, px1, px2, px3;