gtk+3: add patch for Retina screens

Formula/gtk+3.rb

@@ -10,6 +10,9 @@ class Gtkx3 < Formula
     sha256 "9ae80358c79627df484a6e5c144efb86f14cf63f36c52d89234f0853977007f0" => :yosemite
   end
 
+  # see https://bugzilla.gnome.org/show_bug.cgi?id=781118
+  patch :DATA
+
   option "with-quartz-relocation", "Build with quartz relocation support"
 
   depends_on "pkg-config" => :build
@@ -111,3 +114,32 @@ class Gtkx3 < Formula
     system "./test"
   end
 end
+
+__END__
+diff --git a/gdk/quartz/gdkscreen-quartz.c b/gdk/quartz/gdkscreen-quartz.c
+index 586f7af..d032643 100644
+--- a/gdk/quartz/gdkscreen-quartz.c
++++ b/gdk/quartz/gdkscreen-quartz.c
+@@ -79,7 +79,7 @@ gdk_quartz_screen_init (GdkQuartzScreen *quartz_screen)
+   NSDictionary *dd = [[[NSScreen screens] objectAtIndex:0] deviceDescription];
+   NSSize size = [[dd valueForKey:NSDeviceResolution] sizeValue];
+
+-  _gdk_screen_set_resolution (screen, size.width);
++  _gdk_screen_set_resolution (screen, 72.0);
+
+   gdk_quartz_screen_calculate_layout (quartz_screen);
+
+@@ -334,11 +334,8 @@ gdk_quartz_screen_get_height (GdkScreen *screen)
+ static gint
+ get_mm_from_pixels (NSScreen *screen, int pixels)
+ {
+-  const float mm_per_inch = 25.4;
+-  NSDictionary *dd = [[[NSScreen screens] objectAtIndex:0] deviceDescription];
+-  NSSize size = [[dd valueForKey:NSDeviceResolution] sizeValue];
+-  float dpi = size.width;
+-  return (pixels / dpi) * mm_per_inch;
++  const float dpi = 72.0;
++  return (pixels / dpi) * 25.4;
+ }
+
+ static gchar *